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Design and Fabrication of Ultra Light Aircraft

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RESTRICTED DESIGN AND FABRICATION OF ULTRALIGHT AIRCRAFT USING INCOUNTRY RESOURCES By NUST CADET SYED HASSAN MAHMOOD WASTI (060901) NUST CADET MOHAMMAD USMAN USMANI (060906) NUST CADET HUMAYUN YOUSAF (050803) NUST CADET MUHAMMAD ALI (060904) NUST CADET BILAL (060907) COLLEGE OF AERONAUTICAL ENGINEERING PAF ACADEMY, RISALPUR 03 SEPTEMBER 2010 1 RESTRICTED
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DESIGN AND FABRICATION OF ULTRALIGHT AIRCRAFT USING INCOUNTRY RESOURCES

By

NUST CADET SYED HASSAN MAHMOOD WASTI (060901)NUST CADET MOHAMMAD USMAN USMANI (060906)

NUST CADET HUMAYUN YOUSAF (050803)NUST CADET MUHAMMAD ALI (060904)

NUST CADET BILAL (060907)

COLLEGE OF AERONAUTICAL ENGINEERING

PAF ACADEMY, RISALPUR

03 SEPTEMBER 2010

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A Project Report on

DESIGN AND FABRICATION OF ULTRALIGHT AIRCRAFT USING INCOUNTRY RESOURCES

By

NUST CADET SYED HASSAN MAHMOOD WASTI (060901)NUST CADET MOHAMMAD USMAN USMANI (060906)

NUST CADET HUMAYUN YOUSAF (050803)NUST CADET MUHAMMAD ALI (060904)

NUST CADET BILAL (060907)69EC

Submitted to the faculty of Department of Aerospace Engineering

In partial fulfillment of the requirements for the degree of

Bachelors of Aerospace Engineering

Major: Aerospace Engineering

Department of Aerospace Engineering

College of Aeronautical Engineering

PAF Academy, Risalpur

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COLLEGE OF AERONAUTICAL ENGINEERING

PAF ACADEMY, RSIALPUR

DESIGN AND FABRICATION OF ULTRALIGHT AIRCRAFT USING INCOUNTRY RESOURCES

By

NUST CADET SYED HASSAN MAHMOOD WASTI (060901)NUST CADET MOHAMMAD USMAN USMANI (060906)

NUST CADET HUMAYUN YOUSAF (050803)NUST CADET MUHAMMAD ALI (060904)

NUST CADET BILAL (060907)69 EC

A report submitted to the College of Aeronautical Engineering

In partial fulfillment of the requirements for the degree of B.E

APPROVED

(**************) (**************)

Wing Commander Messam Abbas Group Captain ABDUL MUNEM KHAN

Project Advisor Head of Aerospace Deptt.

College of Aeronautical engineering College of Aeronautical Engineering

Contents3

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List of Tables.....................................................................................................................................7

List of Figures....................................................................................................................................7

CHAPTER I........................................................................................................................................8

INTRODUCTION..................................................................................................................................8

Definition of Ultra Light Aircraft.......................................................................................................8

Objective............................................................................................................................................8

Methodology followed.......................................................................................................................8

Market Surveys and Research........................................................................................................8

Conceptual Design...........................................................................................................................8

Aerodynamic Evaluation..................................................................................................................9

Detailed design & CAD modeling...................................................................................................9

Full Scale Fabrication.......................................................................................................................9

CHAPTER II.....................................................................................................................................10

CONCEPTUAL DESIGN....................................................................................................................10

Introduction......................................................................................................................................10

Phases of Aircraft Design..............................................................................................................10

Conceptual Design Process..........................................................................................................11

Selection of Specification...............................................................................................................12

Mission Profile.................................................................................................................................12

Base Structure.................................................................................................................................13

Wing Geometry Selection..............................................................................................................13

Airfoil Selection................................................................................................................................16

Engine Location..............................................................................................................................18

Landing Gear...................................................................................................................................19

Propeller Selection..........................................................................................................................19

Engine Cooling System..................................................................................................................19

Horsepower to Weight Ratio and Wing Loading.........................................................................20

Aircraft Final Specifications...........................................................................................................21

Three Dimensional Conceptual Model.........................................................................................22

CHAPTER III.......................................................................................................................................23

AERODYNAMICS...............................................................................................................................23

Lift Slope Curve...............................................................................................................................23

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Profile Drag......................................................................................................................................23

Induced Drag Factor.......................................................................................................................24

Thrust Available and Thrust Required..........................................................................................25

CHAPTER IV...................................................................................................................................26

DETAILED DESIGN...........................................................................................................................26

Fuselage..........................................................................................................................................26

Cockpit..............................................................................................................................................28

Flight Instruments...........................................................................................................................29

LANDING GEAR ANALYSIS.........................................................................................................42

Firewall.............................................................................................................................................47

Safety...............................................................................................................................................47

Control Surfaces.............................................................................................................................47

Buckling Analysis............................................................................................................................53

Bolt Size Calculation.......................................................................................................................55

POWER PLANT SELECTION.......................................................................................................57

Modifications:...................................................................................................................................58

Alternative engine suggestions:....................................................................................................60

PROPELLER DESIGN...................................................................................................................61

Results..............................................................................................................................................62

Conclusion:......................................................................................................................................66

Solid edge view of the designed propeller:..................................................................................66

Fuel system.....................................................................................................................................67

CHAPTER V....................................................................................................................................68

FABRICATION....................................................................................................................................68

Material Selection...........................................................................................................................68

Fabrication of Connectors..............................................................................................................71

Fabrication of Custom Designed Joints and Hinges..................................................................72

Fuselage Construction...................................................................................................................74

2d Truss Construction....................................................................................................................82

Wing Construction...........................................................................................................................85

Empennage Assembly...................................................................................................................88

Control Surfaces.............................................................................................................................92

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Fabrication of Landing Gear..........................................................................................................99

Fabrication of Aircraft Skin Covering:.........................................................................................103

Solid Edge Figures.......................................................................................................................104

CONCLUSION..............................................................................................................................109

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List of TablesTable 1: Aircraft Specifications....................................................................................................................7Table 2: Airfoil Comparison.......................................................................................................................11Table 3: Wing Loading and HP/W..............................................................................................................14Table 4: Aircraft Final Dimensions.............................................................................................................15Table 5: Loads Estimation..........................................................................................................................23Table 6: Top View showing wing spars and major ribs of the wing...........................................................24Table 7: Side View showing wing spars and struts.....................................................................................24Table 8: Fuselage Truss members..............................................................................................................60Table 9: Wing members.............................................................................................................................63Table 10: Horizontal Tail members............................................................................................................66Table 11: Vertical Tail members................................................................................................................68Table 12: Landing Gear members..............................................................................................................76

List of FiguresFigure 1: Iterative Procedure of Concept Design.........................................................................................6Figure 2: Mission Profile..............................................................................................................................7Figure 3: Base Structure..............................................................................................................................8Figure 4: Clark Y Airfoil Coordinates..........................................................................................................11Figure 5: Clark Y Characteristics.................................................................................................................12Figure 6: Constraint Diagram.....................................................................................................................14Figure 7: Three Dimensional Views of Conceptual Design.........................................................................16Figure 8: Lift Slope Curve...........................................................................................................................17Figure 9: Profile Drag.................................................................................................................................17Figure 10: Profile Drag at Different Altitude..............................................................................................18Figure 11: Induced Drag Factor.................................................................................................................18Figure 12: Drag Polar.................................................................................................................................19Figure 13: Thrust Available and Thrust Required.......................................................................................19Figure 14: Effect of Fineness Ratio on Fuselage Drag................................................................................21Figure 15: Definition of Upsweep and its effect on Drag...........................................................................21Figure 16: FEM Model of the Wing............................................................................................................25Figure 17: Application of Loads on the Wing.............................................................................................25Figure 18: von Misses Stress distribution in wing members......................................................................26Figure 19: Horizontal Tail Geometry..........................................................................................................28Figure 20: von Misses Stress distribution in Horizontal Tail members......................................................29Figure 21: Vertical Tail Geometry..............................................................................................................30Figure 22: von Misses Stress distribution in Vertical Tail members...........................................................31Figure 23: Fuselage Truss dimensions.......................................................................................................32Figure 24: von Misses Stress distribution in modified Fuselage Truss.......................................................35Figure 25: Fuselage Cabin..........................................................................................................................36

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CHAPTER I

INTRODUCTION

Definition of Ultra Light Aircraft

1. The definition of ultra light aircraft varies from country to country the aviation regulatory body of the country decides the weight of an aircraft to be classifies as ultra light aircraft. However, the civil aviation authority of Pakistan has no such definition for ultra light aircraft. As a result we selected the empty weight of our aircraft closer to that used in India and set it to 800lb.

Objective

2. The aim of the project is to design and fabricate a full scale ultra light aircraft using in-country resources.

Methodology followed

a) Market Survey’s and Researchb) Conceptual Designc) Aerodynamic evaluationd) Detailed Design, CAD modelinge) Full scale fabrication

Market Surveys and Research

3. First step was initiated by carrying out a thorough web research followed by many surveys done at Peshawar, Lahore and Karachi flying and ultra light hobby clubs. Raw data of different ultra light aircraft made worldwide and in Pakistan was collected and arranged for comparison purposes. This step helped in setting the initial specification of the aircraft.

Conceptual Design

4. Conceptual design was generated following Design books by Daniel P Raymer and Roskam. An iterative process resulted in optimized conceptual design.

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Aerodynamic Evaluation

5. Aerodynamic characteristic of the aircraft were evaluated using theoretical aerodynamics and final configuration was set.

Detailed design & CAD modeling

6. Structural analysis was carried out using ANSYS software and a detailed sketch of the aircraft was created using Solid Edge software. Geometric drawings were obtained to use for fabrication process.

Full Scale Fabrication

7. After creating detailed geometry, full scale templates of different parts were created. Fabrication was done using tools and technology available locally. Pipe marking, cutting, drilling and welding are few of main processes done in fabrication phase. All the structural parts including cabin, truss, wings, control surfaces, landing gear and empennage assembly were fabricated separately and assembled together to complete the aircraft structure.

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CHAPTER II

CONCEPTUAL DESIGN

Introduction

1. Airplane is the intellectual engineering process of creating. Aircraft design is a separate discipline of aeronautical engineering – different from aerodynamics, structures, propulsion and controls. The job of a designer involves a lot of capabilities including knowledge of the above disciplines, his experience, talent, good approach, hard work and utilization of available resources and tools.

2. A good aircraft design seems to miraculously glide through subsequent evaluations by specialists without major changes being required. Somehow the landing gear fits, the fuel tanks are near the center of gravity, the structural members are simple and light weight, overall arrangement provides good aerodynamics, the engines installed in simple and clean fashion and a host of similar detail seems to fall in space.

Phases of Aircraft Design

3. There are three phases of aircraft design process.

I. Conceptual Design: Conceptual design is the primary phase. It involves configuration arrangement, size, weight and performance parameters. An affordable aircraft will be the one which meets all these requirements.

II. Preliminary Design: A preliminary design begins when major changing is over. During this phase the areas of interest are structures, landing gears and control system. Testing is initiated in areas such as aerodynamics, propulsion and stability and control parameters. The ultimate objective during this phase is to get full-scale development

III. Detail Design: Assuming a favorable decision for entering full-scale development, the detail design phase begins in which the parts of the aircraft to be fabricated are redesigned. For example, individual ribs, bolts etc are designed and analyzed. Detail design ends with the fabrication of the aircraft.

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Conceptual Design Process

4. Conceptual design is the very first step of aircraft designing where the basic configuration, size, layout, weight and performance are set. It is done by going over the set or desired requirements repeatedly while validating their feasibility. This process answers the questions whether an aircraft with the requirements can be built to fly or not. As it has been made clear that there is a set of certain characteristics that the design has to meet. These specifications can be the requirement of the user or the designer. Conceptual design process starts with the rough sketch of the aircraft, which is being designed. This gives us a very crude idea of what we are going to design. This sketch may include approximate wing geometry, location of engines, payload, passengers, cockpit and landing gears etc.

5. After this initial sketch rough weight estimation will be done, it will be followed by wing geometry selection and the calculation of other important parameters of the aircraft such as wing loading, thrust to weight ratio etc. After all this has been done, initial sizing will be carried out. In the last an iteration process will be carried out which will result in the final values of all the parameters of the aircraft.

Figure 1: Iterative Procedure of Concept Design

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Selection of Specification

6. Ultra light aircrafts are usually used for recreation and therefore loiter time rather than the range is more important. As no design requirements were given therefore a survey was conducted and the specifications were selected accordingly.

7. The specifications that were selected were:

Range 10 mileEndurance 20 minStall speed 25 mphMax speed 60 mphCruise speed 52 mphTO distance 400 ftLanding distance 300 ftCeiling 5000 ftClimb rate 550 fpm

Table 1: Aircraft Specifications

Mission Profile

Figure 2: Mission Profile

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TO

RANGE 10 MILES

LOITER 20 MIN

LANDING

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Base Structure

8. Afterwards the base structural design was selected:

Figure 3: Base Structure

Wing Geometry Selection

9. The wing geometry includes taper ratio, aspect ratio, dihedral, sweep, planform, twist, wing location, thickness and incidence.

I. Taper Ratio

High Taper Ratio

Low Taper Ratio

Weight High LowTip stall Good PoorManufacturing

Easy Difficult

Hence, it was decided to have a straight wing as flow separation downstream from the root region causes buffeting as it flows over the horizontal tail, thus providing

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stall warning to the pilot. Moreover, as the wing tip still has attached flow control surfaces would still be operatable. Besides, a straight wing is cheaper and easy to manufacture. However, special efforts would be made in manufacturing as Lift distribution is such that the centroid is away from the root causing greater bending moment.

II. Wing Location

High Mid LowInterference drag Poor Good Poor

Dihedral effect Negative Neutral positive

Visibility Good Good Poor

High wing configuration was selected as:

a. It adds to the lateral stability of the aircraft.b. The wings will not strike the ground on landingc. Safe from FODd. Fuel system can be incorporated in it. (gravity fed)e. Wing box straight through the fuselage.f. Easy to manufacture

III. Monoplane/Biplane

MonoplaneBi - plane

Cantilever BracedWeight High Low Very lowProfile Drag Low High HigherInterference Drag Low High Higher

For less weight and greater structure strength, braced wings would be used and to make sure that drag is not very high, monoplane was preferred over biplane. More importantly from manufacturing point of view monoplane construction is much easier than biplane.

IV. Wing Sweep

None SweepLift curve slope High LowPitch attitude in low speed level flight

Low High

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Ride through turbulence Poor GoodStall Good PoorLateral control at stall Good PoorWing weight Low High

No sweep was selected as it gives lower weight, better performance at low speed (our regime) and gives better stall characteristics(assuring safety).

V. Wing Dihedral

Effect of Dihedral anglePositive Negative

Spiral stability Increased DecreasedDutch Roll Stability Decreased IncreasedGround clearance of wing

Increased Decreased

As Ultra light aircrafts are supposed to be stable therefore a small positive dihedral angle would be used.

VI. Wing Incidence

Large SmallCruise drag High LowCockpit visibility Good Average

As incidence angle would increase drag therefore it was decided to use zero incidence angle.

VII. Wing Thickness

Low t/c High t/cWing weight High LowSubsonic wing drag

Low High

Wing Fuel volume Poor GoodMaximum Lift Poor Good

As greater thickness ratio increases lift as well as decrease weight, we will use higher t/c but greater than 12 Cl max starts to deteriorate, thus , we will use t/c less than 12.

VIII. Aspect Ratio

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HIGH LOWInduced Drag Low HighLift-curve Slope High LowPitch Attitude (approach)

Low High

Ride in Turbulence Poor GoodWing Weight High LowWing Span Large Small

Due to higher L/D, higher aspect ratio is selected. But higher value is limited by increasing weight with aspect ratio. Thus, a trade off is carried out and aspect ratio of 6 is finalized.

IX. Twist

Large SmallInduced drag

High Small

Tipstall Good PoorWing Weight Mildly lower Mildly higher

To decrease complexity and to improve induce drag as wing span is already very large, we will use no twist.

Airfoil Selection

Airfoil CLmax

CLARK Y 1.65NASA GA(W)-1 1.7NASA GA(W)-2 1.8NACA 2412,43012

1.65

Table 2: Airfoil Comparison

Clark Y was used as an airfoil as it is easy to build and is most commonly used is Ultra light aircrafts worldwide.

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Figure 4: Clark Y Airfoil Coordinates

Figure 5: Clark Y Characteristics

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Engine Location

Tractor configuration

Advantages

1. CG moves forward. Improving stability and allowing a shorter and smaller tail2. Propeller works in an undisturbed free stream3. More effective flow of cooling engine

Disadvantages

1. The propeller slipstream disturbs the quality of air over the wing2. Skin friction increases over the wing

Pusher configuration

Advantages

1. Undisturbed flow over the wing and fuselage2. Favorable pressure gradient at the rear of the fuselage prevents flow separation3. Engine noise reduced4. Pilot’s view improved

Disadvantages

1. CG shifts back which causes stability problem2. Propeller damaged by FODs3. Engine cooling problem more severe

After considering the pros and cons of both the configurations it was decided to use the more conventional Tractor configuration. The major factor in making this decision was the use of an automobile engine. As we have modified the engine therefore, it would be a huge risk if we are using the pusher configuration as any cooling problem could result in a crash.

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Landing Gear

Tricycle Tail draggerGroundloop behavior Stable UnstableVisibility over the nose Good PoorFloor attitude on the ground

Level Not level

Weight Medium LowSteering after touchdown Good PoorTakeoff rotation Good Good

Although the Tricycle landing gear has more advantages but the tail dragger configuration was selected as:

Provides clearance for the propeller. Less drag and weight Wing creates more lift as it is already at an angle of attack Easier to fabricate However, it is inherently an unstable configuration during ground roll. If the

airplane starts to turn during ground roll CG tends to swing around causing the turn to get tighter and tighter. So the pilot must keep the airplane always aligned with the runway.

Propeller SelectionThree practical constraints would be kept in mind while buying the propeller:

1. Propeller tip must clear the ground2. Propeller tip should not reach supersonic speeds. As compressibility effects

would ruin the propeller performance.3. Propeller must be large enough to absorb engine power. The power absorption

of propeller is increased by increasing the diameter.

The final choice of propeller used would solely depend on the availability of propeller as they are not easily available.

Engine Cooling System

Updraft cooling system is used as it, unlike downdraft cooling system, flows the cooling air upward through the cylinders and exits it into low pressure air above the fuselage, creating more efficient cooling flow due to a suction effect.

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Horsepower to Weight Ratio and Wing Loading

The thrust to weight ratio (HP/W) and the Wing Loading (W/S) are the two most important parameters affecting the aircraft performance. Wing loading and horsepower to weight ratio are interconnected for a number of performance. The major part of the analytical design is the optimization of these factors as these are more interconnected in the segments of take off, landing, turn and glide etc. To achieve their values, constraint diagram was formulated, using the most critical segment of our profile:

0 2 4 6 8 10 12 140

0.05

0.1

0.15

0.2

0.25

Chart Title

STALL LIMITTO

W/S

HP/W

Figure 6: Constraint Diagram

W/S 4.7941HP/W 0.08Power Loading 12.5

Table 3: Wing Loading and HP/W

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Aircraft Final SpecificationsAfter going through different phases of concept design, final aircraft specifications come out as follow:

All dimensions in feet.

Fuselage Control SurfacesLength 17 AileronWidth 2.5 Chord 0.25 of wingHeight 4.25 Span 0.45 of wingWing ElevatorSpan 28 Chord 0.9 of stabilizerChord 4.66 Span 0.45 of stabilizerSpan area 130.33 RudderSweep 0 Chord 0.4 of finAspect Ratio 6 Span 0.9 of finTaper ratio 1 FlapsDihedral 0 Chord 0.25 of wing

Span 0.55 of wingHorizontal Tail Cl design 0.75136Chord 3.2Span 9.5 Weights Span area 29.7 payload 200Lht 10.2 Structural weight 302Aspect Ratio 3 Engine weight 150Taper Ratio 0.6 Maximum weight (fully

loaded)652

Vertical Tail Clean ConfigurationChord 3.5 K 0.066306Span 4.1 Cdo 0.033043Span area 14.2 Take OffLvt 10.2 Cdo 0.048043Aspect Ratio 1.2 K 0.070726Taper Ratio 0.6 LandingPower plant Cdo 0.098043Power required 60 hp K 0.075778Fuel required 32 lbs.Fuel volume required

20 litres Take off and Landing

Air Cooling System ST/O 286.1Air Intake Area 0.278 sq. ft. Sldg 390Propeller Diameter 4.3 ft.TiresDiameter 12 inch.Width 4.2 inch.

Table 4: Aircraft Final Dimensions21

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Three Dimensional Conceptual Model

Isometric View Front View

Side View Top View

Figure 7: Three Dimensional Views of Conceptual Design

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CHAPTER III

AERODYNAMICS

Lift Slope Curve

Cl alpha versus Mach No:

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.094.278

4.284.2824.2844.2864.288

4.294.2924.2944.296

CL alpha vs M

M

CL a

lpha

Figure 8: Lift Slope Curve

Profile Drag

Profile Drag versus Mach No:

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.090

0.005

0.01

0.015

0.02

0.025

CD vs Mach No.

M

CD

Figure 9: Profile Drag24

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Drag at different altitude:

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.090

0.005

0.01

0.015

0.02

0.025

CD vs M

SL10002000300040005000

M

CD

Figure 10: Profile Drag at Different Altitude

Induced Drag Factor

Induced Drag Factor versus Mach No:

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.090

0.02

0.04

0.06

0.08

0.1

0.12

K vs M

0-0.8above 0.8

M

K

Figure 11: Induced Drag Factor

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Drag Polar

0 0.05 0.1 0.15 0.2 0.25 0.3 0.350

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Drag Polar

CruiseT/OLanding

CD

Cl

Figure 12: Drag Polar

Thrust Available and Thrust Required

Thrust Available versus Thrust Required:

0 0.02 0.04 0.06 0.08 0.1 0.120

2

4

6

8

10

12

Thrust available vs Thrust Required

thrust availablethrust required

Mach

thru

st (l

b)

Figure 13: Thrust Available and Thrust Required

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CHAPTER IV

DETAILED DESIGN

Components of the Aircraft

1. Wing2. Fuselage Cabin3. Fuselage Truss4. Horizontal Tail5. Vertical Tail6. Flaps7. Control Surfaces (Ailerons, Elevators, Rudder)8. Engine Mount9. Wing Mount10. Connectors/Joints11. Landing Gear12. Control System

Fuselage

Fuselage is responsible for the largest portion of overall drag for most of the airplanes. Thus it should be sized and shaped accordingly for minimum drag. It contributes to various drags:

Friction drag. Profile drag. Base drag. Compressibility drag. Induced drag.

To reduce friction drags, two options are available:

Shape the fuselage so that laminar flow is possible. Reduce the length and perimeter as much as possible.

If fuselage length is decreased, for the same level of static stability, tail size can be decreased, thus, decreasing the friction drag. Thus, the optimum fineness ratio is 4 to 8.

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Figure 14: Effect of Fineness Ratio on Fuselage Drag

Upsweep of fuselage:

Upsweep is needed for clearance during take-off. It also gives clearance during taxi in tail dragger arrangement.

Figure 15: Definition of Upsweep and its effect on Drag

As we can see in figure, drag does not increase much up to the upsweep of 15 degrees.

Our proposed design:

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Upsweep 12.5 degreesFineness ratio 4

Cockpit

The basic idea behind the cockpit design is to provide comfort to the pilot besides easy excess to the all vital controls and accessories without diverging the pilot’s attention.

Cockpit design especially for homebuilders:

Our proposed design:

Sidewise motion of stick: 15 degrees.

Distance between rudder pedals: 50cm.

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Flight Instruments

Following are the most common instruments used in most of the homebuilders:

1. airspeed indicator2. altimeter3. magnetic compass4. tachometer5. oil pressure gauge6. oil temperature gauge7. fuel quantity indicator

According to FAR 23, depth of instrument panel should be around 1 foot.

Load Estimation

Before going for further structural design, it is necessary to know the loads the structure is going to sustain. The total takeoff weight of the aircraft is 568 lbs and it will take a Load Factor of 2.0 during its flight. A Factor of Safety of 1.5 will be used for the structural design of the aircraft.

Assuming that the wing generates all the lift, the wing must produce lift equal to the weight of the aircraft. Thus, total vertical force experienced by the wing will be the weight multiplied by both the Load Factor and the Factor of Safety which gives a value of 1700 lbs. Wing drag is estimated to be 10% of its lift which equals 170 lbs.

The lift and drag of horizontal tail is estimated to be 20% of that of the wing. So, lift and drag of horizontal tail becomes 340 lbs and 34 lbs respectively.

Since the vertical tail has similar configuration as half of the horizontal tail, so we can take the side force and drag of the vertical tail to be half of the lift and drag of the horizontal tail respectively. Thus, the side force becomes 170 lbs with a drag force of 17 lbs.

The following table summarizes the load estimation. These loads will be used to analyze the design.

MemberVertical Loads (Lift, lbs)

Horizontal Loads (Drag, lbs)

Lateral Loads (Side Force, lbs)

Wing 1700 170 --Horizontal Tail 340 34 --Vertical Tail -- 17 170

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Table 5: Loads Estimation

Wing Design

Dimensions

As per Conceptual Design, the wing dimensions are:

Span 28 ftChord Length

3.5 ft

The wing is straight rectangular without any twist.

Components

The wing comprises of:

1. Leading edge Spar2. Trailing Edge Spar3. Major and Minor Ribs4. Struts

Construction:

The wing will be constructed in two symmetrical parts which will be later joined at the wing mount. Each of the part will be 13 ft long and a 2 ft connector at the wing mount will make the total span to 28 ft. The following design is proposed for the wing part.

Table 6: Top View showing wing spars and major ribs of the wing

Table 7: Side View showing wing spars and struts

All the members consist of Al pipes. An iterative trial and error structural analysis will determine the dimensions of these pipes.

Determination of Dimensions of Pipes

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In order to determine the outer diameter and thickness of the pipes, the proposed design was analyzed in ANSYS using different combinations of available diameters and thicknesses. The best combination was then selected as the final dimensions of the pipes.

Procedure of Analysis

The basic geometry was predetermined and the variable parameters were outer diameter and thickness of the spars, ribs and struts as well as the span wise location of the struts. So, the basic geometry was generated in ANSYS and arbitrary values of outer diameter and thickness were given.

Figure 16: FEM Model of the Wing

The geometry was then meshed with element type PIPE16. Loads were applied as estimated before at 14 Hard Points. These Hard Points are the points where ribs will be joined. So, applying loads at these points will be quit suitable. It is assumed that the loads are equally distributed among these points. The Load Step was solved and von Misses Stress was plotted and maximum stress was noted. These steps were repeated until a satisfactory result was obtained.

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Figure 17: Application of Loads on the Wing

Result of the Analysis

The analysis showed the following combination to be best suited which was selected as the final dimensions.

Dimension ValueSpar Outer Diameter 2.00 inSpar Thickness 0.78 inStrut Outer Diameter 1.50 inStrut Thickness 0.75 inMajor Rib Outer Diameter

2.00 in

Major Rib Thickness 0.78Strut Location Mid Span

For the above combination, plot of von Misses Stress is shown below:

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Figure 18: von Misses Stress distribution in wing members

The factor of Safety can be calculated as:

Maximum Stress = 29,510 psi

Tensile Strength of Material = 30,000 psi

FOS=Strengt hof MaterialMaximumStress

=30,00029150

=1.03

Since, we have already multiplied the applied loads with 1.5 as a FOS, so the actual FOS will be 1.5 X 1.03 = 1.54.

Minor Rib Construction:

One of the most important parts of wing design is to give its cross section the shape of desired airfoil. In order to do so, seven ribs are placed on each side of the wing at a distance of 2.25 ft apart. The ribs are constructed from two pipes. A straight pipe is used for the lower surface to get a flat bottom, as designed. The upper surface will be given the required curvature by using a bended pipe.

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Horizontal Tail

Dimensions

As per Conceptual Design, the horizontal tail dimensions are:

Span 9.50 ft (114 in)Root Chord Length 3.25 ft (39 in)Taper Ratio 0.60Sweep Angle 15 Deg

Keeping in mind the above dimensions, the following geometry is proposed for the horizontal tail.

Figure 19: Horizontal Tail Geometry

Determination of Dimensions of Pipes

In order to determine the outer diameter and thickness of the pipes, the proposed design was analyzed in ANSYS using different combinations of available diameters and thicknesses. The best combination was then selected as the final dimensions of the pipes.

Procedure of Analysis

The basic geometry was predetermined and the variable parameters were outer diameter and thickness of the spars and ribs. So, the basic geometry was generated in ANSYS and arbitrary values of outer diameter and thickness were given. The geometry was then meshed with element type of PIPE16. Loads were applied as estimated before

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at 06 Hard Points. It is assumed that the loads are equally distributed among these points. The Load Step was solved and von Misses Stress was plotted and maximum stress was noted. These steps were repeated until a satisfactory result was obtained.

Result of the Analysis

The analysis showed the following combination to be best suited which was selected as the final dimensions.

Dimension ValueOuter Diameter

1.50 in

Thickness 0.75 in

For the above combination, plot of von Misses Stress is shown below:

Figure 20: von Misses Stress distribution in Horizontal Tail members

The factor of Safety can be calculated as:

Maximum Stress = 28,496 psi

Tensile Strength of Material = 30,000 psi

FOS=Strengt hof MaterialMaximumStress

=30,00028,496

=1.05

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Since, we have already multiplied the applied loads with 1.5 as a FOS, so the actual FOS will be 1.5 X 1.05 = 1.58.

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Vertical Tail

Dimensions

As per Conceptual Design, the horizontal tail dimensions are:

Span (Height) 04 ft (48 in)Root Chord Length

2.5 ft (30 in)

Taper Ratio 0.60Sweep Angle 15 Deg

Keeping in mind the above dimensions, the following geometry is proposed for the horizontal tail.

Figure 21: Vertical Tail Geometry

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Determination of Dimensions of Pipes

Since, dimensions of pipes for horizontal tail are selected, we will check, whether these dimensions can be used for vertical tail or not. If the Factor of Safety is acceptable, we will use the same pipes for vertical tail construction.

Procedure of Analysis

The basic geometry was generated in ANSYS and the values of outer diameter and thickness were given as 1.5 in and 0.75 in respectively. The geometry was then meshed with element type of PIPE16. Loads were applied as before at 06 Hard Points. It is assumed that the loads are equally distributed among these points. The Load Step was solved and von Misses Stress was plotted and maximum stress was noted.

Result of the Analysis

The von Misses Stress distribution is shown below. The maximum stress comes out to be 26,679 psi.

Figure 22: von Misses Stress distribution in Vertical Tail members

The Factor of Safety can be calculated as:

Maximum Stress = 26,679 psi

Tensile Strength of Material = 30,000 psi

FOS=Strengt hof MaterialMaximumStress

=30,00026,679

=1.12

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Since, we have already multiplied the applied loads with 1.5 as a FOS, so the actual FOS will be 1.5 X 1.12 = 1.69.

The Factor of Safety came out to be 1.69 which is quiet acceptable. So, the same pipes will be used for vertical tail.

Dimension ValueOuter Diameter

1.50 in

Thickness 0.75 inFuselage Truss

Dimensions

The fuselage truss must be 9.5 ft (114 in) long. The other dimensions are as shown below.

Figure 23: Fuselage Truss dimensions

Determination of Dimensions of Pipes

The Fuselage Truss will be constructed from the same pipes used for the tails i.e.

Dimension ValueOuter Diameter

1.50 in

Thickness 0.75 in

Determination of Truss Members

A 2 dimensional truss was proposed as the initial design. This design was analyzed using ANSYS. By noting the results, necessary modifications were made. The proposed design is shown below.

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Procedure of Analysis

The basic geometry was generated in ANSYS and the values of outer diameter and thickness were given as 1.5 in and 0.75 in respectively. The geometry was then meshed with element type of PIPE16. Loads were applied at the attachment points of the horizontal and vertical tail as well as the rear landing gear. The loads at these points were obtained from previous analysis of horizontal and vertical tails. An estimated vertical load of 140 lbs was applied at rear landing gear attachment point. The loads are summarized below:

Loads HT Point 1 HT Point 2 VT Point 1 VT Point 2 Rea LGFX (lbs) 21 15 15 21 --FY (lbs) 75 96 -28 28 140FZ (lbs) 26 -26 97 74 --

The Load Step was solved and von Misses Stress was plotted and maximum stress was noted.

Result of the Analysis

The analysis showed that the lateral displace of the truss structure is very large. The displacement came out to be 20 in which is not acceptable. So, design must be modified to restrict the lateral diplacement of the tail. Plot of lateral displacement is shown below.

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Fuselage Truss Modification

In order to restrict the lateral displacement, members must be added which can take lateral loads. So, four members are added as shown below.

Analysis of Modified Truss

The modified truss was analyzed as done before.

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Lateral Displacement: The lateral displacement of the tail of the modified truss structure came out to be about 4 in. this value is acceptable if the stress does not exceeds the strength of the material used. Plot of lateral displacement is shown below.

von Misses Stress: The maximum von Misses Stress came out to be 26, 385 psi which gives a FOS of about 1.70. So, the design is safe and can be accepted. Distribution of von Misses Stress is shown as under:

Figure 24: von Misses Stress distribution in modified Fuselage Truss

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Fuselage Cabin

Fuselage cabin is the part of aircraft where most of the components get jointed. Wing, landing gears, engine mounts and fuselage truss are connected to the cabin. It also has the provision for installment of flight instruments and control system. It will also serve as the cockpit to house the pilot. The following figures show the sketch of fuselage cabin.

Front View Side ViewFigure 25: Fuselage Cabin

LANDING GEAR ANALYSIS

For the landing gear analysis of ultra light aircraft a standard drop test is carried out. In this test the aircraft is dropped from a height of 3 ft and the impact taken by landing gear is closely observed if the landing gear is able to fully survive the impact it is declared safe. However, we have used ANSYS to simulate all the critical landing loads.

LANDING GEAR CRITICAL LOADS

Critical loads as stated by FAR 23 and those suggested on discussion forums of ultralight aircraft were considered.

According to FAR 23 regulation the most severe conditions for landing were

• Vertical load equal to 75% of max ground reaction

– 10 fps for design landing weight

– 6 fps for design TO weight45

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• Drag 40% of the max weight

• Side force 25% of vertical force

• This combination acts at the wheel axle centerline.

However, most discussion forums on the internet suggested that forces up to 3g’s could be experienced during poor landing and hence vertical loads were selected accordingly. The corresponding loads used were:

◦ Drag/Friction : 280 lbs

◦ Lateral loads due to bad landing : 350 lbs

◦ The vertical reaction on touchdown calculated on suggestions from discussion forums describing landings at 3gs : 1400 lb

Dimensions Selection

Dimensions were selected on the following requirement:

The final landing gear dimensions are:

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SOLID EDGE VIEW

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ANSYS ANALYSIS

The greatest challenge we faced during the analysis was the non availability of damping coefficient and spring constant value of dampers. Although spring constant could be found. It was impossible to calculate the damping coefficient without proper experimental setup. Therefore, it was decided to find the loads in the rods connecting the dampers and hope that a damper could be found with the required load rating inscribed on it.

The element used for landing gear analysis was Pipe 16:

Uniaxial element with tension-compression, torsion, and bending capabilities

The element has six degrees of freedom at two nodes: translations in the nodal x, y, and z directions and rotations about the nodal x, y, and z axes.

Material Used

Steel 4130 N is used. Use of steel also means that the structure can be easily welded therefore analysis of welded structure was done.

Density ρ [kg/dm3] 7.9Elastic modulus E [GPa] 200

Poisson’s ratio ν 0.28Thermal conductivity κ [W/mK] 31.4

Thermal expansion α (1/K) 20 e-6Ultimate Tensile strength (Mpa) 730

PROCEDURE

As we couldn’t get the values of “k” and “c” for the shock absorber and the design papers were only specified for oleo shock absorbers therefore they couldn’t be used

Hence it was decided that if individual load in the member where shock absorber is to be installed could be found then the shock absorber can be selected

The maximum stresses in each member were found.

The load was then calculated by multiplying with area

These loads were then used to find a suitable shock absorber

Usually FOS of 1.5 is used but I have used 2 as the local material might not have perfect strength

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TWO POINT LANDING CONDITION

The results as calculated by ANSYS were max. stress of 3269 psi. which corresponded to a force of 845 lbs. The maximum stress was also less than the failure stress.of 105 ksi

Fig. 2 point landing analysis

The deformation calculated was also acceptable

Fig. deformation diagram

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Firewall

Stainless steel or galvanized iron sheet of minimum thickness .015 inch (according to FAR 23) is installed between cockpit and engine to prevent pilot from engine heat.

Safety

For the safety of pilot, cabin should consist of :

Ballistic Parachute

Fire Extinguisher

Control Surfaces

Flight control systems can be divided into primary and secondary flight control systems.

Primary control systems:

Lateral Controls: ailerons, spoilers and differential stabilizer. Longitudinal controls: elevator, stabilizer and canard. Lateral controls: rudder.

Secondary control systems:

Trim controls: lateral, longitudinal and directional controls. High lift controls: trailing and leading edge flaps and slats. Thrust controls: engine fuel controls (throttle), manifold gates and propeller blade

incidence.

Based on their design, flight control systems are further divided into:

Reversible flight control systems. Irreversible flight control systems.

Reversible flight control systems:

In a reversible flight control system, when the cockpit controls are moved, the aerodynamic surface controls moves and vice-versa. They are typically mechanized with cables, push rods or a combination of both.

Irreversible flight control systems:

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In an Irreversible flight control systems (hydraulic or electrical), when the cockpit controls are moved, the aerodynamic surface controls moves and not vice-versa. Another way of stating this is to say that in an irreversible flight control system an actuator moves the aerodynamic surface controls. The pilot merely signals the actuator to move. This signaling process is usually an irreversible process.

Major advantages associated with reversible flight control system are:

Simplicity. Low cost. Reliability. Relatively maintenance free.

In laying out a reversible flight control systems, the following important design aspects need to keep in mind:

Mechanical design requirements for cable and push-rod systems. Efficiency consideration. Cable and push rod control force levels. Control surface types and hinge moments. Aerodynamic balance requirements. Mass balance requirements.

Major design problems associated with reversible flight control system are:

Cable stretch. Cable slack. Friction. Weight. Handling qualities. Elastic control system deformation. Flutter.

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Cable stretch:

To prevent cable stretch l/s >6.

Cable slack:

Turnbuckles are used to prevent cable slack and to prevent cables from leaving pulley, cable guards are used.

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Friction:

To prevent too much friction, following rules to be considered:

Keep cable runs as straight as possible. Keep the number of guides and pulleys as small as possible.

For every cable turn, additional pulley is needed which introduces extra weight and extra friction.

Elastic control system deformation:

To prevent elastic control system deformation, the following rules should be observed:

Use oversized cables (this will cost weight).

Make sure pulleys are attached to stiff structural components. Do not attach them to flat plates, they deform easily.

Flutter The solution to the control surface flutter is :

To make sure that centre of mass not behind hinge line

try to have chordwise cg at hinge line

prevent any play in the linkages

Design consideration:

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Primary flight control system cables should have a diameter greater than .11inch (2.8mm) according to FAR 23.

Rotation efficiency is highest if the angle between the cable and the driving sector is 90 degrees with the system in its neutral position.

Kinematic feasibility.

Mechanisms A and B are kinematically sound, the quadrangles ABFE and CDFE remain parallelograms when the system is used. Mechanism A is better than B because of its higher rotation efficiency. Mechanism C and D are unworkable because the cable lengths AB and CD do not remain constant after some rotation. Thus mechanism C and D are undesirable.

Our proposed design:

Reversible flight control system is selected, which consists of only cable pulley.

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Three Dimensional Sketches

Front View

Side View

Top View

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Buckling Analysis

Our aircraft cabin contained vertical members that would take compressive stresses at landing as indicated by ANSYS Analysis therefore buckling analysis was necessary. As we had chosen pipes for constructing cabin therefore we had the added advantage in Buckling as a circular pipe is the most efficient column section to resist buckling. This is because it has an equal radius of gyration in all directions and it has its area distributed as far away as possible from the centroid.

For the purpose of Analysis a long column with central loading case was considered. Euler column equation was used and the equation was formed by using boundary condition for the case where both ends of the column are fixed. For obtaining the Euler column formula we began by assuming a pipe of length l loaded by a force P acting along the centroid axis as the bar is bent a negative moment is required, and hence

Fig. showing pipe bending under compressive loads

M = -Py

Comparing with the beam deflection formula d2 ydx 2

=MEI

we get the equation

Solving the differential equation for initial conditions gives us the final buckling analysis

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Since the maximum compressive force to be experienced by the pipes is known we need to keep all variables constant while finding out one variable. In our case P, E, l is known. We decided to keep pipe thickness and internal diameter constant and find out the minimum required outer diameter to keep the pipe from buckling. The Moment of Inertia of pipe is given by

Substituting in Euler Equation and solving we got the final equation:

All the variables were substituted in the equation the result we got for minimum outer diameter requirement was 1.42 inch. Hence it was verified that a pipe of outer diameter 1.5 inch, thickness 2mm would not buckle under the given loads. As with aviation rules a Factor of Safety of 1.5 was also kept in mind while doing calculations.

Fig. showing condition for Euler equation use

To ensure that it’s an Euler column one last check is done the slenderness ratio of this size pipe was found out to be l/k=105.3 which is greater than the limiting slenderness

ratio of hence the use of Euler Equation is justified

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Bolt Size CalculationIn the aircraft bolts have been used to join different members. In order to prevent rotation of members, two bolts were used on each connection point. Before bolt selection the bolt size was determined. The three basic types of failures associated with bolts are:

1. Crushing/bearing failure2. Tearing failure3. Shearing failure

Fig. (a) Crushing failure (b) tearing failure (c) shearing failure

In our case the Crushing or bearing failure is the bolt size determining factor. In order to prevent pipes from crushing during tightening a small 3 in piece of wood was inserted in the pipe before drilling. Hence, the bolt passed through the wood sandwiched between aluminum pipe of thickness 2mm.

To calculate the bolt size software, MITCALC was used however two calculations were also done manually and the answers matched with the software to validate MITCALC.

Pc=t . d . σc

Where,

t= pipe thickness

d= diameter of the bolt

σc= safe permissible crushing stress

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The calculated bolt sizes were as follows:

S No Member/ connections Bolt size required1 Cabin connections 6 mm2 Wing - cabin attachments 8 mm3 Control surfaces / horizontal/vertical stabilizers 4 mm4 Truss-empennage connections 6 mm5 Landing gear attachments 8 mm6 Engine mount 8 mm

Lock nuts were used with bolts. These nuts are not manufactured locally and are imported. However, at the moment lock nuts for size smaller than 6 mm were not available. As a result we were forced to use only 6mm and 8mm bolts.

The carbon steel bolts selected were of highest available grade of 12.9. Allen Key bolts were selected as Hex Bolts of the specified grades were not available. Bolts of length 2.0 and 2.5 inch were used.

Fig. Allen key bolts with wrenches

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POWER PLANT SELECTIONPower requirement for the aircraft was first found out from the initial design which was coming out to be 60 hp. Although aviation engines which fulfilled our requirement were available but financial constraints prevented us from purchasing them. Therefore a market survey was performed to find a suitable car engine which would fulfill our needs.

Car Engine name Rpm Hp Torque (Nm) Weight (lb)Cultus G-10 5100-5500 50 65 139Cuore ED-10 5500 48 83 N/AAlto SS80 5500 62 87 N/ACity 1.3 L (~79 cu in) I4 i-VTEC 5500-6000 100 128 N/ACorolla 2NZ-FE 6000 80 119 N/A

However, all these engines were water-cooled and added weight. Therefore it was decided to use air-cooled engines and hence it was decided to use VW engines another advantage of an original VW engine is that VW claims that its engines can automatically adjust fuel requirement with altitude. An extensive search for VW engines was carried out and a list of VW engines available in Pakistan was made:

Production Date Displacement Engine Number

Horsepower

Dec. 1953 through July 1960 1200cc 1, 2, 3 36August 1965 through July 1966 1300cc FO 50August 1965 through July 1970 1300cc E low comp 37August 1966 through July 1967 1600cc HO 53August 1967 through July 1969 1600cc H5 low comp 50August 1967 through July 1970 1600cc L 50August 1969 through July 1970 1600cc H1 53August 1969 through July 1970 1800cc B 57August 1970 through July 1973 1300cc AC 44August 1970 through Sept. 1971

1800cc AE 60August 1971 through July 1973 1800cc AD 65August 1973 through July 1975 1300cc AR 48August 1973 through Dec 1980 1800cc AS 60From Dec. 1974 (fuel-injected) 1800cc AJ 60

After the survey it was decided to use 1800cc VW engine or 1600cc engine produced in 1966 or 1969. For this purpose the five major VW mechanics and engine suppliers were contacted in Karachi in May and they provided us with surety that the engine would be provided. The estimate engine cost was Rs 20,000/-.

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Modifications:For engine modifications local mechanics and ultra light aircraft owners were consulted. Although help was also taken from internet but local mechanics were unfamiliar with most of these foreign techniques as a result following modifications were finalized:

Removal of outer cowl: This would assist in more efficient cooling

Removal of gear box: As our aircraft would operate at a constant rpm therefore gearbox use was judged irrelevant.

Fig. the removal of bulky gear box would significantly reduce weight

Double carburetor: This would allow the pistons to work differentially allowing for a much better and efficient compression

Engine Overhaul: As these engines are about 30 years old therefore engine overhaul is necessary to ensure optimum performance.

Replacing flywheel: The standard and heavier steel flywheel would be replaced with Al. flywheel. This would cause significant weight reduction.

Fig: A standard flywheel and a custom made flywheel

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Reduction drive installation: In order to change the RPM of engine a reduction drive was necessary. This modification is held till last so as to achieve the most favorable RPM. It is suggested to use engine piston material for making pulleys and thrust bearings should also be used as car engines are not designed to take thrust loads and therefore in order to increase their life thrust bearings should also be used

Fig. a reduction drive popularly used in auto conversion engines

Change Generator: To reduce weight the heavier original generator could be replaced with a lighter generator or the generator could be fully removed and battery can be charged on ground.

Fig. as can be seen the VW generator is quite bulky

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Alternative engine suggestions:Despite promises made by engine suppliers an 1800cc VW engine as required was not made available. As a result a survey was done on the internet for alternate powerplants:

Rotax engine: A second hand dual carburetor Rotax 503 engine was available in Peshawar at a cost of Rs 2 lakh. The engine had flown for 40 hours. It provided 47 hp but at the same time its weight was 85 lbs which is almost half the estimated weight of VW engine. Propeller specifications for Rotax engines are directly available on the internet. For Rotax 503 carrying a weight in the range of 700-850 lbs the propeller specs are: 56x32 where 56 is the diameter and 32 degrees is the pitch.

Fig. Rotax 503

Water-cooled engines: Using water-cooled engine would increase our aircraft weight as the whole cooling mechanism had to be added. However, as a last resort these engines too can be considered. Increasing weight would also increase the Hp requirement as a result cultus and Coure engine were considered inadequate. City and Corolla engines would exceed our requirement. This leaves Alto SS80 engine as the best available option. However this engine was introduced in 2008 and a brand new engine costs a staggering Rs 1.8 lakh. While a used engine costs Rs 50,000/-. For the given Rpm and new weight the propeller was designed using javaprop® software which gave us propeller specification of 58x26.

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PROPELLER DESIGNInitially it was decided that a propeller would be bought directly from the market for the ultra light aircraft. However, no ready made wood propellers were available for sale in the market leaving us with no choice but to fabricate the propeller. A manufacturer was contacted and he asked for the diameter and pitch of the propeller.

For propeller design a free software javaprop® was used. The software is based on Adkins, C. N.: Design of Optimum Propellers, AIAA-83-0190. The main improvements were:

Elimination of the small angle approximation

Elimination of Light loading approximations prevalent in the classical design theory

An iterative scheme is introduced for accurate calculation of the vortex displacement velocity and the flow angle distribution.

Momentum losses due to radial flow can be estimated by either the Prandtl or Goldstein momentum loss function.

In the analysis portion "Blade Element Method" is used and it uses the same airfoil polars as the design procedure

The influence of blade number and tip loss are taken into account by the "Prandtl Tip-Loss Factor

Four major design criterions were kept in mind while carrying out propeller design:

THE NUMBER OF BLADES

The number of blades has a small effect on the efficiency only. Usually a propeller with more blades will perform slightly better, as it distributes its power and thrust more evenly in its wake. But for a given power or thrust, more blades also mean more narrow blades with reduced chord length, so it’s difficult to manufacture.

DENSITY:

The density of the fluid has no influence on the efficiency of a propeller, but strongly affects its size and shape. As the forces and the power are directly proportional to the fluid density. Aircraft operating at high alt. usually need a smaller diameter then those operating at low alt.

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PITCH

Large pitch propellers may have a good efficiency in their design point, but may run into trouble when the have to operate at axial velocity. In this case, the blades tend to stall. Usually the best overall propellers will have a pitch to diameter ratio in the order of 1.

DIAMETER

The propeller diameter has a big impact on performance. Usually a larger propeller will have a higher efficiency, as it catches more incoming fluid and distributes its power and thrust on a larger fluid volume.

ResultsThe software javaprop® is a very user friendly software a six step procedure was followed to come to final result.

Number of Blades 2 blades Diameter 4.6ft Rpm 2700 Thrust at design condition 220 lb Efficiency at design condition 65% Blade angle at 75% R 25 Geometric Pitch 3.8ft

Airfoils were selected according to the most popularly used airfoils in ultralight propellers

At r/R=0 MH 126

Fig. MH 126

MH 126, this airfoil was designed for the root section of a full size propeller. It covers a wide angle of attack range without separation and has the required thickness for this region.

At r/R=0.33 MH 112

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Fig. MH 112

MH 112 16.2%, this airfoil was designed to follow the root section. It covers the typically needed range of lift coefficients for the inboard region.

At r/R=0.67 MH 114

Fig. MH 114

MH 114 13%, this airfoil is well suited for the middle part of the propeller halfway between root and tip.

At r/R=1.0 MH 116

Fig. MH 116

MH 116 9.8%, this airfoil can be used for the tip of propellers operating at tip Mach numbers of 0.6 and below.

Then the front and side view of propeller was found

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Fig. Front and side view of the propeller

Next the thrust graph with respect to velocity were found

Fig. Thrust vs Velocity graph

The thrust graph was then imported to MS Excel and required thrust vs available thrust graph was made

0 0.02 0.04 0.06 0.08 0.1 0.120

2

4

6

8

10

12

Thrust comparison

thrust availablethrust required

Mach

thru

st (l

b)

Fig. Thrust comparison

As can be seen there is excessive thrust available. Especially at cruise Mach which is about 0.067.

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Next Cl, Cd plots were made against r/R. As desired the Cl value is greater than Cd throughout the blade diameter

Fig. Cl, Cd vs r/R

A Mach number vs r/R curve was also plotted. The Mach number throughout the diameter remained below 0.7 Mach as desired.

Fig. Mach vs r/R

A chart showing the velocity of the slipstream of propeller was also made. Vx is the axial velocity, V is the inflow velocity. The graph shows that the flow has accelerated by about 80%.

Fig. Velocity variation graph

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Conclusion:The propeller design was satisfactory as it was close to common propeller results for ultra light aircrafts with 50hp engine as shown in the table below

Commonly used propeller

Propeller designed using javaprop®

Prop Dia. (") 52 56 59 55.2

Pitch (degrees) 28 25

Thrust (lb.) 158 230

The propeller efficiency is 65% which is less than the ideal 80%. However the efficiency is dependent on a number of factors like HP, RPM, Diameter, Velocity etc.In our case the HP is fixed. The rpm and diameter are also restricted with the thrust requirement and the need to keep the tip velocity below 0.75 Mach. All these restraints have resulted in a lower efficiency. An iterative method was used to get the best combination of Diameter and Rpm.

Solid edge view of the designed propeller:

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Fuel systemTwo types of fuel systems were considered:

Gravity fed fuel system Pressure fed fuel system

Gravity-Feed Systems use only the force of gravity to push fuel to the engine fuel-control mechanism. The bottom of the fuel tank must be high enough to provide adequate pressure to the fuel-control component. This type of system is often used in high-wing light aircraft. We have preferred gravity fed system as it is simple, does not need any installation of pump and suits our aircraft configuration i.e. high-wing light aircraft. However, we need to install two valves to ensure fuel supply at all time

Thus, our fuel tank has two valves to counter for every phase of flight. Fuel from these valves merged together before entering into the engine.

Fuel System Components:

Tanks Lines Valves Fuel Flow-meters Filters and Strainers

Fuel line routing:

Fuel lines and hoses should be routed free of conflict with moving parts and should be secured so they will not vibrate against the airframe. It should also be ensured that fuel lines do not hinder pilot’s movement.

The fuel line from the tank to the engine must be routed continuously down hill. If this is not maintained, air pockets or bubbles can get trapped in any high spots and severely restrict the flow of fuel.

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Solid edge view:

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CHAPTER V

FABRICATION

Material Selection

Before starting fabrication it was imperative to select material which had a high strength to weight ratio. Al 6061-T6 is the most commonly used material in ultralight aircraft industry. However, this material is not available locally and hence an alternate Al 6063-T6 was used in aircraft structure. A comparison of AL6061-T6 and AL 6063-T6 is given below:

T 6063 T 6061Density (lb / cu. in.) 0.098 0.097Specific Gravity 2.7 2.7Melting Point (Deg F) 1090 1150Modulus of Elasticity Tension 10 10Modulus of Elasticity Torsion 3.8 3Tensile strength 42,000 psi (290 MPa)  30,000 psi (207 MPa)Yield strength 35,000 psi (241 MPa) 25,000 psi (172 MPa)

Although AL 6061-T6 was a better option, AL 6063-T6 is used as it fulfills our requirement.

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Tools Used

Fabrication process started with acquisition of tools. Due to unavailability of resources expensive tooling equipment could not be purchased that’s why stress was given upon using simple and cheap yet effective tools. A few parts needed welding or machining, and those were farmed out to local professionals. Following tools were used during the fabrication process.

Tools Used: Had Access to:

Flexible tape measure 5 m long Sheet Metal Shear

Carpenters square Sheet Metal Break

Water level 2 foot Drill press

Rivet gun Metal Lathe

1/4-inch Socket wrench set Metal Mill

Open end wrench set Welding torch

4-inch bench vise

Hand Drill

Center punch

Hacksaw

High Speed Electric Cutter

Electric Baby Grinder

Assorted metal files

Handheld Pipe cutter

Pop Rivet Gun

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Fabrication Process Steps

Following steps were taken in building and assembling of the designed ultra light aircraft. Some steps like pipe marking and cutting are in series while others were completed in parallel. it should be noted that all the fabrication work was done in backyard of a house and therefore this project is a true home built product.

Pipe Marking and Cutting

As the standard size of aluminum pipes available from local market was 12 ft..So they had to be cut into smaller pieces so that they can be used on different locations as required by structural design of the aircraft. This Task was completed in two steps

1) Marking:Marking scheme was such that a single 12 ft piece could be fully utilized in making different size pieces and minimum material was wasted. Also the defined nomenclature for different members was used to write Name, Length and Diameter of each piece

2) Cutting:Pipe Cutter was used to cut the larger pipes into smaller precise pieces which were to be used in different parts of aircraft. Procedure followed for cutting purpose was to hold the marked pipe in bench vise and provide a support to keep balance then a straight cut was made which ensured dimensions to be exact as marked on pipes.

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Fabrication of Connectors

Following connectors were obtained from market directly.

I. 3d Elbow connectorThese are 3d joints which were used to join cabin pipes meeting at 90 degree angles. Mild steel material joints were used due to availability and cost constraints.

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II. 3d TEE connectorThese connectors are used to join 04 pipes meeting at 90 degree angles simultaneously. They are also made of Mild steel. They provide ease of assembling as strength to highly stressed portions of cabin.

Fabrication of Custom Designed Joints and Hinges

Due to unavailability of required connectors and joint members from local market, a number of connectors were designed, analyzed and fabricated with the help of local professionals, given below are the details of design and fabrication of different type of joining members

I. 90’ Clip ConnectorsThese types of connectors were most commonly used in fabrication of wing, empennage and control surfaces; they were used to join any 02 pipe members which were at right (90deg) angle to each other.Their fabrication started with cutting a piece of aluminum plate of 6inx4inx04mm and shaping it into desired joint with the help of soft hammering???? and sheet bending techniques.

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II. Angled Clip ConnectorsThis type of connectors were used to join the main members which were inclined to each other at some specified angle, different angle connectors were used in different parts of cabin and empennage assembly, they were fabricated in the same fashion as 90 deg connectors and special care was taken in making the correct angle of joint as well as to prevent the shear of soft aluminum sheet .

III. Plate ConnectorsThis special type of joint was used on rear portion of the cabin; their main purpose was to support the extruded cabin members which support rear struts coming from wing. As this portion is highly stressed and requires stronger joints than simple angled joint, plate joints were designed and fabricated using 04mm thick aluminum plate which connected angled members of rear cabin to extruded strut attachment members.

IV. Ring ConnectorsConnecting Wing airfoils with the main spar was a difficult task. As these types of connectors are unavailable in the market therefore an innovative new ring connector was designed. For their fabrication purpose, Mild steel pipes were found which would snugly fit on the Spar and would be having thickness only1mm as these connectors won’t be taking much stress. Then a jig was made that copied the exact wing dimensions. Once the jig was made exact welding

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location of the smaller pipe onto the 2in pipe was confirmed and the ring connectors were made accordingly.

Control Surface connectors/Hinges

For deflection of flaps and control surfaces some rotating mechanism was necessary, market survey showed that desired deflection could not be achieved using ordinary hinges and so male female couple type hinges of different desired sizes were designed and fabricate, for this purpose MS bars were machined and welded over MS pipes of different required diameters, then these completed hinges were clipped to control surfaces mounted on Horizontal and vertical tail as well as on wing spars.

Fuselage Construction

Fuselage design consisted of two main components

1) Cabin compartment2) 2d Truss Structure

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Both the components were fabricated separately and then joined to complete the fuselage structure. Details of both the processes are given below.

Cabin Construction:

Cabin is a critical portion of aircraft as it gives places for attachment of wing, rear truss, engine mounts, and landing gear ,it also houses the pilot and works as a base for placement of control components. List of members used is given below followed by steps taken to complete the cabin structure.

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Material used in Cabin Fabrication

Vertical Cabin Members

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SN. Members Length(in) Diameter(in) Thickness(mm) Material1 FC 001 30 1.5 2

Al 6063  

2 FC 002 30 1.5 23 FC 003 54 1.5 24 FC 004 54 1.5 25 FC 005 54 1.5 26 FC 006 54 1.5 2

Lateral Cabin Members:

SN. Members LengthDiameter/Width Thickness Material

1 FCL 015 18 1.5 2

 AL6063

 2 FCL 016 18 1.5 2 3 FCL 017 58 1.5 2 4 FCL 018 58 1.5 2 5 FCL 019 50 1.5 2 6 FCL 020 50 1.5 2

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Horizontal and Angled Cabin members:

No. Members Length(in) Diameter(in) Thickness(mm) Material1 FCH 007 30 1.5 2

AL6063

2 FCH 008 30 1.5 23 FCH 009 30 1.5 24 FCH 010 30 1.5 25 FCA 021 30 1.5 26 FCA 022 30 1.5 27 FCA 023 35 1.5 28 FCA 024 35 1.5 2

Landing Gear and Wing Mounts:

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S No. L/g & Wing Mounts Length(in) Width(in)Thickness(mm)  Material

1 FLB01 X 02 50 2 5AL6063

2 FLB02 X 02 50 2 53 FLB03 X 02 50 2 5

Steel4 FLB04 X 02 50 2 55 FLB05 X 02 32 2 5

Connectors Used

S No. Connector Type Quantity Material1 3d Elbow 4 Mild steel2 3d Tee 2 Mild steel3 90’ Clip 4 Al 60634 Angled Clip 4 Al 60635 Plate Joint 2 Al 6063

Other Materials Used:

S No. Part Material Length(in) Width/Dia(in) Thickness(mm)

1 Flooring Hard Plywood 50 30 20

2 WindshieldPlastic Sheet,Al pipes 32,32 24,15mm 7

3 FirewallGalvanized Iron Sheet 66 54 2

Construction process:

I. Pipe Structure and Connections

The pipes were connected using Elbow, TEE and Clip joints????Reason of using MS (Mild steel) for Tee and elbow joints was unavailability of Aluminum joints.The joints were strengthened using wooden pieces of 3inch length and were snugly fit inside the Aluminum pipes .This procedure has been proved effective by previous designs fabricated worldwide.

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Rear portion joints of the cabin were specially designed and custom fabricated to ensure strength and sleekness of this portion. All the joints were Bolted using 6mm diameter,2 and 2.5 inch length Allen Bolts. Lock nuts were used to ensure safety and reliability.

II. Wing Mount and Landing Gear attachments:

As wing and landing gear are two main loads bearing components of the aircraft, their attachments to the cabin needed to be strong enough to bear loads transferred from this component.

To fulfill this requirement L beam of Aluminum and Stain less steel were used for Wing and landing gear attachment respectively. These beams were joined to base pipe structure using nuts and bolts.

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III. Cabin Floor , Wind shield and Cabin Firewall

Cabin floor is required for mounting of pilot seat, control stick and pedals; it also provides a base for installment of various subsidiary components.For construction purpose hard plywood sheet was used. After cutting the sheet in precise dimensions it was attached to base members (pipes and L beams) with the help of nuts bolts and washers.

Wind Shield serves the purpose of protecting the pilot from prop wash, bird strike and foreign objects .It also gives aerodynamic shape to cabin front portion thus reducing drag and increasing performance.It was constructed using plastic sheet which were cut to size. Front portion of wind shield was bended to give curvature, for this purpose aluminum pipes of 15 mm diameter were used. Finally sheet was riveted to Cabin Pipes.

Cabin Firewall is used for thermal insulation or the cabin thus providing a safety wall between engine and cabin so that engine heat might not injure the pilot or damage instruments inside cabin.Galvanized iron sheet was used for this purpose as suggested by Daniel P Raymer.

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2d Truss Construction

Second main portion of fuselage fabrication was construction of rear truss, it provides connections for Empennage assembly and is structural backbone of the aircraft, structural analysis showed adequate strength of simple 2d truss and its ease of construction made it an attractive choice for fabrication. Given below is the list of members used in fabricating this part followed by the procedure of construction

Material Used:

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No. MEMBERS LENGTH (in) Diameter(in) Thickness(mm)

1 FT 001 114 1.5 22 FT 002 116.5 1.5 23 FT 003 23.1 1.5 24 FT 004 27.6 1.5 25 FT 005 18.8 1.5 26 FT 006 28.9 1.5 27 FT 007 15.6 1.5 28 FT 008 23 1.5 29 FT009 10.6 1.5 2

Table 8: Fuselage Truss members

Construction Process:Designed 2d truss was constructed using aluminum members which were joined using 4 ft long,6 in wide and 5mm thick al plates. Members were fitted in two such aluminum plated and bolted to complete the truss ,all the joints which had drilling holes were strengthened by using 3in long snugly fit wooden pieces. Truss also contained the connections for empennage assembly, for tail connection smaller pieces of aluminum plates and L beams were used.

Assembling of Fuselage:

After completion of both cabin and truss structures, they were joined, following joints and strengthening members were used to make the fuselage rigid and to constraint it in all degrees of freedom.

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Members Used:

No. MEMBERS

LENGTH (in) Diameter(in) Thickness(mm)

1 FA001 48 0.7 22 FA002 48 0.7 23 FA 003 36 0.7 24 FA 004 36 0.7 2

Connector Used:

Connector QuantityMaterial

90’ Clip 02 Al 6063

Assembling Procedure: Assembly was joined first with the help of 90 deg clip connectors but they were unable to take all the loads acting on truss so to strengthen the structure members FA001 and FA002 were used which joined the cabin roof L beams to truss while Elements FA003 and FA004 supported the truss by connecting it to cabin base members.

Fuel Tank Installation:Fuel tank provides the engine with required fuel, gravity feed fuel system was used as it is simple and easy to use there is no need of special fuel pump.Following component complete the fuel system

I. Fuel TankLocally available Fuel tank of 5KVA electric generator which has 25 liter fuel capacity was used. It is fitted with fuel level indicator.

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II. Fuel Tank SupportsTwo (02) MS pipes of 0.7in diameter and 1mm thickness were used to support fuel tank, they also served the purpose of giving aerodynamic shape to rear fuselage portion.

Wing Construction

Wing is the lift producing surface. It bears aerodynamic loads like lift and drag and also provides resistance towards flutter and fatigue phenomenon.

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Material Required

S No. member Length Diameter Thickness material1 W 001 13 ft 2 in 2 mm

AL 6063

2 W 002 13 ft 2 in 2 mm3 W 003 13 ft 2 in 2 mm4 W 004 13 ft 2 in 2 mm5 Rib 001 40 in 2 in 2 mm6 Rib 002 40 in 2 in 2 mm7 Rib 003 40 in 2 in 2 mm8 Rib 004 40 in 2 in 2 mm9 Rib 005 40 in 2 in 2 mm10 Rib 006 40 in 2 in 2 mm11 Rib 007 (Qty 14) 40 in 15 mm 2 mm12 Airfoil 001 (Qty 14) 46.2 in 15 mm 2 mm

Table 9: Wing members

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Connectors Used:

S No. Connectors Used Quantity Material1 MS pipes 5 ft long 2 Mild Steel2 90⁰ clip 12 AL 60633 Airfoil ring connectors 28 Mild Steel4 U bolts (dia 8mm grade 12.9) 8 Carbon Steel5 Allen bolts(dia 6mm length 2.5in grade 12.9) 36 Carbon Steel

The aircraft’s wing span was calculated to be 28ft. however; 14ft aluminum pipes were not available in the market. As a result 13ft pipes were bought and to join then a 5ft Mild steel pipe was snugly inserted into the two pipes. This meant that a 1.5ft MS pipe was inserted into each Spar.

The two main spars were connected with 6 ribs of AL diameter 2 inch while 14 15mm ribs were also attached. The positioning of the 2 in Ribs was done to accommodate the control system pulley besides providing strength to the wing. The 2 in ribs were connected with clip joints and were bolted. Riveting was also an option but since the aircraft had to be transported to Risalpur therefore Bolts were given preference.

Next Step was the bending of pipe into airfoil shape. For this purpose a full scale airfoil shape was taken from plotter. Next this shape was cut onto a card board. This template was given to the pipe bender who accurately bent 14 pipes according to the template.

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Airfoils were connected to main wing spars using specially designed ring connectors which gave not only ease of installation of rib but also came up as strong and light weight solution to the problem

Pictures:

Full wing MS pipe Clip connector Welded connector U bolts Jig

Empennage Assembly

Empennage

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Horizontal Tail

Horizontal stabilizer is an integral part of any airplane it provides stability to the aircraft and prevents it from going into spin. As before the material required is tabulated followed by the joints required and then the fabrication process is mentioned

MATERIAL REQUIRED

S.no memberLength (in)

Diameter (in)

Thickness (mm)

material

1 HT 001 (i) 24 1.5 2

AL 6063

2 HT 001 (ii) 24 1.5 2 3 HT 002 (i) 29 1.5 2 4 HT 002 (ii) 29 1.5 25 HT 003 (i) 34 1.5 2 6 HT 003 (ii) 34 1.5 2 7 HT 004 114 1.5 2 8 HT 005 (i) 59 1.5 2 9 HT 005 (ii) 59 1.5 2

Table 10: Horizontal Tail members

JOINTS USED

Joints Used Qty MaterialL beams ( length 6 inch ) 4 AL 6063Plate ( thickness = 5mm) 1 AL 606390 clip⁰ 6 AL 6063Angle clip 6 AL 6063Allen bolts (dia 6mm length 2 in grade 12.9) 40 Carbon SteelMS Struts 2 Mild Steel

During Horizontal tail construction it was of utmost importance that the horizontal tail be kept symmetric. So that during flight the aircraft won’t tilt to one side.

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At first the 90 clips were attached to HT 004. Afterwards members HT001, HT002,⁰ HT003 were cut accurately and joined with the angle clip to HT 004. During this entire process it was necessary that the members should be kept perpendicular to HT 004 for this reason a triangle was kept with the connecting members.

After assembling the horizontal tail a pendulum was used to confirm the symmetry of the Horizontal tail. The pendulum pointed at the midpoint of HT 004 which confirmed that the HT is symmetric. For final test of symmetry diagonal length of the HT was measured from both sides and was found equal.

The horizontal tail was connected by sandwiching the horizontal stabilizer between the L beam and plate. It was ensured that the centre of horizontal stabilizer matched the centre of fuselage truss structure.

As these connections were not sufficient therefore they were enforced by attaching struts to the horizontal stabilizer.

Pics

Uncut pipes at 90 Full HT Connectors Struts Pendulum hanging

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VERTICAL STABILIZER

Vertical stabilizer is an integral part of any airplane it provides stability to the aircraft and prevents it from going into spin.

MATERIAL REQUIRED

S.nomember

Length (in)Diameter (in)

Thickness (mm)

material

1 VT 001 18 1.5 2

AL 60632 VT 002 22 1.5 2 3 VT 003 26 1.5 2 4 VT 004 64 1.5 25 VT 005 49.5 1.5 2

Table 11: Vertical Tail members

JOINTS USED

Joints Used Qty MaterialL beams ( length 8 inch ) 2 AL 6063Plate ( thickness = 5mm) 2 AL 606390 clip⁰ 4 AL 6063Angle clip 3 AL 6063

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Allen bolts (dia 6mm length 2 in grade 12.9)

25 Carbon Steel

Horizontal tail fabrication was relatively easy first we joined members with 90 clips at a distance of 18 in from centre to centre. Afterwards the pipes were cut to size and joined using angle connectors. It should be remembered that the members were cut at an angle to fit them in the vertical stabilizer.

The vertical tail was attached to the truss structure by using two plates of dimension 6x6 in front and by using a 90 connector and 2 L beams at the rear.

Control SurfacesFour control surfaces were to be fabricated: elevators, ailerons, flaps and rudder. The construction of control surfaces was relatively easy.

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Ailerons

MATERIAL REQUIRED

S.no memberLength (in)

Diameter (in)

Thickness (mm)

material

1 AL 001 (i) 60 1.5 2

AL 60632 AL 001 (ii) 60 1.5 2 3 AL 002 (i) 60 1.5 2 4 AL 002 (ii) 60 1.5 25 AL 003 (Qty 6) 18 1.5 2

JOINTS USED

Joints Used Qty Material90 clip⁰ 12 AL 6063Allen bolts (dia 6mm length 2 in grade 12.9) 36 Carbon Steel

The construction of Ailerons was straight forward the Connector’s centre was placed at a distance of 30in from each other. While joining the AL 003 members to AL 001 members it is suggested that first the connector should be placed at the marked position and checked for its perpendicularity with member AL 001. Even a slight mishap in this case would render the whole Aileron useless. Once the AL 003 members have been joined with AL 001 the members should then be joined with AL 002 members if the procedure is correctly followed the AL 003 members should automatically come perpendicular to AL 002.

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Flaps

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MATERIAL REQUIRED

S.no MemberLength (in)

Diameter (in)

Thickness (mm)

material

1 FL 001 90 1.5 2

AL 60632 FL 002 90 1.5 2 3 FL 003 90 1.5 2 4 FL 004 90 1.5 25 FL 005 (Qty 8) 18 1.5 2

JOINTS USED

Joints Used Qty Material90 clip⁰ 16 AL 6063AL connecting pipe (ID 1.5in Length 5ft) 3 AL 6063Allen bolts (dia 6mm length 2 in grade 12.9) 48 Carbon Steel

For flaps it was necessary that the flap leading edge be a single piece as it was to be connected with control system. This would ensure equal and timed movement of the entire flap. To achieve this Aluminum pipe was bought whose internal diameter was 1.5 inch and hence the two FL 001 members would snugly fit into the pipe both the members were inserted 1 ft into the Aluminum pipe.

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Once through with the leading edge of the flap rest of the procedure is same with the connectors joined at a distance of 30 inch from each other and perpendicular to the FL 001 and FL 002.

Rudder

MATERIAL REQUIRED

S.no memberLength (in)

Diameter (in)

Thickness (mm)

material

1 RR 001 9 1.5 2

AL 60632 RR 002 15 1.5 2 3 RR 003 21 1.5 2 4 RR 004 60 1.5 25 VT 005 61.34 1.5 2

JOINTS USED

Joints Used Qty Material90 clip⁰ 3 AL 6063Angle clip 3 AL 6063Allen bolts (dia 6mm length 2 in grade 12.9) 18 Carbon Steel

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Rudder fabrication is similar to Vertical stabilizer construction the 90 clips are placed at⁰ a distance of 29 inch from centre to centre. Rest it should be kept in mind that a triangle should be used while fixing the 90 clip.⁰

Elevator

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MATERIAL REQUIRED

S.no memberLength (in)

Diameter (in)

Thickness (mm)

material

1 EL 001 (Qty 2) 11 1.5 2

AL 60632 EL 002 (Qty 2) 15.25 1.5 2 3 EL 003 (Qty 2) 32 1.5 2 4 EL 004 (Qty 2) 21 1.5 25 EL 005 (Qty 2) 50 1.5 2

JOINTS USED

Joints Used Qty Material90 clip⁰ 4 AL 6063Angle clip (12 )⁰ 4 AL 6063Angle clip (30 )⁰ 4 AL 6063Allen bolts (dia 6mm length 2 in grade 12.9) 36 Carbon Steel

Since the hinges designed for the movement of control surfaces did not allow for a single elevator therefore the two elevators had to be fabricated. The first 90 clip was⁰ positioned at the end while the second was placed at a distance of 20 inch from the centre of the first.

Although the lengths stated above are accurate but it is highly suggested that the angle pipes be kept a bit longer and later cut down after fixing the members. Again it is imperative that both the elevators be kept symmetric.

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Fabrication of Landing GearLanding gear plays a vital role during taxing, taking off and most important at landing, it bears the ground loads and impact loads; landing gear was designed following 3g impact regulation of Federal Aviation Authority (FAA).So it had to be one of strongest components of the aircraft. The design included a shock absorbing system which reduces the impact loads on aircraft.

Coming to the fabrication of the finally selected landing gear design following members were used followed by the steps taken in fabrication.

Members of Landing Gear:

No. Component LENGTH (in) Diameter(in) Thickness(mm) Material1 LR001 45    

Mild Steel2 LR002 45    3 LR003 50    4 LR004 50    

Table 12: Landing Gear members

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Tires Used:

No. Tire Diameter(in) Thickness(In)

Material Feature

1 TR01

14  4 Rubber tire and tube 

Inbuilt brake system

2 TR02

14  4

3 TR03

 6 3  All Hard Rubber Lock mechanism

Shock absorber:

No.

Tire Spring Constant Damping Coefficient Rated load(lb)

1 SA01NA NA 800

2 SA02

Fabrication Process:

I. Main landing Gear

a) Connecting Members: In main landing gear design four (04) connecting members (LR001,LR002,LR003,LR004) were used which bear and transferred the impact load to base cabin members(FLB05,06,07,08),they were cut into size and two (LR003,LR004) of them were bent to take the desired shape as per design. These rods were connecting to cabin base by pin joints so that they can move in 02 degree of freedom, the angle between the aircraft centerlines and front members was set as 27degrees which is in conjunction with FAR regulation of minimum of 25degree of landing gear angle.

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b) Tires: Two tires were selected for main landing gear design, for this purpose local market survey was done to find the closest match to our designed landing gear tires. Finally tires were obtained which met the design specifications and also incorporated the feature of in build shoe brake system for ground brake purposes These tires were welded to landing gear rods to ensure strong joints.

c) Shock Absorbers: As mentioned previously, two shock absorbers were selected using standard testing procedure. They were attached to members (LR001, LR002) with the help of custom made welded holder which acted as pin joints for shock absorbers.

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II. Rear Landing GearAs the aircraft has a tail dragger configuration third landing was placed at rear tail section of aircraft. Rear landing gear is not designed to bear heavy impact loads rather its main purpose is to help in movement and directional control while at ground. An all rubber tire has been used for rear landing gear which is fixed into lower end of vertical tail rear spar. Rear landing gear also features a locking mechanism which enables us to lock its rotational motion as well as its translational motion or both.

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Final Assembling of Aircraft:

After completion of each component separately they were attached as a final assembly consisting of cabin fuselage truss, wing and tail assemblies and in the end control surfaces and landing gears were attached to give the aircraft final shape. All the components fit perfectly and were bolted, hinged and welded to make the whole structure as one piece.

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Fabrication of Aircraft Skin Covering:Aircraft covering is necessary to complete the structure such that it could be installed with propulsion system, covering of wing, empennage and control surface is necessary for production of aerodynamic forces on these parts while fuselage covering gives the aircraft aerodynamic shape hence reducing drag and increasing efficiency.

Material Used:

Parachute material having dimensions 40 x 05 yards was used for fabricating skin of the aircraft.

Rivets of 3mm diameter and 12 mm thickness were used to fix the stitched skin cloth to the aircraft

Fabrication Process:First of all clothing material was cut to dimension of wing, empennage and control surfaces then it was stitched to give a tight fitting so that there won’t be any slack or loose surface left. Last step was to fix the skin with aircraft components with the help of riveting process. Thus giving the aircraft a complete aerodynamic shape.

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Solid Edge Figures

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CONCLUSIONFull detail design of the aircraft was carried out which would ensure the integrity of the aircraft. Every possible aspect of design was taken care off from the selection of Bolt size to installation of aircraft engine. Due to shortage of time the fabrication could not be completed. However, the most important part of fabrication, aircraft structure, was fully completed. Material for aircraft covering and controls has also been acquired while the propeller has also been fabricated. The entire fabrication process was carried out using the most economical resources and it was proven that an aircraft can be fabricated in Pakistan using local resources and that too at an extremely low cost.

It is suggested that this project be continued. Inshallah by next semester this project would be fully completed and CAE would be able to claim that its students have successfully designed and flown their own aircraft.

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