CHAPTER 11 FUEL MANAGMENTRODOLFO GARCÍA BENDÍMEZ - 1691604

CARLOS EDUARDO CHÁVEZ FÉLIX – 1691238

LUZ GRISELA AGUILAR HERNÁNDEZ - 1580110

11.1 STORAGE OVERVIEW

Rigid tanks are usually found in smaller general aviation aircraft. They are installed within the fuselage and/or wings, and are designed to be removable for inspection, replacement, or repair. They do not form an integral part of the aircraft structure.

Bladder tanks are reinforced rubberized bags installed within specific areas of aircraft structure.

Integral fuel tanks are located within the structure on larger aircraft; these are sealed to accommodate fuel storage. These tanks form part of the aircraft structure; they cannot be removed for service or inspection.

11.2 FUEL QUANTITY MEASUREMENT AND INDICATION

Various technologies and methods are used to measure and display fuel quantity: this depends mainly on the type and size of aircraft. The fuel quantity methods described here could equally apply to other fluids, e.g. oil, hydraulic fluid or water.

The methods used for measur-ing fuel quantity can be summarized as:

● Sight glass

● Float gauge

● Resistance gauge

● Under-wing measurement

● Capacitance units.

11.2 FUEL QUANTITY MEASUREMENT AND INDICATION

11.2.1 SIGHT GLASS.

It is based on a simple glass or plastic tube located on the outside of the tank, and visible to the pilot. Fluid level in the tube is the same as the level in the tank; graduations on the tube provide an indication of tank contents.

11.2.2 FLOAT GAUGE.

The float gauge uses a rod projecting through a hole in the tank cap. A float is attached to the base of the rod and this rises and falls with the fuel level. The pilot checks the amount of rod protruding through the cap and this provides a direct reading of fuel quantity. One disadvantage of this method is that it is not very stable during aircraft manoeuvres.

The variable resistor is connected into a DC ratiometer circuit where two opposing magnetic fields are created in each of the coils. The pointer is formed with a permanent magnet and is aligned with the resulting magnetic field created by the coils; the pointer moves in accordance with the ratio of currents in the coil

11.2.3 UNDER-WING MEASUREMENT. A floatstick that comprises a rod, float and magnets located inside the tank The floatstick is stowed when not in use and released via a quarter-turn cam mechanism; it slides out of the tank until the two magnets align and is then retained in this position. The floatstick is moved in and out of the tank until the attraction of the magnets can be sensed. The fuel quantity reading is then taken from a reference point on the surface of the wing. When the reading has been taken, the rod is pushed back and locked into the stowed position.

11.2.4 CAPACITIVE FUEL QUANTITY SYSTEM.

11.2.4.1 Principle of operation

Fuel tank units are formed by concentric aluminum tubes; the inner and outer tubes are the capacitor plates The primary advantages of this technology are no moving parts and fuel quantity is measured in mass rather than volume. (The mass of fuel determines the amount of energy available.)

From basic fundamentals, we know that capacitance is proportional to:

● Plate area

● Air gap

● Dielectric strength.

In the capacitive tank unit, the first two parameters are fixed; the capacitance varies in accordance with the dielectric, i.e. the amount of fuel in the tank

With a high quantity of fuel in the tank, the capacitance is high; capacitance varies in direct proportion to the amount of fuel in the tank.

The tank’s capacitance unit is connected into an impedance bridge circuit. Variation in capacitance ( C ) of the fuel tank unit causes a change in reactance ( XC )

11.2.4.2 Density compensation

The volume of fuel in a tank varies with temperature; as the temperature changes, the mass of fuel remains the same, but the volume changes. The dielectric is therefore affected by fuel density; this density will change with temperature. Increased density is a result of reduced temperature that will cause increased capacitance. Changes in fuel density are measured by a compensation unit

This is an additional tank unit located in the bottom of the fuel tank, therefore it is always immersed in fuel. The compensating unit is connected into the impedance bridge such that changes in fuel density cause the bridge to become unbalanced and this compensates for the change in fuel level.

11.3 Fuel Feed and Distribution.

General Aviation aircraft are normally fitted with an engine-driven pump (EDP), with electrical boost pumps fitted to prime the system during starting.

A simple fuel pump system comprises an electrically driven boost pump motor controlled by an on/of switch.

11.3 Fuel Feed and Distribution.The system is enchanced by a two-stage throttle control system.

• When the boost pump selector switch is set at the ‘ low’ setting, electrical power is switched through the resistor and the motor runs at a low speed.

• With the engine running, then the selector is moved to the ‘ high ’ setting which provides power through the NC contacts of the throttle micro-switch.

• When the throttle is set below one-third open, the resistor remains in series, and the motor continues to run at the low speed.

• When the throttle is advanced, the throttle micro switch changes over via the NO contacts to bypass the resistor and apply full power to motor

11.3 Fuel Feed and Distribution.

11.3 Fuel Feed and Distribution.The typical fuel feed arrangement comprises two booster pumps for each main tank; the motor is located on the tank bulkhead, with the pump located inside the tank.

The fuel distribution system requires electrical power and is controlled by a panel in the flight compartment.

Fuel shut-off valves are connected to the battery bus, and controlled by the engine start lever and fire handle.Important: The fuel system normally has the means of transferring fuel between tanks; this is controlled by a selector switch that operates a crossfeed valve.

11.3 Fuel Feed and Distribution.

The delivery output from each pump feeds into the system via a non return valve. Under normal operating conditions, each pump feeds own engine via a motor driven low-pressure cock.

If a centre tank is fitted as part of a three-tank instalation, this can feed either engine by a fuel transfer system.

Control switches for all pumps, cocks and valves together with warning indications are located on the overhead panel or the flight engineer’s station. LP cocks are automatically closed if the fire handle is activated

11.3 Fuel Feed and Distribution.

11.4 Fuel TransferThis system is used to selectively transfer fuel between tanks; electrically driven fuel pumps and motorized valves are controlled either manually by the crew or by an automatic control system.

On larger aircraft, the complex system comprises a number of motorized valves. • Engine valves are activated by the start lever or fire

handles.• The left, centre and right refuel/defuel valves are

operated from an under-wing panel.• Bypass valves are operated if an electrical pump’s

fuel filter is blocked.• Controls and indications are located on an overhead

panel or flight engineer’s station.• An electrically operated cross-feed valve normally

closed unless fuel is being transferred.

11.4 Fuel Transfer

It is essential that fuel temperature is monitored, either manually or automatically.Fuel temperature is measured by an RTD.

If the fuel temperature is approaching the lower limits, some fuel could be transferred between tanks; alternatively the aircraft would have to descend into warmer air or accelerate to increase the kinetic heating.

Note: 50 C to -50 C

11.5 Refuelling and Defuelling.• A Refuelling control panel and pressure connections are located in the

wing area allowing the fuel to be supplied directly into the main fuel system.

• A bonding lead is always connected between the fuel bowser and aircraft to minimize the risk of static discharge. Selective control of the system’s motorized valves allow specific tanks to be filled as required.

• Defuelling is often required before maintenance, or if the aircraft is to be weighed. The fuel is transferred from the aircraft into a suitable container, typically a fuel bowser.

11.6 Fuel Jettison/Fuel Dumping (Vaciado de combustible)

• When an aircraft takes off fully loaded with passengers and fuel, and then needs to make an emergency landing, it will almost certainly be over its máximum landing weight.

• Fuel has to be disposed of to reduce the aircraft weight to prepare for the emergency landing.

• Bowing 747 can be carrying over 100 tonnes of fuel, almost 50% of the aircraft’s gross Weight.

PESO MAXIMO

COMBUSTIBLE LLENO

CARGA MAXIMA

DE PASAJEROS

11.6 Fuel Jettison

• Two Jettison pumps are installed in each main tank, fuel is pumpued via a jettison manifold to nozzle valves located at each wing tip trailing edge

• Fuel can normally be jettisoned with landing gear and/or flaps extended.

• Its aims to improve aircraft safety by reducing the air displacement of empty space or the volume of air above the fuel in a fuel tank of aviation.

11.7 Fuel Tank Venting (Ventilación del tanque de combustible)

Llenado de gas no

flamable

The fuel level in the tank is reduced during the flight and the oxygen remaining in the empty space ( ullage ) is replaced by non-flammable inert gas. The reduction of oxygen in the fuel tank prevents combustion in the tank

Ram air: Aire forzado a entrar a una abertura dinámica (aire dinámico)

• The venting system takes ram air from intakes on the underside of the wing for two specific purposes:

11.7 Fuel Tank Venting (Ventilación del tanque de combustible)

• When the aircraft is flying, it is used to pressurize the fuel to prevent vaporization at lower atmoshperic pressures.1

• It also pressurizes the fuel tanks to ensure positive pressure on the inlet pors of each pump.

2

11.7 Fuel Tank Venting (Ventilación del tanque de combustible)

• Float-operated vent valves are located at key points in the tank to allow fuel to escpae into the vent system, they also prevent inadvertent transfer of fuel between tanks.

• Venting tanks in the wing tips collect this overspill from the main tanks; the fuel is then pumped back into one of the main tanks.

• Many aircraft have been destroyed due to explosions in empty centre Wing Fuel Tanks.

Common elements:

• Small amount of fuel in the wing tank.

• Air-conditioning packs located in non-vented bays directly under the CWT, had been running before explossions.

• Quite warm outside air temperatures.

11.8 Fuel Tank InertingExplosiones

Why does it happen?

• Small amount of fuel: It had a large amount of evaporated fuel .  

• Air conditioning packs generate heat so it contributes to evaporation in uninsulated tanks

• Evaporation increased with high ambient temperatures .

• Empty fuel tanks retain some fuel is not used , which evaporates in these conditions and creates an explosive mixture when combined with oxygen from the ullage .

11.8 Fuel Tank Inerting

EVITEMOS QUE EL COMBUSTIBLE SE EVAPORE!!

Mejoras

Corto Término

11.8 Fuel Tank Inerting

Aislamiento en tanques de combustible cercanos a

fuentes de alta temperatura

Diseño de

bombas de

tanques de

combustible

Regímenes de

inspección

INERTING

• Ground-Base inerting: The fuel tanks would receibe an amount of nitrogen-enriched air before pushback. Interting would last fir the taxi, takeoff and climb phases.

• On-Board ground inerting: Achieves the same objective; however, the inerting equipment is an aircraft system.

• On-Board inert gas generation system (OBIGGS): It offers tremendous benefitsm although it is the most expensive.

11.8 Fuel Tank Inerting

• Liquid Nitrogen from a ground source.

11.8 Fuel Tank Inerting

1• The aircraft receives a supply of liquid nitrogen from a ground

source.

2• Liquid nitrogen is stored on the aircraft in a vacuum-sealed

insulated container.

3• Oxygen sensors in the fuel tanks provide feedback to the

system’s computer control function.

4• The supply of liquid nitrogen is regulated to keep the fuel tanks

inerted for critical phases of flight.

5• This system would know the tank temperatures at all times,

together with the oxygen content of the tanks.

11.8 Fuel Tank Inerting• Systems NGS (Nitrogen generating systems): Is an onboard

inert gas system; external air is directed into an air separation module (ASM) this separates out the oxygen and nitrogen via a molecular sieve. After separation, the NEWA is supplied into the center wing tank and the OEA is vented onboard. NEA decreases the oxygen content in the ullage to prevent combustion.

CHAPTER 12 LIGHTS.1691344 ERICK ANTONIO GONZÁLEZ GARCÍA

1592175 IDA YAMILEX SALINAS SALAZAR

1591198 UZIEL AGUILAR REYES

Lighting is installed on aircraft for a number of reasons including: safety, operational needs, servicing and for the convenience of passengers.

There are many types of lighting technologies used on aircraft. Lights are controlled by on/off switches, variable resistors or by automatic control circuits.

INTRODUCTION.

12.1 LIGHTING TECHNOLOGIES

Aircraft lighting is based on a number of technologies:

● Incandescence

● electro-luminescent

● fluorescence

● strobe

Incandescence.

Is the radiation of light from an electrical fi lament due to an increase in its temperature. The fi lament is a small length of wire, like tungsten, which resists the flow of electrons when a voltage is applied, thereby heating the filament.

Electro-luminescence.

Is a combined optical and electrical phenomenon that causes visible light to be emitted. This can be achieved with electron flow through a semi-conductor material, or by a strong electric field applied across a phosphor material.

Fluorescent lamps.

Are gas-discharge devices formed from a sealed tube of glass that is coated on the inside with phosphor; the glass tube contains mercury vapor mixed with an inert gas, like argon or neon.

Strobe lights.

Are formed from small diameter (typically 5 mm) sealed quartz or glass envelope/tube filled with xenon gas, see Fig. 12.1. Power from the aircraft bus is converted into a 400V DC supply for the strobe. The tube is formed into the desired shape to suit the installation, it is a wing-tip anti-collision light.

Figure 12.3 It illustrates a typical strobe light circuit.

• Key maintenance point: 400 V DC used in strobe circuits is dangerous: take all necessary health and safety precautions when working near the system.

• Key maintenance point: Do not handle strobe tubes with bare hands; moisture causes local hot-spots that can lead to premature failure.

12.2 FLIGHT COMPARTMENT LIGHTS.

Dome lights: They are located on the ceiling provide non-directional distribution of light in the compartment; it typically contains an incandescent lamp and is powered from the battery or ground services bus.

Flood lighting: Located in the flight compartment from incandescent lamps and/or fluorescent tubes provides a general illumination of instruments, panels, pedestals etc.

Emergency lights: They are installed in the flight compartment for escape purposes. The color of flight compartment lights is normally white; this reduces the power and heat, improves contrast on the instruments, and reduces eye fatigue.

12.2.1 Instruments

Internal instrument lighting is normally from incandescent lamps integrated within individual instruments; lighting must be shielded from causing any.

A transistor circuit provides electronic control direct glare to the pilot and must be dimmable. A typical transistor controlled lighting system The relatively low base currents in the respective transistors can now control a variety of lighting circuits: radio navigation systems, compass, fuel panels. engine indications.

12.2.2 Master warning.

An increasing number of systems are being designed into aircraft; this leads to more warning lights and larger panels with an increased possibility of a warning light being missed by the crew.

Typical panels could have up to 50 individual warning lights, any one of which also illuminates the master warning light. The individual lights could be located on an overhead or side panel.

When the master warning or caution light is illuminated, the pilot cross-refers to a centralized group of warning lights on the relevant panel, each connected to the warning devices of specific systems.

Warning lights can be tested by a separate test switch, or by a centralized master dim and test switch. The night/day switch is used to reduce the intensity of warning lights during low ambient lighting condition.

12.2.3 Emerging technology

A digital processor on each warning and caution module replaces lighted switches with the associated wire bundles. LEDs can now provide sufficient brightness to replace incandescent lighting with 30% power reduction compared with fluorescent lighting.The objectives are to accomplish weight, cost and reliability goals.

12.3 PASSENGER CABIN LIGHTS

• Interior lighting installations for the passenger cabin vary depending on the size of aircraft.

• These lights are controlled from the flight attendants ’ station. LED illumination is being specified on business and passenger aircraft that have pre-programmed settings for specific flight phases and time zones.

12.3 PASSENGER CABIN LIGHTS

• Traditionally, each cabin light is controlled individually; this technology is being replaced by a central control unit connected to all the lights in the cabin.

• The systems are automatically controlled to customize the mixing of colors and lighting levels; this is intended to help passengers combat the fatigue of long-distance travel.

12.3 PASSENGER CABIN LIGHTS

• Additional entry floodlights are provided in the door areas. Exit lights are located adjacent to the emergency exits and are clearly visible, irrespective of whether the door is open or closed. Floor path lighting is used to in emergency situations to provide visual identification of escape routes along cabin aisle floor.

12.3 PASSENGER CABIN LIGHTS

• Interior lighting installations for the passenger cabin vary depending on the size of aircraft.

•These lights are controlled from the flight attendants ’ station.

•Systems are automatically controlled to customize the fixing colors and avoid passengers to be fatigued while traveling long distances.

• Cabin signs like “return to seat” or “no-smoking” are normally activated by the flight crew.

Floor path lighting

• It’s used for emergency situations to provide visual identification of escape routes along cabin aisle floor.

12.4 EXTERIOR LIGHTS

12.4.1 Logo lights

• These are used to illuminate the tail fin, and is primarily for promotional purposes.

• They also are used for additional awareness in busy airspace

TAXI LIGHTS.

• These are known also as run way turn off lights.

• They are sealed beam devices with 250W filament lamps and are located at the nose, landing gear or wing roots.

TAXI LIGHTS.

12.4.2 Landing lights

• These are located on the wing tips, or on the front of the fuselage, usually at fixed angles to illuminate the runway

12.4.3 Wing Illumination

• Ice inspection lights: These are installed to check ice formation on wing leading edge and engines.

12.4.4 Service Lights

• These lights are powered from the aircraft ground servicing bus.

12.4.5 Navigation Lights.

• The primarily external lights required for navigation purposes are the beacons and anti-collisions lights.

• It’s mandatory that these lights are on the plane for flying at night.

• These are located at the extremes of the aircraft and provide an indication of the aircraft’s direction and manoeuvers.

12.4.5.1 Navigation Lights.

• These are based on color regulations

• GREEN: starboard wing divergence of 110°

• RED: port wing divergence of 110°

• CLEAR (WHITE): tail, divergence of 70° on either side of the aircraft center line. 140° total.

12.4.5.2 Anti-collision lights.• Lights often supplement navigation lights, these can be

provided either by a strobe light, rotating beacon or a combination of both.

• Navigation lights used in conjunction with the navigation lights enhance situational awareness for pilots in nearby air-craft