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Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-1
Lesson objective - to discuss
Reliability, Maintainability, Supportability, and Safety
Expectations - You will understand the issues (benefits and penalties) associated with UAV supportability and safety.
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-2
Why Consider Supportability?
• Operations & Support and Safety are Key Cost Drivers for the Overall UAV System- Operations & Support (O&S) Represent the Largest Percentage
of the Life Cycle Cost (LCC)- Reliability & Maintainability Attributes of the Air Vehicle Drive
Support Manpower- Affordability Issues Due to High Attrition Rates Constrain UAV
Market Penetration (Military and Civilian)
• O&S and Safety Issues Need to be Seriously Addressed During Pre-Concept Design - It is Not Something That Can be Delayed- You Get What You Pay For
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-3
Definitions
Reliability The probability that an item can perform its intended function for a
specified interval under stated conditions. Mean Time Between Failures (MTBF) (ususally in terms of flight hours) Failure Rate (failures per unit time) Probability (expressed as a decimal or percentage)
Tasks and Responsibilities During Pre-Conceptual Design* Allocations Predictions Functional Failure Modes & Effects Analysis Design Reviews Trade Studies
* For purposes of this course, a discussion of the reliability issues and your proposed approach will suffice
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-4
Definitions
Maintainability The measure of the ability of an item to be retained or restored to a
specified condition when maintenance is performed by personnel having specified skill levels, using prescribed procedures and resources, at each prescribed level of maintenance and repair. Mean Time to Repair – average of repair times Maintenance Manhours Per Flight Hour Crew Size – Average number of individuals required to accomplish the
maintenance action
Tasks and Responsibilities During Pre-Conceptual Design* Allocations Predictions Time Line Analyses (Combat Turns, etc.) Design Reviews Trade Studies
* For purposes of this course, a discussion of maintainability issues and your proposed approach will suffice
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-5
Definitions
Supportability The degree to which system design characteristics and planned
logistics resources, including manpower, meet system requirements. Direct Maintenance Manpower per Aircraft Logistics Footprint (# transport aircraft sorties to deploy squadron’s
support equipment, manpower and spares) Mission Capable Rate Not Mission Capable Supply (NMCS) Rate
Tasks and Responsibilities During Pre-Conceptual Design* Define Support (Maintenance & Supply) Concept Estimate Manpower; Sortie Generation Rates Define Deployment Concept & Predict Logistics Footprint Trade Studies
* Requirements for this course underlined
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-6
Support Locations
Main Base
Forward Base
Emergency Base
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-7
Support Concept
http://www.fas.org/man/dod-101/sys/ac/row/cl-327.htm
Contractor
Organic
http://www.fas.org/irp/program/collect/predator.htm
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-8
What Kinds of R&M Analyses AreExpected in Pre-Conceptual Design?
Parametric EstimatesParametric Estimates
Concept &Concept & Technology DevelopmentTechnology Development
System Development & System Development & DemonstrationDemonstration Operations & Operations &
SupportSupport
Production & Production & DeploymentDeployment
IOCOT&E
Supplier PredictionsSupplier Predictions
Component TestsComponent Tests
IntegrationIntegrationTestsTests
Flight TestFlight Test
R&M Predictions Fidelity Increase with Design FidelityR&M Predictions Fidelity Increase with Design Fidelity
• M Demos• Surges• Environmental Extremes• Military Maintainers
Field DataField Data
AssessmentsAssessmentsPredictionsPredictions
• Weight• Parts Count• Surface Area• Duty Cycle• Sortie Length • Part Stress
• Environ Mod & Sim• Thermal Surveys• FMEA/FMECA• PHM Mod & Sim• Virtual Human M&S
• Durability Tests• Growth Tests• Qual Tests
• End Users & Maintainers• Production Configuration
Acquisition & Life Cycle Phases
R&M Data Sources & Techniques
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-9
What Is It About UAVsThat Affects Supportability?
Size
CONOPS
Basing
Micro, Mini, or Larger? Proximity to Ground
Interface with Loading Equipment Access to Daily Servicing Points Engine Removal
Transportation / Deployment Considerations Hangar Space Refueling Times / Turnaround Times
Storage vs. Flying Deployment Timelines Optempo Crew Sizes Weapons
Self-Sufficiency Contractor Logistics Support Considerations Infrastructure
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-10
What Is It About UAVsThat Affects Supportability?
Endurance
GroundSegment
Airframe Life Inspection Criteria Consumables Redunancy / Mission Reliability Autonomous Refueling vs. Sizing for Range
Deployment of Ground Stations LOS vs. BLOS Comms Mission Planning for Satellite Coverage Coordination with ATC Coordination with Ground Crews
Design for Testability How Much Redundancy Can You Afford? How Much Safety Analysis Can You Afford? Approach to Support
Cost /Fleet Size
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-11
Air Vehicle Eliminates Man-Rated Systems
O&S Cost Reduction of 8% in Personnel Alone!
• No Egress Shop• Eliminate Survival Skill• Smaller, Less Costly ECS• No LOX Consumables• Less Support Equipment
Man-Rated Systems Are Eliminated Crew Station Instruments Cockpit Structure / Boarding Ladders Canopy Ejection Seat / Escape Provisions Throttle/Control Stick/Rudder Pedal Control Panels
Crew Station Environmental Controls Heating/Cooling Pressurization Defog
Oxygen System LOX or OBOGS Regulator
Emergency/Survival Equipment
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-12
Crew Station Benefits
Equipment Moved Into Ground Control Station Flight Instruments / Information Displays Data Recording
Reduced Environmental Qualification Testing No High “g” Testing Required Reduced Vibration Requirement (Maybe) No High Altitude Testing
Increased Reliability Some Equipment 2-5 Times More Reliable Less Manpower Required for Maintenance Cheaper to Implement Redundancy
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-13
Weapons Loading / Engine Removal
Proximity to Ground For Most UCAVs Complicates Weapons Loading Innovative Loading Schemes Can Mitigate Restricted Access
Consider Hoists; Alternate Lifting Devices X-45 Demo Uses Weapons Dolly and Ejectors Mounted on Weapon Robotic Loading May Help
Considered By Navy for Ships Engine Removal Also Challenging
Drop Down or Lift Out? Existing SE Sufficient?
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-14
Deployment and Transportation
Storable UAVs Can Be Airlifted in Individual Storage Containers USAF UCAV Concept is to Deploy via C-17 (See Demo Below)
Autonomous Aerial Refueling and/or Rearming May Allow Self-Ferry
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-15
This Study Assumed A Similar Level of Maintainability
Pilot Physical Limitations Limit Effective Sortie Length Endurance UAV Sortie Durations May Approach 48-60 Hours! Ground Operators Can Work in Shifts UAVs Have Potential to Remain Aloft Indefinitely
Requires Autonomous Refueling Technology 4 to 5 UCAVs Can Displace 24 Manned Fighters in 24-Hour CAP
Longer Sorties Mean Less Wear and Tear Cycle-Related Fatigue and Duty Cycles Reduced
80% of Fighter Failures are Constant on a Per-Sortie Basis Maintenance Manhours Per Flight Hour Reduction
Knee in Curve at Approximately 24 Hour Sortie Length
Endurance Benefits
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-16
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
0 24 48 72 96 120 144
Average Sortie Length, Hrs
MF
TB
M1
MFTBM1
MMH/FH
This Study Assumed A Similar Level of Maintainability
MFTBM1 - Mean Flight Time Between Maintenance (Inherent)MMH/FH - Maintenance Manhours Per Flight Hour
Long Endurance MeansFewer Sorties Per Flight Hour
• Assumes 80% of Failures are Constant on a Per Sortie Basis
• Manpower Eventually Reduces to a Constant to Retain a Minimum Number of Personnel of Each Specialty for All Shifts
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-17
Pilot Physical Limitations Limit Effective Sortie Length Endurance UAV Sortie Durations May Approach 48-60 Hours! Ground Operators Can Work in Shifts UAVs Have Potential to Remain Aloft Indefinitely
Requires Autonomous Refueling Technology
Longer Sorties Mean Less Wear and Tear Cycle-Related Fatigue and Duty Cycles Reduced
80% of Fighter Failures are Constant on a Per-Sortie Basis Maintenance Manhours Per Flight Hour Reduction
Knee in Curve at Approximately 24 Hour Sortie Length
Endurance Benefits
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-18
Preprogrammed Routes Using dGPS Accurate, Hands-Off Requires Site Survey, Detailed Mission Planning Likely Requires Deconflicted Ops with Other Aircraft
Remote Control By Ground Crew Good Ground Situational Awareness Adds Complexity to Air Vehicle Design
Remote Control By Ground Operator Good Ground Situational Awareness Minimal Impact on Manpower Hardware Intensive
Needs On-Board Camera
Ground Handling Options
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-19
Redundancy Exists for 3 Reasons: Safety Survivability Mission Reliability
Consider Life Cycle Cost Sensitivities Maintenance Savings vs. Increased Loss of Aircraft Consider Mission Reliability Requirements
For Flight Critical Systems (failure = crash): Generally required to fail operational/fail safe (at a minimum) Triplex Redundancy is Most Cost-Effective on $/Flight Hour Basis Extremely High Reliability (>10,000 hrs MTBF) or Extremely Low Cost
(<$1000/Channel) Are Required for Dual Redundancy to Be Cost Effective
For Mission Critical Systems (mission fails or degraded) Generally required to fail operational (albeit degraded) Typically back-up most mission critical systems (radios, GPS, etc)
Redundancy Considerations
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-20
Trade Studies Will Determine Level of Redundancy
Module Cost/Channel: $18,400Average Repair Cost: $6000 Average Sortie Duration: 4 .5 HoursUAV Unit Cost: $10 MillionCritical Failure Rate: 1/3 of MTBF
Redundancy Cost Trades
Redundancy vs. Cost
1.00
10.00
100.00
1000.00
10000.00
100000.00
1000000.00
1 2 3 4
Level of Redundancy
Co
st p
er F
ligh
t H
ou
r
MTBF = 2000
MTBF = 3000
MTBF = 5000
MTBF = 8000
MTBF = 10000
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-21
Manned Aircraft Pilots Maintain Proficiency By Flying Require Minimum of 30 Flight Hours/Month Most Flight Hours In Lifetime are for Training
UAV/UCAV Operator Interface Is Unique Actual vs. Simulated Flight Similar Keep UCAV In Storage Until War
Reduced Spares/Consumables Reduced O&S Costs Note – this ConOps is changing
as we speak
Training Concept
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-22
Next Subject
Review of RM&S Functions
UAV & UCAV RM&S Considerations Supportability Attributes Subsystem Considerations Manpower O&S Cost
UAV Safety Lessons Learned
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-23
UAV and Drone Experience
Mishaps Per 100,000 Flight Hours
Fighter* 4.5
Manned QF-106 Drones* 130Unmanned QF-106 Drones* 70
Pioneer UAV** 167Hunter UAV** 140Predator UAV** 27
*Class A Cumulative Mishap Rate, 1997**Loss Rate (non-combat)
Primary Cause of Drone Mishaps is Old Age and Structural Integrity Primary Causes of UAV Mishaps:
Non-Aviation Qualified Parts (Pioneer & Hunter) Inadequate Emergency Procedures Training / Lack of Concurrency Lack of Redundancy in Flight Critical Systems Inadequate Testing & Configuration Control
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-24
Attrition Cost vs. Flight Hours
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
50 100 150 200 250 300 350 400 450 500
Flight Hours, 1000s
Typical Manned FighterGeneral AviationLow Cost UAVHigh Cost UAV
Attrition Cost Comparison
Losses Per100K Flt. Hrs.
5.0
7.0
167
27
Cost PerVehicle
$25-50M
$200K
$1.0M
$3.0M
Typical Fighter
General Aviation
Low Cost UAV
High Cost UAV
Global Hawk Goal is 10 per 100K Flight Hours
Lower Unit Cost Does Not Necessarily Mean Lower Life Cycle Cost!
… and there’s a reason!
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-25
Carefully Weigh Risk When Considering Redundancy Establish Acceptable Mission Reliability Goals Trade Cost of Redundancy vs. Reduced Attrition Affordability is Usually Achieved at Higher Risk Recognize UAV/UCAV Mishap Rates Will Probably
Exceed Manned Tactical Aircraft Mishap Rates As a Minimum, Consider Redundancy for:
Data Links Flight Controls Propulsion System Controls
Utilize Mil-Spec or Commercial Aviation-Grade Parts Already Qualified for Operating Environment (Temperature, Altitude,
Vibration, EMI, etc.) Better Reliability May Obviate Need for Expensive Qualification Testing Expensive for a Reason
m of n
?
?
?
UAV Lessons Learned
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-26
Use Qualified Test Pilot During Testing Understands Aerodynamics & Engineering First Responsibility is to Save Aircraft Trained to React to Unexpected Events
Place Increased Emphasis on Operator-Vehicle Interface Provide Adequate Fault Annunciation to Operator
Must Be Immediately Recognized Should Indicate Appropriate Operator Response
Consider Operator Workload In Emergency Conditions Consider Operator Skill Level (Pilot, Novice, etc.) Segregate Houskeeping & Maintenance Functions from Flight Ops
Functions Train Emergency Procedures! (Especially for Flight Test)
Adequately Test Hardware Prior to First Flight End-to-End Comms Loop (Including AV Antenna Multipath) Hardware-In-the-Loop Testing is Critical
UAV Lessons Learned
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-27
Software Configuration Control Hazard Analysis Should Include Software Hazards A Software Change is a Configuration Change! Utilize Software-In-The-Loop Testing Automate Repetitive Functions to Alleviate Operator Fatigue and
Improve Safety Plan Adequate Schedule for Software Test
UAV Lessons Learned
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-28
How to Achieve Reliability
Simplification – Fewer parts means less things to fail Standardization – Quality and tolerances all match Stress/Strength Derating – Particularly for avionics Function Isolation – Improved mission reliability Packaging Design – Hermeticity, vibration isolation, etc. Redundancy – Judicious use! Producibility and Tolerance Evaluation – Quality issue Local Environment Evaluation – Avoid “hot” spots Sensitivities – Trade studies Drift and Degradation – Design for it or test for it Development – Test, test, test Reliability Design Checklists – Lessons learned
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-29
Empirical Analysis of Reliability Trends
0.1
1.0
10.0
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Year of Initial Production Delivery
MF
HB
F (
Inh
ere
nt
)
5.0
EW = 30Klb3.0
7-9
HistoricalTrend
TREND: Reliability Doubles Every 15 YearsTREND: Reliability Doubles Every 15 Years• Newer TechnologiesNewer Technologies• Improved Manufacturing Processes (Quality)Improved Manufacturing Processes (Quality)• Increased Emphasis on Design for RM&SIncreased Emphasis on Design for RM&S
EW = 20Klb
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-30
UAV maintenance personnel
Parametric Data Shows Manpower Requirements are a Function of Aircraft Speed, Weight (EW + Wpay) and Type
• UAV Comparison- Global Hawk fits
overall manpower parametric
- Predator falls well outside other aircraft norms
• Use this parametric to estimate maintenance manpower required for your design projects
Maintenance personnel parametric
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0 250 500 750 1000 1250 1500
Maximum speed (kts)
FightersTransportsBombersEWRecceUAV
Predator
Global Hawk
Design of UAV Systems
Reliability, Maintainability, Supportability & Safety © 2002 LM Corporation 12-31
Homework
Assess RMSS for your project (1) What redundancy levels do you think are
appropriate the following subsystems - Flight control computer- Air vehicle up link- Payload down link
(2) From the internet, Janes or other sources pick a UAV that you think is closest to your project UAV- What are the maximum speed and empty and
payload weights?(3) Estimate the number of personnel required to
maintain itSubmit your homework via Email to Egbert by COB
next Thursday. Document all calculations