Design of UAV Systems
Lesson objective - to discuss
Reliability, Maintainability,
Supportability, and Safety
Expectations - You will understand the issues
(benefits and penalties) associated with UAV
supportability and safety.
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-1
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-2
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-3
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-4
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-5
Design of UAV Systems
Support Locations
Main Base
Forward Base
Emergency Base
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-6
Design of UAV Systems
Support Concept
Contractor
Organic
http://www.fas.org/man/dod-101/sys/ac/row/cl-327.htm
http://www.fas.org/irp/program/collect/predator.htm
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-7
Design of UAV Systems What Kinds of R&M Analyses Are
Expected in Pre-Conceptual Design?
Acquisition & Life Cycle Phases
Concept &
Technology Development
System Development &
Demonstration
IOC
Production &
Deployment
Operations &
Support
R&M Data Sources & Techniques
Parametric Estimates
• Weight
• Parts Count
• Surface Area
• Duty Cycle
• Sortie Length
OT&E
Supplier Predictions
Component Tests
• Part Stress
Integration
• Environ Mod & Sim
Tests
• Thermal Surveys
• FMEA/FMECA
• Durability Tests Flight Test
• PHM Mod & Sim
Tests
• Virtual Human M&S •• Growth
Qual Tests
• M Demos
• Surges
• Environmental Extremes
• Military Maintainers
Predictions
Field Data
• End Users & Maintainers
• Production Configuration
Assessments
R&M Predictions Fidelity Increase with Design Fidelity
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-8
Design of UAV Systems
Size
What Is It About UAVs
That Affects Supportability?
 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
CONOPS





Basing
 Self-Sufficiency
 Contractor Logistics Support Considerations
 Infrastructure
© 2002 LM Corporation
Storage vs. Flying
Deployment Timelines
Optempo
Crew Sizes
Weapons
Reliability, Maintainability, Supportability & Safety
12-9
Design of UAV Systems
Endurance
Ground
Segment
Cost /
Fleet Size
© 2002 LM Corporation
What Is It About UAVs
That Affects Supportability?





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
Reliability, Maintainability, Supportability & Safety
12-10
Design of UAV Systems
Air Vehicle Eliminates
Man-Rated Systems
Man-Rated Systems Are Eliminated
 Crew Station
 Instruments
 Cockpit Structure / Boarding Ladders
 Canopy
O&S Cost Reduction of 8%
 Ejection Seat / Escape Provisions
in Personnel Alone!
 Throttle/Control Stick/Rudder Pedal
 Control Panels
• No Egress Shop
 Crew Station Environmental Controls
• Eliminate Survival Skill
 Heating/Cooling
• Smaller, Less Costly ECS
 Pressurization
• No LOX Consumables
 Defog
• Less Support Equipment
 Oxygen System
 LOX or OBOGS
 Regulator
 Emergency/Survival Equipment
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-11
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-12
Design of UAV Systems
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?
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-13
Design of UAV Systems
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-14
Design of UAV Systems
Endurance Benefits
 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
This Study Assumed A Similar Level of Maintainability
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-15
Long Endurance Means
Fewer Sorties Per Flight Hour
Design of UAV Systems
• 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
14.00
MFTBM1
12.00
10.00
8.00
MFTBM1
MMH/FH
6.00
4.00
2.00
0.00
0
24
48
72
96
120
144
Average Sortie Length, Hrs
MFTBM1 - Mean Flight Time Between Maintenance (Inherent)
MMH/FH - Maintenance Manhours Per Flight Hour
This Study Assumed A Similar Level of Maintainability
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-16
Design of UAV Systems
Endurance Benefits
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-17
Design of UAV Systems
Ground Handling Options
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-18
Design of UAV Systems
Redundancy Considerations
 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)
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-19
Redundancy Cost Trades
Design of UAV Systems
Redundancy vs. Cost
Module Cost/Channel: $18,400
Average Repair Cost:
$6000
Average Sortie Duration: 4 .5 Hours
UAV Unit Cost:
$10 Million
Critical Failure Rate:
1/3 of MTBF
Cost per Flight Hour
1000000.00
100000.00
MTBF = 2000
10000.00
MTBF = 3000
1000.00
MTBF = 5000
MTBF = 8000
100.00
MTBF = 10000
10.00
1.00
1
2
3
4
Level of Redundancy
Trade Studies Will Determine Level of Redundancy
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-20
Design of UAV Systems
Training Concept
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-21
Design of UAV Systems
Next Subject
 Review of RM&S Functions
 UAV & UCAV RM&S Considerations
 Supportability Attributes
 Subsystem Considerations
 Manpower
 O&S Cost
 UAV Safety Lessons Learned
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-22
Design of UAV Systems
UAV and Drone Experience
Mishaps Per 100,000 Flight Hours
Fighter*
4.5
Manned QF-106 Drones*
Unmanned QF-106 Drones*
130
70
Pioneer UAV**
Hunter UAV**
Predator UAV**
167
140
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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-23
Design of UAV Systems
Attrition Cost Comparison
Lower Unit Cost Does
Not Necessarily Mean
Lower Life Cycle Cost!
… and there’s a reason!
Cost Per
Vehicle
Losses Per
100K Flt. Hrs.
$25-50M
5.0
General Aviation
$200K
7.0
Low Cost UAV
$1.0M
167
High Cost UAV
$3.0M
27
Typical Fighter
Global Hawk Goal is 10 per 100K Flight Hours
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-24
Design of UAV Systems
UAV Lessons Learned
 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
m of n
?
?
?
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-25
Design of UAV Systems
UAV Lessons Learned
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-26
Design of UAV Systems
UAV Lessons Learned
 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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-27
Design of UAV Systems












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
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-28
Empirical Analysis of
Reliability Trends
Design of UAV Systems
Historical
Trend
10.0
7-9
MFHBF (Inherent )
5.0
3.0
1.0
TREND: Reliability Doubles Every 15 Years
• Newer Technologies
• Improved Manufacturing Processes (Quality)
• Increased Emphasis on Design for RM&S
0.1
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year of Initial Production Delivery
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-29
Design of UAV Systems
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
© 2002 LM Corporation
Predator
Global Hawk
Reliability, Maintainability, Supportability & Safety
12-30
Design of UAV Systems
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 it
Submit your homework via Email to Egbert by COB
next Thursday. Document all calculations
© 2002 LM Corporation
Reliability, Maintainability, Supportability & Safety
12-31