1. Large Crowd Surveillance UAV
International Aircraft Design Team - Spring 2008

2. International Design Team
Aircraft Design projects since 1997
Virginia Tech and Loughborough University
International collaboration
Communication:
Video Conferences
Project Management Websites
MSN, Skype
Various Competition wins and awards from NASA General Aviation Design competitions.

3. Requirements
RELIABILITY “1 or fewer uncontrolled crashes per 100,000 hrs of operation”
Cruise Speed: 50 knots
MTOGW: 300 lb
Top Speed: 70 knots
Payload: 45 lb desired
Range: 15 nautical miles
Noise Levels: < 50 dBA at 200 ft
Endurance: 8 hours (minimum)
10 knot crosswind landing capability
Service Ceiling: 10,000 ft (half fuel)
Conventional landing within a 50 ft by 250 ft
Operational Altitude: ft
Minimum Turn Rate: 6 degrees/sec
Climb Rate: 200 ft/min (sea level)

4. Importance of Reliability
Airworthiness and Safety of Flight
Is it safe to fly overhead in large crowd situations ?
Is it expendable?
Is it capable of performing to specifications?
Acceptance
UAV restrictions due partly to unreliable systems
Key to winning confidence of FAA to regulate UAV flight
Lower long-term costs of UAVs
Increased availability of UAVs for missions

5. Definition of Reliability
Reliability according to the DoD
“The ability of a system to perform its mission without failure, degradation, or demand on the support system.”
Mean Time Between Failure (MTBF)
Period of time a repairable system/component will perform between failures
Mean Time To Failure (MTTF)
Same as MTBF, but for non-repairable systems
What is aircraft failure?
Failure to return to base

6. Current UAV Reliability
F-16 (Manned) Mishap Rate: 3.5 per 100,000 hours

7. Improving Reliability
Methods
Redundant Systems
Backup Systems
Scheduled Maintenance
Diversification
Implications
Cost
Weight
Increase in maintenance responsibilities
RQ-5/MQ-5 Hunter
MQ-9 Predator

8. Main Failure Modes 1 1

9. Summary of Key Reliability Issues
Engine/Propulsive Failure
Control/Communication Failure
Structural Failure
Human (Ground Crew) Error
Methodology Used
-Propulsion/Autopilot – Fault Tree Analysis
-Structure – Joint Probability Distribution Function (PDF)

10. Fault Tree Analysis

11. Structural Reliability