international design team 2008 1 international aircraft design team - spring 2008 large crowd...
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INTERNATIONAL DESIGN TEAM 2008 1
International Aircraft Design Team - Spring 2008
Large Crowd Surveillance UAV
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• Aircraft Design projects since 1997• Virginia Tech and Loughborough University• International collaboration– Communication:
• Video Conferences• E-mail• Project Management Websites• MSN, Skype
– Various Competition wins and awards from NASA General Aviation Design competitions.
International Design Team
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Requirements
• Cruise Speed: 50 knots
• Top Speed: 70 knots
• Range: 15 nautical miles
• Endurance: 8 hours (minimum)
• Service Ceiling: 10,000 ft (half fuel)
• Operational Altitude: 2000 - 3000 ft
• Minimum Turn Rate: 6 degrees/sec
• Climb Rate: 200 ft/min (sea level)
• MTOGW: 300 lb
• Payload: 45 lb desired
• Noise Levels: < 50 dBA at 200 ft
• 10 knot crosswind landing capability
• Conventional landing within a
50 ft by 250 ft
RELIABILITY“1 or fewer uncontrolled crashes per 100,000 hrs of operation”
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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
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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
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Current UAV Reliability
F-16 (Manned) Mishap Rate: 3.5 per 100,000 hours
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Improving Reliability• Methods– Redundant Systems– Backup Systems– Scheduled Maintenance– Diversification
• Implications– Cost– Weight– Increase in maintenance
responsibilities
http://www.designation-systems.net/dusrm/m-155.html
RQ-5/MQ-5 Hunter
http://www.airforce-technology.com/projects/predator/predator6.html
MQ-9 Predator
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Main Failure Modes
1
1
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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)
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Fault Tree Analysis
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Structural Reliability