1 / 23

Be careful, you just might find what you are looking for

An F/A-18 AOC Interaction during asymmetric carriage of underwing stores. Be careful, you just might find what you are looking for. SQNLDR Darren Hughes Test Pilot ARDU FLTLT Dane Petersen Flight Test Engineer ARDU. Introduction. 2006 Hornet Upgrade program

orde
Download Presentation

Be careful, you just might find what you are looking for

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. An F/A-18 AOC Interaction during asymmetric carriage of underwing stores Be careful, you just might find what you are looking for • SQNLDR Darren Hughes • Test Pilot • ARDU • FLTLT Dane Petersen • Flight Test Engineer • ARDU

  2. Introduction • 2006 • Hornet Upgrade program • End to End assessment of GBU-16 • “excessive and objectionable lateral cockpit vibration” • 2010 • Investigate for a full clearance • It was probably just an “anomaly”

  3. The investigation • Hornet unique stores clearance considerations. • A conservative approach. • What we found! • Lessons learned.

  4. Limit cycle oscillation A 5.6 Hz oscillation that is bounded for a given dynamic pressure, and only present during carriage of High pitch inertia stores & wingtip missiles Asymmetric wing motion Pilot’s experience

  5. Helmet mounted camera • (±0.05/±0.06g) moderate level LCO from the pilot’s perspective

  6. A human factors issue! Increasing amplitude = degradation LCO ABORT is Throttles to IDLE

  7. Active Oscillation Control The ailerons move to dynamically suppress LCO AOC uses an upfront controller AOC mode selection > ±0.15 g can not reliably select the AOC mode!

  8. Task Objective • Investigate the ‘objectionable vibration’ to support an full envelope clearance for the GBU-16.

  9. A ‘one-off’ event? • The GBU-16 was cleared by other F-18 users: why would we be different? • Qualitative description was not compelling: turbulence seemed like a plausible explanation Almost heart of the envelope

  10. Risk Assessment • Cause unknown = proceed with caution & LCO safety case 1. Throttles IDLE Standard LCO abort actions: 2. AOC OFF

  11. Happy! A slow build-up in speed... Slow down for undesirable response

  12. Test Configuration

  13. Test Technique 0.73 M 0.93 M Slow accelerations: Level / +1.5g / +2.0g / +3.0g Stick rap Speed (hold/increase) Terminate (0.08g) Telemetry Test aircraft

  14. Results Standard Hornet = AOC OFF ON - this was another matter entirely!

  15. Aileron reduces immediately with AOC OFF selection 0.08g Reduces 0.5 sec after AOC OFF selection IDLE had no effect on recovery IDLE AOC OFF

  16. Outboard wing Both empty Both occupied

  17. What if Safety Chase was used? AOC selection may not have been possible! ±0.15 g an ineffective and inappropriate terminate limit

  18. A structural issue as well! Qualitative similar ‘feel’ to LCO, but almost unrelated! LCO - asymmetric movement AOC driven - symmetric movement Lateral acceleration should not have been the sole terminate limit!

  19. Conclusion Presence of ‘objectionable vibration’ confirmed 0.10 g/s rate of increase 2 seconds Asymmetric captive carriage of the GBU-16 was UNACCEPTABLEabove 0.75 M

  20. Lessons Learnt • ‘Be careful, you just might find what you’re looking for’. • Take time to critically reevaluate the plan when unexpected results are encountered. • Understand the System Under Test

  21. Where to from here? • Check 2000 lbs weapons • Disable the AOC?

  22. Questions?

More Related