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Loss of Control of Light Aircraft: Balancing Cost and Safety in Flight Test

Loss of Control of Light Aircraft: Balancing Cost and Safety in Flight Test. Mike Bromfield Guy Gratton. SETP/SFTE 4 th European Flight Test Safety Workshop London 28~29, September 2010. What’s the question?. GASCo 28 year review of GA fatal accidents 35-50% stall/spin

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Loss of Control of Light Aircraft: Balancing Cost and Safety in Flight Test

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  1. Loss of Control of Light Aircraft: Balancing Cost and Safety in Flight Test Mike Bromfield Guy Gratton SETP/SFTE 4th European Flight Test Safety Workshop London 28~29, September 2010

  2. What’s the question? GASCo 28 year review of GA fatal accidents 35-50% stall/spin Significant type variations Why type variations C150 rate >> C152 rate (~17:1) PA28 “Hershey Bar” wing ~population mean, tapered wing no fatalities Understand the reasons For flying training For design

  3. Spot the difference…? 0.71 fatals/ 100,000 hrs Cessna 150L Cessna 152 0.04 fatals/ 100,000 hrs

  4. 10 events: C150/C152 stall/spin fatalities 5M

  5. Methods & Equipment J31-Calibration Flight Test basics Go-Pro Cockpit mounted camera Appareo GAU1000A Flight Data Recorder Garmin 296

  6. Flight Test Programme Build-up • 8 aircraft • 17 test sorties + 3 checkouts + 1 decline • 25hrs 35mins flight test 7M

  7. Flight Test using Rental Aircraft • Aircraft Variables (ageing?) • maintenance, performance, W&CG • Organisation • Different priorities • Flight test .v. Flight School • Aft CG stalling at 3000ft anybody? • Local environment • Area & procedures, controlled airspace, ATC, Wx 8G

  8. Stick Force to Change AirspeedCessna 150L,M & 152 with Flaps a) UP b) DOWN (L30) Desirable Pull Force to Stall (PFtS – 10 lbf/4.4475daN) Flaps UP Desirable Pull Force to Stall (PFtS – 10 lbf/4.4475daN) Flaps DOWN

  9. Radio Calls >> Increased Workload?? Climbing Flight: Cessna 150M 10M

  10. Flight Test Results • Variability between aircraft, C150 consistently lower pitch forces • Mean gradient factors ~2-3 • C150 sometimes neutral (e.g. L40) • Stick force dependent on:- • (1) Flaps, (2) Power, (3) Trim, (4) Weight, (5) CG • Low stick force >> poor airspeed management • Stall warning • C150 non-compliant with (current) part 23 in certain configs. • Simultaneous stall warning + aerodynamic stall 11M

  11. Simulation Experiments- Scenario-based Testing Simulator • PC7 Fixed-base research simulator • Controllable force feedback • 150 x 40 deg. Visuals Scenarios • 20 pilots x 5 scenarios x 3 stick force gradients • Circuits, EFATO, Climb-out, Go-around, Base to Finals Turn Data /Analysis • Workload (Heart Rate, NASA TLX) • Flight dynamics + RT/intercom

  12. Typical simulator test results: margin of safety & effect of stick forces 13M

  13. Example: Pilot 24 Go-around, Full Pwr / Full Flap Non-dimensionalised AoA .v. Elevator • Pilot 24 (high hrs): • ATPL • 12,000+ hrs PIC • Age 60~64 • Avge 350+ hrs per yr Alpha • Key: • Stick Force Gradients • High • Medium • Low • Pilot 23 (medium hrs): • PPL (no IMC) • 1200+ hrs PIC • Age 65~69 • Avge 33+ hrs per yr Elevator 14M

  14. Conclusions • Type training - C150 and C152 are different • Design factors - Certification standards are too subjective, consider use of Human Factors tools • Aircraft design, loading & configuration influence airspeed management & stall avoidance via pilot cues • Low stick force gradients can result in:- • Poor airspeed management cues & stall avoidance cues • More mentally demanding tasks • Increasing workload • Decreasing safety margins ………which all makes loss of control due to distraction or pilot inattention more likely

  15. Lessons Learned Independence Manage FTI, check maintenance Always check W&CG reports Workup Essential but spread across sites and aircraft Use learning curve Efficiency Critical test points Concentrate flying periods But always review data between sorties Best practice Qualified pilot opinion Redundancy in data collection

  16. Any Questions? • Acknowledgements:- • Dr Mark Young • Thomas Gerald Gray Charitable Trust • GASCo, UK-CAA • Cranfield & Sheffield Universities 17M/G

  17. Fixed Wing <5,700kg (non-microlight) fatal accident causal factors:1980 to 2006 (UK)

  18. BFSL Safety Model Environ. Aircraft Pilot 19

  19. Cessna 152 CG Moves aft = Lower stick forces = More severe stall & spin

  20. HQR - Climb & Point Track C152, F150M

  21. Sim. Experiment 3:Workload Results • ‘High’ Stick Force :- • Lower Mental Workload • Higher Physical Workload 22

  22. Example: Pilot 24Climb-out, Full Pwr / Zero Flap Non-dimensionalised AoA .v. elevator • Pilot 24 (high hrs): • ATPL • 12,000+ hrs PIC • Age 60~64 • Avge 350+ hrs per yr • Key: • Stick Force Gradients • High • Medium • Low • Pilot 23 (medium hrs): • PPL (no IMC) • 1200+ hrs PIC • Age 65~69 • Avge 33+ hrs per yr 23

  23. Example: Handling assessment in climb-out Workload Speed Point Tracking (Maintain) 1.3 VStall 13 (Sat.) ‘Top-down’ 1.2 VStall 46 (Unsat.) 1.1 VStall @crossover switch from ‘top-down’ (point tracking) to ‘bottom-up’ (boundary avoidance) ‘Bottom-up’ 79 (Unaccept.) Boundary Avoidance (Avoid) VStall 10+ Control lost Time Cooper-Harper for boundary avoidance – can be automated 24

  24. Conclusions – Causes of LoC Stall Boundary crossing (not point tracking) Handling characteristics & workload Type training A C150 is not a C152 Design factors Certification standards are too subjective Consider Human Factors tools Further work needed Historical certification standards for stalling Apparent LSS results and models (FCMC in longstabcalcs) 25M

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