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Www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 1M Loss of Control of Light Aircraft: Loss of Control of Light Aircraft:

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1 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 1M Loss of Control of Light Aircraft: 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

2 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 2

3 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 3G 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

4 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 4M Spot the difference…? Cessna 150L Cessna 152 0.71 fatals/ 100,000 hrs 0.04 fatals/ 100,000 hrs

5 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 10 events: C150/C152 stall/spin fatalities 5M

6 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Methods & Equipment Flight Test basics Go-Pro Cockpit mounted camera Appareo GAU1000A Flight Data Recorder Garmin 296 6M J31-Calibration

7 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Flight Test Programme Build-up 8 aircraft 17 test sorties + 3 checkouts + 1 decline 25hrs 35mins flight test 7M

8 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 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

9 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Stick Force to Change Airspeed Cessna 150L,M & 152 with Flaps a) UP b) DOWN (L30) 9M Flaps UP Flaps DOWN Desirable Pull Force to Stall (PFtS – 10 lbf/4.4475daN)

10 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 10M Radio Calls >> Increased Workload?? Climbing Flight: Cessna 150M

11 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 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

12 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 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 12M

13 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 13M Typical simulator test results: margin of safety & effect of stick forces

14 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Example: Pilot 24 Go-around, Full Pwr / Full Flap Key: Stick Force Gradients High Medium Low Pilot 24 (high hrs): ATPL 12,000+ hrs PIC Age 60~64 Avge 350+ hrs per yr Non-dimensionalised AoA.v. Elevator Pilot 23 (medium hrs): PPL (no IMC) 1200+ hrs PIC Age 65~69 Avge 33+ hrs per yr 14M Elevator Alpha

15 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 15 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

16 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 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 16G

17 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Any Questions? 17M/G Acknowledgements:-  Dr Mark Young  Thomas Gerald Gray Charitable Trust  GASCo, UK-CAA  Cranfield & Sheffield Universities

18 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 18 Fixed Wing <5,700kg (non-microlight) fatal accident causal factors: 1980 to 2006 (UK)

19 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 19 BFSL Safety Model Aircraft Environ. Pilot

20 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Cessna 152 CG Moves aft = Lower stick forces = More severe stall & spin 20

21 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design HQR - Climb & Point Track C152, F150M 21

22 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Sim. Experiment 3: Workload Results 22 ‘High’ Stick Force :- - Lower Mental Workload - Higher Physical Workload

23 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design Example: Pilot 24 Climb-out, Full Pwr / Zero Flap Key: Stick Force Gradients High Medium Low Pilot 24 (high hrs): ATPL 12,000+ hrs PIC Age 60~64 Avge 350+ hrs per yr Non-dimensionalised AoA.v. elevator Pilot 23 (medium hrs): PPL (no IMC) 1200+ hrs PIC Age 65~69 Avge 33+ hrs per yr 23

24 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 24 Example: Handling assessment in climb-out 1.3 V Stall 1.2 V Stall 1.1 V Stall Point Tracking (Maintain) Boundary Avoidance (Avoid) V Stall 1  3 (Sat.) Speed Time 4  6 (Unsat.) 7  9 (Unaccept.) 10+ Control lost Cooper-Harper for boundary avoidance – can be automated Workload ‘Top-down’ ‘Bottom-up’ @crossover switch from ‘top-down’ (point tracking) to ‘bottom-up’ (boundary avoidance)

25 www.brunel.ac.uk/about/acad/sed/sedres/cem/bfsl School of Engineering and Design 25M 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 longstab calcs)


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