investigation of factors affecting loss of control of ga

www.brunel.ac.uk/about/acad/sed/sedres/cem/bfs

School of Engineering and Design

InvestigationInvestigationof of

Factors AffectingFactors AffectingLoss of ControlLoss of Controlof GA Aircraftof GA Aircraft

Mike BromfieldMike Bromfield& Guy Gratton (M)& Guy Gratton (M)



Contents

• Background• Programme Objectives• Key Design Factors• Flight Test Programme• Initial Findings• Lessons Learned• Next Steps



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

25%

8%

16%12%

12%

6%

5%4%

4%3% 5%Loss of Control VFRLoss of Control IMCLow Flying/AerosCFITForced LandingMid-air CollisionCollision with Grnd ObjAirframe FailureLow ApproachMedical/SuicideUndetermined

Source: GASCo

??



• UK, US, Canada & Australia, 300+ GA fatal accidents annually– Likely 100-200 LoC related

• Usually LoC at low level– Take-off, landing, go-around, forced

landings– “Low, slow and dirty”

GA fatal accident causal factorscont’d…



Programme Objectives

•Why does LoC happen?

•Why certain types and not others?

•How can we improve operational safety?

•“LoC-proof” future GA designs.



1984-2006: selected statisticsUK Fatalities per 100,000hrs

0.70 0.68

0.050.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

ALL SEP Cessna 150 Cessna 152

Source:

Ferris R., Data Request 281107, UK CAA Nov. 2007. based on 3,395,056 flying hours



Spot the difference…?

Cessna 150L

Cessna 152



What’s the difference?Cessna 150L (‘74)Cessna 150 M (‘75)

Cessna 152 (‘80)

Powerplant 100 hp Continental 110 hp LycomingWeight (lbs) 1600 1670

CG Range (in) 31.5~37.5( 19.9~30.1 %MAC)

31~36.5(19.1~28.4 %MAC)

Flap Range (deg) 0~40, no detents 0~30, detents @ 0/10/20/30

Flap Activation/Monitoring 2-way switch,LH Door post Indicator

Gated 4 position switch, adj. indicator

CR Speeds@60% Pwr/2000’/Std T(KTAS)

89 91

VS0 (KCAS) Pwr Off/Aft CG/MTOW: L(30)

L(40)4241

41N/A

Source: FAA Type Certificate Data Sheet 3A19, FAA, Revision 43, July 25, 2002Thompson, William D., “The C150/C-152 Story” , Cessna Wings for the World 2nd Ed., 1992



Is it CG?- Typical CGs, 2POB + Wf to MTOW

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

30.00 31.00 32.00 33.00 34.00 35.00 36.00 37.00 38.00

CG LOCAT ION (INCHES AFT OF DAT UM)

C152Envelope

C150 Envelope

C152

C150L/M



Flight Test ProgrammePhase 1

A/c 2 A/c 3Baseline CG1 CG2 CG3 CG1 CG1

Mid Mid-Fwd Mid-Aft Mid Mid1 4 6 - -

53% 62%

2 - -52%

3 5 7 - -

57%F150M

A/c 1Phase 2*

F150L

C152



Methods & Equipment

• TPS basics– Handheld force/displacement/timing– Portable CVR

• Headset mounted video for debrief

• Appareo FDR+Garmin 296 GPS supplement / positional

awareness



Methods & EquipmentAppareo GAU 1000A FDR•16 Channels@ 4Hz•WAAS enabled GPS•3 x Gyroscopes•3 x Accelerometers•Barometric pressure sensor•Solid state compass•AS Flight Analysis software•US$ 2000

J31 Calibration Test Flt



Methods & EquipmentFlight Analysis software•2d/3d playback•Google earth integration•Instrument panel•Own or external GPS•Data export

Normal Take-off

260

280

300

320

340

360

380

400

14:4

3:53

.250

14:4

3:55

.750

14:4

3:58

.250

14:4

4:00

.750

14:4

4:03

.250

14:4

4:05

.750

14:4

4:08

.250

14:4

4:10

.750

14:4

4:13

.250

14:4

4:15

.750

14:4

4:18

.250

14:4

4:20

.750

14:4

4:23

.250

14:4

4:25

.750

14:4

4:28

.250

14:4

4:30

.750

14:4

4:33

.250

14:4

4:35

.750

14:4

4:38

.250

14:4

4:40

.750

14:4

4:43

.250

Time (s) >>>

Geo

pote

ntai

l Hei

ght (

ft) >

-40

-30

-20

-10

0

10

20

30

40

50

60

70

Geopotential Alt. (Feet)

Gnd Speed (Knots)

Pitch Angle (Degrees)

Derived AOA (Degrees)Rotate

Unstick50 ft

Start Take-off Roll

A/C= Cessna 152 G-BOFLDate: 12/02/09Gross Wt.= 1650 lbsCG = 34" AoD

Flight Evaluator Software

FDR Parameters•Time•Lat/Long•True Gnd Speed•Pitch/Roll/Yaw Attitude•Pitch/Roll/Yaw Rate•Geo-potential Altitude•Normal, Lat., Long. Accelerations & Velocities



BFSL safety model – the questions

Tracking point (optimal condition) Aircraft characteristics

Condition error Condition cues Actual condition Planned margin Safety margin Safety cues Boundary (Unsafe Condition)

Pilot capacity to respond

Pilot response

HQ assessment: Point tracking versus boundary avoidance



Cooper-Harper task selection- Climb out speed control

Vclimbout(67 KIAS)

1.2 VS(53 KIAS)

1.1 VS(49 KIAS)

RoC= 0 fpm

CH Point Tracking

Task(Maintain)

CH Boundary Tracking

Tasks(Avoid)

Vclimbout

VS(44 KIAS)

HQR1~3 HQR

4~6 HQR7~9



Apparent LSS

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

35 45 55 65 75 85 95 105 115 125

Speed KCAS >>>

Stic

k Fo

rce

Pull

(daN

) >Comparison of Apparent LSS (CR), 150M vs 152

C152F150MF150L



Apparent LSS

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

35 45 55 65 75 85 95 105 115 125

Speed KCAS >>>

Stic

k Fo

rce

Pull

(daN

) >Comparison of Apparent LSS (L30), 150M vs 152

C152F150MF150L



Apparent LSS

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

35 45 55 65 75 85 95 105 115 125

Speed KCAS >>>

Stic

k Fo

rce

Pull

(daN

) >Comparison of Apparent LSS

(CR), 150M vs 152/CG mid-aft

C152

F150MF150L

C152(mid-aft CG)



Initial findings• Apparent LSS

– Low speed LSS much steeper in C152 than C150 models– C150 / LAND / PLF MCP, near-neutral– Indications of CG dependency– Possible cliff-edge change?

• Flaps– Large out of trim forces on retraction– C150 Flap indicator widens scan– Readability issues

• Stall– Power on / flapped stall: C150 only attitude warnings, spin

risk

• Visible pitch attitude changes constantly close to GND



Mike’s lessons – academic FT

• Equipment portability• Limited budget – time is money• Use a ‘calibrated’ TP• Data reduction takes considerable time

– plan for this time between sorties– design test cards for data reduction

• Don’t rely on the technology• Reporting – brevity vs academic rigour• Be prepared for the unexpected!



Guy’s lessons – test conduct

• “Safe” GA aircraft can still bite, and without inanition– Brief for all emergencies

• Flying club environment– Sub-optimal aircraft– At-least 1 in 3 W&CG schedules contain errors

• Consider re-weighing– Weather press-on-itis

• Check everything• Know and stick to no-go criteria

– Keep talking



Next Steps…More aircraft

– Are we looking at the fleet?– Critical cases

Simulator work– Cycle pilots through critical cond.– Pilot workload measurement– Find the HQR 3-4, 6-7, 9-10

boundaries – Be willing to crash!

S. Camber



FDR + CVR: F150L PLF Stall



More Information:

[email protected]@brunel.ac.uk

Questions?



Acknowledgements

• Dr Mark Young• Thomas Gerald Gray Charitable Trust• General Aviation Safety Council (GASCo)• CAA(UK) & FAA(US)• USAF Academy / Bill Gray

investigation of factors affecting loss of control of ga

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