Transportation Safety Boardof Canada

Bureau de la sécurité des transportsdu Canada

Lessons Learned from TSB Investigations of Helicopter

Accidents (1994-2003)

Joel Morley and Brian MacDonald

International Helicopter Safety SymposiumMontreal, QC

September 26-29, 2005

Introduction

• Average of 53 Canadian registered helicopters involved in accidents each year (range of 44 to 68)

• 9.3 accidents per 100 000 flight hours

Accident Rate for Canadian Registered Helicopters (1994-2003)

10.8

11.8

9.8

10.3

9.3

7.6

8.8

7.6

9.7

7.5

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Year

Acc

iden

ts /

100

000

ho

urs

Accident Rate by Aircraft Category (1994-2003)

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Year

Acc

iden

ts p

er 1

00 0

00 h

ou

rs

Airliners

Commuter Aircraft

Air Taxi

Aerial Work

Corporate/Private/Other

State

Helicopters

Method

• Employed sample of occurrences investigated by TSB (N=103)

• Comparison sample of military occurrences investigated (N=37)

• Categorized by a team of TSB investigators (4 step process)

Step 1: Initial Occurrence Categorization

• Power Loss• Structural Failure• Loss of Visual Reference• Struck Object• Loss of Control• Loss of Separation• Training for Emergencies• Other

Occurrences by Category

35%

17%15%

10%

8%

6%

4% 5%Loss of Power

Structual Failure

Loss of Visual Reference

Loss of Control

Struck Object

Training for Emergencies

Loss of Separation

Other

Step 2: Examination of Proportion of Fatal to Non-Fatal Accidents

• To see where greatest human cost was occurring

• Determined:– Number of accidents in each category which

were ‘fatal’ (1 or more fatality)– Number of lives lost in each category

Ratio of Accidents to Fatal Accidents by Category

37

19

15

108

46

4

86

12

4 5

1 02

05

10152025303540

Power L

oss

Struct

ural

Failur

e

Loss

of V

isual

Ref

eren

ce

Loss

of C

ontro

l

Struck

Obje

ct

Loss

of S

epar

atio

n

Traini

ng fo

r Em

erge

ncies

Oth

erNu

mb

er o

f O

ccu

rren

ces

Number of Accidents

Number of Fatal Accidents

Number of Lives Lost by Category

Pow er Loss, 17

Structural Failure, 12

Loss of Visual Reference, 31

Loss of Control, 8

Struck Object, 8

Loss of Separation, 1

Training for Emergencies, 0

Other, 4

Step 3: Further Break-down of Occurrence Categories

• Examined types of events contributing to occurrences

• Selected sub-categories which seemed to capture these factors

• Loss of separation’, ‘training for emergencies’ and ‘other’ not sub-categorized

Sub-Categories for Power Loss

44%

3%8%

24%

5%

16% component failure

contaminated fuel

FOD

improper maintenance

other

undetermined

3(a) Power Loss

3(b) Structural FailureSub-Categories for Structural Failure

56%33%

11%

component failure

improper maintenance

other

3(c) Loss of Visual ReferenceSub-Categories for Loss of Visual Reference

13%

33%54%

snow ball

lack of contrast

VFR into IMC

3(d) Loss of ControlSub-Categories for Loss of Control

10%

30%

10%

30%

10%

10%

dynamic roll-over

loss of tail rotoreffectiveness

flight controlobstruction

rotor decayed

vortex ring state

environmental

3(e) Struck ObjectSub-Categories for Struck Object

13%

25%

25%

37%

trees

wires

terrain

slung object caughtobstacle

Step 4: Conclusions from Analysis

What does this mean to me??

Conclusions – Loss of Visual Reference Accidents

• #3 in frequency, #1 in human cost

• 80% fatal with a total of 31 lives lost

• Civil helicopter flying largely VFR

• Possible counter-measures:– Awareness– Capability– Technology

Conclusions – Power Loss and Structural Failure Accidents (1)

• Together account for 52% of sample

• Improper maintenance 2nd most frequent sub-category in both

• Underscores importance of efforts to understand and mitigate the factors underlying maintenance error such as:– Improved maintenance procedures– Awareness training

Conclusions – Power Loss and Structural Failure Accidents (2)

• Power loss is most heavily populated category but produced the fewest fatal accidents– Training to handle power failures effective

• Multi-engine helicopters also represented in power loss accidents

Conclusions – Loss of Control Accidents

• Well recognized hazards– Loss of tail rotor effectiveness– Decayed rotor RPM– Dynamic roll-over– Vortex ring state– Environmental – Flight Control Obstruction

• Efforts to address these hazards need to be maintained

Conclusions – Struck Object Accidents

• All hazards represented well known

• Potential counter measures could include:– Raising awareness– Revising procedures– Training in risk management

Comparison of Civil to Military Accidents by Category

36

17 1510 8 6 4 5

13

25

9 6

16

28

0 3

05

10152025303540

Loss of Power

Structual Failure

Loss of Visual R

eference

Loss of Contro

l

Struck Object

Training for Emergencies

Loss of Separation

Other

Category

% o

f A

cc

ide

nts

Civil

Military

Conclusion

• Snapshot of accidents investigated

• Hope it will help drive safety management practices

We need to devote

resources to…

Questions???