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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???
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