A synopsis of the Helios Flight 522 aircraft accident and how it relates to the SHEL model

1. Helios Airways Flight 522
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2. Introduction
 International Civil Aviation Organisation
“SHEL” Model
- Quick explanation
 Helios Airways Flight 522
- Back ground
 Sequence of Events
 Relate the “Human Factors” to “SHEL”
 Summary
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3. I C A O “SHEL” Model
(International Civil Aviation Organisation)
Has any one heard of this
model before?
A conceptual model using 4 blocks
to represent interaction between
the different components of
“Human Factors”.
S - Software
H - Hardware
E - Environment
L - Livewire
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4. So what do each of these categories mean?
1. Software
 Interaction with technology, system rules
and SOP’s
2. Hardware
 Controls / Surfaces, Displays and functional
systems
3. Environment
 The “Climate”; Social / Economic, as well as
Natural v “Operating” Environments
4. Liveware
 Human interaction; Flight crew -> Cabin Crew ->
Engineers etc.
Note the “Less than perfect” Interface between categories
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5. Interface between categories:
Any ideas as to why the
“Ragged” interface between
categories?
Essentially it suggests that any
interaction involving human beings
is always less than “perfect”
- Hence the importance of;
“HUMAN FACTORS”
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6. So now to Helios 522
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7. Background
 14AUG05 crashed north of Marathon
& Varnavas, Greece.
 Wreckage located near Grammatiko
community 40 km from Athens
 All 121 on board were killed
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8. Sequence of Events
 Before take-off, crew failed to correctly set pressurisation system.
 Result, gradual decompression. All on board suffering Hypoxia.
 Captain’s conversation with engineer, confirmed he was suffering
hypoxia.
 When Greek air space entered, ATC not contacted. 2 Hellenic Air
Force F-16 fighters scrambled.
 F-16 pilots saw F/A Andreas Prodromou at controls, (trainee
pilot), attempting control of aircraft, (consciousness due to
portable oxygen).
 Aircraft crashed due to lack of fuel. Engines failed in quick
succession.
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9. Lets now look at how “SHEL” relates to:
 “Human Factors”
 Poor decision making
 Poor Communication
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10. “SHEL” / Human Factors relationship:
Liveware - Software (The interface between people and software)
 In this instance, none of significance
Liveware - Hardware (The interface between people and hardware)
 Pressurisation set to “Manual” instead of “Auto” - Importance of SOP’s!
 “Cabin altitude” horn misidentified as a take-off configuration warning
 An “Oxy ON” warning light misinterpreted as “systems” were overheating.
Liveware - Environment (The interface between people and the environment)
 Attempt at cogitative thought in a “Hypoxic” environment, (loss of cabin pressure)
 Re-enforces vital importance of recognition of symptoms and adherence to drills
Liveware - Liveware (the interface between people and other people)
 Cultural differences, East German Captain, Cypriot First Officer, “lack of common language”
 Engineer during discussion identified Hypoxia. Didn’t really “press point” to the Captain
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11. Summary
 International Civil Aviation Organisation “SHEL” Model
 Case Study: Helios Airways Flight 522
- Back ground / Sequence of Events
 Related the “Human Factors” of this accident to the “SHEL” model
“What gets us in trouble is not what we don’t know,
- It’s what we know for sure that just aint so !”
(Mark Twain)
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