Summary REF:
http://members.nbci.com/iasa1/
The Swissair MD11 accident has opened a lot of eyes about many different aspects of
coping with fire in the cockpit. Of course the investigation is as yet incomplete but
sufficient is known for us to make the following reasonable assumptions:
- The pilots were not sufficiently alarmed at the outset for them to try and rush to a
landing. In part this is because of a suspension of belief ("This cant be
happening to me"). True fear (and its urgent motivation) is lacking initially because
large electrical fires always start off as smaller, seemingly innocuous ones. They get to
be bigger catastrophic life-threatening fires because, under the current checklist
philosophies (and switchology), the power never comes off the wires. This lack of alarm
can also be attributed to a "society of success" attitude that prevails in
simulator training. That optimistic doctrine of positivism would have it that, as long as
a crew reacts as per "the book" with the correct CRM approach, all will come
right in the end. Unfortunately real life is not like that. The current protractedly
optimistic trouble-shooting smoke checklist allows an electrical fire to develop (in real
life) simply because the power doesnt come off the wires. In the simulator its
not realistically portrayed as such a potentially cataclysmic circumstance so pilots are
duped into a mindset that has the smoke-in-the-cockpit drill aligned with the
straightforward exercises such as an engine fire or turbine failure. In a
"kaptonized" aircraft the attitudinally correct approach should be that
"all may well be lost if the power doesnt come off the wires - pronto".
The Canadian TSB has confirmed (on 11 Jan 99) that arcing was found on cockpit Kapton
wiring.
- The MD11 (and probably other airliners) sets the "airconditioning smoke"
checklist first (possibly because its not going to take power off the busses and
disrupt meal service). The fact remains that this is a lengthy checklist and the
electrical fire is still being permitted to develop unchecked. The aircon checklist asks
four times: "has the smoke begun to reduce" and the pilots must wait to consult
the cabin attendants about this. At the end of this checklist the conclusion is that the
smoke is not of aircon origin and says that the "Smoke & Fumes of Unknown
Origin" checklist should be started. Obviously these two checklists are in the wrong
order because aircon smoke (from oil-contaminated bleed air) is just not going to kill (or
incapacitate) you but interim developing electrical system fires will.
- The MD11 Smoke/Elec/Air Switch has four positions that de-select (and then re-select) a
third of the aircon and gens and busses at a time. The checklist calls for a pregnant
pause between selections in order to check whether the benign configuration has been yet
reached. There is no mention of what to do if a benign configuration is never
found. During this checklist control must pass between the pilots as one the or other will
lose their flight instruments. The radios will also lose power and the pilots must
remember (but probably wont) to switch their current comms frequency to each
successive "live set". The DFDR and CVR are also powered down at certain stages.
It may be the case that the battery (and GEN reset ability) is insufficiently protected
from a dead short under the MD11s electrical system. An induced fault in one or both
of the epicentric bus-tie sensing relay switches can leave the backup instrumentation
vulnerable to the original electrical fault. At some stage during the checklist the #2
tail-engine is liable to flame-out because of power coming off its pumps (and being too
high-set to gravity feed). This would tend to (audibly and visually) Xmas-tree the cockpit
and distract the pilots (as well as robbing the system of one of two Generators on line).
An electrical system short may then be sufficient to trip the remaining generator and
leave the battery liable to overload (and/or Batt CB trip).
- In night or IMC conditions the critical backup attitude indicator is mounted centrally
(low and forward) on the centre console not really an ideal positioning for either
pilots scan.
- Emergency flood-lighting is still aircraft battery-powered and vulnerable to a total
electrics failure. A fore-head-mounted (atop full-face smoke-mask) focussable light with
an integral battery would be preferred to cockpit flood lights that tend to reflect off
flight-deck screens and windows.
- A third man (the old Flight-Engineer) with good systems knowledge and a role in the
checklist would have been invaluable. In a two-man crew there is evident overloading (see
Annex U). You need a third man to be able to send a technical flightcrew-member down the
back on a portable oxy set.(to check and report or fight fire). The MD11 checklist
prohibits a crew-member from leaving his seat (and oxy set).see annex L and M
landings3.html
- Halon or BCF hand-held fire-extinguishers probably wouldnt make a lot of
difference if an elec fire was still powered. But the question must still be asked:
"who (anyway) has the time to use it in a two man-crew that is locked to their seats
by the umbilical of their oxy systems?". A flight-deck nitrogen inerting system may
well be worthwhile considering (see Annex M).
- The very unwise plumbing of the Swissair Inflight Entertainment System (IFE) into one of
the cockpit busses (AC2), vice an ancillary cabin bus, was obviously done because the high
current-drawing IFE would otherwise have necessitated a complete revamp of the electrical
distribution system (i.e. creation of a Cabin 2 bus). If that had been the case, the
Smk&Fumes Cklist would then have killed any IFE-stoked fire at step one (Cabin P/B
OFF).
- The FAAs obligation (under the FAR) to resolve the dense continuous smoke in the
cockpit problem continues to be studiously ignored. The EVAS equipment is one way to go
(Annex E and http://www.raytheon.com/rac/rapid/evas.htm ). The helmet-mounted display
(incorporating a full-face smoke-mask) proposal at Annex T is another. Kapton incidents
have happened since SR111, luckily with no loss of life
.but it is only a matter of
time (annexes V and F).
- Annexes S & M contain SR111 technical commentary and proposed solutions. In
particular it is recommended that current Smoke & Fumes checklists be examined closely
in light of what is known about Kapton wiring induced electrical system failures and
fires. Maintaining power on busses whilst trouble-shooting is simply not a wise move. In
fact it is foolishly unsafe to do so. It may not be possible to eliminate Kapton from
modern airliners for many years, yet there may be a cheap and practical way to bypass the
catastrophic effects of a large-scale flash-over in a (continuously powered) failed Kapton
wiring bundle. Annex S and the following Internet site
virgin.html discusses the advantages of a
proposed modification that has been termed "the Virgin Bus". It is designedly a
TKT wired add-on that would give crews a readily selectable fallback position; a
stand-alone "get-you-home" flight essential bus with minimal features that would
avoid the undeniable gamble of the present trouble-shooting checklist. Its main feature is
that "everybody lives" and this should become a fine selling point for a public
that may soon be looking in askance at an airline industry that has suffered its next
SR111. The following Internet sites are also dedicated to constructive debate on aircraft
wiring and SR111 in particular: http://members.aol.com/papcecst
indexer.html
http://www.aviationtoday.com/reports/wiring.htm
Conclusion
Neither KLMs safety reputation nor its superior maintenance can protect it
against the depredations of flawed wiring insulation. A slavish adherence to the long-held
doctrine that FAAs Bulletins and Directives are sacrosanct would not be wise for
KLM. The US FAA and the manufacturer are set on a path that has been decreed by their
vested interests. These interests are demonstrably contrary to the safety of the
travelling public. As long as no US airline is involved in a fatal Kapton accident the FAA
policy of denial will run its course. As you can see from Annex E, foreign airline
accidents are of no consequence in determining FAA agendas. Military attitudes (in banning
Kapton) are also claimed to be irrelevant. The lessons of the post-Valujet shake-out of
the FAA hierarchy have been set aside and FAA loyalties have been hopelessly compromised.
KLMs best interests must be determined by itself in light of both what KLM now
knows and the publics forthcoming knowledge of that. Inaction is not an option. |