Crash experts simulate the spreading of smoke in the MD-11
 (This article was written in '00)

By  PHILIPPE PFISTER -LONG BEACH -  Associated Press Writer

 

Following a test flight: Hot trail in the SR 111 case

Last Thursday there was once more smoke on board of a Swissair MD-11 - but this time it was allowed by experts to billow out on purpose: During of a test flight lasting around six hours, with activated on-board television cameras, the Canadian SR-111 investigators in California took comprehensive measurements of air flow.  They wanted to find out in this way how the fire had spread  aboard  flight SR111.  Apparently the investigators are following a hot trail.

Burnt and shattered aircon ducting

 

 "Yes, we flew an MD-11 to Long Beach, California on January 24," confirms Swissair spokesman Urs Peter Naef.  Before that the SR technicians had to configure the plane especially.  The Canadian investigative authority TSB wanted to get a plane that would be practically identical with the "Vaud" that had crashed on September 2, 1998.  In particular, the controversial on-board entertainment system IFEN had to be installed here too.  Since the US Federal Aeronautics Board (FAA) had prohibited the IFEN, an exceptional authorization was given for the test flight.  The experts apparently believe that they know where the fire started. 

 

After landing in long Beach, the Swissair pilots had to take their leave; on the test flight, only experts of TSB and Boeing were present.  The Canadian team, under the direction of SR-111 Investigation Head Vic Gerden, also installed video cameras, in

Barbara and Mark Fetherolf lost daughter Tara, and like many others, remain convinced that the IFEN played a part.

addition to various measuring instruments, in the cockpit and in the forward area of the cabin.  On Thursday the MD-11 took off for its roughly six-hour test flight.  High above the clouds the crash experts simulated the spreading of smoke.  "For this we used artificial smoke, such as is used in theaters for example," said TSB spokesman Jim Harris. 

 

Why such an expensive test with artificial smoke and video cameras?  "We were thus able to make the air flow in the forward part of the plane visible," explained Harris.  The TSB experts wanted to find out how the devastating fire had spread on board of flight SR111 because they apparently have a theory on what the source of the fire had been.  The measurements of airflow could further support this theory.  During the flight the IFEN system was connected to the main power supply and the display screens were switched on.  At the same time, different temperature measurements were also made.

 

 The specialists allow hundreds of cables to be scorched through

A cable fire, started by the IFEN, is still assumed to be one of the possible causes of the SR 111 crash.  Swissair deactivated the IFEN in all of its planes a few weeks after the crash.  For safety reasons, as was claimed at the time.  In the meantime it became clear that the on-board TV system which consumed a huge amount of electrical energy would

Burn patterns may disclose the part that arc-holed oxygen lines played

 never again be used: In the meantime it was removed from one half of all planes.  The manufacturer of the entertainment system, Interactive Flight Technologies has long gone out of business and calls itself now Global Technologies.  According to its own statements it has now gone into the Mexican casino business, among other things. 

 

In the meantime, tests with airplane cables continue in Canadian laboratories.  TSB specialists allow hundreds of cables to scorch through on purpose - sometimes in clean air, sometimes in soot and smoke filled air.  The crumbled insulation material is then subjected to chemical analyses.  What the experts want to know above all is this: Is it possible, based on chemical analysis, to isolate those cables that have burned through in clean air?  If this is possible, the method can also be applied to the scorched cable sections of the crashed MD-11 - it would thus be possible to prove the origin of the catastrophic fire with a high degree of probability.  "The question," says TSB spokesman Harris, "is to know which cables burned through first and which were first damaged by the fire".  The investigative authority is silent on the results.  "We are moving into a new field of science", says Harris.  "The tests are very costly and take much time".

 

 IFEN costs Swissair 46 million

The certification and installation of the on-board entertainment system IFEN in the MD-11 airplanes of Swissair followed a strange course.  Although it is a branch of Interactive Flight Technologies (IFT), an unknown company in the field, it was certified and installed in the record time of six months.  IFT promised to install the system free of charge in the Swissair planes.  Refinancing was expected to come through the proceeds from video films and games of chance.  However the passengers underutilized the entertainment system - IFT encountered financial difficulties and the delivery of the remaining installations was endangered.  Because Swissair had previously played up IFEN as the attraction that would bring in passengers, it had to pick up the pieces.  The entire on-board entertainment system was purchased for 46 million. 

 

 

A few IASA  thoughts on the possible additional aims of theTSB's MD-11 air-testing.


We always knew that the TSB were going to be carrying out airborne air-flow testing .. but I'd thought that it was done a bit later than this.  I had always assumed that this quest was related to the fan-shaped burn patterns found in the crown area. (and which I can only conclude were caused by the arcing creating a pinhole leak in a stainless steel (or aluminium) HP oxygen line - and that then blow-torching very destructively THROUGH the cabin linings and ultimately alarming the pilots. However there was no way that they were ever going to try and re-create that airborne.

I'm guessing here also that:
A.  This MD-11 flight trial was done at about the time that Tom Melody (shortly thereafter) produced his Long Beach Bulletin on the difficulty of MD-11 fire-fighting (and the unsuitability of the MD-11 smoke checklist). Links here and here.

B.  That the chap who wrote this placed a very liberal interpretation upon why the aircraft was asked to be fitted with an operating IFEN. His assumption was that the TSB and Boeing/McDD would be looking at just the IFEN because it was suspected to have been THE cause.... and because it had been disconnected so promptly.

C.  They may have been just as interested in whether the fire and smoke could spread undetected beneath the cabin and flight-deck linings. I'd say that the later SR decision to place CCTV cameras behind the linings more or less proves that that was a well-founded concern.

D.  In addition, there would have been some interest in any change in this pattern once the aircraft was descended to at least 13,000ft and depressurized..... And then the sliding cockpit window(s) opened to vent the smoke. Here they would have been interested in any flash-over/backdraft effect of introducing an air-stream into an oxygen-depleted closed flight-deck.

E.   They might also have trialled EVAS under conditions of smoke... Particularly in order to see whether it was a solution to visibility of the centrally offset standby flight instruments during dense smoke.

F.   They were properly concerned that the induced flow patterns behind the cabin linings - that are designed to dry out the moisture caused by the "Rain in the Plane" phenomenon - are also quite capable of propagating any fire in the mylar thermal acoustic blankets. Did the fire originate near the top of the front pax door tracks or the IFEN main control terminal - or the front galley or restroom? If it was visible in the cabin could it have been accessed by an F/A wielding a Halon handheld extinguisher? Or would a fire-axe attack on the cabin linings be necessary first?

G.   I would also assume that they would have measured the exact power consumption and heat generation characteristics of the IFEN with different numbers of seat stations powered up.... and the effect upon the overall system of failures of individual seat's IFE terminals (i.e. would a failure at seat 7f blow a fuse or cause the whole system to short out because of a lack of inbuilt circuit protective devices (CPD's)?). If the CPD setup was deficient, would one failure "daisy chain" into a cascading failure of equipment or worse, of overloaded wiring? What effect would the lack of an ON/OFF Switch be upon such a failure?

H.   Because the SR MD-11 Chief Pilot had publicly admitted (following SR111) that SR engineers had had to vary the airconditioning controller's authority in order to cope with the heat buildup of the IFEN, they would have been interested in the airflow increase (throughput) that this would have caused. You could liken the effect of increased airflow upon the fire as being similar to a blacksmith's bellows perhaps.

I.    They would have then examined the effect of following the aircon part of the smoke and fumes checklist (i.e. the Swissair standard approach was to first up optimistically assume that any fumes were emanating from an aircon pack). Once the packs were turned off, that then would understandably affect the airflows and the distribution of both the visible smoke and the smell of smoke - as well as the propagation of the fire beneath the linings.  However that checklisting time delay would be additive and allow any electrical fire to take hold.

J.    Once the fire had burnt through the aircon ducting, what localised effects did that have upon the propagation of the fire? - particularly once the aircon flows might have been restored.

K.   And of course they would have been looking at the routing, installation standard and type of wiring and connectors utilised for the IFEN installation. Was the wire a necessarily heavier gauge to cope with the high current load? Were the CPD's underrated or overrated? Were the terminals, clamps and connectors appropriate to the gauge of wiring used? Were grommets and conduit used where they should have been? Were the strictures of FAR 25 (and the STC itself) observed by the installers? Was there anything that the BASL inspectors should have picked up on? Was any additional IFEN wiring bundled with other wires to transit bulkheads or was any wiring set too close to HP oxygen piping or aircon ducts? How vulnerable was the wiring to (and in) the individual passengers' seats? (to incidental trampling,  chafing and spillage).

L.  I would doubt that they would be examining the CB-resetting effect of rotating the Smoke/Elec/Air switch (or bus-tie relay or emerg batt failures). That would be done in an engineering or normal flight simulator. However they may have been looking at flight-deck lighting in different failure modes.... and S/E/A positions, particularly in respect of the standby flight instruments.

In Summary

I would expect that they will have learned enough from these tests and those on the different wiring samples recovered (and tests on wire-types) that they will be able to draw fairly reasonable conclusions about localising the area in which the fire started. Nailing the exact cause would be more suppositional however. There'd be some indications of certain systems failing before others (and others that were disabled by the checklist) but an overall backtracking to the cause via the order of systems failures? That's not going to happen.

 
 
 


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