The search for the cause of the fire that brought down Swissair
Flight 111 on the evening of September 2, 1998, killing all 229 people
aboard, took over four years and cost $39 million. It was one of the
most exhaustive airline crash investigations ever mounted. In this
interview, airline safety expert David Evans takes an authoritative look
at the investigation and what he calls a "confederacy of complacency" in
the airline industry regarding safety improvements following this and
other major accidents. The interview was conducted in October 2003 at
the offices of Air Safety Week, a widely respected airline safety
newsletter that Evans edits.
NOVA: What was known in the immediate aftermath of the crash?
Evans: Well, based on the conversations between the pilots and
air traffic control, the initial indications were that they had some
sort of a smoke event on the airplane. We know that the crew had
declared a Pan, which is a technical problem on the airplane that
affects safety. And moments before the final crash, they declared a
Mayday. What was initially known was a loss of control.
NOVA: So the crew knew there was a fire?
Evans: If we look at what the crew was experiencing as they
were flying along on this nighttime flight, we have to note that smoke
and fire events on aircraft can be seductive. I mean, you've got a sort
of a whiff of something, and then you're going through a procedure,
trying to determine where this smoke is coming from. In pilots'
parlance, the situation is known as Smoke and Fire of Unknown Origin.
I think that the final horror of their grim situation may not have
been fully appreciated until the fire in the attic space over the
cockpit burned its way through the ceiling panel, and Captain [Urs]
Zimmermann was showered with the charred effects of the fire, the burned
plastic, the sudden blast of heat. At that point, I think that that
eruption of hot gas and possibly flame into the cockpit pushed him out
of his seat, because we do know that he was not in the captain's left
seat at the moment the airplane collided with the water.
NOVA: How useful were the black boxes in the subsequent
Evans: The cockpit voice recorder and the flight data recorder
lost power about six minutes before the airplane finally crashed. These
devices, the so-called black boxes, which are actually painted orange,
are really the Rosetta Stones for an accident investigation, because
they enable investigators to recreate the sequence of cascading
failures, what the crew was doing, what they were saying to each other,
and also the wealth of systems data that is captured on modern black
“Clearly we had an uncontrolled, uncontained, runaway
fire on this airplane.”
It's of interest that in the course of this investigation, the
Transportation Safety Board of Canada (TSB), which had primary
responsibility for the investigation, issued safety recommendations
calling for improved black-box capability and an independent power
supply so that if the aircraft lost electrical power, they would keep on
catching any data that was there to be had. They also called for dual
installation, so that you'd have a fully redundant cockpit voice and
flight data recorder capability located both in the nose and in the aft
part of the airplane.
NOVA: Have those recommendations been acted upon?
Evans: The TSB issued its recommendations for improved black
boxes some three years ago now. Those recommendations, primarily calling
for a two-hour recording capability so that they would have a better
capability in the future for reconstructing accident scenarios, have not
yet been acted upon by the authorities. Those recommendations have
simply dropped into a regulatory black hole.
Working the evidence
NOVA: Without the black-box data, how did the TSB pursue its
Evans: The absence of good flight and cockpit voice recorder
data obviously increases the difficulty of the investigation. Let's say
on a scale of difficulty from zero to 10—zero being pretty
straightforward, 10 being extraordinarily difficult—if you've got the
black boxes and good data from them, the level of difficulty might be on
the order of a four or five. Without the black boxes, you're talking a
nine or 10 level of difficulty and trending towards unsupportable
It really pushed the investigators back into sort of a secondary
mode. They began looking at other sources of data: What could they
capture from the non-volatile memory chips in the engines' digital
recorders? How else could they look at this in terms of the physical
NOVA: What did they focus on?
Evans: Well, the investigators began focusing on the source of
the smoke, because where there's smoke, there's fire. And clearly we had
an uncontrolled, uncontained, runaway fire on this airplane.
NOVA: Did the mountain of evidence retrieved from the seafloor
help them pinpoint the source of the fire?
Evans: Well, in the horribly grim circumstances of this
tragedy, the one small footnote of good news perhaps, from an
investigative standpoint, was that the airplane impacted into water,
which had the effect of immediately dousing the fire and freezing in
time the evidence that would be so crucial to unraveling the mystery.
Had the airplane crashed on land, we probably would have just had a
smoking, black, smeared piece of earth with some tiny pieces of aluminum
and wire. It would have been much more difficult.
As it was, the investigators were able to recover the heat-damaged,
charred wires, which were obviously burned from either electrical arcing
or a runaway in-flight fire of some kind. Those wires led them to pursue
the scenario of a runaway, uncontained, in-flight fire of electrical
NOVA: What was known at the one-year anniversary of the crash?
Evans: By the one-year anniversary, the bulk of the wreckage
had been recovered. The notion of an electrically stoked fire on the
airplane had been pretty well established. The investigators were now
facing a major effort to recreate the circumstances surrounding the
fire: how it got started, how it took root, how it was able to
ultimately bring this airplane down.
“I was thinking at the time: These things are flying
I think with respect to the impact on the families, the one-year
anniversary is one of particular symbolism and perhaps personal pain.
There's no closure in terms of the investigation. Who knew that this
investigation would ultimately drag out to four years or more to put
together all the factors, all the latent hazards, all the circumstances
surrounding this tragedy? So at the one-year point, major safety themes
were emerging, but we were a long way from closure in the form of
NOVA: And what was happening at this point in the
Evans: At this point the investigators had an airplane that
began life as four million parts flying in close formation, and now they
had recovered virtually the equivalent of those four million parts, and
those parts were in bins. They had a major challenge: what I would call
forensic reconstruction of what occurred on the airplane. They
determined to try and reassemble the cockpit. They created a steel
frame, or skeleton, on which to mount recovered pieces of the airplane.
They also began focusing in on the forward part of the cabin, including
the attic space, the forward galley, and the cockpit, and on putting the
pieces together—the panels, the aluminum, the wires, the electrical
components—to try and recreate how this case progressed from an
electrical incident to a major accident.
If we look at the amount of flammable material that the investigators
recovered from the airplane and, to their dismay, finding how much of it
was burned—the oxygen-line end caps, the thermal acoustic insulation
blanketing, and other material—I was thinking at the time: These things
are flying firetraps. I mean, how is it that we can put 200-plus people
in an airplane with all this flammable material? This is the tinder
waiting for the match. And the match, as we now know, was the electrical
arcing. [Editor's note: The investigators concluded that electrical
arcing—a discharge of electricity from a damaged cable—triggered a fire
in the plane's insulation materials. The arcing occurred in the attic
space just above and aft of the cockpit, possibly in bundles of wiring
in that space.]
Taking action—and not
NOVA: Had this kind of fire ever been reported before?
Evans: Behind every major aviation accident is a history. In
the case of Swissair Flight 111 and the thermal acoustic insulation
blankets, the Chinese had experienced a number of cases of in-flight
fire and damage in which the blankets had burned. And the Chinese
authorities had contacted our Federal Aviation Administration (FAA) and
advised them "Guys, you may have a flammability problem here." Action
NOVA: What action did the TSB, for its part, take when this
danger of fire became clear?
Evans: Well, by December of 2000, the Safety Board of Canada
felt like it was dealing with a major problem: the vulnerability of
aircraft to in-flight fires. And they had a press conference at which
they expressed publicly their concerns—to wit, that collectively in the
industry we have not done an adequate job of reducing the flammability
and providing greater protection against in-flight fire.
NOVA: Did the TSB add this potential danger to its list of
Evans: Yes. The TSB has issued a number of very important
recommendations to improve the safety of this airplane and of all
airplanes. Those recommendations have been transmitted to the Canadian
regulatory authorities and to our National Transportation Safety Board,
which is the comparable accident investigation body to the Canadians'.
Our Safety Board, to its great credit, has fully endorsed the Canadian
recommendations and has sent them on to the FAA, which is the regulatory
authority responsible for this airplane.
NOVA: Has the FAA endorsed the recommendations?
Evans: In terms of what the FAA is doing, let me cite the
great British Prime Minister Disraeli: "We are making haste slowly."
NOVA: So what would you say is the legacy of this case?
Evans: The legacy of this case is enormous, because we have a
continuing problem with in-flight smoke and fire. I like to say that if
the cabin of a modern jetliner was a restaurant, it would not get an
occupancy permit, because you've got people in a confined space with no
fire detection or suppression, and they're sitting on top of
high-powered electrical circuitry and a big load of fuel. You have all
this in very close proximity.
“We have what I would call a confederacy of
complacency with respect to in-flight fire detection and suppression.”
Now, if we look at, say, rest homes, the mobility of old folks is
likewise limited. Yet to get an occupancy permit for your parents' rest
home, the builders and developers had to demonstrate that every square
inch of that nursing home is covered by detection and suppression. We
can look up in this office space here, and we can see the nozzles for
the fire-protection system. You know that if we have an electrical fire
in this building, we're going to be doused with a spray of water. We are
fully protected, and yet we can get out quickly also. When you're in a
jetliner at 30,000 feet, you're not getting out. You've got to fight it
long enough to get the airplane on the ground.
Now, what do we have in the airline industry? We have what I would
call a confederacy of complacency with respect to in-flight fire
detection and suppression. The National Transportation Safety Board has
said that we need an integrated firefighting philosophy on airplanes.
Yet we've got spaces that we don't have access to that are not
protectable by fire detection or suppression. So the hazard continues to
NOVA: Do you think the apparent industry inaction on this
front is due to a cavalier attitude about the value of human lives?
Evans: No. There is a phrase within the industry to the effect
that "If you think safety is expensive, try an accident." So I don't see
that at work here. What I do see are a combination of forces:
complacency, bureaucratic inertia, "It's too hard," "We're not making
money now," things of this nature.
What strikes me is that so many of these accidents about which I have
written over the years had precursor events that, had action been taken
with alacrity, if we had not been in the Rip Van Winkle mode of
regulatory torpor, could have been prevented. So the issue to me is not
whether you can fly for a thousand years before you're going to be
involved, statistically speaking, in an aircraft accident. The question
is: How many of these accidents were avoidable and preventable? I
haven't seen one yet where structure and systems were involved where it
wasn't avoidable and preventable beforehand. And therein lies the
tragedy. Therein lies the culpability.