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The captain of an airliner that flew over London despite having serious electrical problems which could have caused a fire, will be criticised this week by the government air safety watchdog. The
Air Accidents Investigation Branch describes how the pilot was forced
to order an emergency evacuation
because of smoke and the risk of fire seconds after making an unscheduled
landing at Heathrow. Its
report says that the captain, who had already decided it was too
dangerous to continue on his scheduled route across the Atlantic, should
have reported an emergency on board his aircraft before touching down in
London. That
would have allowed air traffic controllers to divert the United Airlines
Boeing 767-300 to Stansted and away from the heavily populated capital. The
report also points out that the captain’s failure to raise the alarm
meant there were no fire tenders or other emergency services on hand
when the aircraft landed at Heathrow, placing passengers at further
risk. The AAIB, which
will publish its findings on Thursday, blames the incident on an electrical
fault known as “arc-tracking”. It
also lists other incidents caused by the same problem, including one in
which an RAF Nimrod crashed into the Moray Firth and another in which a
fire broke out in the first class section of a Virgin 747 jumbo flying
over Halifax, Nova Scotia. On
that occasion the blaze “self-extinguished”. The
electrical problems on the United Airlines aircraft occurred on a flight
from Zurich to Washington on January 9th 1998. The
fault was discovered at 2.35pm, as the plane passed over Paris, when the
crew began to experience problems with their flight instruments. The
captain, who is described as a 47-year-old male, but not named in the
report, decided that it was too dangerous to fly over the Atlantic and
opted instead for a London diversion. Instead
of reporting an emergency, however, he simply reported experiencing
technical faults, a decision strongly criticised in the report. It
says that in future pilots must consider electrical system failures as a
fire hazard and declare an emergency so that their aircraft can be
diverted. Ed
Block, vice-Chairman of the International Aviation Safety Assn, a member of the United States Federal Aviation Administration’s
aircraft wiring committee, and an expert on “arc-tracking”, said
that there had been a serious risk of the United Airlines jet crashing.
“If that plane was in mid-Atlantic it was gone.
I think it was divine providence it didn’t come down in
London”, he said. Arc-tracking
occurs when the insulation of a type of wiring known as Kapton breaks
down because of age or damage. This
creates a very high temperature short circuit that ignites and destroys
anything around it. More
than 60 wires were destroyed in the United incident, though to have been
caused when engineers fitting a refrigerator in Washington the previous
day damaged the insulation. Numerous
fatalities have been attributed to arc-tracking electrical fires. In 1981, a Lockheed TriStar returned to Riyadh airport in
Saudi Arabia after the pilot reported a fire on board. The aircraft landed safely, but more than 300 passengers
died. A Kapton fire is
suspected. A
crash off the Canadian coast involving a Swissair MD11, which killed all
229 on board, has also been blamed on arc-tracking that slowly deprived
the plane of its power, radio, and controls. The
crash of a TWA Boeing 747, which blew up after take-off from New York,
has also been attributed to a wiring short, which caused an explosion in
the aircraft’s fuel tank. The
majority of the world’s passenger fleet contains Kapton wiring,
including all Airbuses, most Boeings built before 1993, and the BAe 146,
three of which are used to fly the Royal family and the Prime Minister. |
09 Jan 98 (A
Workup for Swissair 111?)
