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Swissair
flight 306 was depart Zurich for Geneva
at 7am the morning of September 4, 1963.
In command of the Sud Aviation Caravelle
that morning was Captain Eugene Holhi
and First Officer Rudolph Widmel. Along
with three flight attendants, there were
74 passengers on board that morning.
Weather was good in the area, but
morning fog was lying in the valley
areas and the airport was still closed
when 306's departure time came. Holhi
asked the tower controller for
permission to taxi out onto the runway
so he could take a look at the
visibility available. A guide vehicle
led the aircraft to the runway and
Holhli taxied the Caravelle about
4,000ft down the runway with the engines
at high power. He then turned around and
taxied back to the start of the runway.
Radioing
the tower, he reported that the
visibility varied along the runway and
that the jet exhaust had blown away some
of the fog. Holhli then asked for
permission to take off and it was
promptly granted. Shortly afterwards,
306 reported being in clear conditions
above the fog and climbing through
1,700ft. The flight was then handed off
to Zurich departure. Only a few minutes
afterwards, the crew made a Mayday call,
which was to be the last transmission
from the aircraft. A farmer working on
the mountainside saw the Caravelle in
flight, trailing smoke from it's port
side followed shortly by an outbreak of
flames. The aircraft then began a
left-turning descent, plunging back into
the fog. Another person on the ground
below the fog reported seeing the
aircraft emerge from the fog in a steep
dive, flames pouring out of the left
side of the aircraft just before it
impacted the ground on the outskirts of
a local village. Wreckage was scattered
around the impact site, damaging homes
and setting structures on fire. No
survivors were found.
Investigators
were able to locate the FDR, but it
provided no clues as to the cause of the
accident. The only information they had
to go on was the eyewitness reports of
fire on the left side of the aircraft.
Investigators found pieces of the
aircraft's left side undercarriage, port
wing, and rear fuselage along the last
six miles of the aircraft's flight path.
Back at the airport, investigators found
part of the outer rim of the left inside
wheel. Near this, there was blow-out
stain and an earthing cable.
Along the
wheel tracks after this stain were
traces of hydraulic oil and and pieces
of the inner port wheel. Investigators
determined that excessive breaking had
to be used to keep the aircraft slowed
down while high engine power was used
during taxiing. This excessive braking
caused extremely high temperatures which
led to the fracture of the outer rim.
They further determined that this
excessive heating could have ignited the
then leaking hydraulic fluid. Further,
once the gear was retracted after
takeoff, the excessive heat could have
further damaged fuel lines and other
critical components in the undercarriage
area, igniting the subsequent fire. In
flight, this fire caused a weakening of
the structural support of the wing and a
loss of hydraulic fluid to the control
systems.
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