Aircraft Weather Radar Display in the Cockpit
A week since the IAF AN 32 disappeared over the Bay of Bengal. What happened to it?
It was smashed by the storm god, Indra -
that's my hypothesis
Flying in
the clouds, the AN 32 encountered a line of thunder squalls, including supercells,
across its flight path. The tops of these cells are much higher than the AN
32's ceiling so it could not fly above them. It could not fly through them
because they are a complex, violent, whirl of updrafts, downdrafts and cross
currents. AN 32 had to weave a path avoiding them. It used its weather radar
(WR) to do that. On the WR, magenta and red indicate the areas of most severe turbulence
and heavy rainfall or hail; yellow indicates moderate turbulence and
uncomfortable ride for the passengers; and green indicates little drizzle and
little or no turbulence. Magenta/red is always avoided; attempt is to fly
through the green or, if inevitable, then, as briefly as possible, through the
yellow.
Flying in
green takes you between the cells in a line of cells. But alas. Sometimes the whirl
and violence in the space between the cells is even more violent than in the
core of the cell. This was the case in this instance. The AN 32, still in
clouds, flying on instruments without visual reference, was suddenly caught by
a violent down draught that made it fall at the rate of thousands of feet a
minute. The pilot pitched the aircraft (a/c) nose up to increase the a/c's angle
to air (angle of incidence, AI) and thus increase the a/c-lift and reduce the
rate of fall. But suddenly there was an updraft and the AI shot up much beyond
the AI at which aircraft control is lost. Aircraft stalled, tumbled and began
to fall. The violent whirl made it fall sometimes nose way up, sometimes way
down, sometimes right-side up, sometimes on its back, sometimes on its side, .
. . . As it tumbled through the sky one, or both , engines failed. In this situation, flight instruments do not tell
what the aircraft is doing. Pilot has never before faced such a situation. In
the absence of visual clues, he is disorientated, that is doesn't know what
aircraft is doing even if the instruments were to tell him.
And so the
AN 32 tumbles and falls and is smashed onto the sea, or is broken to pieces in
the air. In either case, the result is the same. A catastrophe.
AN 32's was
not the first fatal accident caused by extreme turbulence. On 02 May 1953, a
British Airways Comet, the first jet airliner of the world, crashed near
Calcutta. "Structural failure of the airframe during flight through a
thunder squall. In the opinion of the Court, the structural failure was due to
overstressing which resulted from either:- (1) Severe gusts encountered in the
thunder squall, or (2) Overcontrolling or loss of control by the pilot when
flying through the thunderstorm."
On August 6, 1966, Braniff Airways Flight 250, a BAC 1-11 jetliner, crashed. Aircraft structural failure due to extreme
turbulence was the cause.
On April 4, 1977, Southern Airways Flight 242, a DC-9-31 jetliner,
made a forced landing on a highway after losing thrust
on both engines in a severe thunderstorm .
On June 1, 2009, Air France Flight #447, Airbus A330 jetliner, encountered a line of
towering thunderstorms in mid-Atlantic
Ocean. The autopilot disconnected leading to a stall. The pilots
mis-compensated for this by pitching the aircraft nose up instead of down.
Flight crashed in ocean.
So the AN 32 was not the first fatal accident due to weather;
and it will not be the last.
Let me finish this tragic tale on an optimistic note. On Christmas
Eve December 24, 1971, a lightning bolt struck and ignited fuel tank on a
commercial flight. All 91 aboard perished except a 17-year-old German girl, Juliane Koepke.
Strapped to her seat, she fell 10,000 feet to the Amazonian jungle of Peru. She survived with a
broken collar bone and popped eyeballs. For 10 days she wondered through the
jungle and swam down a river till she happened on a lumberman shack and was
rescued! Many documentaries were made on this miracle including one by Werner
Herzog, the well known German film director and producer.
I close with prayers for the 29 aboard the ill-fated AN 32.
