Pilot 'error' under scanner

Black box still untraceable, but cockpit voice recorder found; DGCA begins probe
jith Athrady
Last Updated : 24 May 2010, 06:02 IST
Last Updated : 24 May 2010, 06:02 IST
Last Updated : 24 May 2010, 06:02 IST
Last Updated : 24 May 2010, 06:02 IST

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Even as the crucial black box continues to elude the search team, preliminary investigation by a court of inquiry under the Directorate General of Civil Aviation (DGCA) has found that the ill-fated Boeing 737-800 aircraft was not on a proper glide path.
This could have led the plane to overshoot the runway, causing the pilot to lose control and crashing the aircraft, killing 158 passengers and crew members, Civil Aviation Ministry sources said.

Search of the crash vicinity yielded the cockpit voice recorder, which would provide vital clues about what transpired between the pilot and Air Traffic Control (ATC) just before the plane crash-landed. Mangalore airport sources indicated there could be only two possibilities of the crash––errors pilot Zlatko Gluscia may have committed or a technical glitch at the ATC tower.

Airport sources told Deccan Herald that since Mangalore airport is equipped with one of two kinds of instrument landing systems (ILS)––Category 1, by which the pilot must take control of the flight when 800 metres are left for touchdown––it is possible that Glusica took control just before landing but ignored ATC suggestions or warnings at the moment when he overshot the runway. The probe team, which is studying the records stored at the air traffic control (ATC) tower, is inquiring into a possible lapse on the part of the controllers.

Ministry officials admitted that the ATC at the Mangalore airport could have warned Glusica when it noticed that he would surely overshoot the landing threshold. The probe will take into account the possibility of contradictory information that might have been fed to the computer system either in the ATC or the cockpit.

The officials also admitted that the error could have happened when the aircraft was on a fairly high altitude but later failed to align itself on the glide path.
“After sensing that the touchdown went wrong, the pilot must have applied emergency brakes that led to a burst tyre, forcing the plane off the runway and hitting the ILS facility,” sources said.

Such approach radars, with which airports in Mumbai and Delhi are equipped with, generally monitor approaching aircraft over long distances till they establishes contact with the ILS.

If an approaching aircraft fails to align with the glide path, the controllers manning the ATC can correct the pilot’s error and guide him to follow the precise flight path.

Glide path error may have caused air crash
In the absence of an approach radar at Mangalore airport, the pilot might have made his own judgment after contacting with the ATC and locking with the ILS.
Although it has been reported that there was radio contact between the pilot and the ATC about 10 miles before touchdown and that landing clearance was given when the aircraft was about 4 miles away, aviation officials suspect “something amiss”.
They are not ruling out another contributory factor –– a sudden tailwind that could have “pushed” the aircraft, flying at high speed, forward, leading to loss of control on the part of the pilot. While the cockpit voice recorder will surely throw some light on what went wrong, the investigators will focus on warning systems within the aircraft and at the ATC.

 Vital gadgets

Flight data recorder
 Black box or flight data recorder, mounted in the tail of an aircraft, is considered the most crash-survivable part. It is one of the most important gadgets used to reconstruct the events leading to a crash.
 Black box is a misnomer as its colour is orange. This is done for easier location after a crash. It is enclosed in steel and surrounded by multiple layers of insulation so that it remains protected against crash, fire and extreme climatic conditions.
It records the actual flight conditions, including altitude, airspeed, heading, vertical acceleration and aircraft pitch.
David Warren of Aeronautical Research Laboratories in Melbourne, Australia, is credited with the invention of the black box in 1953.

Cockpit voice recorder
Cockpit voice recorder records radio transmissions and sounds in the cockpit, such as the pilots’ voices and engine noises.
The recorder’s microphone is usually found on the overhead instrument panel between the two pilot seats.
Sounds of interest captured on the recorder are engine noise, stall warnings, landing gear extension and retraction, crew conversation, communications with air traffic control, automated radio weather briefings, any other abnormal noise.
From these sounds, parameters such as engine rpm, speed, system failures and the time at which these events occurred can then
often be determined.

Published 23 May 2010, 03:27 IST

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