ATC Transcripts of Mid Air Collision in India

Date:         15 Nov 96 12:25:36 
From:         shahid siddiqi <s.a.siddiqi@larc.nasa.gov>
Organization: as&m
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I've enclosed the ATC transcripts of radio conversations between the
airplanes and Delhi control.  I pose the following questions.

Typical initial news report inaccuracies and lack of knowledge suggested
3 possible reasons for the crash:

1 - Kazak Airliner crew didn't understand ATC instructions due to English
language fluency.  The transcripts negate this

2 - Indian ATC notorious for poor English - Transcript negates this.
(this is stereotyping bull because most Indians in professional jobs have
English seaking skilla equivalent to or better than many Europeans

3 - Kazak pilot made a meter to feet conversion error - this is possible
and forms the basis of my question:

I's sure both airplanes had Mode C capability so why wouldn't ATC have
know that the Kazak plane was off altitude. The transcript shows that
radar determined that they were 14 miles apart. Lets assume 300 knots
speed for each meaning 10 miles per minute of travel. This would allow
1.4 minutes before collision enough time for at least 10 radar scan paints
if not more. So why didn't the Mode C altitude get picked up??????

Stung by critical reports about possible failure of the Air Traffic Control
(ATC) and obsolete equipment at the Delhi airport, the Ministry of Civil
Aviation today made public the last conversation between the ATC and the
pilots of the ill-fated aircraft which collided mid-air near here killing
all 351 people, including crew members, on board. The commanders of both
the planes could hear the instructions given out by the ATC to each other.

The 15-second conversation shows that the ATC had given instructions to
the commander of the Kazhak plane to descend to an altitude of 15,000 feet
and to the Saudi Boeing pilot to ascend to 14,000 feet. Both the pilots
appear to have followed the instructions and confirmed it too.  Then what
went wrong?

According to experts, either the Kazhak pilot made a mistake in calibrating
the meter gauge into feet and was at a lower altitude, even though he
confirmed that he was at 15,000 feet or did not follow instructions. The
other theory is that one of the aircraft had a defective altimeter. The
ATC has only the pilot's word for the altitude he was flying at.

At the site of the accident, the cockpit and the windscreen of the Kazhak
plane were recovered almost intact. Even the bodies of the people on board
this aircraft were found to be in identifiable condition. In the case of
the Jeddah-bound Saudi Boeing aircraft, which was carrying a huge quantity
of fuel, the bodies were charred beyond recognition and so was the
aircraft.

Sources said the collision did not happen head-on.  It was more likely
that one of the aircraft brushed against the other, hitting a side, which
led to an explosion and the worst ever mid air disaster in aviation
history.

The Director-General Civil Aviation, Mr. H. S.  Khola, today denied that
India had deviated from international norms in allowing a single corridor
for landing as well as take-off of flights. He said both the planes were
allowed to fly at a distance of 1000 feet vertically under the guidelines
of the International Civil Aviation Organisation (ICAO).

The following is the transcript of the last minute conversation between
the ATC and the pilots of both the aircraft.

KZA-1907: Good evening, KZA-1907 passing through 230 for 180, 74 miles
from DPN (Delhi Palam).

RADAR (ATC): Descend 150 report reaching.

KZA-1907: One five zero.

SAUDIA 763: Approaching 100.

RADAR: Cleared to 140.

SAUDIA: Approaching level 140 for higher.

RADAR: Maintaining level 140, standby for higher.

RADAR: KZA-1907 report distance from DPN

KZA-1907: Reached 150, 46 miles DPN radial 270

RADAR: Maintain 150 Identifed traffic 12 o'clock reciprocal Saudia Boeing
747, 14 miles. Report in sight.

KZA-1907: Kazak-1907 Report how many miles?.

RADAR: 14 miles now. Roger 1907.

RADAR: Traffic is 13 miles, level 14,000.

KZA-1907: 1907