Charkhi Dadri Mid-air Collision - Crash Investigation and Report

Crash Investigation and Report

The crash was investigated by the Lahoti Commission, headed by then-Delhi High Court judge Ramesh Chandra Lahoti. Depositions were taken from the Air Traffic Controllers Guild and the two airlines. The flight data recorders were decoded by Kazakhstani Airlines and Saudia under supervision of air crash investigators in Moscow and Farnborough, Hampshire, England, respectively.

The commission determined that the accident had been the fault of the Kazakhstani Il-76 commander, who (according to FDR evidence) had descended from the assigned altitude of 15,000 feet (4,600 m) to 14,500 feet (4,400 m) and subsequently 14,000 feet (4,300 m) and even below that. The report ascribed the cause of this serious breach in operating procedure to the lack of English language skills on the part of the Kazakhstani aircraft pilots; they were relying entirely on their radio operator for communications with the ATC who in turn did not have his own flight instrumentation but had to look over the pilots' shoulders for a reading. Kazakhstani officials stated that the aircraft had descended while their pilots were fighting turbulence inside a bank of cumulus clouds. Also, a few seconds from impact, the Kazakhstani plane climbed slightly and the two planes collided. This was due to the fact that only then did the radio operator of Kazakhstani 1907 discover that they did not fly at 15000 ft. Had the Kazakhstani pilots not climbed slightly, it is likely that they would have passed under the Saudi plane. He asked the pilot to do so and the captain gave orders for full throttle and the plane climbed, only to hit the oncoming Saudi plane. The tail of the Kazakhstani plane clipped the left wing of the Saudi jet, severing both parts off their respective planes. The recorder of the Saudi plane revealed the pilots reciting the prayer that they had to, according to Islamic law, when they face death. The counsel for the ATC Guild denied the presence of turbulence, quoting meteorological reports, but did state that the collision occurred inside a cloud. This was substantiated by the affidavit of Capt. Place, who was the commander of the aforementioned Lockheed C-141B Starlifter which was flying into New Delhi at the time of the crash. The members of his crew filed similar affidavits. The ultimate cause was held to be the failure of Kazakhstan Airlines Flight 1907's pilot to follow ATC instructions, whether due to cloud turbulence or due to communication problems.

Indira Gandhi International Airport did not have secondary surveillance radar, which produces exact readings of aircraft altitudes by reading transponder signals; instead the airport had outdated primary radar, which only produced readings of distance. In addition, the civilian airspace around New Delhi had one corridor for departures and arrivals. Most areas separate departures and arrivals into separate corridors. The airspace had one civilian corridor because much of the airspace was taken by the Indian Air Force. Due to the crash, the air-crash investigation report recommended changes to air-traffic procedures and infrastructure in New Delhi's air-space: Separation of in-bound and out-bound aircraft through the creation of 'air corridors', installation of a secondary air-traffic control radar for aircraft altitude data, mandatory collision avoidance equipment on commercial aircraft operating in Indian airspace and reduction of the airspace over New Delhi which was formerly under exclusive control of the Indian Air Force.

The Civil Aviation Authorities in India made it mandatory for all aircraft flying in and out of India to be equipped with an ACAS (Airborne Collision Avoidance System).