1996 Charkhi Dadri mid-air collision

The 1996 Charkhi Dadri mid-air collision occurred on 12 November 1996 when Saudi Arabian Airlines Flight 763 (SVA 763), a Boeing 747-168B en route from New Delhi, India, to Dhahran, Saudi Arabia, collided in mid-air with Air Kazakhstan Flight 1907 (KZK 1907), an Ilyushin Il-76 en route from Shymkent, Kazakhstan to New Delhi, over the village of Charkhi Dadri, Haryana, India. All 349 people on board both flights were killed, making it the deadliest mid-air collision to date.

History and Cause:

Flight SVA 763 departed Delhi at 6:32 PM local time. Flight KZK 1907 was, at the same time, descending to land at Delhi. The crew of flight 763 consisted of captain Khalid Al Shoujaili, first officer Nazir Khan, and flight engineer Evris. On Flight KZK 1907, Gennadi Cherepanov served as the pilot and Egor Repp served as the radio operator.[1] Flight KZK 1907 was cleared to descend to 15,000 feet (4,600 m) when 74 miles (119 km) from the airport while Flight SVA 763, traveling on the same airway as Flight KZK 1907 but in the opposite direction, was cleared to climb to 14,000 feet (4,300 m). About eight minutes later, around 6:40 PM, Flight KZK 1907 reported having reached 15,000 feet (4,600 m). At this time the controller advised the flight, "Identified traffic 12 o'clock, reciprocal Saudia Boeing 747, 14 miles (23 km). Report in sight." When the controller called Flight KZK 1907 again, he received no reply. He warned of the other flight's distance, but it was too late -- the two aircraft had crashed almost head-on. The left wing of KZK 1907 sliced through the aft and tail sections of SVA 763. Flight SVA 763 disintegrated almost immediately, while the fuselage of Flight KZK 1907 remained structurally intact until it crashed in a field.[2] Rescuers discovered three critically injured passengers of the Saudi aircraft with faint heartbeats; they were taken to hospital but died there.[3]). In the end, all 312 people on board Flight SVA 763 and all 37 people on Flight KZK 1907 perished. Capt. Timothy J. Place, a pilot for the United States Air Force, was the sole eyewitness to the event.[2]

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 the respective airlines under supervision of air crash investigators in Moscow and London. The commission determined that the accident had been the fault of the Kazakh 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 Kazakh aircraft pilots; they were relying entirely on their radio operator for communications with the ATC.[8] Kazakh 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 Kazakh plane climbed slightly to 15,000 feet (4,600 m) and the 2 planes collided. If they had not climbed slightly, it is likely that they would have passed under the Saudi plane. The counsel for the ATC Guild denied the presence of turbulence, quoting meteorological reports, but did state that the collision occurred inside a cloud.[8] This was substantiated by the affidavit of Capt. Place, who was the commander of a US military aircraft flying into New Delhi at the time of the crash.[2] The members of his crew would file similar affidavits.[9] The ultimate cause was held to be the failure of the Kazakh 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; instead the airport had outdated primary radar, which produced approximate readings. 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.[2] 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). This was the first time in the world that ACAS was mandatory.