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Aviation History
1996
1996 - 3020.PDF
AIR TRANSPORT Collision raises doubts on ATC routeings MAX KINGSLEY-JONES/LONDON DAVID LEARMOUNT/DUBAI THE MID-AIR collision near New Delhi, India on 12 November between a Saudi Arabian Airlines Boeing 747-100B and an Ilyushin U-76 of Air Kaza khstan has raised concerns over the safety of Delhi's air-traffic-control (ATC) routeing system. It has also heightened concerns over lan guage problems and me operation of CIS aircraft in international air space, particularly the potential for altitude confusion, because CIS aircraft show altitude in metres, while die rest of die world cali brates its altimeters in feet. The accident occurred when die inbound 11-76 (UN-76435), oper ating a freight charter into Delhi from Chimkent, Kazakhstan, col lided with the 747 (HZ-AIH), which was heading outbound from Delhi on the same route, but in die opposite direction. The 747 was flying a scheduled Saudi Arabian flight (SV763) to Dhahran and Jeddah in Saudi Arabia, with 312 passengers and crew on board. Thirty-eight people were on board the 11-76. All occupants of both air craft were killed. Initially, there were suggestions that the collision may have oc curred after an instruction had been misunderstood. After listen ing to ATC recordings, however, the Indian authorities announced: "It is quite clear diat both crews had understood and confirmed their instructions." The 11-76, built in 1992, may have been equipped only with a metric altimeter. Since at least one of the two aircraft had transgressed its cleared flight level, diere have been suggestions that a metric/ imperial altitude conversion error could have been made by die 11-76 crew. At the moment, New Delhi's Wreckage was strewn over a wide area ATC centre is equipped only with primary airport-surveillance radar (ASR), which provides position information but not alti tude. Details of each aircraft's exact altitude at impact will not be known until their flight-data recorders have been examined. Neither aircraft was equipped with a traffic-alert and collision- avoidance system. ATC authorities accept that ideal practice in terminal areas is to separate arrival and departure tracks laterally, and most of them | undertake that policy. The " Indian Air Traffic Controllers' Guild, in the aftermath of the col lision, alleges that it has been pressing for more than three years to separate Delhi's western departures and arrivals. It says that the Indian air force had refused airspace allowing a widening of the corridor. The air force denies this. Raydieon has been working on a $ 12 0 million contract to install sec ondary-surveillance radar (SSR) which was due to have been com pleted by mid-1996. The latest estimate for entry into operation is early 1997. SSR provides flight identification, altitude and speed information. The last time a mid-air collision between commercial airliners oc curred was on 11 August 1979, involving two Aeroflot Tupolev Tu-134s near Dneprodzerzinsk, Ukraine, killing 165 people. • The sequence of events leading to the mid-air collision THE BOEING 747, ONE of eight Series 168Bs (ie, the -100B) operated by Saudi Arabian, departed New Delhi's Indira Gandhi Inter national Airport at around 18.33 local, and headed on a westerly course (270°) from the Delhi VOR navigation beacon (DPN). The 747, which seems to have been operating a "PARVF westerly standard instrument departure (SID), was cleared to climb to flight level 140 (14,000ft) although it had requested clearance to continue its climb through that altitude. The PARVI SID involves a westerly (270°) track through two reporting points — PARVI and LUNKA — which are 131km (71nm) and 326km (176nm) respectively from the DPN VOR (see illustration). Meanwhile, the Ilyushin 11-76, which was travelling in bound from the LUNKA way point on the reciprocal course (ie, 090°), was descending LUNKA waypoint (326km from DPN) Final routeings of Saudi Arabian 747-100 and Kazakh II-76 Kazakh II-76 Not t0 sca,e Cleared tO Source: Jeppesen flight level 150 track: 090° PARVI waypoint (131km from DPN) Saudi Arabian 747-100 cleared to flight level 140 track: 270° FLIGHT © Reed Business Pub m Indira Gandhi International airport New Delhi Boeing 747 and Ilyushin II- 76 on fatal collision course through FL230 (23,000ft) to FL180 (18,000ft) and reported that it was "74 miles [137km] from the DPN VOR" (ie roughly at the PARVI way- point). The Kazakh aircraft was then instructed to descend to, and to maintain, FL150 (15,000ft), with the intention to vector the aircraft to the south of the airport for a land ing from the east. The Saudi Arabian 747 pilot reported approaching FL140, and requested further climb clearance, but was instructed: "Maintain FL140, standby for higher". The Kazakh pilot in formed Delhi ATC that his air craft had levelled at FL150, that it was "46 miles" (85km) from the Delhi DPN VOR beacon, and that it was on the 270 radi al (ie tracking 090°). ATC instructed the Ilyushin crew: "Maintain 150 [15,000ft]. Identified traffic 12 o'clock reciprocal. Saudi Boeing 747, report when in sight." The Kazakh crew then asked ATC: "repeat, how many miles?" to which ATC replied: "14miIesnow." Moments later ATC reported "...traffic is 13 miles now, level 140 [14,000ft]." At this stage, both aircraft, although travelling directly towards each other, were thought to be separated by 1,000ft vertically. At 18.40, around 1 min after the last instruction to the Kazakh crew, the two aircraft collided near the town of Charkhi Dadri.The accident sites were around 74km from the airport, and the wreckage suggested the 11-76 had collided with the fop of the 747. • 8 FLIGHT INTERNATIONAL 20 - 26 November 1996
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