What happened
On the night of November 30, 2016, a ground collision occurred at Mumbai's Chhatrapati Shivaji International Airport involving an IndiGo A320, registration VT-IFP, and a Kuwait Airways A330-200, registration 9K-APA.
The IndiGo aircraft was preparing for a scheduled flight to Jaipur and had been cleared to taxi via several taxiways, including N, with the specific instruction to remain clear of the Kuwait Airways aircraft, which was taxiing toward taxiway W4. After the Kuwait Airways aircraft moved forward to clear the intersection, the crew of VT-IFX proceeded with their taxi. During the maneuver, the left-hand sharklet of the A320 made physical contact with the right wing of the A330-200.
The collision was brought to the attention of the IndiGo crew by a cabin attendant, who reported that a passenger had witnessed the wingtip strike. The crew immediately decided to return to the bay for inspection. The Kuwait Airways crew also reported feeling a physical jar during the passing.
The investigation
AAIB India examined the circumstances surrounding the movement of both aircraft and the regulatory environment at the airport. The investigation looked into the taxiway restrictions at Mumbai, specifically regarding taxiway N and W4. It was noted that existing local traffic regulations prohibited taxiing on taxiway N when an aircraft was holding at the W4 intersection of Runway 14/32.
The investigation also analyzed the physical damage sustained. The A320 suffered a sheared upper section of its left-hand sharklet and damage to its stainless steel leading edge cap. The A330-200 sustained damage to its outboard aileron lower skin, trailing edge wedge structure, and superficial paint scratches on the wing surface.
Findings
- The primary cause of the incident was an error of judgment by the crew of the A320, who assessed the wingtip clearance as sufficient when it was not.
- Air Traffic Control instructions were in conflict with established taxiway restrictions, as the aircraft was cleared to taxi on a route that was technically prohibited while the other aircraft held at W4.
- Human factors contributed to the incident, specifically the inherent difficulty pilots face in accurately judging absolute separation distances when the line of sight exceeds 10 meters.
- Environmental factors, including relatively dark lighting at the intersection of W4 and N and hazy visibility, may have hindered the crew's ability to maintain visual separation.
- There was a lack of specific guidance from the operator's dispatch regarding the taxiway restrictions and the difficulties of assessing wingtip clearance for aircraft equipped with sharklets.
Safety action
- Recommendations were made for the operator to provide flight crews with guidance regarding the challenges of assessing wingtip clearance.
- Authorities were advised to review taxiing procedures for taxiway N and consider declaring the W4/N intersection a "hot spot."