What happened
On August 28, 2020, two aircraft approaching Cochin Airport experienced a serious loss of separation. The first aircraft, a SpiceJet DH8D (registration VT-SUL), was performing an ILS X approach for Runway 27, while a Qatar Airways A320 (registration A7AHA) was on an ILS Z approach for the same runway.
During the descent, the crew of the VT-SUL failed to engage the altitude selector, causing the aircraft to descend below the required 3,000 ft final approach altitude. Although the air traffic controller alerted the crew to the deviation, the aircraft continued to descend to 2,400 ft. In an attempt to rectify the situation, the SpiceJet crew initiated a go-around at 2,281 ft. However, the increased power during the missed approach caused the aircraft to climb rapidly.
As the aircraft climbed, it intersected the path of the descending Qatar Airways flight. This resulted in a Traffic Collision Avoidance System (TCAS) Traffic Advisory (TA) and subsequently a TCAS Resolution Advisory (RA). The minimum separation between the two aircraft dropped to 2.39 NM laterally and only 500 ft vertically.
The investigation
The AAIB India investigation examined the flight paths, cockpit procedures, and air traffic control instructions. Investigators reviewed the descent profiles and the specific local procedures used at Cochin for sequencing arrivals. The investigation also looked into the cockpit actions of the VT-SUL crew, specifically regarding the altitude selection and the subsequent failure to report the incident to the authorities.
Findings
- The pilot flying on the VT-SUL failed to engage the 'ALT SEL' function during descent, and the pilot monitoring failed to detect this error.
- The crew of the VT-SUL initiated a go-around at an altitude lower than the cleared level, leading to an unplanned climb.
- The climb during the missed approach caused the aircraft to enter a reciprocal track with the descending Qatar Airways aircraft.
- The SpiceJet crew did not report the separation loss or record the incident in the technical log, which is a violation of regulatory requirements.
- The lack of immediate reporting meant that Cockpit Voice Recorder (CVR) data from the subsequent flight was unavailable for review.