What happened
On July 15, 2019, a Vistara Airbus A320, registration VT-TNH, was operating a scheduled flight from Mumbai to Delhi when it encountered deteriorating weather conditions. While approaching Delhi, the flight crew observed significant thunderstorm activity and heavy rain, leading to a decision to perform a missed approach due to high tailwind components on a wet runway.
Following the missed approach, the crew diverted toward Lucknow. During the diversion, the aircraft encountered further severe weather. After initially considering a diversion to Kanpur and then Prayagra/Prayagraj, the crew ultimately decided to return to Lucknow as weather conditions at the airport began to improve. During this period of intense weather and holding, the aircraft's fuel reserves depleted significantly, prompting the crew to declare Mayday Fuel when the estimated fuel on board reached a critical level. The aircraft eventually landed at Lucknow with only 348 kgs of fuel remaining.
The investigation
The AAIB India investigation examined the flight planning, meteorological data, and the decision-making processes of both the flight crew and the airline's Integrated Operations Control Centre (IOCC). The inquiry scrutinized the discrepancies between the transit briefing sheet and the operational flight plan regarding alternate airports, as well as the adequacy of weather updates provided to the crew during the flight. The investigation also reviewed the role of air traffic control in managing the aircraft's arrival sequence during the fuel-critical phase.
Findings
- The investigation identified a lack of coordination between flight dispatch and the flight crew, specifically regarding inconsistent information about the primary and secondary alternate airports.
- The flight crew failed to proactively update themselves on the weather at the Jaipur alternate during the en-route phase.
- The crew's decision to divert to Lucknow instead of Jaipur, despite facing severe weather en-route to Lucknow, was a primary contributing factor.
- There was a lack of assertiveness from the pilot monitoring during discussions regarding the diversion strategy.
- The airline's operations control did not provide timely or proactive guidance regarding en-route weather trends to assist in an earlier diversion decision.
Safety action
The report issued several recommendations to improve operational safety, including the requirement for airline operations control centers to be headed by type-rated pilots with relevant operational experience. It also emphasized that flight dispatchers must ensure consistency between briefing sheets and flight plans, and that flight crews should be encouraged to use ACARS to seek weather updates to aid in timely diversion decisions.