What happened
On 22 July 2019, an Airbus A321, registration YL-LCQ, was conducting a commercial passenger flight approaching London Stansted Airport. At the time, maintenance work was being performed on Runway 22, necessitating a displaced threshold and the use of a specific, steeper RNAV22C approach to ensure clearance over the work area.
The flight crew, unaware that the revised procedure was required, executed the standard RNAV22 arrival. Radar data confirmed the aircraft was flying lower than expected over the maintenance zone and touched down near the displaced threshold. During the approach, the tower controller issued a warning regarding the displaced threshold and instructed the crew not to fly below the PAPI indications. However, the crew misinterpreted this instruction as an order to ignore the PAPI guidance.
The investigation
The AAIB investigation examined radar data, air traffic control (ATC) transcripts, and the flight crew's electronic flight bags (EFB). The investigation established that the pilots had reviewed NOTAMs and airfield charts but were misled by an error in the temporary airfield chart, which incorrectly listed the active work dates.
Analysis of radio communications revealed that while ATC repeatedly referenced the displaced threshold and the specific RNAV22C approach, the crew's readbacks were often incomplete. The controller did not challenge these inaccurate readbacks. Furthermore, the investigation noted that the crew's heavy accents may have impacted the clarity of the transmissions.
Findings
- The crew's reliance on an incorrectly dated airfield chart led them to believe runway works were not in effect.
- Confirmation bias caused the pilots to follow their expected standard arrival procedure and prevented them from noticing ATC's cues regarding the revised approach.
- The flight crew misinterpreted the controller's instruction regarding PAPI indications.
- Incomplete readbacks by the crew were not challenged by the terminal controller.
- An error in data transposition by the chart manufacturer resulted in inaccurate maintenance schedules being presented to pilots.