What happened
On 16 June 2020, an Airbus A321-231, registration G-WUKJ, was performing a non-revenue flight from Doncaster Airport to Stansted. The aircraft had been parked at a remote stand for approximately 12 weeks. During the takeoff roll, the commander noticed an increasing trend on the Primary Flight Display (PFSB) but was momentarily distracted by birds in the takeoff path. Upon returning his attention to the instruments, he observed that the airspeed reading had dropped to zero. The pilot immediately initiated a rejected takeoff at V1, reaching a speed of 120 kt. The aircraft came to a stop on the runway using maximum reverse thrust and automatic braking. There were no injuries to the two crew members and no damage to the aircraft.
The investigation
Following the incident, the aircraft displayed a failure message related to the No 1 Air Data Reference. While initial troubleshooting involved swapping Air Data Inertial Reference Units, a subsequent takeoff attempt also resulted in a rejected takeoff due to the same airspeed issue. During a follow-up investigation, technicians performed a flush of the pitot probe as advised by the manufacturer. This process released three small insect larvae, each roughly the size of a grain of rice, from the No 1 pitot probe. It was determined that these larvae had likely entered the system while the aircraft was parked, as the manufacturer-supplied pitot covers do not provide a completely airtight seal.
Findings
- The primary cause of the airspeed indication failure was the presence of insect larvae within the No 1 pitot probe.
- The larvae likely entered the air data system during the long-term parking period, as the pitot probe covers used do not fully seal the probes.
- The aircraft had been stationary at Doncaster Airport since late March 2020.