The safety of air passengers could be at risk because pilots who did not work during lockdown are out of practice, air accident investigators have warned, after a "serious incident" in which a Boeing 737 hurtled towards the ground at Aberdeen Airport.
The Air Accidents Investigations Branch (AAIB) issued an alert following the incident on the 20th anniversary of 9/11, in which a Tui flight from Spain with 67 passengers and six crew on board unexpectedly gained speed and descended rapidly after pilots were told to abort a landing.
Although they managed to stabilise the aircraft and later landed it normally, the AAIB said there was “clearly a possibility” that a lack of flying time had contributed to a situation that could have resulted in one of Britain’s worst air disasters.
Pilots did not initially notice the “significant deviation from the expected flight path” and a dangerous increase in speed was “not corrected in a timely manner”, an AAIB bulletin issued on Thursday said.
While pilots are required to conduct regular take offs and landings to ensure they can fly safely, many airlines have been forced to meet the requirement using simulators as Covid-19 travel restrictions have meant many flights have been grounded.
While the reasons for the incident are still being investigated, the AAIB raised the prospect that pilot error, due to a lack of recent flying experience, could have been to blame.
The co-pilot in the Aberdeen incident was on only his fourth flight in 11 months, while the 56-year-old commander had just 67 hours of flying time over the previous 90 days.
While both pilots had conducted several sessions on a simulator over the previous 18 months, the AAIB said these could fail to replicate the “real world environment” and unexpected situations, such as being told to abandon a landing.
“The real-world environment creates different demands on crews, and it is possible that this event illustrates that lack of recent exposure to the real-world environment can erode crews’ capacity to deal effectively with those challenges,” the AAIB said.
“Regulators have been concerned that pilots returning to the flight deck following extended periods without flying could be at risk of performing below their normal standard during their first few flights.
“Although this investigation has not established a link between this event and a lack of line flying, this Special Bulletin is published for awareness and because a link is clearly one possibility.”
High rate of descent 'not corrected in a timely manner'
The Palma to Aberdeen flight was coming in to land when the pilots were asked to abandon a landing and conduct a “go-around” so that a search and rescue helicopter could take off instead.
The plane began to gain altitude, before it began to descend at a rate reaching 3,100 ft per minute, meaning it would have plunged into the ground in less than a minute had the pilots not taken action.
The plane’s altitude dropped to just 1,780ft above the ground, when it should have been at 3,000ft, before the crew corrected the error and were contacted by alarmed air traffic controllers. The plane also gained speed unexpectedly during the incident.
They were relying on their instruments during the incident due to weather conditions which meant they were unable to see.
A go-around on a two-engine plane can be a difficult manoeuvre to perform because they were often unexpected and relatively rare, the AAIB said.
Referring to the Aberdeen incident, the AAIB said: “The aircraft descended from close to 3,000 ft for 57 seconds before a climb was re‐established, and this represented a significant deviation from the crew’s expected flightpath.
“There was a high rate of descent, which was reducing the aircraft’s separation from terrain, and an uncommanded and undesirable increase in airspeed that were not corrected in a timely manner.”
A spokeswoman for Tui said: "We have worked closely with the AAIB throughout this investigation and will continue to do so until a final report is published.
"The health and safety of our customers and crew is always our primary concern and we would like to reassure all customers and crew that the safety of the aircraft was assured throughout this flight.
"We provide training that exceeds all regulatory requirements, this includes the additional refresher and recency training completed by all pilots prior to flights being undertaken. The industry has faced unique circumstances with the grounding of many planes and crew due to the Covid-19 restrictions."
