The pilots union has reacted to an interim report which revealed that a Tui aircraft was involved in a “serious incident”.
It involved a Boeing 737-800 with 67 passengers on board occurred during a “go-around” at Aberdeen airport on September 11 on a flight from Palma.
Air accident investigators are examining whether a lack of flying hours due to operations being paused during the pandemic was a contributory factor.
A special bulletin covering the incident was published by the Air Accidents Investigation Branch (AAIB) to “raise awareness” of the event.
It said that the aircraft “deviated significantly from the expected flight path, initially climbing, but just before it reached the cleared altitude began to descend”.
The Tui crew were told by air traffic controllers that they might have to discontinue their approach and “go around” because a search and rescue helicopter needed priority to take off.
The aircraft was told to climb from 2,600ft above sea level to 3,000ft and turn left before returning for a second approach.
As it reached 3,000ft the 737 began an unexpected descent peaking at 3,100ft a minute flying towards an area of higher terrain 900ft above sea level.
During the recovery, the aircraft speed reached 286 knots, instead of the 200 knots selected by the crew.
The AAIB said: “The pilots, like many other airline pilots, had not flown for substantial periods during the 18 months before this incident.
“Although the investigation has not established a link between this serious incident and a lack of recent line flying, it is clearly a possibility.
“This special bulletin is published to raise awareness of this event and highlight that go-arounds from intermediate altitudes on an approach can provoke errors because they are not practiced frequently.”
Investigators acknowledged that airlines have faced “significant challenges in the last 18 months to keep crews current”.
The reported added: “Whilst there are legal requirements for crews to complete three take-offs and landings within 90 days, there are no regulatory requirements laid out for crews to have actually operated the aircraft, especially on commercial flights.
“Operators have had to adapt and develop their own programmes to ensure that crews are prepared and competent to fly, often after significant periods away from the aircraft.”
While flight simulators have been used to try and maintain crew skill levels when operating in both normal and emergency situations, “the challenge has been, and is, to try and represent the real world of flying in a simulated environment.
“It can be difficult in the simulated environment to replicate moments of high crew workload caused by the effects of ATC instructions and background communications, the presence of other aircraft in the area, poor weather and other operational pressures.
‘The safety benefits of simulator training are well established. However, 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.
“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.”
The AAIB added: “There are no specific recommendations at this stage. The investigation continues to examine all pertinent factors which might have contributed to this serious incident.”
A final report will be published “in due course”.
The British Airline Pilots’ Association responded by urging people to “respect the independence and objectivity” of the AAIB and “to avoid speculation before they complete their work”.
Balpa noted that the reason for publication of this special bulletin is that the AAIB wants to alert the industry to the decreased operational and safety resilience resulting from widespread industry shutdown during the pandemic.
General secretary Martin Chalk said: “Just like riding a bike, if you climb back on after a period away, it only takes a short practice to be able to manipulate the bike – set off, turn and stop – just as well as you had before. However, your roadcraft – the anticipation of what others are going to do, for example – takes time and practice to reacquire.
“Although many of our airlines have recognised this and provided extra practice and simulator time, there have also been commercial pressures which act in the opposite direction.
“This is why Balpa has been calling on the government to make available a winter resilience fund to allow our cash strapped airlines the ability to provide extra training and experience to avoid any degradation of aviation’s enviable safety standards.”
Balpa has already called for both the government and airlines to recognise that the minimum return to work training and experience regulations “were designed to return individuals who had been grounded for extended periods of time to the well-oiled machine which is the normal civil aviation system”.
The association added: “No-one anticipated a situation where large parts of the system would have been effectively shut down for 18 months or more and therefore system resilience would be eroded.
“Consequently, many individual pilots and their airlines have been trying to afford themselves more time and practice to develop higher levels of resilience.”
A Tui spokesperson 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.”