UK investigators have determined that an Embraer ERJ-145 landed with its parking brake engaged before veering off runway 27 at Bristol.
The aircraft (G-CKAG) had been operating a BMI Regional flight from Frankfurt on 22 December 2017.
As it touched down in low-visibility conditions, some 486m from the threshold, the aircraft de-rotated unusually quickly, and the crew experienced difficulty in maintaining directional control despite rudder input.
UK Air Accident Investigation Branch analysis found the regional jet drifted right of the centreline before swinging to the left over the course of 280m and exiting onto rough ground.
“The crew identified that the parking brake was applied as the aircraft left the runway,” says the inquiry.
As it veered off, the jet continued for 120m, crossing a disused taxiway and fishtailing as it travelled across grass. All four main wheels sank up to their axles.
The inquiry states that overheated fragments of vulcanised rubber were discovered at various points along the runway, including a cluster of larger pieces about 400m from the touchdown point.
“Material evidence supported the conclusion that the aircraft landed with all the main wheel brakes locked on, which did not allow any rotation of the main wheels,” it says.
Investigators believe the parking brake was inadvertently set during the flight, when it was selected instead of the speedbrake. The levers have a similar shape and are located close to one another.
The error went unnoticed, says the inquiry, which points out that, owing to the weather conditions, the pilots were experiencing a busy cockpit environment and a high workload.
Thrust had been slightly increased as the aircraft yawed after touchdown, possibly in an attempt to regain control. But investigators believe this “exacerbated” the loss of directional control and “probably” led to the excursion.
BMI Regional subsequently revised its landing checklist to include a confirmation that the parking brake is off.