Second A319 inertial reference shock attributed to runway surface at Edinburgh

Inquiry believes recent resurfacing at Scottish capital airport will reduce risk of further incidents.
UK investigators believe a surface irregularity on Edinburgh airport’s runway caused an inertial reference system upset to a British Airways Airbus A319 after take-off – four years after a similar incident on the same runway.

The A319 had been departing runway 06 on 30 October when it ran over several runway centreline lights and a “larger irregularity”.

This generated a vertical shock load from the nose-gear into the airframe and avionics rack housing the air data inertial reference units (ADIRU).

Just after take-off the autopilot and autothrust disengaged and the jet experienced a loss of position information, with a “severe drift” from the inertial reference system, says the UK Air Accidents Investigation Branch.

Although the crew had managed to re-engage the autopilot and autothrust, and proceeded to London Heathrow using radar vectors, the systems disconnected again during the approach.

The crew also encountered a problem with the rudder travel limiter system, and executed a go-around before landing safely. None of the 138 occupants was injured.

According to the inquiry, the precise source of the shock load during the take-off roll “was not determined”, but the cockpit-voice recorder captured two large sound impulses from the nose-gear.

The previous incident at Edinburgh – also involving a British Airways A319 – occurred in August 2021, and was attributed to a jolt from an uneven surface repair.

Edinburgh airport’s operator has overseen a £30 million ($40 million) resurfacing of runway 06/24 which commenced just days after last October’s event, and was completed in April this year.

The inquiry says the resurfacing will “minimise the probability” of surface irregularities affecting other flights.

It states that the particular Northrop Grumman ADIRU model fitted to the incident aircraft was known to be “sensitive” to large vertical acceleration forces.

Investigators state that seven other similar occurrences have been recorded since the August 2021 event, but the issue is known to Airbus, and the ADIRU model involved has not been fitted to new aircraft since 2015.

“Since the shock loads encountered are considered to be outside of the certification standards required of the ADIRU, and the [nose-gear] had been serviced in accordance with the [aircraft maintenance manual], no further manufacturer action has been taken,” the inquiry adds.

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