A Loganair Avions de Transport Regional ATR-42-500, registration G-LMRC performing flight LM-72 from Aberdeen,SC to Sumburgh,SC (UK), was climbing out of Aberdeen when the crew stopped the climb at about 10500 feet after multiple electrical faults occurred and both engines (PW127) showed zero torque. The aircraft descended to 5000 feet, maintained 5000 feet for about 7 minutes and subsequently positioned for a safe landing on Aberdeen's runway 34 about 35 minutes after departure.
The AAIB rated the occurrence a serious incident and opened an investigation.
The British AAIB reported: "During the departure climb the aircraft suffered a loss of multiple electrical systems and the flight crew reported that all the electronic instrument display screens went blank. The displays returned but some system faults remained. The aircraft returned to Aberdeen where it landed normally. A fault with the 1PA electrical contactor was found which had probably contributed to the severity of the incident, but the underlying cause(s) are still under investigation. The aircraft manufacturer published an Airworthiness Operator Message (AOM 2022/04) in October 2022 to recommend that all operators of this aircraft type perform an operational test of the 1PA contactor. The manufacturer is currently in discussions with EASA about publishing an Airworthiness Directive to mandate this initial test and a repetitive test." The investigation is ongoing.
On Aug 27th 2025 the AAIB released an interim statement reading:
This statement provides the mandated update on the third anniversary of a Serious Incident which remains under investigation. The Serious Incident involved an ATR 42-500, registration G-LMRC, after departure from Aberdeen Airport, on 27 August 2022. During the departure climb the aircraft suffered a loss of multiple electrical systems and the flight crew reported that all the electronic instrument display screens went blank. The displays returned but some system faults remained. The aircraft returned to Aberdeen where it landed normally. A fault with the 1PA electrical contactor was found which had probably contributed to the severity of the incident, but the underlying cause(s) are still under investigation. The aircraft manufacturer published an Airworthiness Operator Message (AOM 2022/04) in October 2022 to recommend that all operators of this aircraft type perform an operational test of the 1PA contactor. In October 2023 the European Union Aviation Safety Agency published Airworthiness Directive 2023-0181 which mandated the operational test of the 1PA contactor and for it to be repeated at 1,000 flight hour intervals.
During the past year additional ground testing and flight testing has been accomplished by the aircraft manufacturer to help understand the causes of the event. A final report will be published when the investigation has been completed.
On Mar 5th 2026 the AAIB released their final bulletin concluding the probable causes of the serious incident were:
There was clear evidence from the recorded data that electrical power had been lost from the DC STBY BUS, DC EMER BUS and DC ESS BUS (the emergency electrical network) for about 3 seconds. There was additional evidence from the flight crew and cabin crew reports that DC BUS 2 had lost power or suffered from an undervoltage condition for about 3 seconds. The only failure that could be identified from physical examinations and testing was the failure of contactor 1PA which was stuck in an intermediate position when energised.
This meant that it could not supply backup power to the emergency electrical network, so it was a contributory factor but not a cause of the loss of power.
A single failure involving the battery switch or the wiring between the battery switch, the MFCs, and ground, could explain a loss of the emergency electrical network but no such faults were found.
The failure occurred twice, in the air and then subsequently on the ground, when the landing light switches were turned off, but no faults with the landing light relays or lights were found.
The aircraft manufacturer discounted the high back EMF from the landing light relays as a potential cause due to it being too short in duration. No link between activation of the landing light switches and a loss of power from DC BUS 2 could be identified.
Two previous events on ATR 72-500 aircraft involving unexplained loss of flight display screens were related to turning the landing light switches off. And in two of the three previous screen loss events, replacing the 7PA battery switch reportedly resolved the issues.
Although the cause of the loss of the emergency electrical network on G-LMRC could not be determined, there were no further reoccurrences of the failure mode after the battery switch, landing light relays and 1PA contactor were replaced. This suggests that the battery switch and/or landing light relays may have had a part to play; however, a functioning 1PA contactor could have masked a reoccurrence of the underlying fault by supplying backup power.
Given the potential seriousness of a repeat failure, were it to last for more than 3 seconds and occur at night or in IMC conditions, the AAIB has made a safety recommendation to the aircraft manufacturer to continue investigating possible causes of the electrical failure.
The aircraft manufacturer and EASA have taken safety action to require testing and replacement of 1PA contactors that have failed.
The AAIB rated the occurrence a serious incident and opened an investigation.
The British AAIB reported: "During the departure climb the aircraft suffered a loss of multiple electrical systems and the flight crew reported that all the electronic instrument display screens went blank. The displays returned but some system faults remained. The aircraft returned to Aberdeen where it landed normally. A fault with the 1PA electrical contactor was found which had probably contributed to the severity of the incident, but the underlying cause(s) are still under investigation. The aircraft manufacturer published an Airworthiness Operator Message (AOM 2022/04) in October 2022 to recommend that all operators of this aircraft type perform an operational test of the 1PA contactor. The manufacturer is currently in discussions with EASA about publishing an Airworthiness Directive to mandate this initial test and a repetitive test." The investigation is ongoing.
On Aug 27th 2025 the AAIB released an interim statement reading:
This statement provides the mandated update on the third anniversary of a Serious Incident which remains under investigation. The Serious Incident involved an ATR 42-500, registration G-LMRC, after departure from Aberdeen Airport, on 27 August 2022. During the departure climb the aircraft suffered a loss of multiple electrical systems and the flight crew reported that all the electronic instrument display screens went blank. The displays returned but some system faults remained. The aircraft returned to Aberdeen where it landed normally. A fault with the 1PA electrical contactor was found which had probably contributed to the severity of the incident, but the underlying cause(s) are still under investigation. The aircraft manufacturer published an Airworthiness Operator Message (AOM 2022/04) in October 2022 to recommend that all operators of this aircraft type perform an operational test of the 1PA contactor. In October 2023 the European Union Aviation Safety Agency published Airworthiness Directive 2023-0181 which mandated the operational test of the 1PA contactor and for it to be repeated at 1,000 flight hour intervals.
During the past year additional ground testing and flight testing has been accomplished by the aircraft manufacturer to help understand the causes of the event. A final report will be published when the investigation has been completed.
On Mar 5th 2026 the AAIB released their final bulletin concluding the probable causes of the serious incident were:
There was clear evidence from the recorded data that electrical power had been lost from the DC STBY BUS, DC EMER BUS and DC ESS BUS (the emergency electrical network) for about 3 seconds. There was additional evidence from the flight crew and cabin crew reports that DC BUS 2 had lost power or suffered from an undervoltage condition for about 3 seconds. The only failure that could be identified from physical examinations and testing was the failure of contactor 1PA which was stuck in an intermediate position when energised.
This meant that it could not supply backup power to the emergency electrical network, so it was a contributory factor but not a cause of the loss of power.
A single failure involving the battery switch or the wiring between the battery switch, the MFCs, and ground, could explain a loss of the emergency electrical network but no such faults were found.
The failure occurred twice, in the air and then subsequently on the ground, when the landing light switches were turned off, but no faults with the landing light relays or lights were found.
The aircraft manufacturer discounted the high back EMF from the landing light relays as a potential cause due to it being too short in duration. No link between activation of the landing light switches and a loss of power from DC BUS 2 could be identified.
Two previous events on ATR 72-500 aircraft involving unexplained loss of flight display screens were related to turning the landing light switches off. And in two of the three previous screen loss events, replacing the 7PA battery switch reportedly resolved the issues.
Although the cause of the loss of the emergency electrical network on G-LMRC could not be determined, there were no further reoccurrences of the failure mode after the battery switch, landing light relays and 1PA contactor were replaced. This suggests that the battery switch and/or landing light relays may have had a part to play; however, a functioning 1PA contactor could have masked a reoccurrence of the underlying fault by supplying backup power.
Given the potential seriousness of a repeat failure, were it to last for more than 3 seconds and occur at night or in IMC conditions, the AAIB has made a safety recommendation to the aircraft manufacturer to continue investigating possible causes of the electrical failure.
The aircraft manufacturer and EASA have taken safety action to require testing and replacement of 1PA contactors that have failed.
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