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ASN Wikibase Occurrence # 192390
Last updated: 23 July 2018
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Date:21-DEC-2016
Time:17:33 UTC
Type:Silhouette image of generic AT72 model; specific model in this crash may look slightly different
ATR 72-500 (72-212A)
Owner/operator:Aurigny Air Services
Registration: G-COBO
C/n / msn: 0852
Fatalities:Fatalities: 0 / Occupants: 65
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:near Guernsey, Channel Islands -   United Kingdom
Phase: Initial climb
Nature:Domestic Scheduled Passenger
Departure airport:Guernsey Airport, Channel Islands (GCI/EGJB)
Destination airport:Manchester Airport (MAN/EGCC)
Investigating agency: AAIB
Narrative:
Aurigny Air Services flight GR678, an ATR 72-500, suffered a brief loss of control due to ice accretion on the aircraft while in the climb after takeoff from Guernsey Airport, Channel Islands, U.K.

The flight crew reported for a four-sector duty period involving flights from Guernsey to Bristol and return, and Guernsey to Manchester and return. The first two sectors were without incident.
During the turnaround at Guernsey, for the flight to Manchester, the crew had noted that a frontal weather system would be encountered during the flight over the English Channel, with associated cloud, precipitation and moderate icing conditions.
The aircraft took off at 1718 hrs with a takeoff mass of 21,937 kg. The co-pilot, who had recently qualified on type, was undergoing line training under the supervision of the commander, who was a line training captain. The commander was PF for this sector with the co-pilot PM. Soon after takeoff hi[gh] bank was selected, the autopilot engaged and the aircraft was cleared to climb to FL170. As the aircraft climbed at 170 kt on a northerly track it encountered the weather front and began to accrue airframe icing. Anti-icing systems were activated as the aircraft climbed through 5,300 ft, followed by de-icing systems when actual airframe icing was encountered as the aircraft climbed through FL090. The aircraft was flown at or above the Minimum Icing Speed (this speed, known as the ‘red bug’ speed was 165 kt for the aircraft mass at the time). The crew conducted a review of the Quick Reference Handbook (QRH) ‘SEVERE ICING’ procedure’s memory items in the checklist (but not the notes on Detection) in case it became necessary to perform it later.
As the aircraft passed about FL110, degraded perf [ormance] and increase speed caution messages illuminated. Upon switching the external icing light to on, to check the extent of the ice on the ice evidence probe, the commander commented "…we’ve got a bit [of icing] haven’t we". The commander made a reference to the QRH checklist for the caution, but it was not actioned; however, he did initially increase the target IAS to 175 kt (red bug +10 kt), during which the rate of climb reduced from 420 ft/min to about 25 ft/min and the caution extinguished.
The commander noted that the aircraft was "not climbing very well" and acknowledged that the QRH procedure required an increase in speed to red bug +10 kt but he considered that, as the aircraft was at that moment flying level, it was safe to return the target IAS to 165 kt. This resulted in an increase in the aircraft’s pitch attitude and a climb to the selected level. As he adjusted the speed he commented "…just see if we can get above [the clouds]." The autopilot remained engaged in the IAS and heading capture modes.
About one minute later the increase speed caution message illuminated again. At this point the commander commented "we are picking up quite a bit of ice actually", later adding that it was the first time he had encountered this [deterioration in climb performance]. At this point the aircraft’s rate of climb was about 200 ft/min. The target IAS was again increased to 175 kt. To achieve this the aircraft initially descended, achieving a maximum rate of -540 ft min and descending almost to FL120, where the aircraft levelled off momentarily.
The target IAS was then reduced back to 165 kt, which initiated a further climb.
As it was apparent that the aircraft had insufficient performance to reach its cruising level of FL170, the crew made a request to ATC to level off at FL130 so the aircraft could accelerate, before resuming the climb. ATC approved this and instructed the crew to proceed direct to reporting point NORRY, a change in heading of about 10°. This was achieved by re-programming of the Multifunction Control Display Unit and selecting lnav. The aircraft experienced an in-flight upset as it levelled off and turned towards NORRY. The autopilot had been engaged throughout the climb until that moment.
Recorded data showed that at the point of the upset the aircraft initially rolled left to 32° the autopilot disengaged, before rolling right to 38°. It then rolled left again, reaching attitudes of 73° in roll and 16° nose-down in pitch.
Upon the commander’s instructions the co-pilot actioned the upset recovery items when instructed to do so by the commander. These included extending the flaps to Flap 15.
The commander recovered the aircraft to controlled flight at FL130, having descended through about 1,000 ft. During the recovery, pitch increased from nose-down to a nose-up attitude of 19°, before reducing to a normal value. During these pitch and roll oscillations, the IAS varied between 190 kt and 123 kt.
During the manoeuvres the co-pilot transmitted a MAYDAY call and, once control had been regained and the situation assessed, the decision was made to return to Guernsey. The aircraft subsequently landed at Guernsey without further incident and no injuries were reported.
The aircraft was withdrawn from service pending a maintenance check. Functional tests were conducted on the aircraft’s ice detection, anti-ice and de-ice systems as well as the Aircraft Performance Monitoring (APM) system. No abnormalities were found, but analysis of the FDR data indicated that, during the recovery manoeuvre, the extended flaps sustained an overspeed of 5 kt. The aircraft was subsequently returned to service.

Conclusion:
The aircraft suffered an in-flight upset at FL130 after accruing airframe icing during the climb, resulting in the adverse aerodynamic effect of ice build-up on the wings. The crew were presented with a degraded perf caution but did not action the relevant checklist because they focused on climbing out of the icing conditions. The IAS was not maintained at or above red bug +10 kt and control of the aircraft was lost when a turn was initiated in the lnav mode of the flight director


Weather reported about the time of the incident:
EGJB 211720Z 23006KT 4500 -RADZ BR FEW003 SCT007 BKN048 11/11 Q1022
EGJB 211820Z 24005KT 6000 -DZ SCT004 BKN018 10/09 Q1022 RERA REDZ

Sources:

1. https://www.bea.aero/en/investigation-reports/notified-events/detail/event/serious-incident-to-an-atr-72-operated-by-aurigny-air-services-on-21122016-near-guernsey-island-investigation-led-by-aaib-united-kingdom/

Accident investigation:
cover
  
Investigating agency: AAIB
Status: Investigation completed
Duration: 12 months
Download report: Final report


Images:


Revision history:

Date/timeContributorUpdates
28-Dec-2016 19:00 harro Added
28-Dec-2016 19:06 harro Updated [Narrative]
28-Dec-2016 19:10 harro Updated [Narrative]
15-Sep-2017 23:07 Dr. John Smith Updated [Source, Narrative]
17-Dec-2017 20:35 harro Updated [Time, Total occupants, Source, Narrative]

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