AT43, vicinity Glasgow, UK 2012
AT43, vicinity Glasgow, UK 2012
On 22 February 2012, the crew of an ATR 42 making a radar-vectored ILS approach to runway 23 at Glasgow at night allowed the airspeed of the aircraft to reduce and a stall warning followed. Corrective action then led to an overspeed and further corrective action almost led to a second stall warning. The Investigation concluded that SOPs were not followed, monitoring was ineffective and crew cooperation during recovery was poor. It was considered that crew performance may have been affected by inadequate rest prior to a night flying duty period.
On 22 February 2012, an ATR 42-300 on a night scheduled cargo flight from Newcastle to Glasgow, flying level on the Instrument Landing System (ILS) LOC in Instrument Meteorological Conditions (IMC) to intercept the ILS GS, lost airspeed and the stall warning was activated. The recovery was commenced normally but speed in manual flight was then first allowed to increase above the deployed flap limit speed and then to reduce to the extent that a second stall warning was almost triggered before a stabilised approach was regained as the aircraft approached 3nm from touchdown.
The investigation by the UK AAIB established that the incident flight was the final one of a sequence of three, the first two of which had involved operating from Manchester to Paris CDG to Newcastle. The aircraft commander had acted as PF for the first sector and then again for the incident flight. The CVR record showed that during the Newcastle-Glasgow sector, he had initiated conversation on a range of non operational topics both above and below FL100, the latter being contrary to the operator’s sterile flight deck policy which required that when below FL100, only operational matters were to be the subject of conversation. It was observed that the Co-Pilot’s responses had been “polite but brief” and also that both pilots had missed or mis-heard ATC communications during the flight and some SOPs besides the sterile flight deck policy had not been adhered to.
En route, icing conditions ahead required the selection of anti icing equipment on but upon receipt of the destination weather, the Co-Pilot noted that it would be possible to perform the approach using the non-icing reference speed which was 15 knots lower than the corresponding icing reference speed. However, it was noted from the CVR that in the subsequent briefing by the commander had not clarified which speeds were to be used and had also ignored other topics stipulated in Company procedures. The flight received radar vectors to the ILS 23 with the AP engaged and crew awareness of high ground in the vicinity of the approach track and vertical profile. Just inside 10nm and at 3000 feet QNH and 215KIAS, power was reduced to about 15% and when a further descent to 2000 feet was given together with clearance to establish on the ILS LOC and GS in that order, VS mode was engaged. When the AP levelled the aircraft at 2000 feet QNH with the LOC captured and the GS just above, power was reduced to 3% and, unnoticed by either pilot, the airspeed steadily decreased as the AP attempted to maintain 2000 feet. The stick shaker then activated with the aircraft at approximately 1700 feet agl, at 111 KIAS and with an angle of attack of +11.2°. The AP disconnected and the PM remarked sharply in response to which the PF pitched down and increased power. However, the transition from stall warning recovery to the ILS approach was mishandled and the aircraft then went above the GS and the maximum speed for the deployed flap 15 (170 KIAS) was exceeded. During the response to this, the aircraft speed reduced to 111 KIAS and the angle of attack almost reached the point which would have triggered a second stall warning. Eventually, at a range of 3.4nm from the runway, with the aircraft stabilised and fully configured for landing, the AP was re-engaged and the rest of the approach and landing were completed without further event until touchdown when a nacelle overheat warning activated. The crew did not action the associated procedure.
An engineer met the aircraft and the commander then advised that there had been a problem with the AP to which the Co-Pilot stated that there had been no such problem and that the FDR record should be preserved. No entries were made in the Aircraft Technical Log concerning the stall warning, flap over speed or nacelle overheat and no formal incident reporting action was taken. Subsequently, and when off duty, the Co Pilot had contacted the Company and an internal investigation, which eventually led to the Irish AAIU being informed the following day and the UK AAIB the day after that, was commenced.
Overall, the Investigation concluded that there was evidence that during the incident flight “the commander was not operating in a manner consistent with the company’s procedures:. It was considered that although the commander considered that he had been “well rested” prior to commencing duty, the nature of the duty and the fact that he had driven for nearly 3 hours prior to starting duty at Manchester the previous evening, mean that it was possible that, “knowingly or not, he may have been tired or fatigued”. It was also considered that the manner in which the commander had responded to monitoring calls made by the Co-Pilot had been “likely to have discouraged further input at a time when effective cross-cockpit monitoring would have assisted in ensuring safe flight” and that this effect would have been exacerbated by the diminished quality of pre flight rest achieved by both pilots.
The formally stated Conclusion of the Investigation was that:
“The appropriate airspeed was not maintained during the approach because standard operating procedures were not observed, monitoring was not effective and there was diminished crew cooperation during recovery actions. The performance of the crew may have been affected by tiredness or fatigue, caused by diminished quality of rest in the period prior to flight duty.”
The Final Report of the Investigation was published on 8 August 2013. No Safety Recommendations were made but appropriate Safety Action by both the aircraft operator and its FDR validation contractor in relation to FDR data readout requirements was reported to have been taken.