Description

On 25 November 2019, an Airbus A330-300 (9V-SS) being operated by Singapore Airlines on a scheduled international passenger flight from Singapore to Yangon SQ998 on which line training for a Captain new to type was being conducted by a Training Captain in command made a tailstrike landing at destination after a manually flown day VMC approach. A Senior First Officer acting as a supernumerary ‘Safety Pilot' was occupying the principal flight deck observer seat. Although none of the 295 occupants were injured, substantial airframe damage was caused which rendered the aircraft un-airworthy pending repairs with some associated superficial damage to the runway surface. 

Investigation

A Serious Incident Investigation was carried out by the Myanmar Aircraft Accident Investigation Bureau (AAIB) assisted by relevant data downloaded from both the CVR and the FDR on behalf of the AAIB by the Singapore Transport Safety Investigation Bureau (TSIB). Airport Surveillance video recordings showing the touchdown were also available. 

It was documented that the 52 year-old Training Captain had a total of 19,080 hours flying experience of which 688 hours was on type. The 44 year-old Captain under training was making his first revenue flight on type whilst acting as PF and had a total of 13,026 hours flying experience of which just 2½ hours were on type. He had commenced type conversion training two months prior to beginning line flying and completed 20 hours simulator training satisfactorily and with no areas of weakness which had required additional training. It was noted that he had previously flown the Boeing 777 as Captain and before that had also flown the Airbus A340-300/500. He had not previously flown to Yangon. The 50 year-old Senior First Officer acting as Safety Pilot had a total of 9,522 hours flying experience of which 1,213 hours were on type.

What Happened

It was established that, following an uneventful flight of approximately an hour from Singapore, after disconnecting the AP at 2150 feet agl, the PF Captain undergoing type training had made a stabilised approach to the 3413 metre-long runway 21 in undemanding weather conditions before initiating the landing flare at 100 feet agl. Almost immediately he had done so, the Training Captain said “flare” twice and the PF increased his initial pitch input with the Training Captain responding with “alright and good” as both main landing gear weight on wheels (WOW) switches were briefly activated by a bounced initial runway contact at +7.21° pitch which was followed by a further two seconds with both left and right main gear airborne before a second touchdown.

Two seconds after the second main gear touchdown, both thrust reversers were deployed and after a further second, the ground spoilers were extended. During this time, the PF significantly increased the pitch command on his sidestick despite the pitch already being a recorded +8.61° as the thrust reversers were deployed. The pitch command led to the pitch increasing to its maximum of +10.72° by which time both the thrust reversers and the ground spoilers were fully deployed. Fifteen seconds after being deployed, the thrust reversers were stowed and two seconds after that, the nose landing gear made contact with the runway for the first time.

Just over half a minute later, the aircraft turned left off the runway with the flight crew unaware that a tailstrike had occurred and was taxied to its assigned parking position. Ground maintenance personnel carrying out a post flight inspection subsequently informed the flight crew that they had observed damage to the lower tail section which upon a more detailed inspection was found to be dented, scratching and torn fuselage skin over five frames and bending of a consecutive 14 frames in the same area. Inspection of the runway surface found corresponding superficial damage to the runway surface. This indication of fuselage runway contact was on the runway centreline at approximately 900 metres beyond the runway threshold and was recorded as having extended for 56 metres and been 0.7 metres wide.     

Why it Happened

During interview, it became apparent that when the Training Captain called out “hold the attitude” (several times) he had expected this to be interpreted as an instruction to maintain the current pitch attitude whereas the PF had understood this call to indicate that the aircraft was “losing its pitch attitude” and had consequently responded by making an increase pitch command which had cumulatively led to the excessive pitch and the resulting tail strike. 

The operator’s SOPs required that the PM, in this case the Training Captain (or potentially the safety pilot) to announce ‘PITCH PITCH’ if the pitch reaches 7.5° which did not occur despite FDR data showing that 7.5° had been exceeded three times during the 12 seconds immediately prior to the tailstrike. During interview, the Training Captain recalled that he had been “paying attention to the external environment to ensure that the PF controlled the aircraft to maintain it along the runway centreline” and in the absence of the required callouts, it appeared that he had not noticed that the PFD pitch attitude had exceeded 7.5°. He also stated that he had not at any stage considered taking over as PF or providing dual inputs since he had considered that the PF was reacting appropriately to his instructions and that “the safety of the aircraft was not gravely compromised”. He further advised that although he had on previous occasions during line training flights taken over control or provided dual sidestick inputs, this had “usually involved Second Officer trainee pilots”.  

It was noted that the optional tailstrike prevention system, which provides an aural warning if the pitch angle during takeoff or landing is predicted to exceed 9° and below 400 feet agl adds a tail strike pitch limit indicator to the PFD was not installed on the aircraft. 

The Findings of the Investigation were formally documented as follows:

• During the event landing, the Training Captain repeatedly gave instructions to the PF to “hold the attitude” with the intention for the pitch attitude to be maintained. 
• The PF’s understanding of the phrase “hold the attitude” was that the aircraft was losing its pitch attitude, hence he provided pitch up input to his sidestick. 
• The Training Captain did not announce “PITCH PITCH” in the three instances when the pitch angle of the aircraft exceeded 7.5 degrees, as required by the operator’s procedures.   
• The Training Captain did not take over the controls or provide dual input to control the aircraft despite repeating his instructions “hold the attitude” four times over 12 seconds.

The Primary Cause of the Serious Incident was formally documented as “during the landing, the pitch up inputs by the PF caused the aircraft to reach a maximum pitch angle of 10.7 degrees, resulting in the tail strike”. 

Two Safety Recommendations were made as a result of the Investigation as follows:

• that Singapore Airlines ensure that its instructor pilots have greater urgency to take over controls or provide dual inputs to control the aircraft, especially during landing.   
• that Singapore Airlines ensure that pilots performing pilot monitoring duties use standard phraseology such as “PITCH PITCH” when the pitch angle of the aircraft exceeds 7.5 degrees during landing, as required by its procedures.

The Final Report of the Investigation was published on 11 May 2021.

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