B789, London Heathrow UK, 2020
B789, London Heathrow UK, 2020
On 9 February 2020, the tail strike prevention system on a Boeing 787-9 was annunciated during takeoff from London Heathrow in gusting crosswind conditions. Permission to hold at 6000 feet to conduct the response procedure was given and since this procedure did not permit pressurisation, an overweight return to land followed. The Investigation found that although the tail strike protection system had returned the pitch rate to the correct one after an exceedence just before commencing rotation, lateral control inputs then resulted in a decrease in lift resulting in the tail contact angle being reached whilst still on the runway.
On 9 February 2020, a Boeing 787-9 (VH-ZND) being operated by Qantas on a scheduled international passenger flight from London Heathrow to Perth received a tail strike prevention system annunciation as it took off in day VMC. The required response procedure included not pressurising the aircraft so an overweight return to land followed. The only damage to the aircraft was the abraded tail strike detection sensor.
An Investigation was carried out by the UK AAIB using relevant recorded data from both the FDR and the 787 CPL system and contemporaneous meteorological data both observed and derived. It was noted that the augmented flight crew was led by a 52 year-old Captain who had a total of 13,568 hours flying experience of which 562 hours were on type with just 60 hours flown in the previous 90 days.
It was established that following a normal engine start and taxi the aircraft, at almost its MTOW, was correctly configured for a flap 5 takeoff from runway 27R. Takeoff clearance was given with the surface wind reported as 220° at a mean speed of 28 knots gusting to 44 knots. During the takeoff roll there were airspeed fluctuations consistent with the gusty conditions but acceleration was normal. At 160 KIAS, a strong gust caused the airspeed to increase rapidly to 175 KIAS, just above the calculated 172 knot VR and the Captain began the rotation by moving the control column rearward by a maximum of 9.8° to achieve a 4° pitch up at a pitch rate of just over the recommended 2° per second.
The control column was then moved slightly forward but the recorded pitch rate increased to 3.2° per second and the airspeed then started to increase. This coincided with the control column being moved rearwards again whilst the control wheel deflection was increased from 20° to 33° left of neutral which resulted in roll spoiler deployment to increase from 5° to 20°.
The pitch attitude increased through 6.3° nose-up with the pitch rate nearly 4°/s which was calculated as putting the tail clearance from the runway at 4.5 feet. This caused the tail strike prevention system to move the elevators so as to reduce the pitch rate to just over 2° per second. The recorded data showed the pitch attitude at takeoff as approximately 9.7° and the tail height as just less than 2 feet, sufficient to cause abrasion to the tip of the EICAS-linked tail strike detection sensor.
The crew elected to hold to the southwest of Heathrow at 6,000 feet whilst they carried out the relevant checklist from the QRH. This advised that the aircraft could not be pressurised and so preparations were made to return to Heathrow. The aircraft was radar-vectored for an approach to Runway 27L at Heathrow where an overweight landing was made. A subsequent engineering inspection found no further damage had occurred to the aircraft.
After independently analysing the available FDR and CPL data, Boeing concluded that the automatic spoiler deployment caused by the increase in into wind aileron had decreased lift and necessitated a higher pitch attitude to achieve lift off.
The Investigation noted that the pitch attitude reached of 9.7° is the attitude at which tail contact is likely to occur with the wheels on the runway and the landing gear oleos extended. A normal 787-9 pitch attitude for takeoff is between 6° and 7.5° which gives a minimum tail clearance height of 29 inches (74 cm). The normal tail clearance profile is shown below.
The Normal tail clearance profile during rotation VR and lift off VLOF. [Reproduced from the Official Report]
The Conclusion of the Investigation was formally recorded as:
"During conditions of strong, gusty winds, a high pitch rate near lift-off caused the tail strike prevention system to activate. The tail contact angle was reached, and the crew received an EICAS tail strike message."
The Final Report was published on 12 November 2020.