Updated: May 3, 2022
**EDITORIAL NOTE Somehow I got the date all wrong🙄 The incident happened on the 13th of May, as the title of the blog indicated. I planned to write a blog for the 3rd, somehow got the date wrong 🥴
A Boeing 787 was operating a scheduled passenger flight from Singapore to Melbourne (Australia) on this day in 2017. Onboard the aircraft the two pilots, nine cabin crew, and 231 passengers. The captain was the Pilot Monitoring (PM) and the co-pilot was Pilot Flying (PF) for the flight.
The failed #6 Mainwheel (Left looking forward, right looking rearward (Source &© ATSB)
At 13.25 UTC the engines were started during the pushback, after which the crew received taxi instructions to runway 20C. After a short taxi, the aircraft was lined up on the runway 7 minutes after the engines were started. With the flaps set to flaps 5 for takeoff, a take-off weight of 191 tons the Rotation Speed (Vr) was 169 knots. The acceleration altitude was 3000 feet (the altitude at which the flaps would be retracted from Flap 5 to Flap1 1)
After an uneventful take off the PF called for "Flaps 1" around 3000 feet, which was actioned by the PM. Shortly after that action an EICAS (Engine Indicating and Crew Alerting System) message "FLAPS DRIVE", indicating a fault in the flaps system. ATC was contacted and the aircraft leveled off at 6000 feet, and entered a holding pattern, while the relevant checklist was completed. At that time the roles in the flight deck were changed, the captain became the Pilot Flying (PF) and the first officer became the Pilot Monitoring (PM).
The cabin crew and passengers were briefed accordingly about their intentions and a return to Singapore was prepared. The landing speeds would be higher than normal, due to the fact the flaps were stuck at Flaps 1 (Vref 195 knots at a landing weight of 188 tons. The following landing was uneventful and the aircraft taxied to the gate under its own power. While at the stand engineers inform the crew that they had found damage to the left-wing and one of the mainwheels. Ground handling staff a short while later informed the crew that rubber debris was found on the runway.
The damaged flap (left) and broken flap torque tube (right) (Source &© ATSB)
An inspection of the aircraft revealed the following damage;
#6 mainwheel tread had separated
WIng panel above the #6 mainwheel was punctured
The trailing edge of the left inboard flap was cracked
The flap drive torque tube was broken
.A broken torque tube will interrupt the flap drive system for flaps outboard of the break. Consequently, a change in the flap setting will trigger a misalignment between the flaps, causing a "FLAP DRIVE" message to appear on the EICAS.
The incident was investigated by the Australian Transport Safety Bureau. They concluded their report (available by clicking here) with the following findings;
The number 6 wheel tire experienced shoulder step-wear, which led to cracking and undercutting of the tire tread and subsequent delamination of the number 6 tire, which occurred in less than the normal average life cycles.
Debris from the delaminated tire penetrated the left underwing panel and damaged the flap torque tube, resulting in an asymmetric flap condition when the flaps were commanded to retract.
When retracting the wing flaps, the crew received a flap drive fault indication, which resulted in a return to the departure airport and a high-speed overweight landing.
Following the damage to the flap torque tube, the aircraft protective systems operated as designed and the flight crew completed the checklist as published.
Generic tire construction (Source & © Michelin)