Introduction
On 27 July 2015, a Boeing 747-400F cargo aircraft operated by Cathay Pacific Airways Ltd., registration B-HUL, was involved in a serious incident during landing at Indira Gandhi International Airport, Delhi. The aircraft was on a scheduled cargo flight from Hong Kong to Delhi. There were no passengers on board, and the two crew members (Pilot-in-Command and Co-Pilot, both ATPL holders) sustained no injuries.
History of Flight
The flight departed Hong Kong at 0645 UTC and proceeded uneventfully. Approach and descent to Delhi were normal, with no cockpit indications of any abnormality. The aircraft landed on runway 10 at 1240 UTC. During taxi-in, the ground controller informed the flight crew that a part had separated from the aircraft during landing. After parking, the crew requested a walk-around inspection (WAI), which initially revealed no missing parts. The crew then fully extended the flaps, and a subsequent WAI identified that the left wing inboard trailing edge fore-flap was missing. The separated fore flap was later recovered from the runway, broken into three pieces. A runway sweep found no other debris.
Damage to Aircraft
The left inboard trailing edge fore-flap detached from its mounting. The bull nose (approximately 24 inches from the inboard edge) was missing. The inboard mid-flap cut-out was ripped off. Two dents and a crease with skin puncture were found on the mid-flap upper surface. The No. 4 flap track inboard fore-flap carriage assembly was broken, and the No. 3 flap track carriage assembly was intact but had a broken linkage eye end attached. The linkage (mid-flap track) was sheared off, and the detent roller of the No. 4 sequence carriage was broken and detached. Additional damage included punctures to the bull nose upper surface and skin, deformation of the linkage cut-out bottom angle bracket, and minor scratches on the aileron attachment frame. No other damage occurred.
Personnel Information
The Pilot-in-Command, aged 43, held an ATPL (Hong Kong) and had 9,772 total flying hours, with 4,635 hours on type. The Co-Pilot, aged 45, also held an ATPL (Hong Kong) and had 9,216 total flying hours, with 2,990 hours on type. Both were qualified on the B747-400 and had recent proficiency checks.
Aircraft Information
The B747-400 is a subsonic, medium-range transport aircraft certified in the transport (cargo) category. Its trailing edge flap system comprises triple-slotted flaps on each wing, providing additional lift during takeoff, approach, and landing. The flaps are hydraulically powered with electric backup, controlled by a flap control lever and flap control units. The inboard and outboard flaps are positioned by independent drive systems, with torque tubes and gearboxes transmitting power to ball screw drives.
Conclusions
The Committee of Inquiry concluded that the incident resulted from failure of the inboard trailing edge fore-flap No. 4 flap track carriage assembly due to fatigue. No other factors were identified.
Probable Cause
The probable cause of the incident was failure of the inboard trailing edge fore-flap No. 4 flap track carriage assembly due to fatigue.