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10 January 2017

Thomson Airways flight BY-6248, from Bournemouth (England) to Tenerife South (Spain) was operated by a Boeing 737-8K5, G-FDZY on this day in aviation history in 2017. Onboard 177 passengers and 7 crew for the (approximately) 4-hour flight to the sunny Spanish Island in the Atlantic ocean.

Flight preparation including boarding all went smoothly, the 2 CFM56-7B27E engines were started and the aircraft taxied to Bournemouth’s runway 26 for take off. The take-off run was uneventful up to the moment when Vr (Rotation Speed) was reached and the aircraft was rotated by the pilot flying. Right at that time, a seagull was ingested into the lefthand engine. A change in engine sound was immediately apparent and the engine vibration indication had increased simultaneously. Also, a light airframe vibration was observed. The engine kept on producing the selected take-off thrust without any of the engine limitations being exceeded. The crew continued the climb to 4000 feet ASL (Above Sea Level), where they levelled the aircraft off and assess the situation. ATC had been informed and was asked for the runway to be inspected.

With the aircraft flying level at 4000 feet, the thrust required from the engines was less and the vibration had noticeably reduced, with all other engine parameters with Aircraft Flight Manual limitations. The crew contacted their operations and maintenance departments by radio and the decision was made to abort the flight to Tenerife and divert to London Gatwick, which had a longer runway than Bournemouth. While in the holding the crew prepared themselves and the aircraft for the diversion. The cabin crew was briefed and a PA (Public Address) announcement was made to the passengers. One of the preparations the crew completed was to make a contingency plan in case the vibration would increase, they reviewed the “HIGH ENGINE VIBRATION CHECKLIST” in case the vibration would increase again, for example, if a go-around would have to be flown at Gatwick. It had become apparent to the crew that a thrust increase meant an increase in vibration level. The plan was to make an overweight landing (landing with the aircraft actual Gross Weight above the Maximum Landing Weight) with the Flaps set to 15, the landing performance (data) was confirmed as satisfactory and the flare technique and deceleration were briefed. In the event of a Go-Around, the flaps would be selected to the non-standard flap 1 setting.

Schematic representation of CFM56-7B fan-blade installation, for reference only. Source: Public Domain

With all preparations complete the crew contacted ATC and received clearance to divert to London Gatwick. A PAN PAN call was made when the diversion was initiated and once handed over to Gatwick ATC they were informed by the crew that they intended to vacate the runway after landing and then stop on the taxiway for the Airport Fire and Rescue Service to examine the engine and brakes. Before starting the final approach the cabin crew and passengers were also informed of the (expected) sequence of events. The approach to and landing at Gatwick were uneventful and after receiving the all-clear from the Airport Fire and Rescue Service the aircraft taxied under its own power to a parking stand, with the left engine shut down.

Subsequent inspection of the engine by engineers found three of the engine fan blades damaged by the birdstrike. The engine was repaired, and released to service.

The full Air Accident Investigation Branch report can be found by clicking here.

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