Lessons Learned: Inadvertent Thrust Reduction

Inadvertent thrust reduction during the takeoff roll occurred at the UK’s London Gatwick Airport, June 28, 2024.

The AAIB (Air Accidents Investigation Bureau) highlights the inadvertent thrust reduction that occurred to a Boeing 777-236, G-VIIT.

During takeoff, the copilot began retarding the thrust levers at airspeed V1, instead of removing his hand from them. After momentarily advancing them again, he initiated the rejected takeoff (RTO) procedure around 2 KIAS later. The RTO was performed effectively and the aircraft stopped some distance before the end of the runway surface.

The report considers the complex nature of the takeoff roll and why mental rehearsal of motor actions may benefit pilots, particularly after time off from flying. It discusses the industry-wide challenge of preventing action slips. This operator had already published a methodical approach to control selections, which it has promoted in preflight briefing material. It has included the wider issue of ‘focus’ in its recurrent simulator training.

History of the flight G-VIIT AAIB-30154 The aircraft was taking off from London Gatwick Airport (Gatwick), Runway 26L. On hearing the aircraft’s automatic callout of airspeed “v1 ”1, the copilot (who was PF) inadvertently began retarding the thrust levers, instead of removing his hand from them to continue the takeoff. Simultaneously, the commander called “rotate” as the airspeed continued increasing through Vr 2. The copilot vocalised the error and momentarily advanced the thrust levers again, before performing the RTO procedure. 3. The aircraft stopped before intersection GR (Figure 1). The airport rescue and firefighting service attended the aircraft and extinguished a fire from hot brakes on the right main landing gear.

Figure 1 Excerpt from Gatwick ground chart Information from the operator’s operating manuals The operator’s ‘Flight crew training manual’ (FCTM) described V1 as ‘the maximum speed in the takeoff at which the pilot must take the first action… to stop the airplane within the accelerate-stop distance[4]’ and ‘the minimum speed… following a failure of an engine at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance’. It stated ‘The PF should keep one hand on the thrust levers until V1 in order to respond quickly to a rejected takeoff condition. After V1, the PF’s hand should be removed from the thrust levers.

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