AAIB investigation to Boeing 737-800, G-JZHL
Incorrect thrust set during takeoff, Kuusamo Airport, Finland, 1 December 2021.
Summary:
This investigation was delegated to the AAIB by the Safety Investigation Authority of Finland.
During takeoff from Kuusamo Airport in Finland the flight crew inadvertently left the thrust set at the 70% engine run-up setting rather than the 89% required for takeoff. The aircraft became airborne with 400 m of runway remaining and climbed away slowly. At 250 ft agl the flight crew realised they had insufficient thrust and applied the correct power. The flight continued without further incident.
The thrust was not set correctly because the TOGA button was not pressed. It was not pressed because the co-pilot was startled by the aircraft starting to move when he set 70% power against the brakes. The aircraft started to move because the co-pilot applied insufficient brake pressure. The commander was distracted by a radio call and neither he, nor the co-pilot, checked the thrust was correctly set.
The AAIB has investigated several takeoff performance incidents across the industry. This incident is further evidence that the current barriers designed to prevent these events are not fully effective, and improved reliability is likely only through the introduction of a technical barrier. A Safety Recommendation is therefore made to develop technical specifications and, ultimately, certification standards for a technical solution.
A Safety Recommendation is also made to improve the detection of takeoffs with compromised performance, to support the prompt reporting of occurrences.
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