What happened
On 13 December 2008, a Boeing 767-39H, registration G-OOAN, was preparing for a commercial passenger flight from Manchester Airport to Montego Bay, Jamaica. During the takeoff roll on runway 23L, the commander, acting as the pilot not flying, delayed the V1 call by approximately 10-15 knots. This delay was prompted by a perceived sluggishness in acceleration, which the commander attributed to the possibility that the aircraft was heavier than the calculated figures suggested.
As the aircraft rotated, the co-pilot performed a slow rotation, resulting in a momentary TAILSKID alert on the Engine Instrument and Crew Alerting System (EICAS). Shortly after, the stick shaker activated briefly. The crew responded by applying full power and maintaining a positive rate of climb. Following the completion of after-takeoff checklists, the crew dumped fuel and returned to Manchester for an overweight landing. The aircraft sustained minor damage, consisting of a thin layer of paint scraped from the tailskid, but was declared serviceable after inspections.
The investigation
The AAIB investigation established that the takeoff speeds used by the crew were significantly lower than required for the actual weight of the aircraft. The investigation found that the zero fuel weight (ZFW) had been mistakenly entered into the Computerised Takeoff Performance (CTOP) programme in place of the takeoff weight (TOW). This error resulted in calculated speeds that were roughly 20 knots lower than necessary for the actual mass of the aircraft.
Several contributing factors were identified, including time pressure caused by a late pushback and the crew's focus on navigating taxiway construction at Manchester. Additionally, the commander's lack of recent experience on this specific aircraft type and the requirement to activate engine anti-ice due to heavy rain further distracted the crew from noticing the unusual takeoff speeds.