Investigators have concluded an F-15D fighter jet which was destroyed in a $44.6 million crash in Lincolnshire last year had ‘imperfections’ in its nose.
An Accident Investigation Board (AIB) report conducted by investigators from the US Air Forces in Europe and Air Force Africa concluded there was ‘clear and convincing evidence’ that two factors caused the crash near Spalding, in Lincolnshire, on October 8.
The male pilot, from the 48th Fighter Wing’s 493rd Squadron, ejected at 5,450ft and only suffered minor injuries. There were no civilian casualties when the plane crashed into fields around three miles southeast of Spalding at around 3.30pm.
After borrowing a molbile phone for a passer-by to report back to base, the pilot was rescued by a helicopter from the 56th Rescue Squadron, also based at RAF Lakenheath.
The accident report stated the aircraft went into a spin at 15,200ft during a training exercise after the pilot pulled the nose of the aircraft at an extreme angle and consequently lost control.
The nose sliced to the left, causing the aircraft to go into a spin of 111 degrees per second and lose altitude at an alarming rate.
The report stated the accident cost the United States Government a total of $44,608,743 (£30.1 million), with damage to private property limited to impact and fire damage on a farmer’s field. Environmental clean-up costs came to $604,405 (£407,396).
The AIB report found imperfections in the F-15’s radome (aircraft nose) were responsible for the uncontrollable spin.
A larger than normal gap between the body of the radome and the nose cap and the extruded sealant used to compensate for it caused an uneven aerodynamic surface.
A series of aerodynamic investigations have proven that these imperfections can ‘generate yaw forces that can both induce a spin and delay spin recovery’.
The Board President also found that the ‘inherent reduced stability of the F-15D model’ was a ‘significant contributing factor’.