What happened
On 29 July 2000, a Cessna Citation X, registration N999CX, was undergoing a ferry flight and was being directed into a parking bay at the business jet area of London Heathrow Airport. The manoeuvre involved a significant 230° right turn, transitioning the aircraft from a northerly heading to a south-westerly direction. To facilitate this, the marshaller guided the aircraft north along the taxiway before signalling a turn toward the east.
As the turn progressed, the marshaller moved near a blast wall to monitor the clearance of the aircraft's left wing. After confirming sufficient space during the initial stages of the turn, the marshaller signalled for the aircraft to continue turning toward the south. During this final phase of the turn, the left wing-tip struck the vanes of the blast wall. The pilot felt the impact from within the cockpit and responded by immediately stopping the aircraft and shutting down the engines. There were no injuries to the two crew members on board.
The investigation
The investigation was based on the aircraft accident report provided by the pilot and supplementary information from Heathrow Airport Limited. Investigators examined the mechanics of the turn and the physical dimensions of the aircraft. The Cessna Citation X features a 37° wing sweep and a wingspan of 19.38 metres.
Technical analysis of the aircraft's ground handling characteristics revealed that when using only nosewheel steering, the aircraft pivots around its main wheels. This movement causes the wing-tip to describe an arc that extends significantly beyond the aircraft's straight-line track. Specifically, for a 180° turn, the diameter of the arc traced by the wing-tip is 24.64 metres, which is 5.25 metres greater than the actual wingspan of the aircraft.