The couple were flying to an engagement at the Hay-on-Wye Festival in Wales when the 53-year-old pilot lost control of the aircraft.
A report released by air accident investigators yesterday documented how the chopper lurched to the right, failing to respond to any of the pilot’s attempts to stabilise it.
After repeatedly trying to regain control of the helicopter, the pilot radioed through a mayday call before performing an emergency landing at Denham aerodrome in Buckinghamshire.
The Duke and Duchess of Cornwall and four other passengers were shaken up, but uninjured.
“It was quite a hairy incident,” a royal source told the Daily Mail.
Charles and Camilla completed their journey by car, arriving at their engagement three hours late.
The Air Accidents Investigations Branch traced the cause of the incident to a faulty ball bearing within a system that controls the helicopter’s steering.