London:
Britain's Prince Charles and his wife Camilla had a close shave when his helicopter made an emergency landing after it "began to yaw" or lurch to one side.
The heir to the British throne was travelling with Camilla and four others to the Hay-on-Wye Literary Festival in Wales in May last year when his Sikorsky S-76C helicopter had to land at Denham aerodrome west of London, a report by the Air Accidents Investigation Branch (AAIB) said today.
The AAIB said the fault was traced to the splitting of a metal ball within a system that helps control the helicopter's steering.
"A detailed metallurgical analysis of the ball by the (US) National Transportation Safety Board is continuing. However, the most likely cause of the ball fracture was an anomaly in its heat treatment process during manufacture," the report said.
The helicopter's 53-year-old captain was forced to declare a "pan emergency", one level of danger below a mayday call, and attempt to land at a nearby airfield.
He carried out a "running" landing, used if an aircraft has a problem, and the "abnormality" was still apparent as the helicopter taxied on the ground, the report said.
A royal aide described the incident as "pretty hairy" and "genuinely terrifying".
Charles and Camilla insisted on continuing their journey by car, arriving three hours late but put on a relaxed front and did not allude to the mid-air scare.
The report came in the aftermath of two fatal helicopter crashes in Britain in recent weeks.
Four US airmen were killed in eastern England on Tuesday when their helicopter ditched onto marshland while flying low on a training exercise.
Last November, a police helicopter crashed into a busy pub in the Scottish city of Glasgow, killing all three crew and seven people on the ground.