What happened
On 16 September 2005, a Robinson R44 Astro, registration G-TATY, was conducting its first solo cross-country training flight. The student pilot had departed from Denham airfield with a planned route heading northwest toward Westcott and back. After approximately five minutes of flight, the aircraft was observed flying at a low altitude south of Amersham.
Witnesses reported seeing the helicopter perform several energetic maneuvers at a low height. The aircraft was seen pitching steeply nose-down and performing a 360-degree turn before striking a field near Rodger’s Wood. The impact occurred in a nose-low attitude with a high vertical descent rate. The pilot sustained serious injuries, specifically to the head and neck, and was airlifted to a hospital.
The investigation
The AAIB investigation examined the wreckage, the engine, and the pilot's flight history. The aircraft sustained severe damage, including the destruction of the cockpit canopy and the tail rotor drive shaft. However, the engine remained running after the impact and passed subsequent test runs on a dynamometer, showing it was capable of producing full power.
Investigators analyzed radar and GPS data, which showed the aircraft descending from approximately 1,450 feet to 620 feet in about one minute. While the pilot could not recall the specific events of the flight due to head injuries, the investigation looked into potential technical failures, such as carburetor icing or mechanical issues with the rotor system. The investigation also reviewed the pilot's training, noting that while he was skilled in certain areas, he was less experienced with low-speed, high-power maneuvers and downwind approaches.
Findings
- The investigation found no technical fault with the helicopter that contributed to the accident.
- The aircraft was operating in wind conditions that exceeded the manufacturer's and operator's limitations for a pilot of the student's experience.
- A loss of power, potentially caused by carburetor icing or an attempt to maintain altitude during a distraction, likely led to the reduction in rotor speed and the subsequent uncontrolled descent.
- The pilot may have been distracted by navigating using a 1:500,000 scale chart, which could have diverted attention from the developing situation.