What happened
On 2 December 2003, a McDonnell Douglas Hughes 369E, registration G-LOGO, was performing a private cross-country flight from Shoreham to Cheshire. After a brief stop near Hemel Hempstead to drop off a passenger, the pilot resumed the flight, climbing to approximately 1,500 feet amsl.
Shortly after this climb, the pilot experienced a severe vertical bump and significant mechanical noise, accompanied by heavy vibration. The pilot immediately initiated an autorotation and selected a nearby field for an emergency landing. During the approach, the pilot noted a perceived loss of rotor RPM. The helicopter performed a run-on landing in a soft, muddy field, but the skids dug into the earth, causing the aircraft to pitch forward and eventually roll onto its side. The aircraft was destroyed during the process.
The investigation
The AAIB investigation examined the wreckage and analyzed GPS data from the aircraft. The data revealed that approximately 90 seconds prior to the turbulence event, an Airbus A319 had passed 3/00 feet above the helicopter's flight path.
Investigators found that four of the five main rotor blades had failed near the blade roots. However, the fifth blade exhibited a different failure pattern: the forward blade pin was missing, though the attachment lugs remained undamaged. This led to the blade cuff rotating backward and the blade eventually striking the tail boom. Despite extensive searches using metal detectors, the missing retaining pin was not recovered. The investigation also noted that radio transmissions during the final moments of flight contained a high-frequency signal consistent with a significant change in rotor RPM.
Findings
- The helicopter encountered severe turbulence, which may have been caused by the wake vortex of the preceding Airbus A319.
- The aircraft's landing in a soft, sticky field caused the skids to penetrate the surface, leading to a forward pitch and subsequent rollover.
- The loss of a main rotor blade attachment pin cannot be definitively confirmed, though the physical evidence of the fifth blade's failure was inconsistent with the other four blades.
- The pilot escaped the wreckage without any injuries.