What happened
On the morning of 27 August 1999, a private flight involving a Robinson R22 Beta, registration EI-MAC, resulted in a fatal accident in the townland of Cornakelly, near Ballinamuck, Co. Longford. The flight, operated by Eirecopter Helicopters, was traveling from Weston Aerodrome toward Sligo Airport for the purpose of aerial photography.
During the flight, witnesses observed the helicopter at a very low altitude. One observer reported hearing a loud, grinding noise and seeing a piece of a blade fall from the aircraft. Shortly after the blade separation, the helicopter tilted sharply and crashed into an open field, causing a post-impact fire. The accident resulted in two fatalities, involving both the pilot and the passenger.
The investigation
The AAIU investigation examined the aircraft's maintenance history, the pilot's experience, and the environmental conditions at the time of the crash. The aircraft had recently undergone a 50-hour inspection and was considered airworthy. Meteorological data indicated a fine, sunny morning with good visibility and no significant turbulence.
Investigators also looked into the configuration of the cockpit. It was noted that the dual controls had not been removed from the aircraft, which is a procedure recommended in the pilot's operating handbook for certain flight types. Furthermore, the investigation found that the operator was not subscribed to the Robinson Helicopter Company safety notice service at the time of the accident.
Findings
Technical analysis determined that the main rotor blades struck the fuselage during flight, leading to the failure of the rotor system and a total loss of control. While the investigation could not definitively prove the exact trigger, the primary cause was the rotor strike.
Contributing factors being considered include:
- An inappropriate or abrupt control movement that caused excessive blade flapping or mast bumping.
- A potential main rotor blade stall, which could have been triggered by a drop in rotor RPM due to engine carburetor icing or sudden flight control inputs.
- The aircraft had descended to an altitude of approximately 200 to 300 feet, which is below the 500-foot safety margin typically recommended for single-engine helicopter operations to allow for an emergency autorotative landing.