What happened
On 17 May 1998, a Robinson R22 Beta, registration G-OSEE, was performing a private flight approximately 10 miles east of Manchester Airport. Roughly two minutes into the flight, while the aircraft was climbing away from a private landing site, the engine suffered a sudden loss of power. This loss of power caused the helicopter to yaw, and the low rotor RPM warning horn activated.
As the pilot attempted an autorotation, the red oil and alternator warning lights illuminated, confirming the engine had ceased operation. During the landing sequence, the pilot flared the aircraft and raised the collective to cushion the touchdown. However, upon contact with the ground, the main rotor struck the tail boom, causing damage to both the rotor and the tail boom structure.
The investigation
Investigators examined the aircraft's fuel system following the incident. A ground test revealed that despite the main tank containing approximately 5 to 6 gallons of fuel, no fuel was able to flow from the tank. The investigation established that the fuel vent line leading to the main tank had kinked.
Research into the R22 fuel vent design showed that the original configuration used short lengths of plastic tubing to connect aluminium pipes to the tanks. This specific arrangement was found to be unreliable. The tubing used was single-walled, general-purpose plastic, which was highly susceptible to kinking and could be softened by heat from the engine heat shield. Furthermore, the investigation noted that the specific modification allowing the two tanks to vent through one another had not been implemented on G-OSEE.