What happened
On 1-August-2010, a Robinson R44 helicopter, registration D-HNOC, was performing a positioning flight from Kootwijkerbroek to Stroe. During the pre-flight preparations, the pilot had fitted ground handling wheels to the skids to move the aircraft from its hangar. However, these wheels were not removed prior to departure.
As the pilot performed a hover taxi before landing at the Stroe location, the left ground handling wheel detached from the aircraft after its lifting handle made contact with the ground. While descending toward the landing spot, the right lifting handle also struck the ground. This impact caused the helicopter to pivot sharply around the right handle, forcing the left skid into the ground. The sudden movement caused the tail to strike the earth, resulting in the tail rotor and tail section breaking off. The aircraft rolled onto its side, causing a fuel leak from the left tank. The pilot escaped the 0 fatalities and 0 injuries incident without harm, though the aircraft was severely damaged.
The investigation
The investigation examined the pilot's pre-flight procedures and the mechanical sequence of the crash. It was noted that a telephone call received during the pre-flight inspection had altered the pilot's schedule, making the timeline more critical. While the pilot's specific checklist for start-up and shut-down did not explicitly mention the wheels, the flight manual requires verification that they are removed before flight.
Investigators also reviewed the structural vulnerability of the aircraft's fuel system. The single-walled aluminum fuel tank on D-HNOC was found to be susceptible to leaks during impact, a factor that increases fire risks in helicopter accidents.
Findings
- The primary cause of the accident was that the ground handling wheels were not removed before the flight began.
- The contact between the right lifting handle and the ground created an unexpected pivot that the pilot could not counteract.
- The aircraft's single-walled fuel tank design contributed to a post-impact fuel leak.
Safety action
Following the investigation, the manufacturer implemented several changes:
- A new design for ground handling wheels was introduced. Unlike the older version, the new handles are angled across the skid to prevent them from rotating downward if left attached.
- A service bulletin was issued to retrofit R44 helicopters with double-walled, bladder-type fuel tanks to reduce the risk of leaks and subsequent fires during accidents.