Accident Overview
On July 10, 2011, at approximately 0910 eastern daylight time, a Robinson R22 BETA, registered as N10786 and operated by Ocean Helicopters Inc., was substantially damaged during an emergency autorotation. The accident occurred near Palm Beach International Airport (PBI) in West Palm Beach, Florida. The certified flight instructor (CFI) was not injured, and the student pilot incurred minor injuries. The instructional flight was conducted under 14 Code of Federal Regulations Part 91 in visual meteorological conditions. No flight plan was filed for the local flight, which had departed PBI around 0840.
Sequence of Events
According to the CFI, he and the student pilot performed five or six quick-stop maneuvers before proceeding with a normal takeoff. At about 200 feet above ground level, the helicopter experienced an uncommanded right yaw that could not be corrected with left pedal input. The CFI initiated an autorotation as the yaw continued. During the descent, he observed that the horizontal and vertical stabilizers had separated from the tailboom and were falling to the ground.
A Federal Aviation Administration inspector determined that a fuel cap had separated from the right auxiliary fuel tank and entered the tail rotor system, causing a tail rotor imbalance and partial separation. The helicopter subsequently spun during the autorotation and landed hard. Upon impact, the tail rotor separated, and the fuselage sustained substantial damage.
Post-accident Findings
The separated fuel cap was recovered; it was missing its restraining chain and gasket. Both pilots reported that they had checked the fuel caps during the preflight inspection. The main fuel tank (left) cap remained secured throughout the accident sequence and was found to contain a gasket but no restraining chain.
Review of manufacturer data showed that Robinson Helicopter Company ceased installing restraining chains on fuel caps beginning November 22, 1993. However, the accident helicopter's production was completed in January 1993, and it should have left the factory with restraining chains attached to both fuel caps. Examination of the helicopter's maintenance records did not reveal any instance of the fuel cap restraining chains being removed in the field.
Fuel Cap Examination
The auxiliary fuel tank (right) was not serviced prior to the accident flight. The missing chain and gasket on the right fuel cap contributed to its separation. The left fuel cap, which retained its gasket but lacked a chain, remained secure. The incident highlights the importance of proper fuel cap security and the potential consequences of missing components.