A National Transportation Safety Board investigation into the emergency landing of a helicopter on Fort Street last year has turned up evidence of incorrect installation of a spring in the fuel system, which may have contributed to a sudden loss of engine power.
The information was contained in a NTSB "factual" report released Oct. 7.
On May 8, 2013, at about 3:20 p.m., a Robinson R22 Beta helicopter operated by Mauna Loa Helicopters made a hard landing on Fort Street. No serious injuries were reported, although the helicopter and an unoccupied car that it hit were both damaged.
According to pilot Julia Link, who was transporting passenger Karl Hedburg on a photo assignment above Punchbowl, Hedburg was taking some final photographs when the helicopter lost power.
"I slowed down for Karl’s final shots to about 35 knots when without any warning the engine suddenly quit and it became dead silent in the cockpit," Link wrote in an incident report.
Link chose to land on Fort Street because of the lack of foot traffic and because it is a one-way street.
During a subsequent examination of the helicopter, a Federal Aviation Administration inspector discovered that a mixture cable was separated from the mixture control arm of the carburetor and that a crank was not fully extended to where it should have been.
The inspector consulted with a mechanic who had worked on a recent overhaul of the helicopter, and the two determined that the mixture arm assembly was "improperly rigged," according to the report.
The mechanic said repeated stress on the mixture cable likely caused it to break, which in turn caused an erroneously installed spring to cut off fuel to the carburetor. The mechanic stated that an apprentice under his supervision handled the rigging of the carburetor.
"The mechanic did not visually observe the misrigging, and reported that if he had performed a tactile inspection, he would have detected the error," the report stated.
The NTSB has yet to release a probable-cause report.
