Amateur-built HELICYCLE N519SP accident near Deer Park, Washington

Probable cause

A loss of engine power due to fuel starvation resulting from contamination of the fuel system during low-level flight.

NTSB analysis

The pilot reported that he had not flown the experimental amateur-built helicopter for 3 months, so he performed several practice liftoffs to a hover and landings. He then departed and flew a modified airport traffic pattern with the intent of terminating the approach to a hover. During the circling approach, about 50 ft above ground level (agl), he added power to increase the helicopter’s altitude and airspeed, but the engine lost total power. The pilot attempted to arrest the descent, but the helicopter landed hard, which resulted in substantial damage to the tailrotor driveshaft and tailrotor gearbox.

Postaccident examination of the airframe fuel system revealed that the main fuel tank contained excess hardened sealant pieces found at the base of the tank, near the fuel pickup points that fed into the left and right fuel tanks. The size and shape of the excess sealant was too large to flow through the fuel lines and may have precipitated a fuel starvation event. Foreign object debris in the form of dirt-like particulates were observed from the cross-feed outflow fuel fitting to the fuel filter input. The left and right fuel tanks, fuel filter, and fuel collator all contained foreign object debris in the form of dirt-like particulates.

Given the extraordinary quantity of foreign object debris in the airframe’s fuel system, foreign object debris accumulation, specifically at the fuel fitting entry points, likely resulted in fuel starvation and a loss of engine power during the pilot’s increased collective application and corresponding increased power demand. The source of the foreign object debris was undetermined.

Text from the NTSB. Open the NTSB docket for WPR24LA009 for the full record.