N593C

On April 16, 2019, about 1126 Hawaii time, a McDonnell Douglas 369E helicopter, N593C, was substantially damaged when it was involved in an accident near Hauula, Hawaii. The pilot and three passengers were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 flight.

During the fifth flight of the day, while flying about 1,700 ft mean sea level over mountainous terrain, the pilot noted the engine-out [warning] beeping, the engine-out light, as well as the re-ignition warning light on the caution warning panel. He noted the FUEL LEVEL LOW caution light did not illuminate during the flight. The pilot entered an autorotation and was able to descend to what looked like a more level area. He made a mayday call, flew toward the lowest and most uniform area of trees, and executed a “full down” autorotation. As the helicopter descended through the tree canopy, the helicopter rolled to the right before coming to rest upside down. All four occupants were able to evacuate the helicopter without assistance.

The pilot reported that after having arrived for the first flight of the day at the “Turtle Bay” staging area, he performed his preflight inspection, fueled the helicopter with 64 gallons of fuel, and configured the helicopter for five flights.

The pilot conducted the first four flights between 0750 and 1045, which involved transporting passengers and cargo to different landing zones. He did not shut down the engine between the fourth and fifth flights, and he noted he had about 200 lbs of fuel according to the fuel gauge before he lifted off about 1050. He then flew three passengers to three different landing zones to deploy equipment before starting toward the staging area to refuel. He stated the fuel gauge indicated 100 lbs of fuel remaining when he lifted off from the final landing to fly about 5 minutes to the staging area.

Based on the flight times and shutdown times provided by the pilot, the total flight time was calculated to be about 2 hours and 36 minutes. The total shutdown time was 30 minutes.

The pilot told investigators “…it seems apparent to me that fuel exhaustion was the cause of the engine flaming out and this accident.” He further explained that he planned for enough fuel to complete the missions that morning prior to initial departure but didn’t keep a running track of actual flight time. He also said he knew better than to rely solely on the fuel gauge but had somehow done that.

A Federal Aviation Administration (FAA) inspector examined the wreckage and examined the FUEL LEVEL LOW warning system. He noted the FUEL LOW LEVEL light illuminated when the PRESS TO TEST button was depressed, but it did not illuminate when the [fuel level sending unit] float arm was lowered to simulate a low fuel level. The fuel gauge responded appropriately when the float arm was raised and lowered. Examination of the circuit board that controls the FUEL LEVEL LOW light revealed a disconnected/broken and corroded wire on one end of the resistor on the board.

According to the helicopter manufacturer, the FUEL LEVEL LOW light illuminates based on the configuration of the helicopter. This normally occurs with about 35 pounds of fuel remaining, of which about 22.5 pounds is usable. This would equate to about 3.3 gallons of usable fuel remaining. Considering a fuel burn of about 35 gallons per hour, the engine would operate about 5 minutes until the engine flamed out after illumination of the FUEL LEVEL LOW light.