McDonnell Douglas 369E N698DM

Summary

On 8 February 2008 at about 00:35 local time, a McDonnell Douglas 369E registered N698DM, operated by Tropical Helicopters, was involved in an accident near Hilo, Hawaii, United States. 5 people were on board and 5 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

8 February 2008 at 00:35

Classification

Accident

Location

Hilo, Hawaii, United States

Nearest airport

Hilo (PHTO)

Coordinates

19.7114, -155.1486

Aircraft

McDonnell Douglas 369E

Registration

N698DM

Category

Helicopter

Engines

1

Operator

Tropical Helicopters

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Hilo → Hilo

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

SEA08FA071

5 people had minor injuries.

A leak in the fuel filter pressure differential switch that resulted in a loss of engine power. Contributing to the accident was uneven terrain that hindered a successful emergency landing.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The flight was approximately five miles from the departure airport when the pilot turned back due to a fuel bypass caution light. The pilot heard 2-3 abnormal engine sounds, with simultaneous yawing, during the turn and entered an autorotation. During the final stages of the autorotation, the engine flamed out. The helicopter touched down on uneven terrain and rolled over resulting in substantial damage. Post accident examination of the engine assembly revealed a fuel leak from the fuel filter pressure differential switch. The differential switch was in place and the associated fuel lines, bushing and adapter fitting were not damaged. Examination of the system revealed that one of the three fuel filter pressure differential switch set screws, and associated safety wire segment, was missing. The two remaining screws were in place. One of the screws was fixed, the other finger tight. The corresponding safety wire was attached to the remaining set screws. The distal end of the safety wire leading to the missing set screw was severed. A post accident evaluation of the engine in a production test cell revealed a fuel leak at the pressure differential switch when the engine was motored to 16 percent N1 (compressor speed). The original fuel filter pressure differential switch was removed and replaced with an exemplar differential switch. A second engine start was successful and the engine ran, without leaks, and attained normal operating parameters. Maintenance records indicated that the helicopter's fuel system components were inspected during the 100-hour inspection completed 66 flight hours before the accident. The maintenance "check sheet" indicated that the engine's fuel system components, to include fuel lines and connections, were inspected for leaks or damage, and no anomalies were noted. No record was found in the maintenance records of any work done to the fuel filter pressure differential switch subsequent to the 100-hour inspection. It could not be determined when, or how, the fuel filter pressure differential switch set screws, and associated safety wire came loose. The approved maintenance manual for the helicopter contains multiple warnings indicating that air in the closed fuel system will cause a power reduction or flame out.

Quoted verbatim from the NTSB record.