LAX97FA086

Shortly before 1510, the pilot started the helicopter's engine, then departed on a sightseeing tour flight around the island with two fare-paying passengers. The operator anticipated the flight would last between 0.5 and 0.7 hrs. For weight considerations, the fuel load had been reduced before takeoff by an estimated 10 gallons bringing the usable quantity to between 16 and 19 gallons, as estimated using a dipstick. About 1558, while cruising off shore & nearly parallel to the shoreline, witnesses observed the helicopter fly past while making sounds like its engine was sputtering, stalling, or cutting in and out. The helicopter's course remained unchanged, & seconds later, other witnesses heard a loud bang sound. The helicopter then entered a rapid descent, & impacted in about 2.5-foot-deep ocean water in front of a hotel where people were swimming. An exam of the wreckage revealed a main rotor blade had impacted & severed the tail rotor drive shaft. No evidence was found indicating the pilot had practiced autorotations in the Enstrom helicopter during the 4.5 months since becoming rotorcraft rated. During the structural airframe and engine examinations, no evidence was found of precipitating mechanical malfunctions. Calculations based on maximum anticipated fuel consumption rates, and approximations for the quantity of fuel on board, revealed fuel exhaustion could occur within 0.1 hour of the flight's duration.

History of flight

On January 12, 1997, about 1558 hours Saipan standard time (0558 UTC), an Enstrom F28A, N9087, operated by the Micronesian Aviation Corporation, d.b.a. Macaw Helicopters, experienced a total loss of engine power while cruising offshore near a beach fronting the Saipan Grand Hotel, about 3 miles northwest of the Saipan International Airport, Saipan. The helicopter rapidly descended and was destroyed by impact forces and immersion into the salt ocean water. The accident occurred while the pilot was providing the two fare-paying passengers with a 14 CFR Part 91 sightseeing flight over the island. A company visual flight rules (VFR) flight plan was filed, and visual meteorological conditions prevailed. The commercial pilot and one passenger were fatally injured, and a second passenger was seriously injured. Two bystanders, who were in a designated swimming area in front of the hotel, were seriously injured by debris from the falling helicopter. The accident occurred while the pilot was returning to the Coral Ocean Point Proshop Heliport, where the flight had originated about 1510.

The sole surviving occupant of the helicopter reported (through a translator) that the flight had proceeded normally when he heard a very loud boom sound which was dissimilar to engine noise. Immediately thereafter, an intense vibration was felt, and the helicopter rapidly descended.

Eight statements were received from witnesses located on or near the beach in the vicinity of the Saipan Grand Hotel, and who observed the southbound flying helicopter seconds prior to the crash. The witnesses generally indicated that the helicopter had been cruising nearly parallel to the shoreline when the event occurred. Two statements were received from witnesses whose estimated position was between 2/10 and 5/10-mile north of the crash site, and they too indicated the helicopter had been flying nearly parallel with the shoreline.

In summary, the eight witnesses closest to the crash site generally indicated hearing a noise, which they described as either being a loud bang or an explosion sound, followed by their observations of the helicopter descending at a steep angle with little forward airspeed. Three of these witnesses commented that when the helicopter descended its main rotor blade was rotating slowly. None reported hearing any engine noise.

The two witnesses located north of the crash site both reported hearing engine noises. The witness located about 5/10-mile north of the crash site estimated that when the helicopter flew past his position it was between 300 and 400 meters off shore. The witness provided the following statement regarding his observations of the events which transpired thereafter:

"Shortly after the helicopter had passed us, I heard the aircraft make a sound like the engine was stalling. I heard this sound a second time about two or three seconds later after which I observed the aircraft begin heading down at approximately a forty five degree angle. . . . At this time, I thought the aircraft was trying to land at the beach. About four to five seconds after I first observed the aircraft start heading down, I saw it crashed (sic) into the water."

A witness located about 2/10-mile north of the crash site reported that he heard the engine make a sputtering sound like it was cutting out. Thereafter, he observed the pilot looking outside the helicopter just before it fell into the water. Neither of these witnesses reported observing the helicopter turn toward the shoreline during its descent.

Personnel information

A review of the pilot's personal flight record logbook indicated that he commenced rotorcraft flight training in July 1996, and on August 29, 1996, he passed the commercial pilot check ride. All flight training, including the flight check, was performed in a Bell 47. No evidence of additional dual instruction or autorotation practice was observed recorded in the pilot's logbook following his certification check ride.

The operator reported that he had provided the pilot with a portion of the rotorcraft flight instruction. The pilot had been a company employee since June 2, 1996, and initially worked as a mechanic and fixed wing pilot.

Aircraft information

A review of the helicopter's maintenance records indicated the engine was overhauled in November 1995 by a contract facility. The operator's director of maintenance reported that he installed the engine into the accident helicopter on July 18, 1996. A mechanic, employed by the operator, reported that during the installation process, the engine was found timed to 19 degrees before top dead center (BTDC). The mechanic stated that he reset the timing to the appropriate 25-degree setting.

The operator further reported that since July 18, no one had checked the engine timing or moved the magnetos on their engine mounting pads. All maintenance since the engine installation, including the last annual inspection, was accomplished by the operator's employees.

The operator reported that he flew the accident helicopter on January 10, 1997, which was the last time it was operated prior to the accident flight. During the operator's pretakeoff engine check, the magnetos were functionally checked. The engine speed decreased between 50 and 75 revolutions per minute (RPM) when each magneto was momentarily switched off, and no roughness occurred. No anomalies to any helicopter system were noted during the flight. At its conclusion, the engine shut down procedure was accomplished during which the grounding of each magneto was checked. The engine briefly quit when each magneto was turned off. No anomalies were noted.

The helicopter was not equipped with flotation devices. According to the Enstrom Helicopter Corporation participant, when the helicopter was manufactured shoulder harnesses were not available from the company, and none were installed in the helicopter. They have subsequently become available from Enstrom.

Meteorological information

The operator and persons who resided near the accident site area reported no unusual weather phenomena during the accident flight. The weather was generally described as being a typical "VFR" day with good visibility, calm sea, and a light easterly 5-knot breeze.

Communication

According to air traffic controllers located at the Saipan Airport, all radio communications with the pilot throughout the flight were normal.

Wreckage and impact information

The wreckage was recovered from the accident site and examined by Federal Aviation Administration (FAA) personnel prior to the National Transportation Safety Board's on-scene arrival. According to the Commonwealth of the Northern Mariana Islands, Department of Public Safety, and the helicopter operator, the main wreckage was primarily located in one main area. It was found partially submerged in estimated 2 1/2-foot-deep water. The tail rotor drive shaft (TRDS) was observed severed into two sections. The short section was found about 40 feet from the main wreckage, and the long section was found about 256 feet from the main wreckage. A TRDS bearing was found approximately 70 feet upwind (and up current) from the flight path. There was no evidence of fire.

The FAA coordinator reported to the Safety Board that his examination of the helicopter commenced on January 14, 1997. The FAA coordinator's complete statement is included in the Safety Board's report. The following partially summarizes his observations and findings:

Based upon the observed physical evidence, a main rotor blade struck the tail boom and severed the TRDS into two pieces. When the severance occurred, the drive shaft was rotating very slowly.

The tail rotor blades were found intact. The control cables going to the tail rotor were found severed at the point of the main rotor blade strike.

Three control rods are located within the