SEA99LA031

History of flight

On January 19, 1999, approximately 1445 hours Pacific standard time, a Hiller UH-12E, turbo-shaft powered rotorcraft, N67264, registered to an individual, being operated by Valley Helicopter Service, and being flown by a commercial pilot, was destroyed during collision with trees and terrain following a total loss of power while in cruise approximately five miles northeast of Tensed, Idaho. The pilot and one passenger sustained serious injuries, while the remaining passenger sustained minor injuries. Visual meteorological conditions were reported to exist at the accident site, and a company flight plan (flight following) was in effect. The flight, which was a survey of migrating elk for the Coeur d'Alene Indian Reservation, was operated as a 14 CFR Part 91 flight, and originated from Tensed at approximately 1230.

According to the operator, the aircraft was fueled with 82 gallons of Jet A fuel. The fuel truck driver, through which the flight was maintaining flight following, reported that following the morning flight (0800 until 1145) he refueled that rotorcraft at 1145. He also reported that the rotorcraft departed for the second flight of the day and that "right after he was airborne we made radio contact at 12:33pm." And that he remembered because the pilot said "check your time I have 3.5 hrs of fuel and I will meet you at the CDL Tribe compound at 4:00pm." The driver then refueled his fuel truck. He reported that subsequent to the refueling at 2:40pm "On the return trip from the airport, on the hill area near Skyline Dr, between Potlatch and Tensed I made radio contact. James instructed me to go to Plummer, check into a motel and meet him at the compound." This was the last radio contact the driver had with the rotorcraft (refer to attached statement).

The pilot was interviewed by an inspector from the Federal Aviation Administration's (FAA) Spokane Flight Standards District Office on January 22, 1999. He reported in the interview that "he was flying up a draw and, upon reaching the top, performed a zero airspeed pedal turn to reverse course and fly back down the draw. After performing the turn the aircraft began to settle in a normal fashion. (The pilot) increased collective to arrest the rate of descent and immediately heard the engine spool down (fail). He stated that, in an attempt to re-light the engine he flipped on the auto re-light system but the engine did not respond."

The pilot further reported that "within moments preceding the flameout, he noted that his fuel level had reached approximately 15 gallons in the main tank. At that time he turned on the auxiliary fuel tanks transfer switch. He stated that turning on the transfer switch at 10 to 15 gallons was a normal and routine practice in the Hiller and that he watches the fuel level "like a hawk" to insure the timely transfer of fuel. He said that the time between turning on the transfer switch to the flameout was approximately 45 to 60 seconds to the best of his recollection."

The passenger seated to the pilot's right (minor injury) reported in a telephone interview with the investigator that he was unconscious for a brief period of time following the accident and that he estimated that it took him 1.5 to 2 hours to hike out for help following the accident. He reported calling 911 from a farmhouse and reporting the accident.

The passenger seated to the pilot's left (serious injury) reported in a telephone interview with the investigator that they landed around 1130 on the morning of the accident and stopped for an hour for lunch. He also reported that the last time he noted the time after takeoff was approximately 1430 before the crash. He reported that after the crash approximately 20-25 minutes had passed after which he looked at his watch and it read 1505. He also reported that following the accident he noted he was soaked in fuel which he believed came from the rupture of the left saddle tank.

The Benewha County Sheriff's Department received a 911 telephone notification at 1732 hours reporting the accident.

Personnel information

The pilot reported a total of 4,000+ hours of flight experience of which 1,500+ hours were logged in the UH-12E Hiller/Soloy rotorcraft.

Aircraft information

According to the Model UH-12E Service Manual, the aircraft was equipped with a single, 46 gallon bladder main fuel tank located in the belly of the helicopter. The manufacturer reported that the main tank's unusable fuel was 2.9 gallons. Fuel was fed via engine-driven pump suction from a screened pickup tube within the tank, and then on to the engine. An electric boost pump, which when operating, provided a continuous fuel pressure head to the engine driven pump, was installed upstream of the fuel tank pickup. The boost pump fuel pressure head served to prevent inadvertent air pickup in the fuel lines upstream of the pump, which could result in engine shutdown.

An analog fuel gauge in the cockpit displayed main fuel tank quantity in gallons (refer to photograph 1). The quantity is provided by a combined forward and aft fuel quantity pickup unit within the tank.

Additionally, the aircraft was equipped with two metal, external, auxiliary tanks. The capacity of each of these tanks was reported as 18.8 or 20 gallons, dependent upon the source of information (Flight Manual Supplement or UH-12E Service Manual, respectively). These two tanks were joined at a "tee" fitting which then fed fuel through an electrically operated solenoid into the main fuel tank. According to Hiller Engineering Report 59-51, the fuel transfer (flow) rate from both auxiliary tanks is 73 gallons/hour when the auxiliary tanks are filled to within 15 gallons of full tanks. Cruise fuel flow to the engine was reported at 17-20 gallons/hour (takeoff power fuel flow was reported as 32 gallons/hour).

Wreckage and impact information

The aircraft crashed in heavily wooded terrain consisting of approximately 75 foot high coniferous and deciduous trees (refer to photograph 2). The aircraft came to rest on its left side (refer to photographs 3 and 4).

Another inspector from the FAA's Spokane Flight Standards District Office traveled to the crash site and reported the following initial observations:

1. The right "saddle" tank was approximately 1/3 full and fuel was observed leaking from the tank. 2. The left "saddle" tank was deformed/compromised and fuel had leaked out. 3. The "AUTO RELIGHT" switch was found in the ON position. 4. No fuel was observed in the rotorcraft's main fuel tank. 5. No fuel was found in the fuel line which connects the tank to the engine fuel nozzle.

Tests and research

Subsequent to the recovery of the wreckage, the FAA inspector and a representative from the engine manufacturer (participant) re-examined the rotorcraft and reported the following observations:

1. A vacuum check of the fuel system was conducted with no abnormalities noted. 2. No fuel was found within the engine driven fuel pump filter . 3. No fuel was found within the power turbine governor fuel filter. 4. The airframe fuel filter was opened and found to be approximately half full of fuel. 5. The main fuel tank contained less than one gallon of fuel. 6. The auxiliary (saddle) fuel tank solenoid transfer valves were electrically tested with no malfunction noted. 7. The electric boost pump was tested with no malfunction noted. 8. Fifteen gallons of fuel was placed in the main fuel tank and left for two hours. No evidence of a fuel leak within the bladder was observed. (Refer to ATTACHMENT FAA-I)

Additionally, the aircraft's fuel gauge was observed to have no markings on the glass faceplate (refer to photograph 1). The gauge was marked with a white band over an approximate 90 degree arc. The left end of the arc was identified with the letter "E" and the right end of the arc was identified with the letter "F." The arc was graduated at its