NTSB Factual Report

On March 8, 2002, approximately 1455 Pacific standard time, a Bell/Garlick UH-1H, N116DR, registered to/being operated by Northwest Helicopters, Inc., and being flown by an airline transport rated pilot, was substantially damaged during a hard landing following a loss of engine power during cruise approximately three nautical miles west of the Shelton airport, Shelton, Washington. The pilot was uninjured. The pilot reported the meteorological conditions at the time/place of the accident as VMC, and no flight plan had been filed. The flight, which was engaged in fertilizer dispensation, was operated under 14CFR137, and had departed from the remote service site earlier in the afternoon.

The pilot reported he had completed a fertilizer drop and was returning to the servicing area for fuel with the empty, 300-pound bucket attached by a 30-foot line. He was one-half mile from the intended landing site when he heard a series of loud reports coming from the engine. The helicopter yawed and the low RPM audio warning sounded. He reported N1 speed as deteriorating as the aircraft was traversing 100-foot high trees. The helicopter was approximately 300 feet above ground at 80 knots airspeed. The pilot lowered collective and maneuvered north toward an area of smaller trees, which he estimated, were 10-25 feet tall. He then jettisoned the empty bucket and began a flare to the intended landing area (a road).

The pilot reported that as he pulled pitch there was little inertia left in the rotor system. The rotor blades began contacting trees and slowed rapidly and the helicopter impacted terrain in a slightly left/nose level attitude. He reported that upon exiting the aircraft the fuel gauge read 680 pounds (refer to attached NTSB Form 6120.1).

The pilot was interviewed by an inspector from the Federal Aviation Administration's (FAA) Renton Flight Standards District Office (FSDO) and reported that the fertilizer dump zone was approximately 30-40 seconds flying time from the refill truck. He also reported that refueling of the rotorcraft occurred when the fertilizer truck needed refilling, or approximately every 11 trips to the zone; and that the rotorcraft was hot-fueled taking approximately 30-50 seconds. Fuel was added until the fuel gauge read 800 to 900 pounds (approximately 50-60 gallons taken on at each refueling). The pilot reported that fuel consumption for the rotorcraft was about 80 to 90 gallons per hour (refer to attached statement PIS-I).

The pilot also explained that the rotorcraft was equipped with a low fuel warning system, which included an annunciator light, and that the annunciator light normally illuminates when the rotorcraft is flying with a load due to adverse operating angles. Once the rotorcraft's load is released and it returns to a level attitude, the light goes out. He reported that the light is designed to provide a 20 minute warning before fuel is exhausted. He also remarked that the system was operating normally prior to the accident and that during the return flight after the last fertilizer drop, the light remained illuminated (refer to attached statement PIS-I).

The Technical Manual for the UH-1H rotorcraft (TM 55-1520-210-10) contained a reference within the emergency procedures section relating to the "20 Minute Fuel Caution Light" which stated that should the light illuminate the pilot should land as soon as practicable. An additional reference within the same manual stated that the "20 MINUTE FUEL caution light will illuminate when there is approximately 170 pounds remaining." (refer to attachment TM-I).

Post-crash examination of the aircraft's Lycoming/Honeywell T53-L13B turboshaft engine was conducted under the oversight of an inspector from the FAA's Renton FSDO. The examination was conducted at the facilities of Northwest Helicopters, Inc. Prior to the examination, approximately 30 gallons of fuel was recovered from the rotorcraft's fuel tanks. The examination determined that both the two-stage gas producer (N1) turbine and the two-stage power (N2) turbine were free to rotate. Manual rotation of the N1 turbine resulted in commensurate rotation of the compressor assembly and accessory drive output, while rotation of the N2 turbine resulted in commensurate rotation of the reduction gearing assembly. There was no evidence of any turbine or stator blade damage noted during the turbine section examination. Additionally, the fuel system was examined from the fuel tank up to but not including the fuel control/pump/governor unit. No evidence of a fuel delivery problem was noted. The fuel indicating system was checked with no discrepancy noted and fuel was found within the fuel control filter. The compressor section was also removed and examined and there was no significant evidence of foreign object damage or ingestion noted (refer to attachment NWH-I).

The Chandler Evans Control Systems (fuel control/pump/governor unit) was examined and tested at the facilities of B.F. Goodrich, d/b/a Pump & Engine Control Systems, Goodrich Corp. West Hartford, Connecticut. No significant anomalies were noted during the examination and testing (refer to attached Goodrich report number S-1652).

NTSB Probable Cause

A loss of power for undetermined reason(s). Contributing factors were the pilot's delayed decision to jettison the empty bucket and the trees impacted during the auto-rotation landing.