NYC94LA097

The aerial application flight had been airborne for approximately 30 minutes, in the turbine engine converted bell 47. The helicopter was over hilly terrain with tree lines. The pilot was flying an uphill run at 30 to 40 feet above tree level, at 60 to 65 miles per hour, when there was a partial loss of engine power. The pilot attempted to fly to an open area with partial power. The helicopter struck a tree as it approached the edge of a clearing. After the helicopter came to rest on the ground, the pilot shut the engine down with the twist grip throttle. The transmission, the free wheeling unit and the tail rotor gearbox were examined, and no defects were noted. Examination of the engine revealed accident related impact damage to the combustion liner. The liner was replaced and the engine performed normally during a test run.

On May 31, 1994, at 0730 eastern daylight time, a Bell 47G3 Soloy, N121CD, owned by Helicopter Applicators, Inc., and piloted by Dirk Dekker, was destroyed during a forced landing to a hillside near Friendsville, Maryland. The pilot was seriously injured. Visual meteorological conditions prevailed and no flight plan had not been filed for the flight operating under 14 CFR 137.

The helicopter had departed at approximately 0700 to perform an agriculture application mission. The pilot reported that after about 30 minutes of flying he was established on an up hill application run, about 30 to 40 feet above the trees, and at an airspeed of 60 to 65 miles per hour (MPH).

In the NTSB Form 6120.11, the pilot stated:

"...[I] estimate 15 to 20 seconds after spray on, I felt considerable shuddering, slight yaw, change in control feel (roughness), a difference in sound and some loss of power. I ...made a right turn towards the clearing I had observed...I tried to fly to the clearing using what power may have been left ...hoping to clear the trees and build up more rotor RPM into the clearing to make some sort of landing. I could not avoid a tree in my path at the edge of the clearing, and collided with it, ending upright and nose down in the clearing...After the ground impact...I heard the turbine engine still running though it seemed at reduced RPM...[I] shut the engine down with the collective/twist grip throttle..."

According to the Federal Aviation Administration (FAA), Baltimore Flight Standards District Office (FSDO) Inspector's report, the main transmission was disassembled and revealed no defects. This included the free wheeling unit and the tail rotor gearbox.

According to the FAA, FSDO, Dallas, Texas, Aviation Safety Inspector's report, the engine was examined at Aviall Inc., in Dallas, Texas. The engine showed impact damage to the combustion liner and this component was changed to allow the engine to placed in condition for a test run. The engine was subjected to a functional test which lasted about 25 minutes. The report stated; "...The subject engine performed properly under all conditions during the test...."

The Bell Helicopter Flight Manual for the Model 47G-3B-1, contains an Airspeed vs. Altitude Chart. This chart depicts the areas to avoid continuous operations in, in the event of an engine failure.

The area of 65 MPH and 40 feet above the ground indicates that in the event of an power loss, "This region safe over smooth landing surface only."