19980823021849A

1967 Bell 47G-4A helicopter experienced an interruption of engine power at a low altitude, and the acft made an emergency hard landing. (.4) history of flight - on August 23, 1998, about 1600 central daylight time, a Bell 47G-4A, N7162M, registered to southern helicopters, operating as a 14 CFR part 137 aerial application flight, experienced a reported total loss of engine power. The helicopter landed hard during a forced landing in the vicinity of carrolton, Alabama. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter sustained substantial damage. The commercial pilot reported no injuries. The flight originated from a field site location about 5 minutes before the accident. The pilot stated he had just completed a swath run and was in cruise flight over trees at about 75 feet when the engine quit. He started a right turn before he entered autorotation. He did not monitor his engine or rotor RPM. He started a deceleration at about 30 feet with very little forward airspeed. The helicopter entered a vertical rate of descent. He pulled all collective pitch at about 10 feet. The helicopter collided with the ground hard and the main rotor blades collided with the tailboom assembly. Personnel information - information pertaining to first pilot information is found on page 3 of this report, and in NTSB form 6120.1/2 pilot information. Aircraft information - review of the engine logbooks revealed the last recorded annual inspection and engine overhaul was conducted on January 20, 1998. The engine had accumulated 246.5 hours since overhaul/annual inspection. The last recorded 100-hour inspection was conducted on June 9, 1998. The last recorded 50-hour inspection was conducted on July 1, 1998. According to the airframe and powerplant mechanic with inspection authority, the engine was overhauled by himself at his company in guam named tropic helicopters inc. the company was closed and the engine was shipped to his residence in Alabama, and installed on N7162M. Meteorological information - visual meteorological conditions prevailed at the time of the accident. (For additional information see weather information on page 4 of this report). Wreckage and impact information - according to the pickens county sheriff department, Carrollton, Alabama, the wreckage of N7162M was located in a field about 2.9 miles east of highway 17 south and county road 22 in the vicinity of Carrollton, Alabama. No accident crashsite investigation was conducted by the federal aviation administration (FAA) or NTSB. The accident was reported to the NTSB on August 25, 1998, by the FAA birmingham flight standards district office, birmingham, Alabama, as a reported engine failure which resulted in substantial damage. On August 26, 1998, the NTSB investigator-in-charge (iic) was contacted by an insurance adjuster from carson-brooks, inc., atlanta, Georgia. The adjuster informed the iic that there appeared to be a bullet hole in the engine crankcase next to the number 4 cylinder. Local law enforcement authorities were notified and the helicopter was transported to an authorized repair facility for analysis by the NTSB, FAA, and law enforcement personnel. Examination of the helicopter revealed scarring was present on the bottom of the helicopter tail guard assembly from contact with the ground. The helicopter continued forward and collided with the ground in a right skid low attitude. The forward and aft cross tube assemblies were bowed in the middle with evidence of right lateral shift on the saddle straps. The left skid was rotated to the right 90 degrees. The forward and aft legs failed forward and to the right. The right skid was rotated to the right about 30 degrees. The forward and aft legs failed forward and to the right. The aft leg separated from the skid assembly. The right underside fuselage was compressed upward with the floor assembly on the cabin assembly. Minor damage was present on the left underside fuselage of the cabin assembly. The bubble assembly was broken. The left and right fuel tanks were not damage. The lower truss type fuselage failed at the jack point at FS80. The upper right truss attach point failed 10 inches outboard of the attach point, and was bowed in to the right at about FS90. The upper left truss attach point was intact. The truss type attach fuselage separated at FS160, FS179, and FS225. The vertical fin, tailrotor extension shaft, and tailrotor guard assembly separated from the truss type fuselage. Examination of the main rotor system and tailrotor system revealed no evidence of a precrash mechanical failure or malfunction. The yellow main rotor blade collided with the truss type fuselage, tailrotor extension shaft, and the drag brace separated from the main rotor blade. A hole was present on the bottom side of the main rotor blade 20 inches inboard of the blade tip. Chordwise scarring and transfer of blue and white paint was present on the bottom and top of the main rotor blade. No leading edge damage was present. The red main rotor blade collided with the truss type. (-23) nelson e. tucker was returning to his flatbed trailer, at about 75 feet AGL, after dispensing product, when the engine in the Bell 47 helicopter failed. During the emergency landing. Mr. Tucker momentarily delayed autorotation, resulting in a very hard landing and substantial damage ot the helicopter. Mr. Tucker was not injured. Further investigation revealed the engine failed due to crankshaft counterweights failure. Further investigation revealed improper procedures during maintenance (improper installation of circlips in crankshaft counterweights).