CHI93DEP05

As the helicopter was lifting off an elevated stand on a loading truck, the pilot heard a loud bang followed by a loss of engine power. The pilot used the rotor inertia to guide the helicopter away from the stand and truck when the helicopter descended into and collided with the terrain. Subsequent investigation revealed a fractured intake valve retainer (keeper) in the number one cylinder.

History of flight

on August 25, 1993, at 0910 CDT, a Bell 47-G5, N1464W, registered to Badger Helicopters, Inc., Janesville, Wisconsin, and operated by Mr. Gordon Patterson, collided with terrain during takeoff in a field near Edgerton, Wisconsin. The pilot received minor injuries and the aircraft sustained substantial damage. The aircraft was being operated as an aerial application flight by Badger Helicopters, Inc., under 14 CFR Part 137 when the accident occurred. The local flight originated at 0910 CDT. Visual meteorological conditions prevailed at the time and no flight plan was filed.

The pilot stated that on August 25, 1993, at approximately 0905 CDT he loaded 60-70 gallons of spray mix into N1464W. The helicopter was on a landing pad on top of a mix truck which would place the aircraft approximately 10 feet above the ground. The pilot then attempted to take off from the mix truck. When the aircraft was six to eight inches above the landing pad of the mix truck, he heard a loud bang.

The helicopter veered to the left. In his attempt to clear the landing pad and avoid hitting the mix truck with main rotor blades, the pilot stated he used all rotor RPM available. The helicopter struck the ground, bounced back into the air, then came to rest on the left side of the aircraft. He also stated he did not know exactly when the engine quit producing power, but the engine was not running when the aircraft came to rest on its left side.

Damage to aircraft

The plexiglas cockpit enclosure was completely destroyed. The main rotor blades and main rotor system sustained substantial damage. The tail rotor was undamaged, but the tail boom separated from the aircraft aft of the engine area.

Personnel information

The pilot-in-command held a Commercial Pilot Certificate with Airplane Single Engine Land and Helicopter Instrument Ratings. He has accumulated 10,722 hours total time, and 4,600 hours in this model aircraft. He holds a Second Class Medical Certificate, with date of last examination being July 2, 1993.

Meteorological information

The following are the weather conditions reported by the pilot at 0905 CDT on August 25, 1993:

Sky - clear; Visibility - 20 sm; Temperature - 80 F; Wind- 210 at 3 kts; Altimeter - 29.90" Hg; Dew point - 60 F.

Aircraft information

The aircraft, a Bell 47G-5, Serial Number 7933, Registration Number N1464W received an annual inspection on June 1, 1993, with a total time of 14,183 hours. Total airframe time at the time of the accident 14,257 hours. Total time since last inspection was 74 hours. The aircraft was registered to Badger Helicopters, Inc., Rt 7, Highway 51 South, Janesville, Wisconsin.

Wreckage and impact information

Initial ground impact was with the skids. The aircraft bounced back into the air, then impacted the ground with the left side of the aircraft. The engine stopped sometime during the impact sequence. The cockpit enclosure and the main rotor blades were destroyed by impact. The tail boom separated the aircraft aft of the engine area.

Tests and research

There was no damage found to the main rotor gearbox. The number one cylinder was removed from the engine. Inspection of the valve train revealed that the intake valve of the number one cylinder fell into the combustion chamber and was driven through the cylinder head by the piston. The valve spring retainer, P/N 68327 was found broken in half. Both valve springs and the valve spring keepers were found in the rocker arm area. The engine was overhauled by Technical Airmotive, Inc., of Janesville, Wisconsin on September 12, 1988, with an engine total time of 1,531 hours. the engine had accumulated 747 hours since overhaul at the time of the accident.

Additional information

Mr. Gordon Patterson, the owner of the aircraft took possession of the wreckage on August 31, 1993.