19980827022279A

(.19)On August 27, 1998, at 1545 hours pacific daylight time, an aerospatiale SA316B, N605RA, operated by the U.S. Department of the interior, sustained substantial damage after entangling a bambi bucket in a tree in Porterville, California. The airline transport pilot, the sole occupant, was not injured. The public-use aircraft was performing a fire mission at the time of the accident. No flight plan was filed and visual meteorological conditions prevailed. Witnesses saw the helicopter fly down the side of a ridge with the bambi bucket on a 100-foot-long line. The bucket became entangled in some trees and the line snapped and wrapped itself around the tail rotor. The tail rotor gearbox separated and the helicopter spun to the ground and rolled down a steep slope. A federal aviation administration inspector from the fresno, California, flight standards district office reported that there were wire marks on the tail rotor blades and around the output shaft of the gearbox. (.4) the helicopter had a bambi bucket on a 100-foot-long line. The bucket became entangled in some trees and the line snapped and wrapped itself around the tail rotor. The tail rotor blades and gearbox sep arated from the aircraft and the helicopter spun to the ground and rolled down a steep slope. The pilot did not report any mechanical malfunction with the aircraft prior to the accident. Wire marks were found on the tail rotor blades and around the output shaft. (-23) aerospatiale SA316B, N605RA, contracted by the u. s. department of the interior was destroyed after entangling a water bucket in a tree east of Porterville, CA. The pilot, sole occupant, was not injured. The public use a/c was performing an external load fire mission at the time of the accident. Witnesses saw the helicopter fly down the side of a ridge with a water bucket on a 100 foot long line. The bucket became entangled in some trees and the long line snapped and wrapped itself around the tail rotor. The tail rotor gearbox separated and the helicopter spun to the ground and rolled down a slope. Detailed narrative follows: the a/c,pilot, and three fire crew members were dispatched to a wild land fire at the tule indian reservation. The fire crew members were off loaded near the fire site. A fire crew member attached a long line water bucket clevis into the cargo hook assembly a manual and electrical check of the hook release system was performed. While the a/c was performing the fourth water drop, an individual observed the long line entangled in a oak tree. Moments later a loud "pop" was heard. Attention was directed towards the a/c. others that heard the loud "pop" witnesses the long line wrapped around the tail rotor, and saw parts of the tail rotor departing and parts flying from the a/c. it was witnessed that the a/c made three, three hundred sixty degree spins, and then impacted a hill side on its side, then rolled into a tree upside down. The tail rotor gearbox that separated from the airframe was eighty feet from the impact point. One of the three tail rotor blades missing, deep spiral blemsih marks were noted around the tail rotor output shaft and leading edge of a tail rotor blade. The tail rotor failure appears to be the effect of the long line wrapping around the tail rotor assembly, caused by not maintaining sufficient terrain separation by the pilot.