NTSB Factual Report

HISTORY OF FLIGHT

On May 20, 2002, approximately 1745 Pacific daylight time, a Kaman K-600 (HH-43), N286M, registered to/operated by JC Helicopter Services LLC, and being flown by a commercial pilot, sustained a jammed collective condition while entering a hover at a logging site near Cocolalla, Idaho. The pilot was uninjured and the aircraft sustained no damage during the pilot's use of alternate controls to affect an emergency landing. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was engaged in logging operations, was operated under 14 CFR 133, and originated from a local site nearby.

The pilot reported that he had been engaged in log-slinging operations and that after about two hours while flaring in anticipation of another load pickup, he began to reduce collective to stop the climb and bring the hook into position. He determined that the collective was jammed at a high power setting and could not be reduced further. He was able to stop the climb and establish level flight by applying throttle outside the governed range and selecting manual on the governor control switch. He was then able to initiate a slow descent by reducing RPM and after approximately 20 minutes of practiced flight operations in this regime during which he determined that control response was marginal, he initiated a landing to an open field. Approximately eight feet above ground entering ground effect he began to lose control of the rotorcraft, rolled the throttle to flight idle and executed a successful landing.

Post-incident investigation revealed that the four hex head bolts that secure the RPM compensator assembly control box into the cabin ceiling had been installed such that each bolt head was at the top of the control box with each threaded bolt end extruding downward through the control box bolt retaining ears. The threaded (nut) ends of all four bolts were observed extending out the bottom of the control box retaining holes such that the threaded end of each bolt faced down and at least one bolt end was found to interfere with the movement of the RPM compensator telescopic unit clevis (refer to photo 1). Further examination revealed that when the bolts were installed with each hex head end at the bottom of the control box and the nuts at the top, the maximum extension of the bolt from the bottom of the control box was confined to the thickness of the hex head. This installation would ensure that none of the four bolts would interfere with the RPM compensator telescopic unit.

AIRCRAFT INFORMATION

Timber Choppers, Inc. holds the Type Certificate for the civil variant of the Kaman HH-43 series rotorcraft (refer to Attachment TC-I). N286M, a Kaman K-600, also previously designated for military use as the HH-43B rotorcraft, had been acquired from military surplus and had been certificated by the Federal Aviation Administration for restricted category operations. The total airframe and engine time was not reported and the rotorcraft was reported as being on a continuous airworthiness inspection program with the most recent (phase) inspection being conducted May 20, 2002, four hours prior to the accident.

The maintenance instructions contained in the Technical Order (T.O.) for the HH-43 (refer to Attachment TO-I) were reviewed, specifically, the sections covering the removal and installation of the RPM compensator assembly control box. The installation procedure was described under Section III, paragraph 3-91 (x) as follows:

"Position control box assembly (13) on cabin ceiling and secure with four bolts, eight washers and four nuts."

The Technical Order provided no guidance as to the proper orientation (up or down) for the bolts upon installation.

NTSB Probable Cause

The reverse installation of the RPM compensator assembly control box bolts resulting in the threaded end of the bolt impinging on a clevis and jamming the collective during climb. A contributing factor was the lack of adequate documentation provided by the technical order instruction for installation of the compensator.