SEA96LA139

The helicopter's left main landing gear collapsed as the pilot attempted a normal landing from a hover at his personal helipad. After the collapse, the main rotor blades and tail rotor blades contacted the ground, causing substantial damage to the tailboom and fuselage. The pilot stated that he saw three green landing gear cockpit lights, just before the accident, indicating that the landing gear was down and locked. He also stated that he heard a 'snap' noise in the tailboom just prior to the accident. An examination of the wreckage did not reveal any evidence of preimpact mechanical malfunction, deficiency, or structural failure. The left main landing gear failed in overload. The wind was reported to be 350 degrees at 17 knots, gusting to 24 knots.

On July 1, 1996, at 1657 Pacific daylight time, N808GM, an Augusta A109 helicopter, operated by the owner/pilot, collided with terrain during landing near Newport, Oregon, and was substantially damaged. The commercial pilot and his passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The personal flight departed from Hillsboro, Oregon, and was destined for Newport. The flight was conducted under 14 CFR 91.

In a telephone interview with the pilot immediately following the accident, the pilot stated that the helicopter's left main landing gear collapsed as the pilot attempted "a normal landing" from a hover at the pilot's personal heliport. The pilot stated that "All of a sudden, we rolled..." and the main rotor blades and tail rotor blades contacted the ground, causing substantial damage to the tailboom and fuselage. The pilot stated that he saw "three green lights" indicating that the landing gear was down and locked prior to the landing.

In a written statement (attached) later submitted to the Safety Board, the pilot stated: "While hovering over the helipad, fore and aft positioning had been obtained at about 6 [inches] hover height. Lateral position was almost obtained, when a tail rotor vibration was felt, immediately after a "snap" sound. I lowered the collective, the [helicopter] settled, and rotated and rolled left. The main rotors contacted the ground..."

The pilot further stated that he "believed" that the "tail rotor slider bearing set had failed, "... which may have caused the tail cone to crack...just aft [of the] attach plane. When the tail cone sagged down, [the tail rotor] drive shaft disconnected at spline..." He also stated that he saw "3 green lights indicating the landing gear down ...before and after accident."

The pilot later stated that a preexisting crack in the tailboom may have failed at the time of the hover, causing the tailboom to sag and the tail rotor drive shaft to disconnect.

An examination of the available wreckage and helipad was performed by FAA aviation safety inspectors from Hillsboro. A report of the examination is attached. According to the report:

The tailboom skid exhibited cracking around both upper attach fitting support structure.... No sign of preaccident fatigue or failure in this area was noted.... The Tailrotor driveshaft had disconnected in the area of the Thomas coupling above the tailboom. Rotational scaring around the Thomas coupling gives indication of drive to the tail rotor at the time of the accident. The tailboom transition section exhibited skin wrinkling in the lower areas. This is [an] indication that flexing of the tailboom transferred these loads to this area before the boom skin failed at the upper attachments.... All damage to the left landing gear struts, and supports appeared to be overload failures. No preexisting fatigue or failures were noted.

The FAA report of examination also stated that "... evidence of a failure that could have caused the noise or vibration..." was not found. Also, a review of Augusta A109 Helicopter Service Difficulty Reports, FAA Airworthiness Directives, and previous Augusta A109 accidents revealed "...no similar cases or reports."

The recorded wind conditions in the Newport area at the time of the accident were: winds from 350 degrees magnetic at 17 knots, gusting to 24 knots.