Central, AK, USA
N4186Y
ROBINSON HELICOPTER COMPANY R44 II
The airline transport helicopter pilot reported that he was on a Title 14, CFR Part 135 passenger flight and was approaching a mountain ridge to drop off two technicians at a radio repeater site. Before beginning his approach, the pilot circled the site to determine the wind conditions, and then began his approach into a 10 knot wind. During the approach to the 5,657 foot level site, the pilot said he encountered a downdraft as the helicopter approached the site, and the helicopter descended below his anticipated approach path. He initiated a go-around, but the helicopter continued to descend, and landed hard, about 150 feet short and down slope of his intended touchdown point. During touchdown, the toes of the helicopter’s skids broke, and the helicopter rocked forward and aft, sustaining substantial damage to the right side of the tail boom. The pilot reported wind conditions on the ground as variable, gusting between 10 and 20 knots. In the pilot’s written statement to the NTSB, he reported that there were no preaccident mechanical problems with the helicopter.
On September 6, 2009, about 1735 Alaska daylight time, a Robinson R44 II helicopter, N4186Y, sustained substantial damage during a hard landing while on approach to a mountain ridge, about 38 miles southeast of Central, Alaska. The helicopter was being operated by Alpine Air Alaska, Inc., Girdwood, Alaska, as a visual flight rules (VFR) on-demand charter flight, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135. The airline transport pilot and the two passengers were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight departed the Fairbanks International Airport, Fairbanks, Alaska, about 1400, en route to various communication sites near Central. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on September 15, the pilot reported that the purpose of the flight was to transport two maintenance technicians to various mountaintop radio repeater sites in the area. He said that before beginning his approach to the 5,657 feet msl site, he circled the area to determine the wind conditions, and then planned his approach into a 10 knot headwind. During the approach to the treeless, tundra and rock-covered site, the pilot said he encountered a strong downdraft, and the helicopter began to descend below his anticipated approach path. He initiated a go-around, but the helicopter continued to descend, and it landed hard, about 150 feet short and down slope of his intended touchdown point. During touchdown, the toes of the helicopter’s skids broke, and the helicopter rocked forward and aft. The helicopter sustained substantial damage to the right side of the tail boom. The pilot characterized wind conditions on the ground as variable, gusting between 10 and 20 knots. In the pilot’s written statement to the NTSB he indicated that there were no preaccident mechanical problems with the helicopter. Additionally, he recommended relocating the landing site to an area above the ridge to minimize the exposure to downdrafts, and to install a functioning windsock. During a telephone conversation with the NTSB IIC on April 2, 2010, a representative from Alpine Air reported that the owner of the remote radio repeater site recently installed a new windsock, and is considering relocating the existing landing site.
The pilot’s failure to maintain control of the helicopter after an in-flight encounter with a downdraft while landing. Contributing to the accident was the pilot’s inadequate evaluation of wind conditions.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
