TONYS TRUCKING INC: http://registry.faa.gov/N6181A
FAA Flight Standards District Office: FAA Spokane FSDO-13
NTSB Identification: WPR16LA188
14 CFR Public Aircraft
Accident occurred Monday, September 12, 2016 in Rockport, WA
Aircraft: BELL 206B, registration: N6181A
Injuries: 2 Uninjured.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
On September 12, 2016, about 1345 Pacific daylight time, a high skid-equipped Bell 206BIII helicopter, N6181A, sustained substantial damage after landing in remote mountainous terrain on Mount Prophet in the North Cascades National Park, about 30 miles northwest of Rockport, Washington. The certificated commercial pilot and the sole passenger sustained no injury. The helicopter was registered to, Tony's Trucking, Inc. Darrington, Washington, and operated by Hi Line Helicopters, Inc., Darrington, as a day, visual flight rules (VFR) public use flight in contract with the National Park Service (NPS). Visual meteorological conditions prevailed at the time of the accident, and company flight following procedures were in effect. The flight originated from a helicopter landing zone near Diablo Lake about 8 miles south of the accident site, about 1330.
The pilot reported in the National Transportation Safety Board (NTSB) Accident/Incident Reporting Form 6120.1 that the purpose of the flight was to conduct external load operations into the Firn Lake and Skymo Lake areas on Mount Prophet. The pilot reported that a NPS employee was onboard, where his duty was to depart the helicopter after landing, and assist with external load operations from the ground by attaching a long line to the helicopter and then wait to receive the external load. The helicopter arrived at Firn Lake about 1340 and the pilot conducted a high reconnaissance to locate a suitable area for landing and to also identify a suitable spot to place the external load. The pilot reported she selected a landing spot on the south end of the lake in a flat area. After the landing, the pilot brought the throttle to idle and the NPS employee departed the helicopter from the left seat in the cockpit. While the NPS employee was securing the cockpit door closed, the pilot reported the helicopter started to move with lateral oscillations. The pilot adjusted the flight controls, increased the throttle, and the lateral oscillations ceased. The pilot shut down the engine and a postflight inspection was conducted which revealed substantial damage to the transmission system. The pilot reported that the wind condition at the accident site was variable, 5 to 10 knots, and gusting plus or minus 5 knots. The pilot verified that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
During a telephone interview with the NTSB investigator-in-charge (IIC) on October 12, 2016 the pilot stated this was her first time landing at Firn Lake. After conducting the high reconnaissance, she executed an approach to a spot but did not fully set the helicopter down due to suitability concerns with the terrain. The pilot then repositioned the helicopter about 180 degrees to a different spot which was "fairly flat" and landed the helicopter. After the landing and reducing the throttle to idle with the cyclic centered, she discussed with the NPS employee their plan of action for the external loads and he departed the helicopter. The oscillations started as he was securing the cockpit door closed. The pilot stated she then moved the cyclic slightly forward to cease the oscillations, which appeared to make the oscillations worse. The throttle was increased, the oscillations ceased, and the engine was shut down.
An air safety investigator from the Department of Interior Office of Aviation Safety (DOI OAS) reported to a NTSB air safety investigator on September 23, 2016 that the operator was conducting a "call-when-needed" mission for the NPS when the accident occurred. The DOI OAS air safety investigator further reported that after the accident, the helicopter was secured and transported as an external load via helicopter back to the operator's hangar in Darrington. The DOI OAS air safety investigator also submitted on September 29, 2016 a written statement from the NPS employee who reported that the landing area utilized was flat and covered with vegetation and interspersed with basketball-sized boulders. The NPS employee further reported that while he was securing the cockpit door closed, the helicopter "bounced and lurched" and he visually confirmed that the tail rotor system did not strike an object or terrain.
On September 21, 2016, an airworthiness inspector from the DOI OAS traveled to the operator's hangar to conduct an inspection of the airframe and engine. In a written report submitted to the DOI OAS, the inspector reported that he was not given full access by the operator to conduct a thorough airframe and engine inspection. The inspector performed a limited inspection and noted substantial damage sustained to the main rotor mast and to the transmission system.
The closest official weather observation station is located at the Bellingham International Airport, Bellingham, Washington, about 55 miles to the west of the accident site. At 1353, an Aviation Routine Weather Report (METAR) was reporting, and stated in part: Wind 340 degrees at 6 knots; visibility 10 statute miles; clouds and sky condition, clear; temperature 75 degrees F; dew point 36 degrees F; altimeter 30.17 inHg.