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N186CH accident description

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Tail numberN186CH
Accident dateAugust 31, 2001
Aircraft typeKawasaki KV-107-II
LocationEmigrant, MT
Near 45.323334 N, -110.731667 W
Additional details: None

NTSB description

HISTORY OF FLIGHT

On August 31, 2001, approximately 0905 hours mountain daylight time, a Kawasaki KV-107 II rotorcraft, N186CH, registered to and operated by Columbia Helicopters Leasing, Inc., and being flown by two commercial pilots, was destroyed when it collided with terrain following a loss of control in flight during a cruise/climb phase of operation. The crash site was approximately three miles south of Emigrant, Montana. Both pilots and the onboard mechanic were fatally injured. A post-crash fire destroyed much of the rotorcraft. Visual meteorological conditions existed and no flight plan had been filed. The flight, which was a non-mandatory maintenance check flight following a phase five inspection, was to have been operated under 14CFR91, and originated from the Fridley Helibase staging site approximately eight nautical miles north of the crash site and slightly north of Emigrant, Montana. The rotorcraft was estimated to have departed on the check flight approximately 0845. The aircraft was under contract with US Forest Service and was engaged in firefighting operations in support of the Fridley Fire centered approximately eight nautical miles north and west of Emigrant, Montana.

The rotorcraft departed the Fridley helibase approximately 0845 hours with both pilots and a mechanic aboard. At this time the rotorcraft had been released from the United States Forest Service (USFS) contract and would remain so for the duration of the test flight (refer to Attachment USDA-I). Immediately prior to departure the ground crewman observed the copilot occupying the right seat within the cockpit (refer to Attachment EK-I).

WITNESS DATA

There were seven witnesses located circumferentially around the accident site who observed the rotorcraft immediately prior to or during the crash sequence. The witnesses were located throughout all four quadrants of the compass (N/S/E/W) at distances ranging from less than one-half a mile up to three miles from the crash site (refer to Chart I which shows the approximate location of all seven witnesses).

A synopsis of key observations from each of the witness's statements follows (refer to attached individual witness statements one through seven for additional details):

Witness #1, who was located approximately one-half mile south of the accident site, and was looking north at the rotorcraft, reported that he saw it "dropping," facing south while rotating very slowly to the left; and that the rotorcraft was starting to drop to the left side. The witness believed that the tether and bucket were still below the rotorcraft at the time he observed it and that the rotorcraft was approximately 300 feet above the ridge when he first saw it dropping.

Witness #2, who was located approximately one mile south of the accident site, and was looking north at the rotorcraft, reported that he saw something "spinning" and "dropping fast out of sight."

Witness #3, who was located approximately one and one-half miles east of the accident site, and was looking west at the rotorcraft, reported that he saw it "wobbling" and then it "started down spinning."

Witness #4, who was located approximately three miles north of the accident site, and was looking south at the rotorcraft, reported that he saw "a chopper with [the] water bucket flying erratically." He commented that it seemed that the rotors "were not functioning properly" and that the rotorcraft was "going down fast in a circular pattern." He also reported the rotorcraft as rolling from side to side about 1,000 feet above ground.

Witness #5, who was located approximately two miles northwest of the accident site, and was looking southeast at the rotorcraft, reported that he had a side view of a light colored helicopter, which was "flying northbound" and "pulling a water bucket" and that "all looked fine." He reported further that after about five to six seconds of observation he witnessed the "aft (back) drop down and the forward (front) end rise up and go completely upside down." Additionally, he reported that as the aircraft approached a fully inverted attitude nearly horizontal with the ground he witnessed "the aft rotor blade catch the water bucket's cable and sling it around and round wildly." He then observed the rotorcraft descend inverted in a "left to right turn" with the bucket and cable entangled.

Witness #6, who was located approximately two miles west northwest of the accident site, reported that she observed the helicopter fly over highway 80 towards the Yellowstone River with the "basket hanging below and slightly behind [the] helicopter as it flew." After crossing over the Yellowstone River the helicopter appeared to climb and turn northward roughly paralleling the river. She reported that as the helicopter made this left turn "it seemed to suddenly start a sharp descent," "the nose seemed to dip lower" and "the left hand turn became sharper." The helicopter was observed to "lean steeply to the left" and the basket remained attached by its line and "became parallel to the helicopter as it continued its descent." She reported that the helicopter then turned back to the right and seemed to descend in a clockwise rotation at which point the "rotors appeared to have stopped rotation." The helicopter turned back to the left and rolled slightly on its side at which time "the basket was almost above the helicopter." She observed the helicopter then turn back to the right and level out slightly, during which "there was no rotation of the blades." The helicopter made one last turn to the left before descending from view.

Witness #7, who was located approximately one mile south southwest of the accident site, and was looking generally north at the rotorcraft, reported seeing the helicopter fly over and then turn north while carrying a water bucket. She reported that about one mile north of her location she observed the helicopter "pause and then descend with great speed," and that while it was descending she observed "one of the propellers and other parts from the top area of the helicopter fly off as it was descending."

PERSONNEL INFORMATION

PILOT-IN-COMMAND:

The pilot-in-command (PIC), who according to the operator would have been assigned the left cockpit seat, held a commercial pilot certificate with helicopter and instrument (helicopter) ratings as well as a type rating in the BV-107 (VFR only limitation). According to the operator, he had accrued approximately 3,889 hours of flight experience, all logged in rotorcraft, and approximately 1,715 hours were logged as PIC time. Additionally, he was reported to have logged approximately 1,631 hours in the Vertol V-107 model rotorcraft of which approximately 671 hours were as PIC. He had been issued a second class medical with no waivers/limitations on September 14, 2000.

CO-PILOT:

The co-pilot, who according to the operator would have been assigned the right cockpit seat, held a commercial pilot certificate with helicopter and instrument (helicopter) ratings and private pilot ratings in both airplane single engine land and instrument (airplane). He was not type rated in the BV-107 rotorcraft. He also held a certified flight instructor certificate with ratings in both helicopter and instrument (helicopter). According to the operator, he had accrued a total of approximately 1,354 hours of flight experience of which approximately 1,076 hours were as PIC and approximately 1,298 hours were logged in rotorcraft. Additionally, he was reported to have logged approximately 154 hours in the Vertol V-107 model rotorcraft, none of which was logged as PIC time. He had been issued a first class medical with no waivers/limitations on January 4, 2001.

CREWMAN:

The crewman, whose location in the rotorcraft could not be determined, held an FAA airframe and powerplant mechanic certificate. According to the operator, he had been engaged in maintenance on the rotorcraft during its preparation for flight testing and, as was customary for the operator, was assigned to assist during the test flight.

AIRCRAFT INFORMATION

N186CH, serial number 4005, was a Kawasaki model KV107-II manufactured derivative of the Boeing-Vertol model BV107 rotorcraft and was built in 1963. According to records maintained by the Federal Aviation Administration (FAA), the rotorcraft was owned by and registered to Columbia Helicopters Leasing, Inc. as of May 22, 1991. The rotorcraft had a total of approximately 41,559.1 hours of airframe time at the time of the most recent inspection (the day previous to the accident), and had flown for approximately 20 additional minutes on the morning of the accident.

According to the Aircraft Contract Daily Diary for N186CH on August 31, 2001, a morning fire briefing was conducted at 0630 at the incident command post followed by an air operations briefing which was conducted at the Fridley helibase at 0730 hours during which the pilot in command of N186CH indicated that he "...wanted [a] test flight to 'tweak' [the] logic system..." (the logic system is that portion of the electrically operated/mechanically actuated engine synchronization and control system). The diary continued with an entry logged as "0845 - Beginning Hobbs = Yesterday end Hobbs = 1288.7" (refer to Attachment ACDD-I).

The same 0730 entry also contained an entry following "...mechanic installed fuel actuator #2 engine...." There was no engine/airframe logbook entry supporting the installation of the fuel actuator for the #2 engine and the aircraft's status (grease) board located in the maintenance trailer, and which was documented by an FAA inspector, contained no reference to a change or installation of a fuel actuator/control unit.

N186CH had a maximum gross takeoff weight (MTGW) of 20,000 pounds for internal loads and this limit could be extended to 22,000 pounds for external loads. The rotorcraft was equipped with two General Electric CT58-140-1 turboshaft engines.

At the time of the accident, N186CH was equipped and operating with an external bucket used for firefighting operations. The bucket weight was approximately 700 pounds (empty) and the bucket was attached to the rotorcraft's external long line with an approximate 25-foot line. The external long line, from the bucket attach line point to the rotorcraft, was approximately 125 feet in length. The Operator reported that the bucket and long line were used on the accident flight to facilitate the check of the engine control unit, which could be accomplished at greater power settings with the bucket load than without such a load. However, alternative methodologies for providing such load effects were available. The aircraft had departed on the accident flight with 2,400 pounds of Jet A fuel.

N186CH was maintained under a continuous airworthiness program in accordance with the requirements specified in 14 CFR 91.409f(4). The most recent inspection, a phase 5 airframe inspection, was conducted on the rotorcraft on August 30, 2001. A maintenance check flight was not required following the completion of this inspection.

A review of the rotorcraft's maintenance records for the 45 days previous to the accident was conducted and an abbreviated maintenance history was compiled (refer to Attachment MT-I). No significant trends were noted. The number two engine was removed and replaced for overhaul on August 21st and again on August 26th for low torque indications and a hot air leak.

METEOROLOGICAL INFORMATION

Visual clear day meteorological conditions existed at the time of the accident. An aerial photograph taken of the crash site several hours after the accident showed a light column of smoke ascending above the tree line and gradually trailing toward the northeast quadrant (refer to photograph 1). The temperature at the accident site and time of the accident was estimated to be approximately 70 degrees Fahrenheit.

Aviation surface weather observations taken at Cody, Wyoming, and Livingston, Bozeman and West Yellowstone, Montana, for the morning of the accident reported, in part, the following conditions:

Cody (located 85nm east-southeast) reported clear skies, visibility of 10 miles and winds 190 degrees true at 5 knots at 0855.

Livingston (located 22nm north-northeast) reported clear skies, visibility of 10 miles and winds 310 degrees true at 10 knots at 0853.

Bozeman (located 33nm northwest) reported clear skies, visibility of 10 miles and calm winds at 0856.

West Yellowstone (located 42nm south-southwest) reported mostly cloudy skies, visibility 15 miles and winds calm at 0951.

WRECKAGE AND IMPACT INFORMATION

The rotorcraft crashed three nautical miles south of Emigrant, Montana, within the Emigrant Creek drainage and within an area moderately populated with a mix of deciduous and conifer trees. The primary ground impact site of the wreckage (fuselage) was approximately 5,200 feet above mean sea level (MSL) with the aft rotor head at 45 degrees 19.340 minutes north latitude and 110 degrees 44.056 minutes west longitude (refer to Charts I and II).

The rotorcraft was observed at the primary ground impact site resting on its right side and with its longitudinal axis oriented roughly along a north/south magnetic bearing. The cockpit area was located at the southernmost point with the fuselage progressing north through the cabin section to the engine and aft transmission area (refer to photograph 2). The area immediately aft of the cockpit including the control closet (upper fuselage) was observed to have a large tree trunk extending upwards vertically through the wreckage (refer to photograph 3). Aside from the cockpit section of the fuselage including the forward transmission assembly and pylon, the remainder of the rotorcraft had been subjected to a significant post crash fire, which consumed the center (cabin) section and most of the skin structure of the aft section. The magnesium aft transmission case had been completely consumed in the post crash fire leaving the internal gearing lying in place on the ground. Both turboshaft engines, the mixing box, aft rotor drive shaft and aft rotor head were found lying on the ground consistent with the rotorcraft having come to rest on its right side (refer to photograph 4). All five segments of the synchronization drive shaft extended between the forward transmission head and aft into the mixing box, and although the center section had significant fire damage and melting, all segment couplings were located along the vicinity of the drive shaft axis (refer to photograph 5).

The remains of the bucket, consisting of its steel circumferential retainer attached to the associated cabling was observed a short distance north of the aft rotor head (refer to photograph 6). The 150 foot long cabling, comprised of a braided, multi-strand steel support cable, along with an electric actuation line and two hydraulic operation lines was observed extending back into the primary wreckage area near the aft landing gear struts and progressing along the underside (east) of the fuselage and looped around the nose gear strut (refer to photographs 5 and 7).

Several areas of scrape marks characteristic of the steel braided bucket cable were noted in different locations within the wreckage. Specifically, prominent diagonal cross scrapes were observed along the nose gear strut (oleo) along with less prominent indications on one of the aft landing gear struts (refer to photograph 8). Additional scrape marks matching the cable braid pattern were noted along the forward left side of the fuselage, the aft and upper portion of the left cockpit bubble window, the forward rotor pylon and the forward rotor rain shield (refer to photographs 9 and 10).

The aft rotor head was missing all three rotor blades and each blade was observed to have separated at a location about two to three feet outboard of the blade to hub attach point (refer to photograph 11). Likewise, the forward rotor head was missing all three rotor blades and each blade was observed to have separated at a location about two to three feet outboard of the blade to hub attach point (refer to photograph 12). The remainder of the wreckage was distributed over three general areas as described i

(c) 2009-2011 Lee C. Baker. For informational purposes only.