Boeing Vertol BV-107 II N196CH

Summary

On 4 October 1996 at about 19:15 local time, a Boeing Vertol BV-107 II registered N196CH was involved in an accident near Canby, Oregon, United States. 3 people were on board and 3 died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

4 October 1996 at 19:15

Classification

Accident

Location

Canby, Oregon, United States

Coordinates

45.2108, -122.6605

Aircraft

Boeing Vertol BV-107 II

Registration

N196CH

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Aurora → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA97FA001

3 people died.

failure of maintenance personnel to install a cotter pin in a clevis bolt in the flight control system, which resulted in the aft directional and lateral control output pushrod to become disconnected from a bellcrank in the forward portion of the first stage mixing unit. A factor relating to the accident was the use of an improper bellcrank, which was wider in the clevis area.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The Boeing Model BV-107-II departed on a maintenance check flight with 1.4 hrs total flight time after conversion from a Model HKP-4 per FAA Project #TDO639NY-R. About 37 min later, witnesses saw the rotorcraft moving erratically & tumbling out of control. Postcrash exam of the rotorcraft's flight control system revealed a disconnect between the lower bearing end of the aft directional and lateral control pushrod & the inboard clevis of the forward mixing unit section bellcrank. A bolt, consistent with hardware for that connection, was found in the control closet area. An improper part (collective bellcrank, PN 107C2606-8) was found in place of the required lateral bellcrank (PN 107C2606-9). Clevis width of the -8 part was slightly larger than the -9 part; thus, the clevis bolt was not long enough to allow a cotter pin to be properly installed through the nut & bolt with the required washers (2 thick & 1 thin) installed. To compensate (allow for installation of the cotter pin), 2 thin washers were used in place of the 2 thick and 1 thin washers. Metallurgical exam of the bolt revealed evidence that a nut had been applied to the threaded end, but there was no evidence that a cotter pin had been inserted. No pre-accident engine malfunction or crew impairment was evident.

Quoted verbatim from the NTSB record.