Robinson R44 N144SM

Summary

On 11 May 2005 at about 16:45 local time, a Robinson R44 registered N144SM was involved in an accident near Gustine, California, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

11 May 2005 at 16:45

Classification

Accident

Location

Gustine, California, United States

Nearest airport

Gustine (3O1)

Coordinates

37.2625, -120.9631

Aircraft

Robinson R44

Registration

N144SM

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Los Banos → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX05LA164

Nobody was injured.

the improper installation of the nut/bolt assembly connecting the left cyclic push-pull tube to the non-rotating swashplate by maintenance personnel, which led to a loss of roll control during takeoff.

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

Read the full NTSB narrative

The helicopter landed hard and rolled over after the nut/bolt assembly connecting the left cyclic push-pull tube to the swashplate came loose, causing a loss of roll control during takeoff. No mechanical anomalies were noted during the preflight. The certificated flight instructor (CFI) and student departed to do training at another airport. During takeoff to return to their home base, the CFI heard a clicking noise coming from the helicopter and decided to make a precautionary landing; however, the helicopter began a roll to the right. The CFI attempted to correct the roll to the right with the application of left cyclic, but there was no corresponding response. The right skid contacted the ground and the helicopter rolled over, coming to rest on its left side. Following the accident, the bolt, nut, and two spacers that connected the left cyclic push-pull tube to the swashplate were located on the runway. When the Federal Aviation Administration inspector arrived, he also walked the accident area and found the self-locking nut. A review of the aircraft logbook indicated that the left rib at the top of the mast fairing had been installed at the last 100-hour inspection, 2.5 hours before the accident. In order to remove the left rib (bulkhead), the bolt and nut assembly that attaches the left cyclic push-pull tube to the left lug of the non-rotating swashplate had to be disassembled, and then reassembled after the rib (bulkhead) replacement. According to the manufacturer's Illustrated Parts Catalog, left cyclic push-pull tube connection to the non-rotating swashplate assembly requires a bolt and self-locking nut, 3 spacers (2 of the 3 spacers were found at the accident site), a washer, and a locking palnut, were not found. A metallurgical examination of the swashplate assembly, left push-pull tube, left rib (bulkhead), nut and bolt and associated hardware was conducted. All of the fracture surfaces examined revealed no preexisting damage. The absence of the bolt between the left cyclic push-pull tube and the non-rotating swashplate after the accident and the thread imprints within the hole of the left lug of the non-rotating swashplate indicated that the bolt had been backing out of the hole over time. The bolt and nut that were recovered were in good condition, and the hole in the left lug of the non-rotating swashplate was not significantly ovalized, indicating that the bolted connection was not subjected to excessive loads of any kind. The loss of the nut (and subsequent backing out of the bolt) indicates that the connection was not properly assembled following the recent maintenance, which required the bolted connection to be disassembled.

Quoted verbatim from the NTSB record.