Hughes OH-6 N353RK

Summary

On 5 December 2002 at about 15:00 local time, a Hughes OH-6 registered N353RK, operated by Freelance Air Inc., was involved in an incident near Moberly, Missouri, United States. One person was on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

5 December 2002 at 15:00

Classification

Incident

Location

Moberly, Missouri, United States

Nearest airport

Omar N Bradley Airport (MBY)

Coordinates

39.4639, -92.4275

Aircraft

Hughes OH-6

Registration

N353RK

Category

Helicopter

Engines

1

Operator

Freelance Air Inc.

Operating rule

Public Use

Purpose of flight

Ferry

Phase of flight

Not recorded

Route

St. Louis → Omaha

Aircraft damage

Minor

Weather

VMC

Light

Day

NTSB number

CHI03IA033

Nobody was injured.

The loss of tail rotor effectiveness during cruise flight due to the bellcrank pivot pin becoming separated from the non-rotational swashplate. The plain brass liner of the non-rotating swashplate and the bellcrank pivot pin were worn.

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

Read the full NTSB narrative

The helicopter lost tail rotor effectiveness during cruise flight, and the pilot executed a run on landing to a paved runway. The pilot reported that he was in cruise flight for approximately one hour when the helicopter "entered an estimated 20 degree uncommanded yaw to the right." Applying pressure to the anti-torque pedals had no effect. The pilot reported that there had been no advance auditory indications or unusual vibrations prior to the yaw occurring. The pilot flew to an airport about 12 nautical miles away, and executed a successful run on landing. The inspection of the helicopter revealed that the tail rotor bellcrank pivot pin was dislodged from the non-rotating swashplate and was rotated inboard towards the boom. The plain brass liner, which is a pressed liner internal to the non-rotating swashplate and surrounds the tail rotor gearbox output shaft, was broken into 15 identifiable pieces. No evidence of fatigue or abnormal wear was found on the pieces of the plain liner. The splined brass liner within the non-rotating swashplate was damaged. Eight of the seventeen splines of the swashplate splined liner had fractured areas and one of the splines was cracked. No evidence of fatigue was found on any of the fractures. The splined liner was still riveted to the rotating swashplate and was still capable of bearing a load. The tail rotor gearbox was replaced with an overhauled gearbox 29.4 flight hours prior to the time of the incident. There was no record of any mechanical discrepancies to the tail rotor assembly, including the non-rotating swashplate, when the overhauled tail rotor gearbox was installed.

Quoted verbatim from the NTSB record.