Eurocopter France AS350 B3 N414HP

Summary

On 15 December 2007 at about 00:20 local time, a Eurocopter France AS350 B3 registered N414HP, operated by California Highway Patrol, was involved in an incident near Fresno, California, United States. 2 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

15 December 2007 at 00:20

Classification

Incident

Location

Fresno, California, United States

Nearest airport

Fresno Yosemite International (FAT)

Coordinates

36.7761, -119.7181

Aircraft

Eurocopter France AS350 B3

Registration

N414HP

Category

Helicopter

Engines

1

Operator

California Highway Patrol

Operating rule

Part 91: General Aviation

Phase of flight

Not recorded

Route

Fresno → Unknown

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

LAX08IA042

Nobody was injured.

Malfunction of a hydraulic servo while on final approach due to excessive wear of the locking finger.

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

Read the full NTSB narrative

The certified flight instructor (CFI) configured the helicopter for a practice emergency maneuver with the hydraulic system off. Upon disengaging the hydraulics, he immediately noticed that an abnormal force was required on the cyclic control to prevent the helicopter's nose from pitching up and to the left. He elected to continue the landing with the hydraulics off and began to slow the airspeed as the helicopter adjoined final approach. He was convinced that he would not be able to land the helicopter without it incurring damage due to the severe control restriction. He managed to complete a run-on landing without mishap by maintaining an airspeed of about 10 kts. When the helicopter came to rest, the pressure was released on the cyclic and the second pilot restored the hydraulics via the collective switch. Immediately thereafter, the cyclic began a hard over and displaced to the left against the CFI's leg. He attempted to center the cyclic with both hands, but he was unable to move the control. After 40 seconds the pressure released and the second pilot centered the cyclic with ease. The hydraulic servos were tested and a complete teardown of each servo was performed. The pressure testing of one of the servos revealed that the unlocking pressure was out of tolerance (too high). Upon disassembly of this servo, wear was observed on the conical surface of the locking finger and on the diameter in contact with the bearing. According to the servo manufacturer, the wear resulted in excessive friction in the bearing, which led to the high unlocking pressure.

Quoted verbatim from the NTSB record.