Aerospatiale AS-350D N3593S

Summary

On 28 December 1999 at about 18:50 local time, a Aerospatiale AS-350D registered N3593S was involved in an accident near Avalon, California, United States. 7 people were on board and one was seriously injured, 6 had minor injuries. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

28 December 1999 at 18:50

Classification

Accident

Location

Avalon, California, United States

Coordinates

33.4164, -118.4653

Aircraft

Aerospatiale AS-350D

Registration

N3593S

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Avalon → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX00FA061

1 person was seriously injured.

A loose pneumatic fitting caused the engine to go to flight idle power at a low altitude, which resulted in a forced landing in hilly terrain.

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

Read the full NTSB narrative

The helicopter collided with terrain following a loss of engine power while maneuvering at low level on a sightseeing flight. As the helicopter passed about 250 feet above ground level (agl) over a ridgeline, the pilot began a descending and decelerating right turn to observe a herd of buffalo. About midway down the ridge, the low rotor rpm warning horn sounded. The pilot lowered collective and the horn stayed on. He noted the rotor speed was down between 300 and 320 rpm and concluded that he would have to make an immediate landing. The helicopter landed downslope at an estimated 10 to 15 mph, and the tail rotor struck the ground first. The helicopter pitched forward, continued to slide down the hill, collided with trees, and rolled onto its right side. An 80-psi check of the pneumatic system revealed two calibrated leaks and an additional leak. The attachment fitting for the P3 air accumulator on the governor pressure (Pg) line was 3/4 of a turn loose. The engine was removed and shipped to the manufacturer for testing. Several discrepancies due to damaged hardware were corrected during preparation for the test run. The engine was placed in a test stand and started normally. The engine completed a test protocol with no discrepancies noted. The P3 accumulator fitting was loosened and the engine immediately went to flight idle. The engine would not accelerate above idle power with the P3 accumulator fitting loose. Once the fitting was loosened less than finger tight, it continued to loosen to 3/4 to a full turn loose.

Quoted verbatim from the NTSB record.