MD Helicopters 369D N501EF

Summary

On 7 March 2009 at about 18:00 local time, a MD Helicopters 369D registered N501EF, operated by Airwest Helicopters, Inc., was involved in an accident near Trona, California, United States. 3 people were on board and 3 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

7 March 2009 at 18:00

Classification

Accident

Location

Trona, California, United States

Coordinates

36.2167, -117.0839

Aircraft

MD Helicopters 369D

Registration

N501EF

Category

Helicopter

Engines

1

Operator

Airwest Helicopters, Inc.

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Inyokern → Rogers Peak

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR09LA144

3 people had minor injuries.

The pilot's failure to maintain control while landing in a high density altitude environment due to a loss of tail rotor effectiveness.

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

Read the full NTSB narrative

The helicopter pilot was flying passengers and equipment to a landing zone on a peak with an elevation of 9,993 feet. He made one high pass around the summit and assessed the wind as light and variable. He made a right circling approach and slowed from 60 knots to 40 knots. The airspeed suddenly decreased to 20 knots and the helicopter yawed 90 degrees to the right. He temporarily stabilized the situation, but then the helicopter went into a violent and uncontrollable right spin. It spun down vertically until it collided with terrain, rolled onto its right side, and slid about 75 yards before coming to a stop facing uphill. One of the passengers held a rotorcraft/helicopter pilot certificate. He indicated that on the first landing attempt the pilot appeared to be running out of left pedal. The second attempt was at a different angle to the landing zone, but once again the pilot seemed to run out of left pedal and the helicopter began to spin. The pilot could not recover during the attempt and the helicopter made three turns before colliding with the terrain. The Rotorcraft Flying Handbook refers to unanticipated yaw that does not subside on its own as a loss of tail rotor effectiveness. It notes that, if not corrected, this can lead to a loss of control. It may occur in all single-rotor helicopters at airspeeds less than 30 knots. A common cause is insufficient tail rotor thrust for a given power setting at higher altitudes, where tail rotor thrust and efficiency are reduced. Another potential cause is encountering a quartering tailwind from certain directions.

Quoted verbatim from the NTSB record.