Bell 412SP N412SM

Summary

On 28 February 2001 at about 17:24 local time, a Bell 412SP registered N412SM, operated by Petroleum Helicopters, Inc., was involved in an accident near Grand Junction, Colorado, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

28 February 2001 at 17:24

Classification

Accident

Location

Grand Junction, Colorado, United States

Nearest airport

St. Mary's Helipad (29CO)

Coordinates

39.2606, -108.5300

Aircraft

Bell 412SP

Registration

N412SM

Category

Helicopter

Engines

2

Operator

Petroleum Helicopters, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Flight Test

Phase of flight

Not recorded

Route

Grand Junction → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

DEN01FA058

1 person died.

the pilot's failure to maintain rotor speed during an intentional autorotation, which resulted in a loss of control.

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

Read the full NTSB narrative

During a test flight, following maintenance on the helicopter, which required a functional flight check for vibration and autorotation, the helicopter was observed by witnesses to enter a rapid descent. During this maneuver, the rotor system was observed to slow down and the rotor blades to "fold" over the top of the helicopter. Pieces, which were later identified as fragments from the transmission cowling, were observed exiting the helicopter when the rotor system slowed down. The helicopter descended into the ground in a right hand turning maneuver. Examination of the wreckage revealed no evidence of either a structural or system failure or malfunction. According to the helicopter's manufacturer, as the main rotor system slows while under aerodynamic load, the main gear box can "walk" (horizontal orbital movement) on its mounting structure, which can result in contact between the transmission cowling and the main rotor control rod ends. Examination of the engines revealed evidence that engine power was applied when the rotor system was at low rotational speed. No evidence of preimpact engine failure or malfunction was found. According to available information, the pilot had received no training from the operator regarding the conduct of a maintenance test flight, not does the FAA require such training.

Quoted verbatim from the NTSB record.