Bell 47G2 N9021R

Summary

On 12 December 1998 at about 00:45 local time, a Bell 47G2 registered N9021R was involved in an accident near Helendale, California, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

12 December 1998 at 00:45

Classification

Accident

Location

Helendale, California, United States

Coordinates

34.7393, -117.3493

Aircraft

Bell 47G2

Registration

N9021R

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Kramer's Jct → Helendale

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

LAX99LA047

Nobody was injured.

The pilot's failure to follow proper procedures to recover from main rotor blade aerodynamic retreating blade stall.

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

Read the full NTSB narrative

The pilot encountered retreating blade stall while flying at 100 mph. He reported that the helicopter began to shake and it felt like an 'out of balance feeling, like when the washing machine gets unbalanced.' The rotor rpm began to decay. When he reduced power and stabilized the airspeed to about 60 to 65 mph, the shaking stopped. The pilot stated that he was not able to maintain lift, so he entered an autorotation over the hilly terrain. The tail rotor blades impacted an embankment and the main rotor blades severed the tail boom. The pilot's manual for the Bell 47G2 indicates that the 'never-exceed speed' (Vne) for the helicopter is 100 mph. According to the FAA's Basic Helicopter Handbook, the recovery procedure for retreating blade stall is to reduce the collective pitch, increase rotor rpm, reduce forward airspeed, and minimize maneuvering.

Quoted verbatim from the NTSB record.