Bell 47D1 N4251A

Summary

On 8 November 2011 at about 22:25 local time, a Bell 47D1 registered N4251A was involved in an accident near San Diego, California, United States. 2 people were 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

8 November 2011 at 22:25

Classification

Accident

Location

San Diego, California, United States

Nearest airport

Brown Field (SDM)

Coordinates

32.5722, -116.9800

Aircraft

Bell 47D1

Registration

N4251A

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

San Diego → San Diego

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR12LA029

Nobody was injured.

The flight instructor's inadequate supervision of the student pilot during a simulated autorotation and the pilots’ failure to use carburetor heat while operating at reduced engine power while in carburetor icing conditions, which resulted in a loss of engine power.

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

Read the full NTSB narrative

During an instructional flight, a practice autorotation was initiated with the intention of performing a power recovery. The student maintained directional control while the certified flight instructor (CFI) adjusted the rotor rpm. The student initiated the power recovery, but the engine did not respond. The student then relinquished control of the helicopter to the CFI, who attempted to cushion the landing, but the helicopter landed hard. The helicopter's engine was equipped with a float-type carburetor, and the weather conditions provided for the possibility of serious carburetor icing at glide power. The accumulation of carburetor ice likely resulted in the loss of engine power. Neither the CFI nor student applied carburetor heat during the autorotation, nor they did not monitor the carburetor temperature gauge during the maneuver. During the postaccident examination of the engine, no mechanical failures or malfunctions were revealed which would have precluded normal operation. The CFI's flight experience in piston-powered helicopters was limited to the 6 hours of training he had provided in the accident helicopter, with his prior rotorcraft experience occurring exclusively in turbine-powered helicopters. This was also the first time he had performed an autorotation in the accident helicopter.

Quoted verbatim from the NTSB record.