Robinson R-22 HP N21439

Summary

On 25 January 1991 at about 15:40 local time, a Robinson R-22 HP registered N21439, operated by Arizona Wing & Rotor, Inc., was involved in an accident near Scottsdale, Arizona, 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

25 January 1991 at 15:40

Classification

Accident

Location

Scottsdale, Arizona, United States

Coordinates

33.6109, -111.8908

Aircraft

Robinson R-22 HP

Registration

N21439

Category

Helicopter

Engines

1

Operator

Arizona Wing & Rotor, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX91LA079

Nobody was injured.

THE FAILURE OF THE DRIVE BELTS DUE TO EXCESSIVE WEAR OF THE CLUTCH ASSEMBLY UPPER SHEAVE AND THE PILOT'S INACCURATE FLARE DURING THE TERMINATION OF THE AUTOROTATION. A FACTOR IN THE ACCIDENT WAS THE INADEQUATE DESIGN OF THE CLUTCH ASSEMBLY UPPER SHEAVE.

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

Read the full NTSB narrative

THE PILOT, AFTER SEEING THE HELICOPTER'S CLUTCH CAUTION LIGHT ILLUMINATE, HEARD A LOUD 'BANG'. HE LOWERED THE COLLECTIVE AND ENTERED AN AUTOROTATIVE DESCENT. HE TERMINATED LOW TO THE TERRAIN, AND THE AIRCRAFT STRUCK TAIL STINGER FIRST, CAUSING IT TO BOUNCE AND THEN ROLL OVER. A VISUAL INSPECTION OF THE HELICOPTER REVEALED TWO OF THE DRIVE BELTS HAD FAILED, CAUSING A DRIVE TRAIN SEPARATION. THE HELICOPTER MANUFACTURER DISCOVERED THE BELTS FAILED AS A RESULT OF EXCESSIVE WEAR ON THE CLUTCH ASSEMBLY UPPER SHEAVE. THE EXCESSIVE WEAR ON THE SHEAVE WAS CAUSED BY THE BELTS, GRITS, AND SAND. THIS CREATED A SHARP EDGE ON THE SHEAVE WHICH CAUSED THE FAILURE OF THE BELTS.

Quoted verbatim from the NTSB record.