- Date
- January 25, 1991, 08:40 local (15:40 UTC)
- Place
- Scottsdale, AZ
- Injuries
- 1 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N21439Robinson R-22 HP
- Weather
- Visual (VMC) · Day
- Status
- Completed · report March 31, 1993
- Report
- Approved by Office Director
- Safety recommendations
- Yes
- FAA report
- 19910125001109A
- Case key
- 27098
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
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.
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
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.
Aircraft
- Registration
- N21439
- Reported as
- Robinson R-22 HP
- Category
- Helicopter
- Serial number
- 0096
- Engine
- Lycoming O-320-B2C, 160 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Instructional · Part 91
- Operator
- Arizona Wing & Rotor, Inc.
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 25
- Certificate
- Student
- Medical
- Class 2, Valid Medical--no waivers/lim.
- Flight hours
- 58 total · 58 in this make and model · 58 in the last 90 days · 48 in the last 30 days · 2 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- Calm
- Visibility
- 10 statute miles
- Lowest ceiling
- None
- Temperature
- 55 °F, dew point -0 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.