ASN Wikibase Occurrence # 284274
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| Date: | Friday 14 September 2007 |
| Time: | 10:15 LT |
| Type: |  Robinson R22 Beta |
| Owner/operator: | Universal Air Academy |
| Registration: | N877HF |
| MSN: | 3589 |
| Year of manufacture: | 2004 |
| Total airframe hrs: | 1708 hours |
| Engine model: | Textron Lycoming O-360-J2A |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | El Monte, California -
 United States of America
|
| Phase: | Unknown |
| Nature: | Training |
| Departure airport: | El Monte-San Gabriel Valley Airport, CA (EMT/KEMT) |
| El Monte-San Gabriel Valley Airport, CA (EMT/KEMT) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While in cruise flight about 1,700 feet agl, the flight instructor heard a loud "bang" from the back of the helicopter. The alternator warning light illuminated, and he initiated the alternator emergency procedure. He noticed the engine's rpm was fluctuating with the main rotor rpm indicating high and the engine rpm low. He entered an autorotation and landed on uneven terrain; the main rotor struck the tail boom, and the helicopter rolled over onto its left side. The helicopter was examined by a Safety Board investigator. The two main drive V-belts were located in the drive compartment with one positioned on the drive pulleys in the middle slot (between the normal operating positions for the forward and aft belts), and the other was located completely off of the drive pulleys. Both belts exhibited damage on the inside including scratch marks, material and color transfers, and gouges consistent with damage by a rubber based foreign object. Rubber and color transfer in a transverse orientation inconsistent with the drive belts was noted on the upper and lower pulleys. The alternator belt was missing and not recovered. The clutch assembly was located in the up position with the actuator fully extended, and the safety stop activated. The oil cooler sustained damage to the outer fins. Rubber transfer was located on the oil cooler, starter, oil lines, and exhaust tube on a plane with the alternator belt's rotation. The alternator belt is located directly below the lower main drive pulley. No other preimpact anomalies with either the airframe or engine were discovered. As a result of this investigation Robinson is changing the specification for the alternator drive belt.
Probable Cause: a failure of the main rotor drive system V-belts due to damage sustained when the alternator drive belt failed and pieces of that belt got between the main drive belts and their associated pulleys. A contributing factor was the uneven terrain encountered in the forced landing.
Accident investigation:
 |
|
Sources:
NTSB LAX07LA274
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-Sep-2022 14:17 | ASN Update Bot | Added |
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