ASN Wikibase Occurrence # 154117
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| Date: | Thursday 14 March 2013 |
| Time: | 14:45 |
| Type: |  Robinson R44 Raven II |
| Owner/operator: | Leading Edge Aviation, Inc. |
| Registration: | N392GP |
| MSN: | 11238 |
| Year of manufacture: | 2006 |
| Total airframe hrs: | 2167 hours |
| Engine model: | Lycoming IO-540-F1B5 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | A field near Eagles Nest, NM -
 United States of America
|
| Phase: | En route |
| Nature: | Training |
| Departure airport: | Dalhart, TX (KDHT) |
| Monte Vista, CO (KMVI) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight instructor and student pilot were cruising about 800 feet above ground level when they heard a loud “bang,” followed immediately by the low rotor rpm horn, a warning light illumination, and a rapid decrease in rotor rpm indication. In response, the instructor initiated an autorotation by lowering the collective, and the engine immediately lost power. The helicopter touched down and then rocked forward due to soft and downward-sloping terrain. The instructor applied slight aft cyclic to prevent the main rotor blades from contacting the ground; however, the main rotor blades struck and severed the tail boom.
The engine was functionally tested, and it operated normally. However, one of the magnets used to provide rotor rpm indications was missing from the rotating transmission yoke and was found affixed to a bolt just aft of the yoke. It likely had become loose in flight, and its movement was the bang heard by the pilots. Scarring was found on one of the sensors opposite the magnet, indicating that the magnet had contacted the sensor. The separation of the magnet caused the rotor rpm indication to drop and the low rotor rpm warning horn and light to activate. Due to the control linkage between the collective and the throttle, when the instructor lowered the collective, the throttle closed rapidly. According to Robinson Helicopters, rapid throttle changes can result in a fuel-air ratio becoming too rich or too lean to sustain engine operation and result in an engine failure.
Probable Cause: A total loss of engine power due to a rapid throttle change during autorotation, which the flight instructor initiated in response to a low rotor rpm warning, which resulted from the separation of one of the magnets used to provide rotor rpm indications from the rotating transmission yoke. Contributing to the accident was the flight instructor's aft cyclic input upon landing.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=392gp
History of this aircraft
Other occurrences involving this aircraft
| 28 May 2014 | N392GP | Global Positioning Services Inc | 1 | Birchwood Airport, AK | |
w/o |
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Mar-2013 10:04 | gerard57 | Added |
| 15-Mar-2013 10:55 | edbu | Updated [Aircraft type, Registration, Cn] |
| 15-Mar-2013 19:50 | Geno | Updated [Time, Aircraft type, Operator, Location, Nature, Source, Narrative] |
| 19-Mar-2013 09:27 | Anon. | Updated [Aircraft type, Narrative] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 28-Nov-2017 14:15 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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