ASN Wikibase Occurrence # 45128
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| Date: | Monday 4 August 2003 |
| Time: | 18:35 |
| Type: | Wright Hughes 1-B |
| Owner/operator: | Private |
| Registration: | N258Y |
| MSN: | 2 |
| Total airframe hrs: | 74 hours |
| Engine model: | Pratt & Whitney R-1535-11 |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Yellowstone Nat, WY -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Private |
| Departure airport: | Gillette, WY (GCC) |
| Eugene, OR (EUG) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Several witnesses at Yellowstone National Park's Midway Geyser basin area reported seeing the airplane approaching them at a "low altitude" from the southeast. The airplane was quiet, and was observed gliding with its wings tipping back and forth. Next, it was observed to corkscrew, or spiral to the ground. The airplane's propeller was a highly modified constant speed Hamilton Standard 12D40 hub. Neither of the two 7 pound counterweights were found at the accident site. Examination of the #2 counterweight bracket revealed a fatigue crack at the proximal end of the counterweight slot. The propeller's shim plates exhibited impact signatures of the two blades indicating an angular difference of 10 degrees. The propeller's cylinder was crushed on one side, locking the piston inside the cylinder; the location of the piston inside the cylinder correlated to a blade angle of 34.9 degrees. If a propeller counterweight had separated in flight, aerodynamic forces would have driven the blade towards fine pitch or low blade angle. The blade's rotation would be limited to the low blade angle, of 24 degrees, by the remaining portion of its counterweight bracket arm which would contact and be stopped by the propeller’s barrel. If one blade was at the low blade angle of 24 degrees, the measured angular difference of 10 degrees, would indicate that the other blade was at an angle of 34 degrees. The agreement between this derived blade angle of 34 degrees and the piston position of 34.9 degrees suggests that one blade was still slaved to its counterweight at the time of impact and one blade was not.
Probable Cause: The in-flight loss of a propeller counterweight, followed by the pilot's loss of aircraft control during a forced landing attempt and subsequent inadvertent stall/spin to the ground.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20030815X01342&key=1
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 28-Oct-2008 00:45 | ASN archive | Added |
| 21-Dec-2016 19:24 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 08-Dec-2017 19:10 | ASN Update Bot | Updated [Source, Narrative] |
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