ASN Wikibase Occurrence # 357394
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| Date: | Thursday 16 May 1996 |
| Time: | 15:00 LT |
| Type: |  McDonnell Douglas MD 520N |
| Owner/operator: | FAA |
| Registration: | N520DD |
| MSN: | LN0030 |
| Total airframe hrs: | 185 hours |
| Engine model: | Allison 250-C20R/2 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Bethany, OK -
 United States of America
|
| Phase: | Standing |
| Nature: | Unknown |
| Departure airport: | (KPWA) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Prior to the landing, the instructor pilot verified the wind from the tower (180 degrees at 19 knots, gusting to 22 knots). With the helicopter stable on the ground, downwind from a nearby building, the flight controls were frictioned down and normal shut down procedures were started. Passing through 19% rotor RPM, the rotor brake was applied. To demonstrate that the rotor would continue turning without rotor brake application, the instructor released the brake at 10% RPM and allowed the rotors to turn down to 9% RPM. The rotor brake was then re-applied, and while the rotor was decelerating, 'two or three thumps were heard', and the instructor observed the rotors 'jerk and come to a stop.' The instructor stated that wind being redirected around the building may have caused the rotors to flap down into the tail boom. Examination of the aircraft revealed that at least two of the three main rotors contacted the tail boom. No mechanical defects were found in the flight control and rotor systems. According to the manufacturer's flight manual, the shut down sequence and rotor brake application were conducted in accordance with current published procedures.
Probable Cause: The main rotor blades' contact with the tail boom due to gusting winds during rotor deceleration.
Accident investigation:
 |
|
Sources:
NTSB FTW96TA222
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 13-Mar-2024 17:27 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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