ASN Wikibase Occurrence # 136921
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| Date: | Monday 27 June 2011 |
| Time: | 12:23 |
| Type: |  Robinson R22 Beta |
| Owner/operator: | Private |
| Registration: | N7779M |
| MSN: | 1229 |
| Year of manufacture: | 1990 |
| Total airframe hrs: | 2295 hours |
| Engine model: | Lycoming O-320-B2C |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Caldwell Lane, DeValle, near Garfield, SE of Austin, Texas -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Taylor Municipal Airport, Taylor, Texas (FAA LID: T74) |
| Luling, Caldwell County, Texas | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On June 27, 2011, at 12:23 CDT (Central Daylight Time), a Robinson R22 BETA helicopter, N7779M, struck trees and impacted terrain near Del Valle, Texas. The pilot, the sole occupant on board, was fatally injured. The helicopter was substantially damaged and a post-impact fire ensued. The helicopter was registered to and operated by the operator under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The cross-country flight originated from Taylor (T74), Texas, about 12:05 CDT, and was en route to Luling, Texas.
According to the owner, the pilot was en route to Luling to give a friend his first helicopter ride. There were two witnesses standing on the south side of the Colorado River. They said the helicopter was flying north to south just above the trees. As it crossed the Colorado River, they heard a loud "pop" or "bang" and saw something separate from the helicopter and fall into the river. Asked if the object floated or sank, the witnesses said they did not pay any attention because when they heard the helicopter crash and saw the smoke, they ran to the crash site.
The helicopter impacted trees and terrain on the south side of the Colorado River. The burnt wreckage was at the base of a large tree. A piece of tail boom skin was in the tree. One main rotor blade was found approximately 780 feet from the wreckage. The other main rotor blade was found approximately 975 feet from the wreckage in the opposite direction. Both blades were intact with no leading edge damage.
Because the witnesses said they had seen something fall from the helicopter, the river was searched and dragged by the Texas Department of Public Safety. Nothing was found or recovered. The head of one bolt that attached one of the main rotor blades to the hub, and the nut and shank portion of the other bolt that attached the second main rotor blade were recovered. Missing was the head of the second bolt and the nut and shank portion of the first bolt. Effectively, only parts from two different bolts were recovered. Examination of the remainder of the wreckage revealed no other missing components.
Both rotor blades had separated from the main rotor hub at their coning hinges. All components of the helicopter were accounted for with the exception of portions of both coning bolts. The investigation was unable to locate the object observed falling from the helicopter or determine what it was. Examination of the rotor head components, including the recovered portions of the coning bolts, revealed fracture features consistent with overload failure and mechanical damage indicative of mast bumping (contact between the main rotor blades and the mast).
The main rotor blade pitch links and attaching hardware displayed compression buckling and bending overload features consistent with an out-of-control main rotor that had diverged from its normal plane of rotation.
The helicopter manufacturer reported that the damage signatures were consistent with both low-G mast bumping and low rotor rpm rotor stall. Low-G mast bumping is a phenomenon specific to two-bladed teetering rotor systems in which the rotor disc becomes unloaded, typically due to a cyclic pushover. Low rotor rpm rotor stall is a different phenomenon in which the main rotor blades experience an aerodynamic stall due to low rotor rpm caused either by the pilot raising the collective too much or by a loss of engine power followed by the pilot lowering the collective too slowly. Rotor blade stall can lead to mast bumping. The pilot’s control inputs leading up to the event are unknown, and, therefore, the reason for the main rotor divergence could not be determined.
Probable Cause: The divergence of the main rotor from its normal plane of rotation for reasons that cannot be determined because the pilot’s control inputs leading up to the event are unknown, resulting in mast bumping and main rotor blade separation.
Accident investigation:
 |
|
Sources:
1. NTSB Identification: CEN11FA422 at https://www.ntsb.gov/about/employment/_layouts/ntsb.aviation/brief2.aspx?ev_id=20110627X51003&ntsbno=CEN11FA422&akey=1
2. FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?omni=Home-N-Number&nNumberTxt=7779M
3. http://helihub.com/2011/06/27/27-jun-11-n7779m-robinson-r22-garfield-us-texas/
4. https://planecrashmap.com/plane/tx/N7779M/
5. https://en.wikipedia.org/wiki/Taylor_Municipal_Airport
Location
Media:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Jun-2011 13:43 | gerard57 | Added |
| 27-Jun-2011 16:24 | RobertMB | Updated [Aircraft type, Registration, Cn, Operator, Other fatalities, Location, Source, Narrative] |
| 30-Jun-2011 12:29 | JWatkins | Updated [Source, Embed code, Narrative] |
| 09-Oct-2016 00:58 | Dr.John Smith | Updated [Time, Location, Departure airport, Destination airport, Source, Embed code, Narrative] |
| 21-Dec-2016 19:26 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 27-Nov-2017 16:57 | ASN Update Bot | Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative] |
| 16-Sep-2018 02:16 | Dr.John Smith | Updated [Time, Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative] |
| 16-Sep-2018 02:21 | Dr.John Smith | Updated [Operator, Narrative] |
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