ASN Wikibase Occurrence # 190787
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| Date: | Tuesday 12 May 2009 |
| Time: | 13:30 |
| Type: |  Robinson R44 |
| Owner/operator: | Alaska State Troopers |
| Registration: | N7196H |
| MSN: | 0994 |
| Year of manufacture: | 2001 |
| Total airframe hrs: | 1535 hours |
| Engine model: | Lycoming O-540 SERIES |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | 57 miles NW of Iliamna, AK -
 United States of America
|
| Phase: | Landing |
| Nature: | Passenger - Non-Scheduled/charter/Air Taxi |
| Departure airport: | Iliamna Airport, AK (ILI/PAIL) |
| Iliamna Airport, AK (ILI/PAIL) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On May 12, 2009, about 13:30 ADT (Alaska Daylight Time), a Robinson R-44 helicopter, N7196H, sustained substantial damage during a hard landing, about 57 miles northwest of Iliamna, Alaska. The helicopter was being operated by the State of Alaska, Department of Public Safety, Anchorage, Alaska, (usually known as the Alaska State Troopers) as a visual flight rules (VFR) public use flight under Title 14, CFR Part 91, when the accident occurred. The commercial pilot and the two passengers were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect.
During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on May 12, the director of maintenance for the operator said the flight was made by the Alaska State Troopers, Fish and Wildlife Service, who were doing a game management patrol. He said the pilot told him that he had taken off from a ridge, and climbed about 300 feet above the ground. The helicopter was flying about 90 knots indicated airspeed when the pilot felt an unusual medium-frequency vibration in the controls. He said the pilot decided to make an immediate precautionary landing. During the descent the pilot told him the vibration increased. He said the helicopter landed hard, and the main rotor blades struck the tail boom. The pilot did not report any unusual mechanical problems prior to the accident.
On May 15, the helicopter was examined by the IIC at the State Trooper facility in Anchorage, Alaska. The IIC was accompanied by representatives from the FAA, and the State Troopers. No preaccident mechanical anomalies were discovered, and a review of the helicopter's logbooks showed no discrepancies. Small dents were noted in the cabin top fore and aft of the main rotor mast fairings.
In a written report to the NTSB dated May 21, the pilot wrote that about one and one-half minutes into the flight he felt a vibration he had not felt before. he said the vibration was mostly in the pedals, and then a slight yawing motion developed. He said about the same time his passenger said "Is that normal?" referring to the vibration. The pilot told the passenger it was not, and that he was going to land immediately. He said the vibrations turned to oscillations, in both yaw and pitch, to the point he felt the helicopter was going to come apart. He said an emergency landing was his only option. He reported that he picked a spot on the ground and made a controlled descent, while fighting to maintain control of the helicopter. He said his only concern was to get the helicopter on the ground in one piece, and subsequently he touched down with 5-10 knots of forward airspeed. During the landing the pilot said the main rotor contacted the tailboom.
According to the pilot, after the accident he recalculated the weight and balance for the helicopter, and determined that the helicopter was loaded under the gross weight for the helicopter, but slightly forward of the forward center of gravity limit, about 1.1 inch.
Probable Cause: The main rotor transmission mount design, which resulted in an in-flight vibration/oscillation, and damage to the helicopter during an emergency descent and hard landing. Contributing to the accident was the lack of information from the manufacturer regarding this known flight oscillation, and loading the helicopter beyond the forward center of gravity limit by the pilot.
Accident investigation:
 |
|
Sources:
NTSB
2. FAA Registration: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?omni=Home-N-Number&nNumberTxt=N7196H
3. https://www.verticalmag.com/press-releases/ntsb-makes-recommendations-on-r44-mast-rocking-html/
4. http://helihub.com/2009/05/12/12-may-09-n7196h-robinson-r44-iliamna-us-alaska/
5. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=50470
6. http://www.impdb.org/index.php?title=Alaska_State_Troopers#Robinson_R44
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Oct-2016 11:43 | harro | Added |
| 02-Dec-2017 14:55 | ASN Update Bot | Updated [Cn, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 05-Nov-2018 21:51 | Dr.John Smith | Updated [Time, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 26-Feb-2022 00:11 | Captain Adam | Updated [Location, Departure airport, Destination airport, Source, Narrative] |
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