Robinson Helicopter R44 accident near Iliamna, Alaska, May 12, 2009
On May 12, 2009 at about 9:30 pm local time, a Robinson Helicopter R44, registered N7196H, was substantially damaged in an accident during initial climb near Iliamna, Alaska. It was a public-use flight (state) under public-use (government) rules. No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 12, 2009 · about 9:30 pm local time
- Place
- Iliamna, Alaska · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Robinson Helicopter R44 · all R44s on the register
- Registration
- N7196H · registry record · serial 0994
- Damage
- Substantial damage
- Flight
- Public-use flight (state) · public-use (government) rules
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was on a public use helicopter flight in support of a state agency under Title 14, CFR Part 91. The pilot reported that shortly after takeoff he felt a vibration in the anti-torque pedals he had not felt before, and he noticed a slight yawing motion. He said the vibrations turned to oscillations, in both yaw and pitch, to the degree he felt the helicopter was going to come apart. He reported he made a descent while fighting to maintain control. The pilot said he touched down with 5-10 knots of forward airspeed, and subsequently the main rotor contacted the tailboom. He said after the accident he recalculated the weight and balance, and determined that the helicopter was loaded under the gross weight, but forward of the forward center of gravity (CG)limit about 1.1 inch. Research by the NTSB investigator-in-charge disclosed that operators of the same model helicopter were aware of similar events, and that the condition had been dubbed as "chugging." Further research revealed that similar accidents had been reported. Following a similar accident in Ireland the manufacturer reported to authorities that there were no further vibration issues, and that they would not be issuing a service bulletin. The manufacturer said they were familiar with the phenomenon known as chugging, and that they had conducted flight tests related to the phenomena. The tests determined that an oscillation may develop at high gross weight, about 90-100 knots, and that the oscillation was more of a "bucking" movement due to the fore-and-aft movement of the rotor mast. According to the manufacturer, the tests determined that chugging could occur within the normal CG range, most typically at or near a gross weight with a CG near the forward limit. The manufacturer believes that the oscillation is not destructive to the helicopter, and that the oscillation can be mitigated by the application of power. The manufacturer attributes the oscillation to the degree of firmness of the transmission mounts. Currently there are no manufacturer service bulletins or FAA Safety Alerts referencing the phenomena, and there is no manufacturer provided pilot training or guidance pertaining to chugging and its remedy.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Sys/Comp malf/fail (non-power) during initial climb defining event
- Hard landing during landing
The NTSB's findings
- factor Organizational issues › Development › Manufacture/production › Document/info production › Manufacturer
- factor Personnel issues › Task performance › Planning/preparation › Weight/balance calculations › Pilot
- cause Aircraft › Aircraft propeller/rotor › Main rotor drive › Main rotor trans mount › Design
- Aircraft › Aircraft oper/perf/capability › Aircraft capability › CG/weight distribution › Capability exceeded
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: single-engine land; single-engine sea; instructor: airplane single-engine; instrument: airplane
- Flight time: 4,800 hours in all; 364 in this make and model; 31 in the last 90 days; 14 in the last 30 days; 4,600 as pilot in command
- Last flight review: February 7, 2008
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 1,535 hours
- Last inspection: 100-hour inspection, August 25, 2008
- Maximum gross weight: 2,400 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-540 SERIES (piston); 0 hours total
- Operator: State Of Alaska
The flight
- Departed from: Iliamna AK at 4:30 pm
- Destination: Iliamna AK
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.