ANC09GA040 · Robinson Helicopter R44
State of Alaska Robinson Helicopter R44 · Accident: system/component malfunction/failure (non-power) during initial climb
From Iliamna, AK to Iliamna, AK
Narrative check · The NTSB narrative appears to contradict this record's location. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- ANC09GA040
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Government
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Robinson Helicopter R44
- Aircraft type
- Robinson R44
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N7196H
- Operator
- State of Alaska
- Onboard fatalities
- Unknown
- Route
- From Iliamna, AKTo Iliamna, AK
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Public Aircraft
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Initial climb
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- System/component malfunction/failure (non-power)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft propeller/rotor
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
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.
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC09GA040
- Event ID
- 20090513X60228
- Case number
- ANC09GA040
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 47aa8066c5955cb39522810c20d0a4da27ddbfb7e96aaea8aa6d621197c0681f; retrieved 2026-09-15T11:02:57.409Z.