Hughes 369D accident near Southbend, Washington, June 8, 1999
On June 8, 1999 at about 3:15 pm local time, a Hughes 369D (helicopter), registered N8306F, was substantially damaged in an accident near Southbend, Washington. It was an other work-use flight under external-load helicopter rules (Part 133). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The complete loss of power, due to a failure of the compressor impeller disk. Factors include the low altitude of the helicopter at the time of the power loss, and the need to autorotate in a confined area.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 8, 1999 · about 3:15 pm local time
- Place
- Southbend, Washington · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Hughes 369D · all 369Ds on the register
- Registration
- N8306F · registry record · serial 2740
- Damage
- Substantial damage
- Flight
- Other work-use flight · external-load helicopter rules (Part 133)
The NTSB's narrative final · quoted from the NTSB record
Just after releasing his external load, the pilot applied power in order to climb away from the release area. As he applied power, a puff of smoke came from the engine, followed immediately by a complete loss of power. The helicopter then began spinning to the left and descending rapidly. The pilot attempted an autorotation in a confined area, and the aircraft impacted the ground sufficiently hard to result in substantial damage. A teardown inspection of the engine determined that a three-inch section of the compressor impeller disc had separated, leading to total failure of the engine. Metallurgical examination of the impeller revealed that the disc failed due to the propagation of fatigue cracks that initiated in corrosion pits on the aft face of the disc. According to the metallurgist, the corrosion was due to exposure to environmental elements, and not due to repetitive cyclic operation.
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
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 25,000 hours in all; 12,000 in this make and model; 25,000 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 11,504 hours
- Last inspection: annual inspection, May 20, 1999; 9 hours since
- Maximum gross weight: 3,500 lb
- Seats: 3
- Landing gear: fixed
- Engine: Allison C20-B (turboshaft); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 235° at 5 knots
- Visibility: 5 statute miles
- Sky: broken clouds at 2,000 ft; not recorded
- Temperature: 50°F (10°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
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.
Other NTSB records under N8306F the same tail number, which may have belonged to a different aircraft at the time
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.