Hiller UH-12E accident near Stites, Idaho, November 2, 1999
On November 2, 1999 at about 7:18 pm local time, a Hiller UH-12E (helicopter), registered N5388V, was substantially damaged in an accident near Stites, Idaho. It was a public-use flight under public-use (government) rules. 2 people were seriously injured; 1 other was unhurt. The weather was conditions the NTSB did not record.
The NTSB's probable cause their words, unchanged
Inadequate inspection of the control rotor cuff by a company mechanic and subsequent fatigue fracture of the cuff, resulting in an inflight separation of the control rotor blade. Factors contributing to the accident were: inadequate quality control during manufacture; insufficiently defined manufacturer's inspection and repair procedures; inadequate FAA approval of the manufacturer's inspection and repair procedures; power lines in the helicopter's emergency descent flight path; and reduced aircraft controllability following the control rotor separation.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 2, 1999 · about 7:18 pm local time
- Place
- Stites, Idaho · map
- Type
- Accident
- Injuries
- 2 people were seriously injured; 1 other was unhurt.
- Weather
- conditions the NTSB did not record
- Aircraft
- Hiller UH-12E · all UH-12Es on the register
- Registration
- N5388V · no longer on the register · serial 2099
- Damage
- Substantial damage
- Flight
- Public-use flight · public-use (government) rules
The NTSB's narrative final · quoted from the NTSB record
During a low-altitude fish survey, the helicopter experienced a separation of a control rotor while leveling off from a climb to about 400 feet above ground level (AGL). The pilot initiated an emergency descent but, due to severely reduced cyclic controllability resulting from the separation, was unable to avoid power lines in the aircraft's emergency descent flight path. The helicopter struck the power lines about 50 feet AGL and fell to the ground, landing hard but upright. Post-accident examination disclosed a fatigue failure in the cuff which retains the control rotor blade. The fatigue originated on two opposite sides of a retaining bolt hole that appeared to have been unevenly hand chamfered or deburred during original manufacture of the cuff, with gouging and sharp-bottomed dents visible at the origins. However, while a company mechanic had signed off an Airworthiness Directive (AD) requiring recurring inspection of the cuff about two months/56 flight hours before the accident, post-accident examination disclosed evidence indicative of inadequate inspection and maintenance of the assembly, including: old dried grease between the cuff and control rotor blade spar, large areas of the spar missing required paint with associated corrosion areas, and zinc chromate primer in corrosion pits. The FAA-approved Hiller service bulletin referenced by the AD contains procedures for inspection of spar tube retention bolt holes for 'elongation, corrosion, burrs, pitting or fretting' and associated repair procedures, but does not contain any instructions to inspect or repair bolt holes in the control rotor cuff for those same conditions.
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: 32,275 hours in all; 22,000 in this make and model; 228 in the last 90 days; 87 in the last 30 days
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 22,137 hours
- Last inspection: 100-hour inspection, October 29, 1999; 57 hours since
- Landing gear: fixed
- Engine: Lycoming VO-540-C2A (piston); 0 hours total
The flight
- Departed from: Clarkston WA at 5:30 pm
- Destination: Grangeville ID
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 50 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 | 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.
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.