Hiller UH-12E accident near Merrimac, Wisconsin, June 10, 1984
On June 10, 1984 at about 6:36 pm local time, a Hiller UH-12E (helicopter), registered N93431, was destroyed in an accident near Merrimac, Wisconsin. It was a public-use flight under general aviation rules (Part 91). 1 person was killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 10, 1984 · about 6:36 pm local time
- Place
- Merrimac, Wisconsin · map
- Type
- Accident
- Injuries
- 1 person was killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Hiller UH-12E · all UH-12Es on the register
- Registration
- N93431 · no longer on the register · serial 1768
- Damage
- Destroyed
- Flight
- Public-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE ACFT CRASHED AND BURNED AFTER AN IN-FLT EXPLOSION AT ABOUT 75 FT AGL AS THE ACFT APPROACHED TO LAND. THE ACFT HAD EXPERIENCED ELECTRICAL PROBLEMS OF OVERHEATING GENERATORS AND IRREGULAR VOLTAGE OUTPUTS ON 2 PREVIOUS OCCASIONS. THE PLTWAS TOLD AFTER SOME REPAIRS THAT IF HE SMELLED ANYTHING HOT TO PULL THE GENERATOR CIRCUIT BREAKER. POST-ACCIDENT ACFT EXAMINATION SHOWED A CONDITION OF THE VOLTAGE REGULATOR WHICH WOULD HAVE CAUSED CONTINUOUS CHARGING OF THE BATTERY. THE GENERATOR SHOWED SIGNS OF OVERHEATING AND THE BATTERY HAD EXPLODED AWAY FROM THE WRECKAGE WITH THE TERMINAL POLES MELTEDOFF.
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, private
- Ratings: single-engine land; rotorcraft: helicopter
- Flight time: 781 hours in all; 567 in this make and model; 50 in the last 90 days; 25 in the last 30 days; 687 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 1,837 hours
- Last inspection: annual inspection, December 19, 1983; 4 hours since
- Maximum gross weight: 3,100 lb
- Seats: 3
- Landing gear: fixed
- Engine: Lycoming VO-4540-C2A (piston); 0 hours total
- Fire in flight and on the ground
The flight
- Departed from: Baraboo WI at 6:00 pm
- Flight plan: VFR
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 230° at 23 knots, gusting 33
- Visibility: 10 statute miles
- Sky: scat at 4,000 ft
- Temperature: 75°F (24°C), dew point 57°F (14°C)
- Altimeter: 29.00 inHg
- Observation at 6:45 pm from MSN, 30 miles away
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.
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.