Amateur-built REVOLUTION MINI-500B accident near Grove, Oklahoma, May 20, 1998
On May 20, 1998 at about 2:25 pm local time, a amateur-built REVOLUTION MINI-500B (helicopter), registered N6144S, was destroyed in an accident near Grove, Oklahoma. It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The improper alignment of the main drive belt by the owner/pilot/mechanic, which resulted in the failure of the main drive belt. A factor was the lack of suitable terrain for the forced landing.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 20, 1998 · about 2:25 pm local time
- Place
- Grove, Oklahoma · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built REVOLUTION MINI-500B REVOLUTION
- Registration
- N6144S · registry record · serial 0426
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
While cruising at an altitude of 1,350 feet MSL, the pilot felt a 'sudden hesitation and [smelled the] odor of smoke.' While 'determining if [a] serious malfunction existed,' the helicopter experienced a loss of main rotor drive and altitude, 'along with a stronger burning odor.' The pilot initiated an autorotation to a field adjacent to a school. However, prior to reaching the intended landing area, the helicopter struck a pickup truck, 'flipped over, landed in [the] field and started on fire.' The pilot reported that prior to the flight he had adjusted the alignment of the main drive belt and engine.
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: private
- Ratings: rotorcraft: helicopter
- Flight time: 59 hours in all; 14 in this make and model; 14 in the last 30 days; 59 as pilot in command
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 14 hours
- Last inspection: annual inspection, May 20, 1998; 14 hours since
- Maximum gross weight: 855 lb
- Seats: 1
- Landing gear: fixed
- Engine: Rotax 582-UL-DCDI (piston); 0 hours total
- Fire on the ground
The flight
- Departed from: 1H7 at 2:20 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 180° at 7 knots
- Visibility: 5 statute miles
- Sky: clear
- Temperature: 75°F (24°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.
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.