Amateur-built REVOLUTION MINI 500 accident near Moorpark, California, October 4, 1998
On October 4, 1998 at about 10:15 pm local time, a amateur-built REVOLUTION MINI 500 (helicopter), registered N418MB, was destroyed in an accident near Moorpark, California. It was a personal 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 improper use of the cyclic flight control by the pilot, which resulted in low g flight load condition, which resulted in rotor disk divergence (mast bumping), and the main rotor blade striking and severing the tail boom.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 4, 1998 · about 10:15 pm local time
- Place
- Moorpark, California · map
- Type
- Accident
- Injuries
- 1 person was killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built REVOLUTION MINI 500 REVOLUTION
- Registration
- N418MB · registry record · serial 0279
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The helicopter did not return from an afternoon local area flight and the wreckage was located early the following morning. Both main rotor blades, the tail rotor assembly, the tail boom, and a section of the tail rotor drive shaft were found in a debris field approximately 1/8 mile from the fuselage wreckage. Both main rotor blades separated from the hub outboard of the root doubler and exhibited leading edge damage near the tip and downward bending. Additionally, the 'A' blade was bent smoothly aft approximately 30 degrees over its span. The tail boom was separated from the fuselage approximately 2 feet forward of the tail rotor gearbox. The separation exhibited a diagonal slicing appearance from upper forward to lower aft on the boom. The tail rotor drive shaft was separated at the same fuselage station as the tail boom, and the shaft had a dented appearance which resembled the leading edge radius of the main rotor blade. The main rotor mast exhibited a mast-bumping dent on one side of the mast at the hub attachment but no similar dent on the opposite side. Examination of the aircraft did not reveal any mechanical malfunction of the engine or flight control system.
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: 100 hours in all
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 33 hours
- Last inspection: annual inspection, April 18, 1998; 33 hours since
- Maximum gross weight: 840 lb
- Seats: 1
- Landing gear: fixed
- Engine: Rotax 582 (piston); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 030° at 6 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 61°F (16°C), dew point 45°F (7°C)
- Altimeter: 29.00 inHg
- Observation at 10:51 pm from OXR, 20 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.