Amateur-built REVOLUTION M500 accident near San Carlos, California, March 31, 1996
On March 31, 1996 at about 9:47 pm local time, a amateur-built REVOLUTION M500 (helicopter), registered N750GL, was substantially damaged in an accident near San Carlos, California (San Carlos airport). 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 pilot's failure to recognize a drive train disengagement and initiate an autorotation. The inadequate engine-to-transmission drive belt/pulley design, and the pilot's limited training and experience in rotorcraft operations were factors in this accident.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 31, 1996 · about 9:47 pm local time
- Place
- San Carlos, California · San Carlos · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built REVOLUTION M500 REVOLUTION
- Registration
- N750GL · no longer on the register · serial 0062
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
According to FAA airman records, the pilot did not hold a rotorcraft category rating. FAA inspectors examined the pilot's logbook and reported that he received a solo endorsement in helicopters about 1 1/2 years ago. The pilot was returning to the airport following a local area flight. About 1 mile west of the airport, the pilot began to smell something burning and said he sensed something was wrong. Shortly thereafter, he heard a 'slap' sound as the helicopter transitioned through 50 feet and 50 knots about 1/4 mile from the runway. The pilot stated that he 'didn't do anything [with the controls] but keep it headed for an open area between the taxiway and the runway.' The pilot said he did not flare or touch the collective, and the helicopter hit hard in the open area and rolled on its left side. An FAA airworthiness inspector examined the helicopter and found the engine to transmission drive belt fragmented, with rubber transfer throughout the engine compartment. Rubber transfer on the pulleys showed a forward movement pattern of the belt off the pulley. The inspector reported that the pulley was designed without a flange or other means to keep the belt aligned.
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: single-engine land
- Flight time: 310 hours in all; 70 in this make and model
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 70 hours
- Last inspection: annual inspection, January 25, 1996; 70 hours since
- Maximum gross weight: 860 lb
- Seats: 1
- Landing gear: fixed
- Engine: Rotax 582 (piston); 0 hours total
The flight
- Departed from: HAF Half Moon Bay CA at 9:15 pm
- Destination: SQL
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 180° at 12 knots
- Visibility: 30 statute miles
- Sky: broken clouds at 15,000 ft; scat at 7,500 ft
- Temperature: 77°F (25°C), dew point 34°F (1°C)
- Altimeter: 29.00 inHg
- Observation at 9:45 pm from SQL
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.