Amateur-built ZENITH CH750 CRUZER accident near Louviers, Colorado, November 27, 2017
On November 27, 2017 at about 10:20 pm local time, a 2017 amateur-built ZENITH CH750 CRUZER, registered N956GM, was substantially damaged in an accident during enroute near Louviers, Colorado. It was a flight test under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The engine’s excessive cylinder head temperatures and the subsequent seizing of the engine, which resulted from an engine control unit that caused the engine’s fuel-air mixture to be too lean.
Source: NTSB aviation accident database, copy made November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 27, 2017 · about 10:20 pm local time · cases in 2017
- Place
- Louviers, Colorado · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built ZENITH CH750 CRUZER NO SERIES, built 2017
- Registration
- N956GM · registry record · serial C75-10359
- Damage
- Substantial damage
- Flight
- Flight test · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was conducting a flight in an experimental airplane to assess engine performance after installing a replacement engine control unit (ECU) with updated programming. During the flight, the engine monitor provided an alert regarding a high engine coolant temperature. Shortly afterward, the engine seized. The pilot attempted two engine restarts, including a complete reboot of the ECU, without success. The pilot made a forced landing in an open field. The airplane struck a barbed wire fence, causing damage to the nose landing gear, engine cowling, right wing strut, and right wing skin. Also, the pilot noticed that the coolant expansion tank had overfilled due to overheating. A postaccident examination revealed that the ECU had caused the engine fuel-air mixture to be too lean, resulting in excessive cylinder head temperatures, which caused the engine to seize. The excessive cylinder head temperatures also resulted in the unseating of the head gasket, which pressurized the coolant jacket and evacuated engine coolant overboard. Coolant was found in three of the four cylinders, and oil was mixed in the coolant under the thermostat, resulting in the rapid rise of coolant temperature.
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
What happened, in order
- Loss of engine power (total) during enroute defining event
- Off-field or emergency landing during emergency descent
- Collision with terrain or object (not controlled flight into terrain) during landing (landing roll)
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng liquid cooling › Failure other cases naming the engine
- Environmental issues › Physical environment › Terrain › Rough terrain › Contributed to outcome
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instrument: airplane
- Flight time: 3,100 hours in all; 32 in this make and model; 39 in the last 90 days; 10 in the last 30 days; 3,100 as pilot in command
- Last flight review: May 13, 2017
- Medical certificate: BasicMed (without waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 32 hours
- Last inspection: condition inspection, September 17, 2017; 32 hours since
- Maximum gross weight: 1,645 lb
- Seats: 2
- Landing gear: fixed
- Engine: Viking 130GDI (piston); 32 hours total
The flight
- Departed from: BJC Broomfield CO at 9:40 pm
- Destination: BJC Broomfield CO
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 220° at 16 knots, gusting 27
- Visibility: 10 statute miles
- Sky: broken clouds at 22,000 ft; a few clouds at 11,000 ft
- Temperature: 77°F (25°C), dew point 10°F (-12°C)
- Altimeter: 29.65 inHg
- Observation at 9:53 pm from APA, 9 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Photographs from the investigation 1 picture from the NTSB's docket, as the NTSB released them
The NTSB's photographs with the NTSB's captions, at screen size. Open a picture to see it full size or to report one that should not be shown.
Documents from the investigation the NTSB's docket: the evidence folder behind the report
3 documents, released by the NTSB on March 8, 2018. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | Record of Conversation | PDF, 1 page | View Download |
| 3 | Report Photos | PDF, 4 pages · our copy | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Connections how this case links to the rest of the register
- N956GM on the register today · the tail number may have moved to another aircraft since
- Engine: Viking 130GDI 5 aircraft carry this series today · as the NTSB recorded it
- Rocky Mountain Metro Airport · departed from
- Accidents and incidents in Colorado 2,860 since 1982 · 384 in the last ten years
- Colorado 7,464 aircraft registered
The whole map of how records connect · these connections as data: /graph/accident/CEN18LA042.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
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 does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.