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).
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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 October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 27, 2017 · about 10:20 pm local time
- 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
- 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 |
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.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number CEN18LA042.