Amateur-built EUROPA - TRIGEAR accident near Hanksville, Utah, August 16, 2021
On August 16, 2021 at about 9:15 pm local time, a 1999 amateur-built EUROPA - TRIGEAR, registered N133AC, was substantially damaged in an accident during enroute (climb to cruise) near Hanksville, Utah. It was a personal flight 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 pilot’s installation of a non-original equipment manufactured radiator cap, which resulted in the loss of coolant and the engine’s exceedance of the maximum admissible cylinder head temperature. Contributing to the accident 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
- August 16, 2021 · about 9:15 pm local time
- Place
- Hanksville, Utah · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built EUROPA - TRIGEAR, built 1999
- Registration
- N133AC · no longer on the register · serial A060
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot replaced lost fluid in the airplane engine’s cooling system with water and after a successful ground run, the pilot departed. During a “stair-stepped” climbout, the engine’s cylinder head temperature (CHT) increased into the red arc of the CHT gauge (the maximum admissible cylinder head temperature of 180°C [356°F]). The pilot immediately reduced the throttle setting to ide and elected to conduct a forced landing. The airplane sustained substantial damage to the wings and fuselage after impacting rough terrain during the landing. Postaccident examination of the cooling system revealed that system components were secured and void of all fluid. Testing of the accident radiator cap revealed that it was a non-original equipment manufactured (OEM) part by a third-party vendor and that the pressure relief valve opened and released air pressure about 0.2 bar (3 psi), less than the manufacturer’s recommended coolant system maximum pressure value of 1.2 bar (18 psi). It is likely that the lack of pressure created by the non-OEM radiator cap reduced the coolant boiling point and system pressure. The pressure reduction and lowering of the boiling point would have allowed the coolant to evaporate, leading to a loss of coolant in the system and the engine’s exceedance of the maximum admissible cylinder head temperature of 180°C (356°F).
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
- Off-field or emergency landing during landing (landing roll)
- Aircraft maintenance event during prior to flight
- Powerplant sys/comp malf/fail during enroute (climb to cruise) defining event
The NTSB's findings
- Aircraft › Fluids/misc hardware › Fluids › Coolant › Fluid level
- Personnel issues › Task performance › Maintenance › Replacement › Pilot
- Environmental issues › Physical environment › Terrain › Rough terrain › Effect on equipment
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 410.5 hours in all; 295 in this make and model; 4.3 in the last 90 days; 22.5 in the last 30 days; 331.1 as pilot in command
- Last flight review: July 18, 2020
- Medical certificate: Class 3
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 1,099 hours
- Last inspection: condition inspection; 41.2 hours since
- Maximum gross weight: 1,450 lb
- Seats: 2
- Landing gear: fixed
- Engine: Rotax 914 (piston); 1,000 hours total
The flight
- Departed from: U96 Halls Crossing UT at 2:20 pm
- Destination: 41U Manti MT
- Flight plan: VFR
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 93°F (34°C), dew point 37°F (3°C)
- Altimeter: 29.98 inHg
- Observation at 3:15 pm from KHVE, 22 miles away
Weather report (METAR): METAR KHVE 162115Z AUTO 00000KT 10SM CLR 34/03 A2998 RMK AO2=
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
6 documents, released by the NTSB on March 22, 2023. 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, 11 pages | View Download |
| 2 | Photo Docket | PDF, 8 pages | View Download |
| 3 | Rotax Reference Manuals Excerpts | PDF, 56 pages | View Download |
| 4 | Cooling System Examination | PDF, 10 pages | View Download |
| 5 | Record of Conversation - Pilot | PDF, 4 pages | View Download |
| 6 | Release of Wreckage | PDF, 2 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
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.