# NTSB WPR21LA325: Stout Garry V Europa - Trigear, N133AC, Hanksville, UT, August 16, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: August 16, 2021, 15:15 local (21:15 UTC) - Place: Hanksville, UT · uneven open terrain - Coordinates: 38.0586, -110.96113 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.0586&lon=-110.9611&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA - NTSB case key (mKey): 103718 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA325 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103718/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103718 - Page: https://openairdocs.org/ntsb/WPR21LA325 ## Probable cause 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fluids: coolant](https://openairdocs.org/ntsb-findings/01071025): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-findings/01071025/cases.md?model=05605R3), [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01071025/cases.md) - [Maintenance: replacement](https://openairdocs.org/ntsb-findings/02062020): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-findings/02062020/cases.md?model=05605R3), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/02062020/cases.md) - [Terrain: rough terrain](https://openairdocs.org/ntsb-findings/03021015): Environmental issues › Physical environment · Effect on equipment (probable cause); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-findings/03021015/cases.md?model=05605R3), [All aircraft, 442 cases](https://openairdocs.org/ntsb-findings/03021015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=05605R3), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Enroute-climb to cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=05605R3), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Landing-landing roll: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Stout Garry V EUROPA - TRIGEAR, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05605R3), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis 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). ## Factual narrative On August 16, 2021, about 1515 mountain daylight time, a Europa Trigear, N133AC, was substantially damaged when it was involved in an accident near Hanksville, Utah. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that during the preflight, he noticed that the coolant in the cooling system’s expansion tank was low. He removed the cowling and did not notice any pooling of coolant in the engine compartment, so he replaced the coolant with about 16 ounces of water. He completed the preflight and ground run without further incident and continued with the departure, which he characterized as a “stair-stepped” climb out to assist with the engine cooling on a hot day over rough terrain. After 30 minutes, the pilot reported that the engine’s CHT was pegged in the red arc [maximum admissible head cylinder temperature of 180°C (356?)] and he immediately reduced the throttle setting to idle and elected to conduct a precautionary landing. While the airplane was descending, he cycled the engine off and on to reduce the CHT, but the temperature remained in the red arc. During the landing roll on an unimproved dirt road, the airplane impacted rough terrain. Postaccident examination of the cooling system revealed that the expansion tank, coolant hoses, and water pump were unremarkable, and that the system was void of any coolant. The manufacturer states that the coolant capacity for the engine is about 0.4 US gallons (about 1.5 liters). TEST AND RESEARCH The pilot stated that about 2 weeks before the accident flight, he removed the original radiator (pressure screw) cap and replaced it with a non-original equipment manufactured radiator cap from a third-party vendor. The original cap and the installed cap were both labeled to maintain system pressure up to 1.2 bar (18 psi) and both caps contained an upper pressure seal, lower pressure seal, pressure relief valve, and return(vacuum) valve. A pressure test of the original/replaced cap revealed that the pressure relief valve opened about 0.8 bar (12 psi). The accident radiator cap was also pressure tested and revealed that the valve opened about 0.2 bar (3 psi). According to the manufacturer, the engine boiling point is influenced by the system pressure and that if temperature exceeds the boiling point, the engine can quickly overheat due to loss of coolant. According to the manufacturer, the radiator cap sits on top of the expansion tank and provides a tight seal to maintain pressurization of the cooling system, which increases the system’s boiling point. As the system pressure reaches the cap’s rated pressure, the cap’s pressure relief valve opens, and the pressurized coolant flows into the overflow bottle; this allows for the expansion of the heated coolant. Conversely, as the temperature drops and the coolant contracts, a vacuum is created within the cooling system. The vacuum seal within the cap opens and allows thecoolant to flow from the overflow bottle back into the radiator. Figure 1. Rotax 914 Cooling System Flow Diagram According to Rotax Service Letter SL-914-012R6 Revision 13 May 2022: The use of any third-party replacement kits, modifications and non-genuine ROTAX® components or accessories for ROTAX® engines is NOT approved by ROTAX® and is very strongly discouraged. Use of any improper third-party replacement kits, improper modifications and non-genuine ROTAX® components or accessories may cause engine damage resulting in catastrophic engine failure. As stated in the manufacturer’s maintenance manual, a rise in the cylinder head temperature above normal operations is a clear signal for a failure in the cooling system, to include the pressure relief valve. Figure 2. Cylinder Head Table from Rotax 914 Maintenance Manual 05-50-00 Edition 2, Revision 2 ## Aircraft - Registration: [N133AC](https://openairdocs.org/deregistered/N133AC-2022-07-30), registration cancelled 2022-07-30, S/N A060, built 1999 (OpenAirDocs) - Reported make and model: STOUT GARRY V EUROPA - TRIGEAR - Registry model: [Stout Garry V EUROPA - TRIGEAR](https://openairdocs.org/model/stout-garry-v-europa-trigear) (registry code 05605R3) (OpenAirDocs) - Registry engine: [Rotax 914 series](https://openairdocs.org/engine/rotax-914-series) (registry code 55575, 4 cycle) (OpenAirDocs) - Category: Airplane - Serial number: A060 - Year built: 1999 - Airframe hours: 1099 - Engines: Rotax 914 115 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Departed: U96, Halls Crossing, UT - Destination: 41U, Manti, MT - Flight plan: VFR - Equipment: Stall warning system, Satellite tracking device, Onboard weather, Handheld GPS, Electronic flight bag or handheld device, Auto-pilot, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; private; airplane ratings: single-engine land; medical: class 3; last flight review July 18, 2020; seat: left; restraint: 3-point; flight hours: 410.5 total, 295 in this make and model, 331.1 as pilot in command, 4.3 in the last 90 days, 22.5 in the last 30 days, 2.9 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 93 °F, dew point 37 °F - Altimeter: 29.98 inHg - Observed at: KHVE, 22 nm away - METAR: METAR KHVE 162115Z AUTO 00000KT 10SM CLR 34/03 A2998 RMK AO2= ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20210816014369A](https://openairdocs.org/incident/20210816014369A), Aug 16, 2021: Stout Garry V EUROPA - TRIGEAR, Hanksville, UT, Substantial damage. 08/16/2021, 1715 MDT N133AC emergency landed on a dirt road after cooling system failure, 1 POB no injuries, aircraft had substantial damage near Hanksville,… ## Docket (6 files) The files NTSB released with the investigation on March 22, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103718. 11.4 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14964823&FileExtension=pdf&FileName=6120%20325_Redacted-Rel.pdf - Photo docket (item 2, PDF, 8 pages, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14992162&FileExtension=pdf&FileName=Docket%20Photos%20325-Rel.pdf - Rotax reference manuals excerpts (item 3, PDF, 56 pages, 5.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14991077&FileExtension=pdf&FileName=ROTAX%20Reference%20Manuals-Rel.pdf - Cooling system examination (item 4, PDF, 10 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15069294&FileExtension=pdf&FileName=Cooling%20System%20Examination-Rel.pdf - Record of conversation - pilot (item 5, PDF, 4 pages, 108 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15069888&FileExtension=pdf&FileName=RECORD%20OF%20CONVERSATION%20325-Rel.pdf - Release of wreckage (item 6, PDF, 2 pages, 162 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15177371&FileExtension=pdf&FileName=Retention-Release-of-Wreckage-Form%20325_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.