# NTSB WPR21LA059: Cessna TU206, N878AH, Twentynine Palms, CA, November 21, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: November 21, 2020, 12:50 local (20:50 UTC) - Place: Twentynine Palms, CA - Coordinates: 34.134311, -115.95868 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.1343&lon=-115.9587&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 6 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA - NTSB case key (mKey): 102327 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA059 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102327/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102327 - Page: https://openairdocs.org/ntsb/WPR21LA059 ## Probable cause The pilot’s decision to takeoff with a known mechanical engine anomaly, and the failure of the No. 2-cylinder exhaust valve, which resulted in a total loss of engine power during the initial climb and subsequent impact with terrain. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Cessna TU206G, 2 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=2073357), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cessna TU206G, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=2073357), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Cessna TU206G, 4 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2073357), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis The pilot reported that during the first cross-country flight after an annual inspection, he experienced a rough running engine. He noted that when the engine roughness began, the airplane’s airspeed decreased by 23 knots, and the No. 2 cylinder head temperature decreased from 1,350° F to 650° F. He decided to continue flight at the slower airspeed. The engine roughness once again returned, and the pilot elected to land as soon as practical and have a mechanic look at the engine. However, there were no mechanics available, so the pilot decided to refuel and takeoff. The first takeoff attempt was unsuccessful because the pilot felt a slight hesitation in the engine power during the takeoff roll, and he aborted the takeoff. During the second takeoff attempt, at 250 ft agl, the engine lost power. The airplane descended to the ground, impacted a sand berm, and nosed over. It sustained substantial damage to the right wing and wing left strut A postaccident examination of the engine revealed that the No. 2-cylinder exhaust valve failed. The No. 2 cylinder exhaust valve was missing about 45 percent of the valve head and foreign object compression signatures were sustained to the No. 2 piston and cylinder head. The missing exhaust valve head was not present in the No. 2 cylinder. Additionally, the No. 5 cylinder piston and cylinder head sustained foreign object compression signatures. The No. 5 cylinder intake valve exhibited material deformation around the valve seat. The engine total time was 2,180.1 hours when the annual inspection was completed. The engine had acquired 3 hours since the last annual. The engine was overhauled after acquiring 909 hours. At the time of the accident, the engine had amassed 1,274.1 hours since major overhaul. It is likely that the initial engine roughness and partial loss of engine power, followed by the total loss of engine power during takeoff was due to the failure of the exhaust valve. ## Factual narrative On November 21, 2020, about 1250 Pacific standard time, a Cessna TU206G, N878AH, was substantially damaged when it was involved in an accident in Twentynine Palms, California. The pilot and his five passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the accident flight was the first flight after the completion of the airplane’s annual inspection. He departed from South Valley Regional Airport (KU42), in Salt Lake City, Utah with the destination of Jacqueline Cochran Regional Airport (KTRM) in Thermal, California. The pilot recalled that about 275 nm into the flight, the engine began running rough, the No. 2-cylinder head temperature decreased from 1,350° F to 650° F, and the airplane’s airspeed decreased about 23 knots. The pilot decided to continue the remaining 200 nautical mile (nm) flight to his destination. However, about 168 nm later, the pilot once again noticed a “slight roughness” then it seemed to be “ok”. The pilot switched the fuel selector from the left tank to the right tank and the engine lost total power. He turned on the auxiliary fuel pump and the engine regained power. The pilot elected to land at the nearest available airport and have a mechanic look over the engine. Twentynine Palms Airport was the nearest available airport, but there were no mechanics available to assist. The pilot refueled the airplane taking on 35 gallons of 100LL and taxied to runway 26 with the intent to fly the remaining 32 nm to his destination airport. He reported that he had completed an engine run-up, entered the runway and initiated the takeoff roll. About halfway into the takeoff roll, he felt a “slight hesitation” in engine power, and he aborted the takeoff. The pilot taxied back to runway 26 and completed another engine run-up during the takeoff roll, the engine power appeared to be normal; however, upon reaching about 250 ft agl, a total loss of engine power occurred, and the airplane descended. The pilot made a slight left turn during the descent to avoid colliding with a home and the airplane touched down on the sand covered desert terrain. The airplane impacted a sand berm and nosed over, sustaining substantial damage to the right wing and wing left strut. Examination of the airplane’s fuel system revealed no anomalies or malfunctions. An external examination of the airplane’s engine and accessory case revealed no anomalies. The top spark plugs were removed from each cylinder and thumb compression could not be obtained on cylinders Nos. 2 and 5. A lighted borescope was used to examine each of the effected cylinders and revealed that the No. 2 cylinder exhaust valve was missing about 45 percent of the valve head. Foreign object compression signatures were sustained to the No. 2 piston and cylinder head. The missing exhaust valve head was not present in the No. 2 cylinder. Additionally, the No. 5 cylinder piston and cylinder head sustained foreignobject compression signatures. The No. 5 cylinder top and bottom spark plugs sustained damage to the three ground electrode points, and the center electrode to the copper core. The No. 5 cylinder exhaust valve and intake valve were present and sustained foreign object compression signatures. According to the airplane’s maintenance logbook, the engine total time was 2,180.1 hours when the annual inspection was completed. The engine had acquired 3 hours since the last annual. The engine was overhauled after acquiring 909 hours. At the time of the accident, the engine had amassed 1,274.1 hours since major overhaul. ## Aircraft - Registration: [N878AH](https://openairdocs.org/deregistered/N878AH-2021-01-28), registration cancelled 2021-01-28, S/N U20604570, built 1978 (OpenAirDocs) - Reported make and model: CESSNA TU206 (G) - Registry model: [Cessna TU206G](https://openairdocs.org/model/cessna-tu206g) (registry code 2073357) (OpenAirDocs) - Registry engine: [Continental TSIO-520 series](https://openairdocs.org/engine/continental-tsio-520-series) (registry code 17040, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: U20604570 - Year built: 1978 - Airframe hours: 4555 - Engines: Continental TSIO-520-M 310 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: T V Specialists Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 1, 2020, 3 hours before - Destination: TRM, Thermal, CA - Airport: TNP, 29 Palms Airport, runway 26, 5,531 × 75 ft, asphalt - Equipment: ADS-B, Auto-pilot, Handheld GPS ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: basicmed, with waivers/limitations; last flight review May 25, 2020; seat: left; restraint: 3-point; flight hours: 1,550 total, 1,500 in this make and model, 1,550 as pilot in command, 8 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 27 °F - Altimeter: 30.06 inHg - Observed at: KPSP, 33 nm away - METAR: METAR KPSP 211953Z 00000KT 10SM CLR 29/M03 A3006 RMK AO2 SLP177 T02941028= ## 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 20201121021789A](https://openairdocs.org/incident/20201121021789A), Nov 21, 2020: Cessna TU206G, Twenty Nine Pal, CA, Substantial damage. Pilot departed from ktnp and felt loss of power @250 feet. Aircraft made emergency landing in the desert just outside of the airport where it flipped over and… ## Other investigations on N878AH (1) 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. - [NTSB DEN82DA096](https://openairdocs.org/ntsb/DEN82DA096), May 25, 1982: Cessna TU206G (N878AH), Price, UT, substantial damage ## Docket (5 files) The files NTSB released with the investigation on August 25, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102327. 12.3 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14295130&FileExtension=pdf&FileName=6120_1_Redacted-Rel.pdf - N878AH examination report (item 2, PDF, 16 pages, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14306007&FileExtension=pdf&FileName=N878AH%20Examination%20Report-Rel.pdf - Engine logbook entries (item 3, PDF, 8 pages, 7.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14296653&FileExtension=pdf&FileName=Engine%20Logbook%20Entries_Redacted-Rel.pdf - Work order invoice (item 4, PDF, 1 page, 546 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14297208&FileExtension=pdf&FileName=Work%20Order%20Invoice_Redacted-Rel.pdf - Photo confirming substantial damage (item 5, PDF, 1 page, 580 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14298913&FileExtension=pdf&FileName=Photograph-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.