# NTSB WPR21LA151: Piper PA-28-140, N665FL, Yacolt, WA, March 29, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: March 29, 2021, 15:47 local (22:47 UTC) - Place: Yacolt, WA - Coordinates: 45.851889, -122.2613 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.8519&lon=-122.2613&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA - NTSB case key (mKey): 102838 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA151 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102838/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102838 - Page: https://openairdocs.org/ntsb/WPR21LA151 ## Probable cause A partial loss of power caused by carbon build up in the cylinders, which prevented the exhaust valves from seating properly. Contributing to the accident was flying in moderate icing conditions which resulted in reduced aircraft performance and vibrations. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Piper PA-28-140, 6 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=7102802), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md) - [Temp/humidity/pressure: conducive to structural icing](https://openairdocs.org/ntsb-findings/03031025): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [Piper PA-28-140, 1 case](https://openairdocs.org/ntsb-findings/03031025/cases.md?model=7102802), [All aircraft, 103 cases](https://openairdocs.org/ntsb-findings/03031025/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Piper PA-28-140, 47 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=7102802), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) ## Analysis The airplane was the subject of a Federal Aviation Administration Alert Notification (ALNOT) when the pilot reported a rough running engine and then radio contact was lost with the airplane. A few hours later, the airplane’s wreckage was located by Navy search and rescue in heavily forested terrain. The pilot reported that while in cruise flight at 8,000 ft mean sea level (msl), and in instrument meteorological conditions (IMC), he felt a vibration in the airplane and thought it was from airframe icing, however he soon realized that the engine was running rough. He applied carburetor heat and requested a lower altitude. However, the engine seemed to run worse and lose power, so the pilot requested vectors to the nearest airport. While being vectored and after exiting IMC, he elected to make a forced landing in a nearby clearing. While the pilot reported no airframe icing, a review of weather conditions in the area and a sounding model performed over the accident site revealed that the freezing level was about 3,227 ft mean sea level (msl) and supported broken to overcast clouds from about 3,000 ft to 8,000 ft msl and icing in the clouds. Additionally, AIRMET Zulu was current over the area for occasional moderate icing conditions from the freezing level, estimated at 3,000 ft, to 12,000 ft msl. It is likely that airplane experienced moderate icing conditions that contributed to the decrease in the airplane’s performance and some of the vibrations felt by the pilot. Postaccident examination of the engine revealed that during manual rotation, thumb compression was not obtained on the Nos. 1 and 3 cylinders. Borescope examination of the cylinder’s interior revealed carbon deposits lodged in the area where the exhaust valve seats, preventing proper sealing. ## Factual narrative On March 29, 2021, about 1547 Pacific daylight time, a Piper PA-28-140 airplane, N665FL, was substantially damaged when it was involved in an accident near Yacolt, Washington. The pilot and pilot rated passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane was the subject of a Federal Aviation Administration Alert Notification (ALNOT) when the pilot reported a rough running engine and then radio contact was lost with the airplane. A few hours later, the airplane’s wreckage was located by Navy search and rescue in heavily forested terrain about 5 miles east of Yacolt, Washington. The pilot reported that while at cruise altitude about 8,000 ft mean sea level, and in instrument meteorological conditions (IMC), he felt a vibration in the airplane and initially thought that it was airframe icing. There was none and realized that the engine started to run rough. He applied carburetor heat and requested a lower altitude. However, the engine seemed to run worse and lose power, so the pilot requested vectors to the nearest airport. While being vectored and after exiting IMC, he elected to make a forced landing in a nearby clearing. The airplane impacted several trees and was substantially damaged during the landing. A review of the weather conditions in the area by a National Transportation Safety Board (NSTB) senior meteorologist revealed that a low-pressure trough extended from northern Idaho and across Washington around the time of the accident. The accident site was located ahead of the trough in an area of westerly winds and overcast cloud cover. An area of continuous snow was depicted north of the accident site near Tacoma, Washington. A sounding model run over the accident site revealed that the freezing level was about 3,227 ft mean sea level (msl) with broken to overcast clouds from about 3,000 ft to 8,000 ft msl and icing in the clouds. Additionally, AIRMET Zulu was current over the area for occasional moderate icing conditions from the freezing level, estimated at 3,000 ft, to 12,000 ft msl. Two jet aircraft reported and confirmed the moderate icing below 8,000 ft. Flying in moderate icing conditions would decrease the airplane’s performance and additionally potentially cause vibrations. Postaccident examination of the engine revealed that during manual rotation, thumb compression was not obtained on the Nos. 1 and 3 cylinders. Additionally, leaking air was heard from the exhaust piping. A compression check revealed that the No. 1 cylinder was 5 psi, and the No. 3 cylinder was 0 psi. Borescope examination of the cylinder’s interior revealed that the No. 3 cylinder exhibited scoring on the walls and had carbon deposits lodged in the area where the exhaust valve seats. Examination of the other cylinders revealed a similar built up of carbon deposits, except that the No. 2 cylinder had substantially less build up than the other two. No other anomalies wereobserved that would have precluded normal operation. The pilot reported that the last annual inspection was accomplished about 6 months before the accident and the airplane had accumulated 25 hours since that inspection. The engine had accumulated about 1,929 hours since overhaul. ## Aircraft - Registration: [N665FL](https://openairdocs.org/deregistered/N665FL-2023-08-23), registration cancelled 2023-08-23, S/N 28-7125587, built 1971 (OpenAirDocs) - Reported make and model: PIPER PA-28-140 - Registry model: [Piper PA-28-140](https://openairdocs.org/model/piper-pa-28-140) (registry code 7102802) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 28-7125587 - Year built: 1971 - Airframe hours: 3842 - Engines: LYCOMING O-360-A1A 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Treetop Flyers LLC - Registered owner: Treetop Flyers LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 2, 2020 - Departed: BDN, Bend, OR - Destination: TIW, Tacoma, WA - Flight plan: IFR - Equipment: Stall warning system, Electronic flight bag or handheld device, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 75; injuries: minor; commercial, flight instructor, airline transport, flight engineer; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review March 20, 2020; seat: left; restraint: 3-point; flight hours: 19,427 total, 498 in this make and model, 13,831 as pilot in command, 11 in the last 90 days, 7 in the last 30 days, 4 in the last 24 hours - Pilot-rated passenger; injuries: minor; private; airplane ratings: single-engine land; seat: right ## Weather - Conditions: Visual (VMC), Day - Wind: 350° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: 3,500 ft broken - Temperature: 57 °F, dew point 45 °F - Altimeter: 30.09 inHg - Observed at: KPDX, 21 nm away - METAR: METAR KPDX 292253Z 35003KT 10SM BKN035 14/07 A3009 RMK AO2 SLP189 T01440072 ## 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 20210329004679A](https://openairdocs.org/incident/20210329004679A), Mar 29, 2021: Piper PA-28-140, Yacolt, WA, Substantial damage. Correction to 8020-9. Aircraft is a PA-28. During a personal flight from bdn to tiw, N665FL, a PA-28, started to experience engine trouble. According to the… ## Docket (4 files) The files NTSB released with the investigation on January 26, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102838. 4.8 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14848276&FileExtension=pdf&FileName=NTSB%206120%20Final_Redacted-Rel.pdf - Weather information (item 2, PDF, 8 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14849027&FileExtension=pdf&FileName=WPR21LA151%20Weather%20Data-Rel.pdf - Engine examination summary (item 3, PDF, 4 pages, 596 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14849289&FileExtension=pdf&FileName=WPR21LA141%20Engine%20and%20Airframe%20Examination%20Summary-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 4, PDF, 1 page, 234 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14848935&FileExtension=pdf&FileName=2021%20Retention-Release-of-Wreckage-Form%20N665FL%20Final_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.