# NTSB WPR20LA136: Cessna 172, N734NW, Fresno, CA, May 2, 2020 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: May 2, 2020, 09:30 local (16:30 UTC) - Place: Fresno, CA - Coordinates: 36.840278, -119.869445 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.8403&lon=-119.8694&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FSDO - NTSB case key (mKey): 101227 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR20LA136 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101227/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101227 - Page: https://openairdocs.org/ntsb/WPR20LA136 ## Probable cause The partial loss of engine power for reasons that could not be determined based on available evidence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Cessna 172N, 24 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2072434), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/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 (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Cessna 172N, 23 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=2072434), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) ## Analysis Shortly after takeoff on runway 30, as the airplane reached about 300 to 400 ft above ground level, the engine lost partial power. The pilot prepared for a downwind landing to runway 12 and when he realized the airplane had excess energy, he deployed the flaps and performed a forward slip maneuver. The airplane touched down about halfway down the runway and continued off the end and through a fence. The airplane then passed over the two westbound lanes of a road and nosed over in the median. Examination of the engine revealed low compression on two of the six cylinders (around 25 to 75 percent compression loss on cylinder numbers 3 and 5). The valve rocker arms were tapped with a rubber mallet and compression recovered to approximately 25 percent loss in the number 3 cylinder and 15 percent loss in the number 5 cylinder. An internal borescope examination of the engine cylinders revealed the piston tops and cylinder sidewalls appeared normal and no evidence of foreign object ingestion was observed. No other pre-impact mechanical anomalies were identified during the examination. Although the reason for the low compression could not be determined, it was noted that the engine was disassembled 1.9 hours before the accident flight. ## Factual narrative On May 2, 2020, about 0930 Pacific daylight time, a Cessna 172N, N734NW, was substantially damaged when it was involved in an accident near Sierra Sky Park Airport (E79), Fresno, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated the airplane had recently undergone maintenance; this was to be the third flight after the maintenance, and he planned to stay in the local area. He conducted a preflight inspection and observed 28 gallons of fuel in the fuel tanks; he also confirmed there was no contamination in the fuel by visually checking the fuel strainer. The pilot estimated the wind was about 9 to 10 knots straight down runway 30 (headwind). He initiated a takeoff and when the airplane reached about 300 to 400 ft above ground level, the engine power began to fluctuate. The engine then remained at “low” power and the pilot pitched the airplane to maintain 70 to 80 knots of airspeed. He prepared for a downwind landing on runway 12 and when he realized the airplane had excess energy, he deployed the flaps and performed a forward slip maneuver. The airplane touched down about halfway down the runway and continued off the end and through a fence. The airplane then passed over the two westbound lanes of a road and nosed over in the median. A postaccident examination was performed on the airplane and engine. The crankshaft was rotated by hand using the propeller. Rotational continuity was established throughout the engine and valve train. Equal movement was observed on all of the intake and exhaust valve rocker arms. Thumb compression and suction was obtained on four of the six cylinders. Cylinder numbers 3 and 5 had very minimal thumb compression. A differential pressure gauge was connected to the numbers 3 and 5 cylinders, which exhibited around 25 to 75 percent compression loss. The valve rocker arms were tapped with a rubber mallet, and compression recovered to approximately 25 percent loss in the number 3 cylinder and 15 percent loss in the number 5 cylinder. An internal borescope examination of the engine cylinders revealed the piston tops and cylinder sidewalls appeared normal. No evidence of foreign object ingestion was observed. Examination of the fuel strainer revealed the drain pull handle used for draining the strainer was inoperable. An examination of the fuel strainer found the drain valve cable to be dirty without evidence of frequent actuation (the cable showed no signs of sliding in and out of the cable housing). The fuel strainer drain valve cable was disconnected and the drain valve was opened manually without restriction. The fuel strainer housing (bowl) was removed, and the internal screen was free of debris. The fuel remaining in the strainer bowl was clear and bright. Examination of the maintenance records for the airplane revealed the engine was disassembled and the carburetor and fuel strainer were overhauled 1.9 hoursbefore the accident flight. ## Aircraft - Registration: [N734NW](https://openairdocs.org/deregistered/N734NW-2022-03-19), registration cancelled 2022-03-19, S/N 17268993, built 1977 (OpenAirDocs) - Reported make and model: Cessna 172 (N) - Registry model: [Cessna 172N](https://openairdocs.org/model/cessna-172n) (registry code 2072434) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17268993 - Year built: 1977 - Airframe hours: 3515 - Engines: PZL Franklin 6A-350-C1R 220 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 7, 2020, 1.9 hours before - Destination: Same as departure - Airport: E79, Sierra Sky Park, runway 12, 2,473 × 50 ft, asphalt - Equipment: Stall warning system, ADS-B, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review May 17, 2018; seat: left; restraint: 3-point; flight hours: 784 total, 696 in this make and model, 784 as pilot in command, 9 in the last 90 days, 3 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 50 °F - Altimeter: 30.09 inHg - Observed at: FCH, 7 nm away ## 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 20200502006029A](https://openairdocs.org/incident/20200502006029A), May 2, 2020: Cessna 172N, Fresno, CA, Substantial damage. The aircraft departed r/w 30 into a 20 kt headwind. Climbing above 400' AGL, the pilot and witnesses observed / heard engine surging and the PIC stated power… ## Docket (5 files) The files NTSB released with the investigation on June 8, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101227. 20.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 5.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13230598&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Airframe and engine exam (item 2, PDF, 1 page, 155 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13230539&FileExtension=pdf&FileName=N734NW%20-%20Examination%20-%2024Feb2021-Rel.pdf - Initial FAA inspection (item 3, PDF, 1 page, 217 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13230208&FileExtension=pdf&FileName=N734NW%20Accident%20E79%205-2-20%20Pics%20-%20logs_Redacted-Rel.pdf - Wreckage release memo (item 4, PDF, 1 page, 145 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13264051&FileExtension=pdf&FileName=Memo%20for%20record%20-%20wreckage%20release-Rel.pdf - Photos (courtesy of FAA) (item 5, PDF, 2 pages, 14.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13230648&FileExtension=pdf&FileName=FW_%20N734NW%20Media%20pics_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.