# NTSB WPR19LA233: Cessna 120, N4237N, Livermore, CA, August 21, 2019 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: August 21, 2019, 11:50 local (18:50 UTC) - Place: Livermore, CA - Coordinates: 37.689445, -121.818885 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.6894&lon=-121.8189&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: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 100119 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR19LA233 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100119/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100119 - Page: https://openairdocs.org/ntsb/WPR19LA233 ## Probable cause A partial loss of engine power due to fouled spark plugs in the No. 4 cylinder. Contributing to the accident was the pilot’s exceedance of the airplane’s critical angle of attack and a subsequent loss of control during the initial climb. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Ignition system: spark plugs/igniters](https://openairdocs.org/ntsb-findings/01057421): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Cessna 120, 2 cases](https://openairdocs.org/ntsb-findings/01057421/cases.md?model=2071402), [All aircraft, 38 cases](https://openairdocs.org/ntsb-findings/01057421/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Cessna 120, 22 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2071402), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: angle of attack](https://openairdocs.org/ntsb-findings/01062042): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Cessna 120, 2 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md?model=2071402), [All aircraft, 990 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340); cases with it: [Cessna 120, 3 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2071402), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Cessna 120, 7 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=2071402), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Takeoff: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); cases with it: [Cessna 120, 6 cases](https://openairdocs.org/ntsb-events/490/sequence.md?model=2071402), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md) ## Analysis The accident flight was the first flight following the airplane’s annual inspection. The pilot reported that, during the takeoff roll, the airplane took longer than expected to accelerate, and after becoming airborne, did not seem to be producing full power. Witnesses stated that the airplane made a sharp left turn about 100 feet above the ground and the left wing impacted the ground; the airplane cartwheeled before coming to rest, resulting in substantial damage. A postaccident examination revealed that the upper and lower spark plugs from the No. 4 cylinder and the lower spark plug from the No. 3 cylinder exhibited oil and soot bridging the gap between the electrodes. All other spark plugs exhibited black soot build-up on the electrodes and insulators. The reason for the fouled spark plugs was not determined based on the examination. The mechanic who completed the annual inspection reported that he cleaned, gapped, and functionally tested all of the spark plugs. After the inspection, he conducted an engine run-up and found that one of the plugs had become fouled. He cleaned the plugs a second time and reinstalled them using new gaskets. He ran the engine up a second time, and it ran smoothly. Based on the condition of the No. 4 cylinder spark plugs, it is likely that the engine was not producing nominal power and that its takeoff and climb performance was degraded. The witness observations of a steep left turn and descent to impact is consistent with an aerodynamic stall due to the pilot exceeding the airplane’s critical angle of attack during the initial climb. ## Factual narrative On August 21, 2019, about 1150 Pacific daylight time, a Cessna 120 airplane, N4237N, was substantially damaged when it was involved in an accident near Livermore, California. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, in 2018, the airplane had an issue with the “fuel leads” to the engine. After repairs, she flew the airplane back to her home airport and parked it in a hangar until its annual inspection the month of the accident. The accident flight was the first flight following the annual inspection. The airplane started normally, the runup revealed no anomalies. During the takeoff roll, the airplane took longer than expected to accelerate. The pilot reported that, after the airplane became airborne and began a shallow climb, the engine seemed like it wasn’t operating at full power despite sounding normal. The airplane stopped climbing and the pilot made a left turn for a forced landing. During the emergency descent, the left wing impacted either brush or the ground before the airplane tumbled and came to rest in an area of brush-covered terrain. A witness reported that the airplane’s engine was not sputtering, but it did not sound like it was producing full power. About 100 feet above the ground, the airplane made a sharp left turn and started to descend. The left wing impacted the ground and the airplane cartwheeled before coming to rest. The mechanic who completed the annual inspection also witnessed the accident. He reported that he saw the airplane low over the runway after takeoff and it did not appear to be climbing. Shortly thereafter, the airplane banked “steeply” to the left and impacted the ground. The mechanic reported that, as part of the annual inspection, he cleaned, gapped, and functionally tested all of the spark plugs. After the inspection, he conducted an engine run and “found a rough-running magneto.” He removed all spark plugs and observed that one had become fouled. He cleaned the plugs a second time and reinstalled them using new gaskets. He ran the engine up a second time, and it ran smoothly. During a postaccident engine examination, the spark plugs were removed from the engine. Both the upper and lower spark plugs from the No. 4 cylinder and the lower spark plug from the No. 3 cylinder exhibited oil and soot bridging the gap between the electrodes. All other spark plugs exhibited black soot build-up on the electrodes and insulator. The ignition harness exhibited damage consistent with impact and could not be functionally tested. The magnetos were removed and disassembled; no anomalies were noted with their internal components. The oil filter was removed and opened; no particulates were noted within the filter element. The propeller assembly and valve covers were removed from the engine. The engine was rotated by hand; thumb compression was established on all cylinders, and the valves moved consistentlythroughout. Borescope examination of the cylinders revealed no anomalies. The pilot did not complete and submit the National Transportation Safety Board form 6120.1, nor did she provide copies of the accident airplane’s most recent maintenance logbook entries. ## Aircraft - Registration: [N4237N](https://openairdocs.org/deregistered/N4237N-2020-07-10), registration cancelled 2020-07-10, S/N 13708, built 1947 (OpenAirDocs) - Reported make and model: Cessna 120 - Registry model: [Cessna 120](https://openairdocs.org/model/cessna-120) (registry code 2071402) (OpenAirDocs) - Registry engine: [Continental C85-12F](https://openairdocs.org/engine/continental-c85-12f) (registry code 17125, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 13708 - Year built: 1947 - Engines: Continental O-200-A 85 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 19, 2019, 0 hours before - Departed: LVK, Livermore, CA - Airport: LVK, Livermore Municipal Airport, runway 25L, 2,699 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 69; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; flight hours: 1 total, 1 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 55 °F - Altimeter: 29.94 inHg - Observed at: LVK ## 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 20190821018039A](https://openairdocs.org/incident/20190821018039A), Aug 21, 2019: Cessna 120, Livermore, CA, Substantial damage. On 21 August 2019 at 11:50 am PDT, aircraft N4237N, a Cessna 120, was involved in an off field landing/crash off the departure end of Livermore municipal… ## Docket (7 files) The files NTSB released with the investigation on March 16, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100119. 5.4 MB in all. - Pilot statement (item 1, PDF, 2 pages, 116 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12746438&FileExtension=pdf&FileName=pilot%20statement-Rel.pdf - Record of conversation - witness (item 2, PDF, 1 page, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12744447&FileExtension=pdf&FileName=rom%20witness%20statement-Rel.pdf - Record of memorandum - FAA engine examination (item 3, PDF, 7 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12745927&FileExtension=pdf&FileName=ROM%20faa%20engine%20exam-Rel.pdf - Mechanic statement (item 4, PDF, 1 page, 873 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12744578&FileExtension=pdf&FileName=mechanic%20statement_Redacted-Rel.pdf - Record of memorandum - NTSB pilot/operator 6120.1 form (item 5, PDF, 1 page, 125 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12752403&FileExtension=pdf&FileName=Record%20of%20Memorandum%20no%206120%20or%20mx%20logs-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 491 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12745937&FileExtension=pdf&FileName=Wreckage%20Release%20-%20N4237N_Redacted-Rel.pdf - On scene photos - courtesy of local law enforcement (item 7, PDF, 4 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12744909&FileExtension=pdf&FileName=on%20scene%20photos-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.