# NTSB ERA11LA156: Cessna 172G, N3740L, Clarksville, FL, February 23, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 23, 2011, 13:56 local (19:56 UTC) - Place: Clarksville, FL - Coordinates: 30.448333, -85.198333 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.4483&lon=-85.1983&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Fuel starvation](https://openairdocs.org/ntsb-events/191) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report November 17, 2011 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: Cessna Aircraft Company, FAA/FSDO, Continental Motors - NTSB case key (mKey): 78415 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA11LA156 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78415/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78415 - Page: https://openairdocs.org/ntsb/ERA11LA156 ## Probable cause A loss of engine power due to fuel starvation as a result of the owner's improper maintenance of the fuel selector valve, which resulted in a lack of fuel supply from the right fuel tank. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fuel system: fuel selector/shutoff valve](https://openairdocs.org/ntsb-findings/01022823): Aircraft › Aircraft systems · Incorrect service/maintenance (probable cause); cases with it: [Cessna 172G, 1 case](https://openairdocs.org/ntsb-findings/01022823/cases.md?model=2072420), [All aircraft, 176 cases](https://openairdocs.org/ntsb-findings/01022823/cases.md) - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Owner/builder (probable cause); cases with it: [Cessna 172G, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=2072420), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/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 (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Cessna 172G, 10 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2072420), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Enroute-cruise: Fuel starvation](https://openairdocs.org/ntsb-events/191) (defining event); cases with it: [Cessna 172G, 2 cases](https://openairdocs.org/ntsb-events/191/sequence.md?model=2072420), [All aircraft, 733 cases](https://openairdocs.org/ntsb-events/191/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 172G, 12 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2072420), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 172G, 21 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2072420), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis According to the pilot, prior to conducting low level power line inspection flights, he filled both fuel tanks. During the flight, the pilot noted the right fuel tank guage showed about 3/4 full, and the left guage showed about 1/4 full. He was not concerned because he knew he had sufficient fuel due to timing. About 2 hours, 45 minutes of flight time after refueling, the engine lost power. The pilot's attempts to restart the engine by switching fuel tanks and applying carburetor heat were unsuccessful. The airplane descended into trees, coming to rest nose-down in a near-vertical attitude. The following day, the pilot and an FAA inspector saw fuel leaking from the right wing fuel cap vent, but not from the left. A postaccident engine test revealed that, with fuel in both tanks, the engine would start and operate with fuel selected from the left tank and both tanks, but not from the right tank. Additional examination revealed that a small steel ball from the right supply side of the fuel selector had migrated to the gascolator. The steel ball would have normally been able to push against a spring-loaded larger steel ball, which then would have been displaced away from an orifice to allow fuel to flow. The airplane's owner and a friend, who were not certificated mechanics, had previously performed maintenance on the fuel selector, which likely dislodged the small steel ball. The dislodged small steel ball would normally have prevented fuel flow from the right tank immediately. However, the right tank did supply fuel to the engine for about 10 subsequent hours of airplane operation, likely because the larger steel ball had been temporarily jammed into an open position due to debris found in the fuel selector. ## Factual narrative On February 23, 2011, at 1456 eastern standard time, a Cessna 172G, N3740L, was substantially damaged during a forced landing in Clarksville, Florida. The certificated commercial pilot and the passenger were not injured. Visual meteorological conditions prevailed. No flight plan had been filed for the flight, between Tri-County Airport (1J0), Bonifay, Florida, and Sandy Creek Airpark (75FL), Panama City, Florida. The aerial observation flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the pilot, he first took off in the borrowed airplane from 75FL with half-filled fuel tanks, and about 1/2 hour later, landed at Bountstown Airport (F95), Bountstown, Florida. There, he completely filled both tanks, with the left tank taking perhaps slightly more fuel. He then took off again on a power line inspection flight, landing at 1J0 for a rest break. He subsequently took off once more to continue the power line inspection, and about 2 hours, 45 minutes of flight time after refueling, the engine lost power. The pilot switched the fuel tank selector valve from "Both" to the left tank, then to the right tank, with no improvement noted. He then applied carburetor heat, also with no improvement. After that, he pumped the primer knob, and was able to observe a couple of short bursts of power, but the airplane descended into trees, coming to rest nose-down in a near-vertical attitude. The pilot and the passenger subsequently released their seat belts and dropped to the ground without injury. When asked about the fuel gauges, the pilot stated that during the accident flight, the fuel gauges had read differently, with the left tank gauge, when checked, indicating about 1/4 full while the right tank gauge was indicating off the full mark, perhaps around 3/4 full. The pilot also stated that he didn't think much of it, since he had the fuel selector on Both, the gauges normally showed greater burn from the left tank, he had seen fuel sending units go bad, and he knew by timing that he had more than enough fuel onboard to complete the mission. The pilot further stated that he did not run the airplane out of fuel. When he returned to the accident site with a Federal Aviation Administration (FAA) inspector the next day, there was a strong odor of fuel and there was fuel leaking from the right wing fuel cap vent. When asked if the owner had mentioned any maintenance of the airplane prior to the accident, the pilot stated that the owner informed him that an O-ring in the fuel selector had been replaced. Weather, recorded at an airport 20 nautical miles to the north, at 1453, included clear skies, calm winds, temperature 26 degrees C, dew point 8 degrees C, and an altimeter setting of 30.12 inches Hg. A carburetor icing probability chart did not predict any probability of carburetor icing. On August 5, 2011, the engine and fuel system were examined at a recovery facility under NTSB oversight. According to the NTSBinvestigator's written observations, the airplane's wings and empennage had been removed for its transport from the accident site. The propeller and spinner remained attached to the engine, and the engine remained attached to the firewall with no observed damage to the engine mounts. The right wing root fuel line opening was clear. The left wing root fuel line opening contained a small amount of organic material that appeared to be small, dried flower petals. The gascolator was opened to check for contamination. When the bowl was dropped, a small steel ball, approximately 3/16 inch in diameter, fell out. Otherwise, the bowl was clean. No damage was noted to the ball. The fuel strainer brass screen was clean except for a very small amount of fibrous, lint-like material on the outside of the screen. When the engine top spark plugs were removed, they appeared normal in color and wear when compared to a Champion inspection chart. They were then reinstalled and the engine was prepared for a test run on the airframe. The airplane battery was dead and a start cart was used to energize the starter. A portable plastic fuel tank was plumbed to the left wing root fuel line. With external battery power applied directly to the starter, the engine was started and run at low power for about 50 seconds before being shut down due to no oil pressure indication. Subsequent turnover of the engine revealed positive oil pressure, consistent with an oil pressure indication problem. The engine was then run a second time for about 3 minutes. The engine was run at low power initially; then power was increased to about 2,000 rpm. Magneto checks were normal. The external fuel tank was subsequently plumbed to the right wing root fuel line with the fuel selector in Right position. The engine was started and ran at low power for about 40 seconds before it lost power and quit. Two additional attempts to start the engine with the fuel selector in the Both position were also unsuccessful. A final attempt to run the engine was made, but with the fuel selector valve bypassed. The external fuel tank was plumbed directly to the gascolator inlet. The engine started immediately and ran smoothly for about 1 minute, up to 2,400 rpm. The fuel tank finger screens were removed and did not reveal evidence of blockage. There was no fuel tank contamination observed using a flashlight to inspect the interior of the tanks. The fuel selector valve was disassembled. There was some debris inside the valve, and a small steel ball was missing from the right-tank side of the selector. There were no internal failures evident that would have resulted in the ball liberating itself from the valve in flight. According to a representative from the airplane manufacturer, as supplemented by the illustrated parts diagram for the fuel selector valve assembly, the fuel selector shaft included a cam at its lower end, which, when rotated, would normally press against one or two small balls, depending if the valveselected was for the right tank, the left tank or both tanks. For a selected fuel tank source, each small ball would push a spring-loaded larger ball away from an orifice, which would then allow fuel to flow from that source. The smaller balls rested against the cam; if the cam was displaced upward, the smaller balls could fall into the main fuel selector chamber, then be passed through the single fuel feed line leading to the gascolator. According to the airplane's owner, about 10 flight hours before the accident flight, he and a friend had fixed a fuel leak in the fuel selector by tightening the four retaining screws for the fuel valve cover/gasket. The owner also noted that the cover was under significant pressure against the tightening. When asked if he had noticed any difference in fuel burn between the left and right tanks after the fix, the owner stated that he hadn't flown the airplane much, and that the accident pilot could better answer the question since he had been flying the airplane more often. Neither the owner nor the friend was an FAA-certificated mechanic. During a follow-up interview with the accident pilot, he stated that he had smelled fuel in the airplane before the owner had advised him of the fix, and did not smell fuel after the fix. He also stated that he had flown the airplane several times after the fix, for about 8 hours, and had filled the fuel tanks before the day of the accident, but couldn't recall if one fuel tank took more fuel than the other. The pilot further noted that during each preflight inspection, he would always check to see if the fuel selector would work by checking all positions, including Both and Off. Subsequent to the fix, he did not notice anything abnormal when doing so. According to the airplane's maintenance records, new O-ring seals and a cover gasket were last installed in the fuel selector on July 16, 1992. ## Aircraft - Registration: [N3740L](https://openairdocs.org/deregistered/N3740L-2018-02-13), registration cancelled 2018-02-13, S/N 17253909, built 1965 (OpenAirDocs) - Reported make and model: CESSNA 172G - Registry model: [Cessna 172G](https://openairdocs.org/model/cessna-172g) (registry code 2072420) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17253909 - Airframe hours: 3244 - Engines: CONT MOTOR O-300 SER 145 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 3, 2010, 26 hours before - Departed: 1J0, Bonifay, FL - Destination: 75FL, Panama City, FL ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review March 24, 2010; seat: left; flight hours: 4,885 total, 1,530 in this make and model, 4,835 as pilot in command, 34 in the last 90 days, 16 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 46 °F - Altimeter: 30.12 inHg - Observed at: MAI, 20 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 20110223003189A](https://openairdocs.org/incident/20110223003189A), Feb 23, 2011: Cessna 172G, Clarksville, FL, Substantial damage. Loss of power during powerline patrol resulting in off airport emergency landing in thick pine forest. ## Docket (18 files) The files NTSB released with the investigation on September 30, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78415. 10.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 334 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354051&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Memorandum for Record (item 2, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354053&FileExtension=.PDF&FileName=Memorandum%20for%20Record-Master.PDF - Record of Conversation - Pilot (item 3, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354095&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Pilot-Master.PDF - Record of Conversation - Pilot Follow-Up (item 4, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354056&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Pilot%20Follow-Up-Master.PDF - Record of Conversation - Pilot Second Follow-Up (item 5, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354619&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Pilot%20Second%20Follow-Up-Master.PDF - Excerpt, Cessna 172 Illustrated Parts Catalog (item 6, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354062&FileExtension=.PDF&FileName=Excerpt,%20Cessna%20172%20Illustrated%20Parts%20Catalog-Master.PDF - Record of Conversation - Owner (item 7, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354058&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Owner-Master.PDF - Record of Conversation - Airplane Manufacturer Representative (item 8, .PDF, 51 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354060&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Airplane%20Manufacturer%20Representative-Master.PDF - 1992 Fuel Selector Logbook Entry (item 9, .PDF, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354096&FileExtension=.PDF&FileName=1992%20Fuel%20Selector%20Logbook%20Entry-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 10, .PDF, 114 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354061&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Photo 1 - Gascolator Body and Small Steel Ball that was Found Within (item 11, .PDF, 175 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354063&FileExtension=.PDF&FileName=Photo%201%20-%20Gascolator%20Body%20and%20Small%20Steel%20Ball%20that%20was%20Found%20Within-Master.PDF - Photo 2 - Fuel Sector Valve (item 12, .PDF, 284 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354064&FileExtension=.PDF&FileName=Photo%202%20-%20Fuel%20Sector%20Valve-Master.PDF - Photo 3 - CAM Inside Fuel Selector Valve Housing (item 13, .PDF, 298 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354065&FileExtension=.PDF&FileName=Photo%203%20-%20CAM%20Inside%20Fuel%20Selector%20Valve%20Housing-Master.PDF - Photo 4 - Fuel Selector Valve Cover, Gasket, CAM (item 14, .PDF, 331 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354066&FileExtension=.PDF&FileName=Photo%204%20-%20Fuel%20Selector%20Valve%20Cover,%20Gasket,%20CAM-Master.PDF - Photo 5 - Fuel Selector Valve Internal Parts General Layout (Courtesy Continental Motors) (item 15, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354084&FileExtension=.PDF&FileName=Photo%205%20-%20Fuel%20Selector%20Valve%20Internal%20Parts%20General%20Layout%20(Courtesy%20Continental%20Motors)-Master.PDF - Photo 6 - Closeup of Fuel Selector Valve Internal Parts on Left Fuel Tank Side (Courtesy Continental Motors) (item 16, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354090&FileExtension=.PDF&FileName=Photo%206%20-%20Closeup%20of%20Fuel%20Selector%20Valve%20Internal%20Parts%20on%20Left%20Fuel%20Tank%20Side%20(Courtesy%20Continental%20Motors)-Master.PDF - Photo 7 - Closeup of Fuel Selector Valve Internal Parts on the Right Fuel Tank Side (Courtesy Continental Motors) (item 17, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354475&FileExtension=.PDF&FileName=Photo%207%20-%20Closeup%20of%20Fuel%20Selector%20Valve%20Internal%20Parts%20on%20the%20Right%20Fuel%20Tank%20Side%20(Courtesy%20Continental%20Motors)-Master.PDF - Photo 8 - Fuel Selector Valve Inlet (from Right Tank) (Courtesy Continental Motors) (item 18, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354094&FileExtension=.PDF&FileName=Photo%208%20-%20Fuel%20Selector%20Valve%20Inlet%20(from%20Right%20Tank)%20(Courtesy%20Continental%20Motors)-Master.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.