# NTSB CEN21LA386: Acro Sport II, N169BF, Fishers, IN, August 25, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: August 25, 2021, 18:22 local (22:22 UTC) - Place: Fishers, IN · Accident site near intersection of 96st Street and Sargent Road. - Coordinates: 39.927205, -86.00699 - Nearby events: https://openairdocs.org/map.md?lat=39.9272&lon=-86.0070&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration - Indianapolis FSDO - NTSB case key (mKey): 103760 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA386 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103760/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103760 - Page: https://openairdocs.org/ntsb/CEN21LA386 ## Probable cause The airplane’s total loss of engine power due to fuel exhaustion as a result of leaking fuel from a loose fuel inlet fitting to the fuel control unit. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel control/carburetor](https://openairdocs.org/ntsb-findings/01057322): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-findings/01057322/cases.md?model=05624YC), [All aircraft, 195 cases](https://openairdocs.org/ntsb-findings/01057322/cases.md) - [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=05624YC), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md) - [Fuel system: fuel distribution](https://openairdocs.org/ntsb-findings/01022820): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-findings/01022820/cases.md?model=05624YC), [All aircraft, 141 cases](https://openairdocs.org/ntsb-findings/01022820/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Fuel related](https://openairdocs.org/ntsb-events/190); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-events/190/sequence.md?model=05624YC), [All aircraft, 361 cases](https://openairdocs.org/ntsb-events/190/sequence.md) - [Enroute-cruise: Fuel exhaustion](https://openairdocs.org/ntsb-events/192) (defining event); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-events/192/sequence.md?model=05624YC), [All aircraft, 804 cases](https://openairdocs.org/ntsb-events/192/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Freckman Bill ACRO SPORT II, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05624YC), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot was conducting a post-maintenance flight in the experimental airplane to “break-in” two engine cylinders that were replaced on the day before the accident. The engine was operated at maximum speed with a full rich mixture setting throughout the flight. The pilot stated that the airplane lost total engine power about 1 hour after takeoff. During the forced landing, the airplane impacted a street signpost, resulting in substantial damage to a structural fuselage tube. The pilot reported that the fuel tank contained 23 gallons of fuel at the start of the flight. Postaccident examination found that the airplane’s fuel tank was empty and that only 2 to 3 fluid ounces of fuel were recovered from the fuel system. Evidence of a fuel leak was found within the engine compartment and on the exterior lower fuselage skins aft of the firewall. Examination of the fuel system revealed that the fuel inlet fitting to the fuel control unit was finger tight. In preparation for a postaccident engine test, the loose fuel inlet fitting was tightened, and the fuel system was pressurized to confirm that no other leak sources existed. The engine started and ran normally without any hesitation, stumbling, or interruption in power. There was no evidence of a fuel system leak following the engine run. Based on data collected during the engine test, the fuel consumption rate at maximum engine power on the ground (static power) was about 13.69 gallons per hour (gph) at an engine speed of 2,260 rpm. The estimated fuel consumption rate while in flight at maximum engine power (2,800 rpm) was about 16.96 gph. With a full fuel tank (23 gallons) at departure, the airplane’s fuel endurance was about 1 hour 21 minutes if the engine was operated at maximum power with a full rich mixture setting. Other than the loose fuel inlet fitting, the engine examination and test run revealed no mechanical malfunctions that would have prevented normal engine operation during the flight. Air traffic control radar data showed that the airplane was airborne for about 1 hour 15 minutes during the accident flight. Thus, it is likely that the loose fuel inlet fitting leaked fuel during the flight, which resulted in fuel exhaustion and the subsequent total loss of engine power. ## Factual narrative The experimental biplane was designed for aerobatic flight, and its engine was modified with oversized cylinders and pistons. The engine had no data plate or serial number. During the airplane’s last condition inspection, the tachometer was reset to 0 hours. At that time, the airframe total time and engine time since overhaul were 641 and 60 hours, respectively. On August 24, 2021, cylinder Nos. 3 and 4 were replaced after being refurbished due to low compression. The mechanic, who was also the pilot/owner, reported no issues during his engine runup after the cylinder replacements. At that time, the airframe total time and engine time since overhaul were 669 and 88 hours, respectively. Air traffic control radar track data showed that the pilot flew the airplane about 1 hour 15 minutes (1.25 hours) during the accident flight. Thus, at the time of the accident, the airframe total time and engine time since overhaul would have been 670 and 89 hours, respectively. On August 25, 2021, about 1822 eastern daylight time, an Acro Sport II experimental airplane, N169BF, was substantially damaged when it was involved in an accident near Fishers, Indiana. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the purpose of the flight was to “break-in” two engine cylinders that were replaced on the day before the accident. According to the pilot’s statement and fueling documentation, the airplane’s 23-gallon fuel tank was topped off before the flight. The pilot reported that the engine was operated at maximum speed (2,800 rpm) with a full rich mixture setting throughout the flight and that the airplane lost total engine power about 1 hour after takeoff. During the forced landing, the forward right side of the fuselage impacted a street signpost, resulting in substantial damage to a structural tube in the fuselage. Postaccident examination of the airplane found that its fuel tank was empty, with 2 to 3 fluid ounces of fuel recovered when the fuel system was drained during the examination. Evidence of a fuel leak was found within the engine compartment and on the exterior lower fuselage skins aft of the firewall. This evidence included areas of fuel pooling, droplets of fuel dripping from control cable clamps, a fuel sheen on the firewall, and fuel streaking on the exterior lower fuselage skins aft of the firewall. Engine control continuity was confirmed from the cockpit controls to the throttle arm and mixture control at the fuel servo. The fuel inlet fitting to the fuel control unit was finger tight. In preparation for an engine test the loose fuel inlet fitting was tightened (to determine the fuel consumption at the maximum static engine rpm), and the fuel system was pressurized at least twice, which confirmed that no other leak sources existed. During the test, the engine started and ran normally without any hesitation, stumbling, or interruption in power. No evidenceof a fuel system leak was found after the engine run. The fuel consumption rate at maximum engine power on the ground (static power) was about 13.69 gallons per hour at 2,260 rpm. On the basis of the engine test run results, the estimated fuel consumption rate while in flight at maximum engine power (2,800 rpm) was about 16.96 gallons per hour. With a full fuel tank (23 gallons) at departure, the airplane’s fuel endurance would have been about 1 hour 21 minutes (1.35 hours) if the engine was operated at maximum power with a full rich mixture setting. Other than the loose fuel inlet fitting, the engine examination and test run revealed no mechanical malfunctions that would have prevented normal engine operation during the flight. ## Aircraft - Registration: [N169BF](https://openairdocs.org/aircraft/N169BF), registered now, S/N 1392, built 1995 (OpenAirDocs) - Reported make and model: Acro Sport II (NO SERIES) - Registry model: [Freckman Bill ACRO SPORT II](https://openairdocs.org/model/freckman-bill-acro-sport-ii) (registry code 05624YC) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 1392 - Year built: 1995 - Airframe hours: 670 - Engines: Lycoming (Experimental) IO-360 205 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, March 21, 2021 - Departed: UMP, Fishers, IN - Destination: UMP, Fishers, IN - Airport: UMP, Indianapolis Metro Airport - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 6, 2021; seat: rear; restraint: 5-point; flight hours: 14,500 total, 186 in this make and model, 58.5 in the last 90 days, 35 in the last 30 days, 1.5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 82 °F, dew point 79 °F - Altimeter: 30.12 inHg - Observed at: KMQJ, 8.5 nm away - METAR: METAR KMQJ 252215Z AUTO 20003KT 10SM CLR 28/26 A3012 RMK AO1= ## 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 20210825013969A](https://openairdocs.org/incident/20210825013969A), Aug 25, 2021: Freckman Bill ACRO SPORT II, Fishers, IN, Substantial damage. On August 25, 2021, about 1705 eastern time (EST) a Freckman Bill biplane Acro Sport II, N169BF, departed Indianapolis Metro Airport (kump) to break-in the… ## Docket (8 files) The files NTSB released with the investigation on September 7, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103760. 12.2 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16018891&FileExtension=pdf&FileName=01%20-%20Pilot%20Report_Redacted-Rel.pdf - FAA inspector statements (item 2, PDF, 3 pages, 438 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16018502&FileExtension=pdf&FileName=02%20-%20FAA%20Inspector%20Statements_Redacted-Rel.pdf - Wreckage examination summary (item 3, PDF, 5 pages, 120 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16022625&FileExtension=pdf&FileName=03%20-%20Wreckage%20Examination%20Summary-Rel.pdf - Maintenance logbooks (excerpts) (item 4, PDF, 5 pages, 6.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16018339&FileExtension=pdf&FileName=04%20-%20Maintenance%20Logbooks%20(Excerpts)_Redacted-Rel.pdf - Fueling documentation (item 5, PDF, 2 pages, 899 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16018901&FileExtension=pdf&FileName=05%20-%20Fueling%20Documentation_Redacted-Rel.pdf - FAA radar track data (item 6, CSV, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16017985&FileExtension=csv&FileName=06%20-%20FAA%20Radar%20Track%20Data-Rel.csv - Weather summary (item 7, PDF, 2 pages, 107 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16017995&FileExtension=pdf&FileName=07%20-%20Weather%20Summary-Rel.pdf - Photos (item 8, PDF, 3 pages, 3 photos, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16018911&FileExtension=pdf&FileName=08%20-%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.