# NTSB ERA21LA304: Boeing B75N1, N1720B, Lexington, KY, July 28, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: July 28, 2021, 08:20 local (12:20 UTC) - Place: Lexington, KY · private driveway - Coordinates: 37.953781, -84.406687 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.9538&lon=-84.4067&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: Eastern Region Aviation - Parties: FAA/FSDO - SAIBs cited in the narratives: [SAIB CE-09-35](https://openairdocs.org/saib/CE-09-35) (OpenAirDocs) - NTSB case key (mKey): 103572 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA21LA304 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103572/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103572 - Page: https://openairdocs.org/ntsb/ERA21LA304 ## Probable cause A loss of engine power for undetermined reasons. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft](https://openairdocs.org/ntsb-findings/01050000): Aircraft › Aircraft power plant · Unknown/Not determined (probable cause); cases with it: [Boeing B75N1, 1 case](https://openairdocs.org/ntsb-findings/01050000/cases.md?model=1380144), [All aircraft, 151 cases](https://openairdocs.org/ntsb-findings/01050000/cases.md) - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Boeing B75N1, 1 case](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=1380144), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/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: [Boeing B75N1, 3 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=1380144), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Boeing B75N1, 4 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1380144), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The private pilot and passenger were on a local area personal flight in the single-engine airplane. The pilot reported after flying for 20 minutes, he was at 1,500 ft mean sea level when the airplane began to lose engine power and he was unable to maintain altitude. The pilot added full power, full mixture, and carburetor heat, but was still unable to maintain altitude. The pilot subsequently performed a forced landing to a private driveway. A postaccident examination of the wreckage revealed no evidence of preimpact mechanical anomalies that would have prevented normal engine operation. In addition, fuel was plumbed into the engine and the engine ran without anomaly. Although the weather conditions at the time of the accident were conducive to the accumulation of carburetor icing at glide power, the pilot reported that he used carburetor heat, which would have prevented the accumulation of ice. ## Factual narrative On July 28, 2021, about 0820 eastern daylight time, a Boeing B75N1, N1720B, was substantially damaged when it was involved in an accident near Lexington, Kentucky. The private pilot sustained minor injuries and the passenger was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot he departed with 46 gallons of fuel, after flying for 20 minutes, he was at 1,500 ft mean sea level when the airplane began to descend, and he was unable to maintain altitude. The pilot added full power, full mixture, and carburetor heat, but was still unable to maintain altitude. The pilot performed a forced landing to a private driveway. The airplane impacted a telephone pole just prior to touchdown. According to the Federal Aviation Administration (FAA) inspector who responded to the accident site, initial examination of the airplane revealed that the wings sustained substantial damage. All engine and flight controls functioned normally and were verified from the cockpit controls to their respective control surfaces. The magneto switch was jammed in the BOTH position. The inspector was able to manually rotate the propeller with no binding in the engine. The engine was examined on the airframe at a salvage facility by an FAA inspector. The engine was prepped for a field test run and fuel was plumbed into the engine, it started after a few tries, and then ran smoothly with no anomalies noted. At 0854, the weather reported at Blue Grass Airport (LEX), about 11 miles northwest of the accident site, included a temperature of 22°C and a dew point 19°C. The calculated relative humidity at this temperature and dewpoint was 83%. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed the atmospheric conditions at the time of the accident were "conducive to serious icing at glide [idle] power." According to FAA Advisory Circular 20-113, "To prevent accident due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The circular recommended that when operating in conditions where the relative humidity is greater than 50 percent, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of induction system icing during takeoff and climb-out, especially when the relative humidity is above 50 percent, or when visible moisture is present in the atmosphere." ## Aircraft - Registration: [N1720B](https://openairdocs.org/aircraft/N1720B), registered now, S/N 75-6017 (OpenAirDocs) - Reported make and model: BOEING B75N1 - Registry model: [Boeing B75N1](https://openairdocs.org/model/boeing-b75n1) (registry code 1380144) (OpenAirDocs) - Registry engine: [Lycoming R680](https://openairdocs.org/engine/lycoming-r680) (registry code 41540, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 75-6017 - Year built: 1945 - Airframe hours: 2407.9 - Engines: Lycoming R680-13 300 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 1, 2021 - Departed: KLEX, Lexington, KY - Equipment: Handheld GPS, Stall warning system, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 69; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review September 1, 2020; seat: rear; restraint: 4-point; flight hours: 1,500 total, 300 in this make and model, 1,500 as pilot in command, 20 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 66 °F - Altimeter: 30.11 inHg - Observed at: LEX, 11 nm away - METAR: KLEX 281254Z 00000KT 10SM CLR 22/19 A3011 RMK AO2 RAB45E51 SLP185 P0000 T02220194 ## 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 20210728012059A](https://openairdocs.org/incident/20210728012059A), Jul 28, 2021: Boeing B75N1, Lexington, KY, Substantial damage. According to Lexington approach control, the accident pilot departed Lexington blue grass airport (klex) with the intention to take a friend on an aerial tour… ## Other investigations on N1720B (2) 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. - [NTSB SEA75DYG23](https://openairdocs.org/ntsb/SEA75DYG23), Mar 8, 1975: Stearman E75N1 (N1720B), Craigmont, ID, substantial damage - [NTSB SEA74DYG36](https://openairdocs.org/ntsb/SEA74DYG36), May 7, 1974: Stearman A75 (N1720B), Craigmont, ID, substantial damage ## Docket (4 files) The files NTSB released with the investigation on June 28, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103572. 26.9 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15705126&FileExtension=pdf&FileName=NTSB%206120_Redacted-Rel.pdf - FAA inspector's statement (item 2, PDF, 1 page, 99 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12629943&FileExtension=pdf&FileName=Memorandum%20for%20Record%20FAA%20Inspector%20Statement-Rel.pdf - FAA inspector's statement engine run (item 3, PDF, 6 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12629463&FileExtension=pdf&FileName=Inspector%20Statement%20Stearman%20N1720B-Rel.pdf - Video file (item 4, MP4, 21.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12656205&FileExtension=mp4&FileName=DSCN0067_Engine%20run-Rel.mp4 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.