# NTSB CEN21LA315: Cessna 421C, N66NC, Longmont, CO, July 10, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: July 10, 2021, 08:45 local (14:45 UTC) - Place: Longmont, CO - Coordinates: 40.16726, -105.16927 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.1673&lon=-105.1693&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Minor injuries - Injuries: 4 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 103460 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA315 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103460/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103460 - Page: https://openairdocs.org/ntsb/CEN21LA315 ## Probable cause The loss of performance for reasons that could not be determined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Cessna 421C, 6 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=2076016), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Performance/control parameters: climb rate](https://openairdocs.org/ntsb-findings/01062035): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01062035/cases.md?model=2076016), [All aircraft, 265 cases](https://openairdocs.org/ntsb-findings/01062035/cases.md) - [Temp/humidity/pressure: high density altitude](https://openairdocs.org/ntsb-findings/03031020): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/03031020/cases.md?model=2076016), [All aircraft, 278 cases](https://openairdocs.org/ntsb-findings/03031020/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 421C, 10 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2076016), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-events/900/sequence.md?model=2076016), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) - [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Cessna 421C, 15 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=2076016), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Takeoff-rejected takeoff: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Cessna 421C, 9 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=2076016), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot reported that he performed the “before starting engine” and “starting engine” checklists and everything was normal before taking off in the twin-engine airplane. He performed an engine runup and then started his takeoff roll. The pilot reported that about halfway down the runway the airplane was not accelerating as fast as it should. He attempted to rotate the airplane; however, “the airplane mushed off the runway.” The airplane settled back onto the runway, then exited the departure end of the runway, where it sustained substantial damage to the wings and fuselage. The airplane engine monitor data indicated the airplane’s engines were operating consistent with each other at takeoff power at the time of the accident. Density altitude at the time of the accident was 7,170 ft and according to performance charts, there was adequate runway for takeoff. The reason for the loss of performance could not be determined. ## Factual narrative On July 10, 2021, about 0845 mountain daylight time, a Cessna 421C airplane, N66NC, was substantially damaged when it was involved in an accident near Longmont, Colorado. The pilot and three passengers received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he performed the “before starting engine” and “starting engine” checklists and everything was normal. He performed an engine runup and then started his takeoff roll. The pilot reported that about halfway down the runway he sensed the airplane was not accelerating as fast as it should. He attempted to rotate; however, “the airplane mushed off the runway.” The airplane settled back onto the runway, then exited off the departure end of the runway. The airplane came to rest upright, and a post-crash fire ensued. The airplane sustained substantial damage to both wings and the fuselage. The airplane was equipped with a JPI EDM 760 engine monitor. The unit was retrieved from the airplane and the NVM (nonvolatile memory) downloaded. According to the engine manufacturer, the data indicated the airplane’s engines were operating consistent with each other at takeoff power until power was reduced for the rejected takeoff. Referring to the Cessna 421C Pilot’s Operating Handbook, for the conditions at the time of the accident, the airplane’s normal takeoff distance would have been about 2,700 ft to clear a 50 ft obstacle. Density altitude at the time of the accident was 7,170 ft. ## Aircraft - Registration: [N66NC](https://openairdocs.org/deregistered/N66NC-2023-12-26), registration cancelled 2023-12-26, S/N 421C0519, built 1978 (OpenAirDocs) - Reported make and model: CESSNA 421C - Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs) - Registry engine: [Continental GTSIO-520 series](https://openairdocs.org/engine/continental-gtsio-520-series) (registry code 17039, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 421C0519 - Year built: 1978 - Airframe hours: 5476 - Engines: Continental GTSIO-520 reciprocating; Continental GTSIO-520 reciprocating - Damage: Substantial damage - Fire: On-Ground - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 18, 2020 - Destination: KASE, Aspen, CO - Airport: LMO, Vance Brand Airport, runway 29, 4,799 × 75 ft, concrete - Equipment: Electronic flight bag or handheld device, Auto-pilot, ADS-B, Video recording device, Onboard weather, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 39; injuries: minor; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review June 12, 2021; seat: left; restraint: 3-point; flight hours: 2,801 total, 169 in this make and model, 2,584 as pilot in command, 32 in the last 90 days, 26 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 140° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 48 °F - Altimeter: 30.31 inHg - Observed at: KLMO - METAR: METAR KLMO 101515Z AUTO 14003KT 10SM CLR 26/09 A3031 RMK AO2 T02570094 ## 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 20210710010559A](https://openairdocs.org/incident/20210710010559A), Jul 10, 2021: Cessna 421C, Longmont, CO, Substantial damage. According to the PIC, the aircraft loaded 3 passengers and luggage. The fuel on board was 100 gallons. Aircraft was 900 pounds below mgw. N66NC taxied for… ## Docket (9 files) The files NTSB released with the investigation on September 14, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103460. 10.0 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791590&FileExtension=pdf&FileName=NTSB%20Form%206120%20Pilot%20Operator%20Report%20CEN21LA315_Redacted-Rel.pdf - Photographs (item 2, PDF, 2 pages, 6.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791776&FileExtension=pdf&FileName=Photos%20(2)-Rel.pdf - Engine monitor report (item 3, PDF, 2 pages, 182 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791374&FileExtension=pdf&FileName=Factual%20Report%20JPI%20EDM760%20(CEN21LA315)-Rel.pdf - Jpi readings (item 4, PDF, 2 pages, 234 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791897&FileExtension=pdf&FileName=JPI%20readings-Rel.pdf - Jpi raw data (item 5, CSV, 22 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791907&FileExtension=csv&FileName=Attachment%201%20-%20Tabluar%20data-Rel.csv - E-mail, Continental motors review of engine monitor data (item 6, PDF, 3 pages, 179 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15791677&FileExtension=pdf&FileName=Fwd_%20%5BEXTERNAL%5D_Redacted-Rel.pdf - Cessna 421C takeoff and climb performance charts (item 7, PDF, 3 pages, 118 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15974584&FileExtension=pdf&FileName=Cessna%20421C%20Takeoff%20and%20Climb%20Performance%20Charts-Rel.pdf - Density altitude calculator (item 8, PDF, 3 pages, 76 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15974542&FileExtension=pdf&FileName=Density%20Altitude%20Calculator-Rel.pdf - Vance brand airport information (item 9, PDF, 4 pages, 202 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15811182&FileExtension=pdf&FileName=KLMO-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.