# NTSB ERA21LA159: Cessna 210, N7736K, Marianna, FL, March 18, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Limited · Final report - Date: March 18, 2021, 12:53 local (17:53 UTC) - Place: Marianna, FL · On airport - Coordinates: 30.838221, -85.182224 - Nearby events: https://openairdocs.org/map.md?lat=30.8382&lon=-85.1822&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Electrical system malf/failure](https://openairdocs.org/ntsb-events/332) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 102790 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA21LA159 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102790/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102790 - Page: https://openairdocs.org/ntsb/ERA21LA159 ## Probable cause The failure of the alternator control unit housing plug connection, which resulted in insufficient battery power to fully extend the landing gear. Contributing to the accident was the pilot’s decision to not use the emergency gear extension handle to secure the gear prior to landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Electrical power system: electrical pwr sys wiring](https://openairdocs.org/ntsb-findings/01022497): Aircraft › Aircraft systems · Inoperative (probable cause); cases with it: [Cessna P210N, 1 case](https://openairdocs.org/ntsb-findings/01022497/cases.md?model=2073454), [All aircraft, 44 cases](https://openairdocs.org/ntsb-findings/01022497/cases.md) - [Electrical power system: battery/charger](https://openairdocs.org/ntsb-findings/01022432): Aircraft › Aircraft systems · Damaged/degraded (probable cause); cases with it: [Cessna P210N, 2 cases](https://openairdocs.org/ntsb-findings/01022432/cases.md?model=2073454), [All aircraft, 37 cases](https://openairdocs.org/ntsb-findings/01022432/cases.md) - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Cessna P210N, 11 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=2073454), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Landing gear system: gear extension and retract sys](https://openairdocs.org/ntsb-findings/01023230): Aircraft › Aircraft systems · Not used/operated (probable cause); cases with it: [Cessna P210N, 12 cases](https://openairdocs.org/ntsb-findings/01023230/cases.md?model=2073454), [All aircraft, 416 cases](https://openairdocs.org/ntsb-findings/01023230/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Electrical system malf/failure](https://openairdocs.org/ntsb-events/332) (defining event); cases with it: [Cessna P210N, 7 cases](https://openairdocs.org/ntsb-events/332/sequence.md?model=2073454), [All aircraft, 182 cases](https://openairdocs.org/ntsb-events/332/sequence.md) - [Landing-flare/touchdown: Landing gear not configured](https://openairdocs.org/ntsb-events/095); cases with it: [Cessna P210N, 10 cases](https://openairdocs.org/ntsb-events/095/sequence.md?model=2073454), [All aircraft, 584 cases](https://openairdocs.org/ntsb-events/095/sequence.md) - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094); cases with it: [Cessna P210N, 21 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=2073454), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis The pilot was diverting to an airport to refuel when the airplane’s turbine inlet temperature (TIT) warning light illuminated. Shortly after, the autopilot “fail” light came on and the autopilot disengaged, followed by other electrical components losing power or ability to operate. The pilot said that he was able to extend the landing gear, but the light that confirmed that the gear was down and locked was not working. He said that the gear sounded and appeared to be fully extended, so he chose not to use the emergency gear extension handle to make sure the gear was fully extended. On the subsequent landing rollout, both main landing gear collapsed, resulting in substantial damage to the left horizontal stabilizer. Postaccident examination of the airplane revealed that the housing plug for the alternator control unit (ACU) was loosely fitted and not properly mated. It is likely the housing plug came loose during turbulence, and the battery drained to a point that it could not provide adequate electricity to fully extend and lock the landing gear. The pilot reported no previous issues with the electrical system and no maintenance had been done to the ACU after a recent annual inspection. ## Aircraft - Registration: [N7736K](https://openairdocs.org/aircraft/N7736K), registered now, S/N P21000420, built 1979 (OpenAirDocs) - Reported make and model: CESSNA 210 (N) - Registry model: [Cessna P210N](https://openairdocs.org/model/cessna-p210n) (registry code 2073454) (OpenAirDocs) - Registry engine: [Continental TSIO-520 series](https://openairdocs.org/engine/continental-tsio-520-series) (registry code 17040, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: P21000420 - Year built: 1979 - Airframe hours: 4041 - Engines: Continental TSIO 520P6 310 hp reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 10, 2021, 7.4 hours before - Departed: SAV, Savannah, GA - Destination: Same as departure - Airport: MAI, Marianna Municipal, runway 18, 6,001 × 100 ft, asphalt - Equipment: Handheld GPS, Electronic flight bag or handheld device, Auto-pilot, ADS-B, Stall warning system, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review November 30, 2020; seat: left; restraint: 3-point; flight hours: 882 total, 306 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 15 knots - Visibility: 10 statute miles - Temperature: 79 °F, dew point 54 °F - Altimeter: 29.79 inHg - Observed at: KMAI ## 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 20210318001829A](https://openairdocs.org/incident/20210318001829A), Mar 18, 2021: Cessna P210N, Marianna, FL, Substantial damage. Landing gear collapsed after touchdown on runway 18. Airplane veered to the left, exited the runway into the grass area and turned 180 degrees. The left side… ## Other investigations on N7736K (1) 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 DEN04LA107](https://openairdocs.org/ntsb/DEN04LA107), Jul 20, 2004: Cessna P210N (N7736K), Douglas, WY, substantial damage. Probable cause: the failure of the engine's crankshaft due to the rotation of the engine's number two bearing, which resulted in the oil starvation of the crankshaft's number 2 main journal. Contributing factors… ## Docket (6 files) The files NTSB released with the investigation on August 3, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102790. 5.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12427269&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - NTSB record of conversation - pilot (item 2, PDF, 1 page, 126 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12428656&FileExtension=pdf&FileName=NTSB%20Record%20of%20Conversation%20-%20Pilot-Rel.pdf - Written statement - FAA (item 3, PDF, 1 page, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12428436&FileExtension=pdf&FileName=Written%20Statement%20-%20FAA_Redacted-Rel.pdf - Maintenance records - last annual inspections (item 4, PDF, 3 pages, 128 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12427448&FileExtension=pdf&FileName=Excerpt%20Maintenance%20Records%20Last%20Annuals%202021_Redacted-Rel.pdf - Photos (item 5, PDF, 2 pages, 2 photos, 203 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12427185&FileExtension=pdf&FileName=Photos%20Marianna-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12429523&FileExtension=pdf&FileName=wreckage%20release_Redacted-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.