- Date
- March 18, 2021, 12:53 local (17:53 UTC)
- Place
- Marianna, FL · On airport
- Injuries
- 3 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N7736KCessna 210
- Defining event
- Enroute: Electrical system malf/failure
- Weather
- Visual (VMC) · Day
- 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
- FAA report
- 20210318001829A
- Case key
- 102790
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
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 · 4
NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.
Sequence of events
The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.
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
- Reported as
- Cessna 210 (N)
- Category
- Airplane
- Serial number
- P21000420
- Built
- 1979
- Airframe hours
- 4,041
- Engine
- 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
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 64
- Injuries
- None
- Certificate
- 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
Docket · 6
The files NTSB released with the investigation on August 3, 2021, on NTSB’s docket system: statements, records, photos and specialists’ reports. 5.7 MB in all.
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.
Other investigations on N7736K · 1
Matched to the same aircraft by N-number and date.