CESSNA 172RG near Opa Locka, FL — 2017-11-16

Probable cause

A failure of the airplane 's electrical system, which led to the failure of the landing gear system, for reasons that could not be determined because postaccident examination and testing revealed no mechanical anomalies that would have precluded normal operation. Contributing to the accident were the inoperative landing gear unsafe warning horn and the low voltage warning light.

NTSB narrative

The pilot reported that while practicing instrument approaches for an upcoming checkride, she moved the landing gear selector to the down position, verified that the landing gear position light was illuminated green, set the flaps to 20°, and completed the before landing checklist. Shortly thereafter, when the airplane was about 500 ft above ground level (agl), the GPS blinked, and electrical power and radio communications were lost. When the airplane was about 150 ft agl, the lights on the airplane's instrument panel blinked and remained illuminated. The pilot selected flaps to 30° and configured the airplane for landing. The pilot then moved the landing light switch to the on position and again lost all electrical power. Upon touchdown, the right main landing gear collapsed, and the airplane departed the runway, which resulted in substantial damage to the right horizontal stabilizer. The pilot stated that no electrical or landing gear warning lights were illuminated for the duration of the flight. A postaccident examination revealed that the airplane's battery had been depleted. Further examination revealed no anomalies with the airplane's electrical charging system, landing gear system, or its actuators. However, both the landing gear unsafe horn and low voltage warning light were inoperable. Given that the landing gear unsafe horn and low voltage warning light were inoperable, it is unlikely that the pilot would have been alerted to an electrical system failure, which ultimately would have depleted the battery and affected the operation of the landing gear system.

Analysis

Primary failure mode

Mechanical failure

First missed decision gate

Pilot could have aborted the approach after losing electrical power.

NTSB coding

• Electrical system malf/failure · Approach-IFR final approach

Evidence available

• Photos
• 5 docket documents

Docket documents5

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Statement of Party Representatives to NTSB Investigationinterview
• POH Landing Gear System Excerptother
• Record of Conversation (Jones)other
• Photosphotos

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