Introduction
On March 9, 2021, about 1215 central standard time, a Cessna 170A, registration N9515A, was substantially damaged when it nosed over during a precautionary landing near Poplar Bluff, Missouri. The pilot, who was the sole occupant, was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal cross-country trip.
Flight History
The pilot departed Shawnee Regional Airport (SNL) in Shawnee, Oklahoma, around 0900, with the intention of landing at Poplar Bluff Regional Business Airport (POF) in Poplar Bluff, Missouri. The aircraft was equipped with a communication radio but lacked very high frequency omni-directional range (VOR) equipment and a transponder. Although the pilot had access to a handheld Garmin GPSmap 396 device, he did not use it for navigation during the flight, relying instead on dead-reckoning and visual references such as roads. He occasionally consulted a mobile phone application that displayed a digitized visual flight rules (VFR) sectional chart to verify his position. The pilot acknowledged that he did not carry traditional paper VFR sectional charts.
Approximately 15 to 20 minutes before reaching Poplar Bluff, the pilot's mobile phone powered off due to a depleted battery. He then attempted to power the Garmin GPS device by inserting its adapter into the aircraft's cigarette-lighter socket, but the GPS did not turn on. Continuing on his current heading, the pilot flew directly over the city of Poplar Bluff but did not see the airport to the east. He then turned south for a few miles before executing a 180° course reversal and flying northbound over the city again.
Precautionary Landing
After traveling several miles north of Poplar Bluff, the pilot decided to locate a suitable field for a precautionary landing because of diminishing fuel. The left fuel tank gauge indicated "empty," and he estimated that the right tank held about ten minutes of fuel. He turned the aircraft into the wind and landed in what he believed was a suitable field. The engine was still running throughout the landing. Following touchdown, the airplane rolled approximately 200 to 300 feet before the main landing gear dug into soft terrain, causing the aircraft to nose over. The accident resulted in substantial damage to the vertical stabilizer and engine mounts.
Post-Accident Examination
During a telephone interview, a National Transportation Safety Board investigator asked the pilot to connect the Garmin GPSmap 396 to his vehicle's 12-volt direct current (DC) cigarette-lighter socket using the Garmin adapter. The GPS device powered on automatically when connected, both with and without the device's battery installed. When disconnected from the power source, the GPS did not power on even with the battery installed. The last known position displayed on the GPS was from a flight completed two days before the accident.
The wreckage was recovered and examined by two Federal Aviation Administration (FAA) airworthiness inspectors. The airframe battery, which was not an aviation-certified type and was consistent with a motorcycle battery, had been removed during recovery. Without any electrical load, the battery measured 12.45 volts with a digital multimeter. Under a 5-second electrical load from an automotive battery tester, it registered 11.8 volts. When reconnected to the aircraft and the master switch activated, the communication radios powered on and the cigarette-lighter socket provided 12.45 volts. An FAA inspector inserted a personal USB charger adapter into the socket and confirmed sufficient power to charge a mobile phone.
Additional bench testing of the alternator, voltage regulator, and battery revealed no anomalies that would have prevented normal operation of the airplane's electrical system.