Piper PA-28R-201 N786BG accident near Bowling Green, Ohio

Probable cause

The pilots’ failure to complete the Emergency Landing Gear Extension checklist and maintenance personnel’s failure to correctly repair spliced wires on the left main landing gear down limit switch, which prevented the pilots from knowing whether the gear was down and locked.

NTSB analysis

The two commercial pilots, one of whom was a flight instructor, were planning to conduct touch-and-go landings; the flight instructor reported that he was providing "employee training" to the other pilot. After takeoff and upon returning to the downwind leg of the traffic pattern, the pilot receiving training activated the landing gear switch to lower the landing gear; however, the landing gear control circuit breaker opened. When the circuit breaker was reset, it immediately reopened, which disabled the gear warning system and landing gear annunciator lights. The pilots made a low pass over the runway and maintenance personnel told them that the landing gear appeared to be down. The flight instructor then landed the airplane, and as she was turning it off the active runway, the right main landing gear collapsed.

Postaccident examination of the airplane revealed that neither of the main landing gear were down and locked. Subsequently, the school's director of maintenance entered the airplane and used the emergency gear extension, and the landing gear dropped into the down-and-locked position, and the landing gear annunciator lights illuminated. Although he did not report resetting the circuit breaker, he had to have performed that action for the annunciator lights to illuminate. He later cycled the landing gear numerous times, and it operated normally. The circuit breaker remained closed, and all landing gear indications were normal.

During the postaccident examination, the left main gear down limit switch wire was found dislodged from the terminal. The wire did not appear to have been properly crimped because the crimp mark was not well defined. Based on maintenance records, a new down indicator switch had been spliced in place less than a month earlier. The electrical schematic showed the wire to be energized.

Maintenance personnel reexamined the airplane to determine why the landing gear indication circuit breaker was tripping. According to their report to Federal Aviation Administration, the left main gear down limit switch wire was spliced using the wrong type and gauge of wire. The spliced wires were soldered using heat shrink to cover the splices, which did not cover the wires completely. The three spliced down limit switch wires were bundled together in the left gear well, which allowed them to short, causing the landing gear circuit breaker to trip.

The pilots did not complete the Emergency Landing Gear Extension checklist, which calls for the emergency gear extension lever (which releases pressure in the hydraulic system and allows the gear to free fall) to be pushed down. The pilots should have completed the Emergency Landing Gear Extension checklist in an attempt to ensure that the landing gear were in the down-and-locked position, which could have prevented the right main landing gear from collapsing during the turn off the active runway.

Text from the NTSB. Open the NTSB docket for CEN16LA374 for the full record.