Accident
On September 13, 2016, about 0840 eastern daylight time, the right main landing gear on a Piper PA-28R-201, N786GB, collapsed as the airplane was taxiing from landing at the Wood County Airport (1G0), Bowling Green, Ohio. The instructor and student pilot were not injured, and the airplane was substantially damaged. The airplane was registered to and operated by Bowling Green State University Flight Center LLC under 14 CFR Part 91 as an instructional flight. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The local flight had just originated from 1G0.
Sequence of Events
According to the chief pilot and flight instructor, the purpose of the flight was employee training, with planned touch-and-go landings in the traffic pattern. After takeoff and upon turning onto the downwind leg for runway 28, the pilot activated the landing gear switch to lower the gear. The landing gear control circuit breaker opened. When reset, it opened again, disabling the gear warning system and landing gear annunciator lights. Maintenance personnel were summoned. Several attempts were made to lower the gear, and a low pass was made over the runway; the pilots were told the gear appeared down. The instructor landed the airplane. As she turned off the runway, the right main landing gear collapsed. Post-accident examination revealed a crack in the rear fuselage bulkhead.
Post-Accident Examination
When the airplane was placed on jacks for retrieval, the left main landing gear was not locked. Further examination showed neither main landing gear was down and locked. The school's director of maintenance (DOM) entered the aircraft and used the emergency gear extension; the gear dropped into the full down and locked position and the annunciator lights illuminated.
The airplane was moved to a hangar for further examination. The DOM checked the landing gear pump, hydraulic fluid level, gear warning horns, and lights, finding no anomalies. With the airplane on jacks, the gear cycled numerous times and operated normally; the circuit breaker remained closed and all indications were normal. The emergency extension also operated normally.
Maintenance History
The flight instructor referenced a previous grounding maintenance squawk and a current level 3 squawk seeking feedback on the landing gear. BGSU uses SkyManager software to track maintenance; squawks are classified as 5 (grounding), 3 (non-grounding discrepancy), or 1 (information only).
Examination of the airframe logbook revealed six recent landing gear maintenance entries, including replacements and adjustments of down lock switches and repairs of broken wires between January and August 2016.
FAA Inspection
A Federal Aviation Administration inspector oversaw the examination and noted:
- A flight discrepancy on August 19, 2016: "Gear position lights failed to operate properly." The logbook entry on August 24 replaced a MLG down indicator switch but did not specify which gear switch was replaced.
- A flight discrepancy on September 2, 2016: "Landing gear light did not illuminate when gear was put down." In SkyManager, the DOM wrote "Fixed broken wire," but no logbook entry was made.
- A flight discrepancy on September 12, 2016, was entered in SkyManager with a response "Ground ops check satisfactory. Need feedback." The accident occurred the following day.
The inspector found a wire dislodged from a terminal. The crimp mark was not well defined, and the wire was grounding (shorting) against the landing gear, causing the CNTRL LNDG GEAR circuit breaker to trip. The DOM had pulled the wire while troubleshooting after the accident. The inspector noted the DOM had spliced a new limit switch about six inches from the switch; the wire bundle passed into the wing. The electrical schematic showed the wire to be energized. The inspector advised the DOM to make the splice in the wing.
Maintenance Personnel Re-examination
Maintenance personnel re-examined the airplane and reported to the FAA that the left main gear down limit switch wire was spliced using the wrong type and gauge of wire. The spliced wires were soldered with heat shrink that did not cover the wires completely. The three wires were bundled together in the left gear well, allowing the down limit switch wires to short together, tripping the circuit breaker.
Checklist Usage
The FAA inspector noted that the flight instructor-chief pilot did not use the emergency checklist completely. According to the checklist, the first step in an emergency gear extension is to cycle the gear, which could not be done because the circuit breaker was open. The next step—pushing down on the emergency gear extension lever to release hydraulic pressure and allow free fall—was not performed. Finally, the aircraft should be yawed abruptly with the rudder to shake the gear loose.
The inspector told the instructor that when advised the gear "appears to be down," it may not be locked over center. Additionally, the airplane should never be turned with a landing gear issue; it should be kept straight on the runway and brought to a complete stop.