Date: 201207
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Landing
Airspace: Class G ZZZ
ATC / advisory: CTAF ZZZ
Aircraft component: Gear Extend/Retract Mechanism
Component problem: Failed
Reporter organization: FBO
Reporter function: Instructor; Pilot Not Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Human factors: Training / Qualification; Troubleshooting; Workload
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I departed with a flight student. This flight student is currently working on a Commercial Certificate; and this local instructive flight was part of his commercial training. We remained within approximately 12 nautical miles of the airport; and we remained north/northwest of the airport. After approximately 30 to 40 minutes had elapsed in the flight; my student and I decided to work on simulated emergency descents. When we tried to extend the landing gear; my student and I both realized that the gear light ('down and locked' green light) was not illuminated; and the gear warning horn was going off. Upon further inspection; I was able to see that the right gear was down and locked; but my student was unable to see the left gear at all. (Naturally; we were unable to see the nose gear). We recycled the landing gear; however; only the right main gear was extending. My student and I then ran through the emergency checklists and procedures with respect to landing gear failures. Per the emergency checklist/procedures; we utilized the emergency hand pump; however; this was not successful in lowering the left main gear. We were able to contact our home base maintenance via radio (utilizing our CTAF 122.7); and then we switched to 123.45 in order to further discuss our gear situation. With the gear handle in the 'down and locked' position; my student and I were able to make a low approach over the runway in an effort to have the A&P and the owner/operator visually inspect the landing gear. Further; my student was able to open his window in an attempt to look at the gear; and he stated that the gear was 'flapping.' After a visual inspection; it was apparent that the left main gear was 'trailing;' so my student and I departed the traffic pattern in an effort to perform some g-loading maneuvers. We hoped that performing these maneuvers would force the gear down; and hopefully; lock the gear in place. Our efforts to get the left main gear lowered and locked were unsuccessful; thus; after consultation with the owner/operator; my student and I returned to the airport where we successfully executed a gear-up landing. My student and I were not injured in this landing. It was determined that the left gear actuator failed (cracked).




Synopsis: A C-172RG left landing gear actuator cracked when the gear was lowered. Unable to lock the gear in place; the Instructor completed a successful gear up landing.