A C-172RG left landing gear actuator cracked when the gear was lowered. Unable to lock the gear in p...

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).

Original NASA ASRS Text

Title: 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.

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).

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1024565
Time
Date	201207
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Landing
Flight Plan	None
Component
Aircraft Component	Gear Extend/Retract Mechanism
Person 1
Function	Instructor Pilot Not Flying
Qualification	Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 161.7 Flight Crew Total 1118 Flight Crew Type 91.3
Events
Anomaly	Aircraft Equipment Problem Critical

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.