Narrative:

Flight departed as a training mission for an initial CFI candidate with the captain/instructor pilot sitting in the left seat and the CFI student sitting in the right seat. The CFI student was to be pilot flying and demonstrate teaching traffic pattern operations in a complex airplane. The preflight cram briefing included that the instructor pilot was the PIC and that in the event of any emergency the instructor pilot would maintain positive aircraft control and the CFI student would assist with checklists; communication; and troubleshooting. We departed direct to a nearby airport to practice takeoffs; traffic patterns; and landings. Upon climbing out from the third touch and go at the practice field we requested to return to our home base because company policy prohibits more than 3 traffic patterns before switching tasks to help prevent complacency toward gear-up landings. On gear retraction while turning toward to our home airport; the 3 gear down/locked indicator lights extinguished and the 'warn: gear unsafe' light illuminated while the pump began running to retract the landing gear. The pump turned off as indicated by the cessation of its running noise and the decrease in electrical load showed on the ammeter; but the 'warn: gear unsafe' light remained illuminated. Instructor pilot cycled the gear; with the same result; and we decided to first extend and leave the gear down and locked for our short (15 minute) return to base contact our dispatch and maintenance through our company frequency. Maintenance advised to leave the gear extended; check that the manual gear extension knob was fully closed in the normal position; and request that the tower visually check the landing gear. We followed these recommendations; noting that we had all three gear down/locked indicator lights illuminated; and that the manual gear extension knob was fully closed. Instructor pilot contacted tower west of the field and was instructed to report right abeam the runway for landing. Instructor pilot requested clearance for low approach and visual confirmation of landing gear position; which was reported to look normal for down/locked. After the go-around we remained in the pattern and made an uneventful normal landing and taxied back to our ramp. Overall; cooperation from company maintenance; flight crew; and air traffic control all combined to help easily make a successful and desirable outcome to the abnormal situation. One factor that was less than ideal; however; was the CFI student's overzealous desire to handle the situation in the cockpit. Contrary to the cram briefing; the instructor pilot took control of the airplane and radios; taking some of the split responsibility of the CFI student and unnecessarily increased his own workload. Also; from a teaching perspective; this could have been an opportunity to ask the CFI student what he would have done had he been the sole pilot on board when the problem initially arose. I do not think this problem could have been thwarted preflight because the problem necessitated that the gear be retracted to discover it which obviously cannot safely be done by the pilot preflight. Maintenance suspects that one of the three gear up-limit switches failed to close; causing a false gear unsafe warning since the pump was able to swing the gear to the retracted position and then build enough hydraulic pressure to close the pressure switch that closes the shuttle valve and turns off the hydraulic pump; holding the gear retracted with the trapped hydraulic pressure.

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Original NASA ASRS Text

Title: A PA28's 'Warn: Gear Unsafe' light illuminated after a touch and go. The pilot put the gear down and flew by the Tower who reported they looked down and locked. Maintenance suspected an uplock microswitch malfunctioned.

Narrative: Flight departed as a training mission for an initial CFI candidate with the Captain/Instructor pilot sitting in the left seat and the CFI student sitting in the right seat. The CFI student was to be pilot flying and demonstrate teaching traffic pattern operations in a complex airplane. The preflight CRAM briefing included that the Instructor pilot was the PIC and that in the event of any emergency the Instructor pilot would maintain positive aircraft control and the CFI student would assist with checklists; communication; and troubleshooting. We departed direct to a nearby airport to practice takeoffs; traffic patterns; and landings. Upon climbing out from the third touch and go at the practice field we requested to return to our home base because Company policy prohibits more than 3 traffic patterns before switching tasks to help prevent complacency toward gear-up landings. On gear retraction while turning toward to our home airport; the 3 gear down/locked indicator lights extinguished and the 'Warn: Gear Unsafe' light illuminated while the pump began running to retract the landing gear. The pump turned off as indicated by the cessation of its running noise and the decrease in electrical load showed on the ammeter; but the 'Warn: Gear Unsafe' light remained illuminated. Instructor pilot cycled the gear; with the same result; and we decided to first extend and leave the gear down and locked for our short (15 minute) return to base contact our Dispatch and Maintenance through our Company frequency. Maintenance advised to leave the gear extended; check that the manual gear extension knob was fully closed in the normal position; and request that the Tower visually check the landing gear. We followed these recommendations; noting that we had all three gear down/locked indicator lights illuminated; and that the manual gear extension knob was fully closed. Instructor pilot contacted Tower west of the field and was instructed to report right abeam the runway for landing. Instructor pilot requested clearance for low approach and visual confirmation of landing gear position; which was reported to look normal for down/locked. After the go-around we remained in the pattern and made an uneventful normal landing and taxied back to our ramp. Overall; cooperation from Company Maintenance; flight crew; and Air Traffic Control all combined to help easily make a successful and desirable outcome to the abnormal situation. One factor that was less than ideal; however; was the CFI student's overzealous desire to handle the situation in the cockpit. Contrary to the CRAM briefing; the Instructor pilot took control of the airplane and radios; taking some of the split responsibility of the CFI student and unnecessarily increased his own workload. Also; from a teaching perspective; this could have been an opportunity to ask the CFI student what he would have done had he been the sole pilot on board when the problem initially arose. I do not think this problem could have been thwarted preflight because the problem necessitated that the gear be retracted to discover it which obviously cannot safely be done by the pilot preflight. Maintenance suspects that one of the three gear up-limit switches failed to close; causing a false gear unsafe warning since the pump was able to swing the gear to the retracted position and then build enough hydraulic pressure to close the pressure switch that closes the shuttle valve and turns off the hydraulic pump; holding the gear retracted with the trapped hydraulic pressure.

Data retrieved from NASA's ASRS site as of April 2012 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.