Narrative:

Incident occurred during dual instruction in recently acquired (1/4 share partnership) aircraft. We had flown several similar flts over the prior 2.5 months west/O incident. We met by prior arrangement at aircraft's base after after a full day of work at our respective jobs. At cfii's suggestion, we were practicing visibility ground reference maneuvers for less than 1 hour, and had just done a pretty firm landing at a small, less busy, turf runway airport. After next takeoff, cfii requested we get away from airport and try simulated engine-out landing. Knowing the relatively high sink rate of this aircraft at low power settings, and my low time in it, I requested this be modified for the first try to an overhead 360 degree turn. Instrument agreed. I announced intentions on traffic frequency on downwind and again on runway heading. 1000' AGL, just past threshold, I pulled throttle back and commenced turning approach. Somewhat after 180 degrees through the turn, I recall lowering gear select lever. No flaps had been selected yet. Indicated speed was 90-100 mph. Late on short final, I lowered flaps. At same time I checked gear position lights and called '3 greens,' indicating gear down. My intention was to select 1/2 flaps, though in my hurry may have pulled full flaps. Afterward, neither cfii nor I recalled hearing gear unsafe horn. Aircraft touched down slightly left of runway center, and not hard. Rollout seemed unremarkable for for an estimated 200 yds and the aircraft had slowed considerably. First indication of problem was aircraft settling, first to right and then forward. Aircraft commenced a gradual, uncorrectable turn to right, decreasing in radius as it slowed. There had been rain the preceding days, and the grass and earth were moist. Aircraft came to rest at approximately 90 degrees (right) to runway heading, just short of right row of runway lights. After turning off master, mags and shutting fuel valve, cfii and I noted gear handle in up position. Neither had any idea when or how the handle had gotten to that position. An immediate examination of the aircraft showed the right main and nose gear retracted/collapsed(?) and the propeller tips bent backward, consistent with the fact that the engine had been idling when the propeller tips contacted the turf. Little if any other damage was apparent. The soft ground facilitated tracking the course of the aircraft back to T/D. Ground tracks showed some ripped sod where the mains touched, but nothing unusual until much later. Gradual settling was supported by the large # and slowly increasing depth of successive swaths cut by propeller blades. Both cfii and I commented about being somewhat fatigued by the day's work. The relative unfamiliarity of both with the particulars of this aircraft may have contributed, as well the rushed prelndg procedures associated with simulated engine failure. Though afterward, neither could point to a particular action/inaction contributing to the incident. The examination of the aircraft, to determined if hidden damage and if mechanical failure contributed to incident, is continuing. On the day after the incident, while raising the aircraft back onto its gear, the left main, noted by the mechanic supervising the operation as being locked over center, collapsed. Any # of theories have been considered: 1) failure to extend gear initially. Counter argument: no recollection of gear horn by either cfii or reporter, both recalled seeing 3 green gear position lights, automatic gear extension below a certain airspeed and uneventful initial rollout. 2) inadvertent raising of gear selector on short final or after T/D. Counter argument: better than theory #1, but still doesn't account for airspeed switch on the automatic gear extension. No particularly vigorous bumps were recalled. 3) some combination with #2 with a mechanical failure, perhaps from the earlier firm landing or a pre-existing condition. Counter argument: will have to wait for mechanic's assessment. Seems most plausible to reporter. Preventive recommendations: these are only conjectural until mechanic's analysis is complete. If a bounce raising the aircraft off the squat switch enough to allow the retraction sequence to start was involved, a short (.5-1 second) time delay relay in the squat switch circuit could eliminate transient activation west/O much effect on normal departure retraction. Solid state time delay relays are cheap and reliable. Certainly, the reporter intends to do more dry run (stationary) emergency procedure practice. Just going through the motions of the simulated emergency could reduce the likelihood of moving the wrong switch, whether or not that was involved in this case. Fatigue/normal work stress may have been factors. The reporter intends to decline simulated emergency procedures in future unless well-rested, at least until more familiar with the aircraft.

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Original NASA ASRS Text

Title: GEAR COLLAPSED ON LNDG.

Narrative: INCIDENT OCCURRED DURING DUAL INSTRUCTION IN RECENTLY ACQUIRED (1/4 SHARE PARTNERSHIP) ACFT. WE HAD FLOWN SEVERAL SIMILAR FLTS OVER THE PRIOR 2.5 MONTHS W/O INCIDENT. WE MET BY PRIOR ARRANGEMENT AT ACFT'S BASE AFTER AFTER A FULL DAY OF WORK AT OUR RESPECTIVE JOBS. AT CFII'S SUGGESTION, WE WERE PRACTICING VIS GND REF MANEUVERS FOR LESS THAN 1 HR, AND HAD JUST DONE A PRETTY FIRM LNDG AT A SMALL, LESS BUSY, TURF RWY ARPT. AFTER NEXT TKOF, CFII REQUESTED WE GET AWAY FROM ARPT AND TRY SIMULATED ENG-OUT LNDG. KNOWING THE RELATIVELY HIGH SINK RATE OF THIS ACFT AT LOW PWR SETTINGS, AND MY LOW TIME IN IT, I REQUESTED THIS BE MODIFIED FOR THE FIRST TRY TO AN OVERHEAD 360 DEG TURN. INSTR AGREED. I ANNOUNCED INTENTIONS ON TFC FREQ ON DOWNWIND AND AGAIN ON RWY HDG. 1000' AGL, JUST PAST THRESHOLD, I PULLED THROTTLE BACK AND COMMENCED TURNING APCH. SOMEWHAT AFTER 180 DEGS THROUGH THE TURN, I RECALL LOWERING GEAR SELECT LEVER. NO FLAPS HAD BEEN SELECTED YET. INDICATED SPD WAS 90-100 MPH. LATE ON SHORT FINAL, I LOWERED FLAPS. AT SAME TIME I CHKED GEAR POS LIGHTS AND CALLED '3 GREENS,' INDICATING GEAR DOWN. MY INTENTION WAS TO SELECT 1/2 FLAPS, THOUGH IN MY HURRY MAY HAVE PULLED FULL FLAPS. AFTERWARD, NEITHER CFII NOR I RECALLED HEARING GEAR UNSAFE HORN. ACFT TOUCHED DOWN SLIGHTLY LEFT OF RWY CENTER, AND NOT HARD. ROLLOUT SEEMED UNREMARKABLE FOR FOR AN ESTIMATED 200 YDS AND THE ACFT HAD SLOWED CONSIDERABLY. FIRST INDICATION OF PROB WAS ACFT SETTLING, FIRST TO RIGHT AND THEN FORWARD. ACFT COMMENCED A GRADUAL, UNCORRECTABLE TURN TO RIGHT, DECREASING IN RADIUS AS IT SLOWED. THERE HAD BEEN RAIN THE PRECEDING DAYS, AND THE GRASS AND EARTH WERE MOIST. ACFT CAME TO REST AT APPROX 90 DEGS (RIGHT) TO RWY HDG, JUST SHORT OF RIGHT ROW OF RWY LIGHTS. AFTER TURNING OFF MASTER, MAGS AND SHUTTING FUEL VALVE, CFII AND I NOTED GEAR HANDLE IN UP POS. NEITHER HAD ANY IDEA WHEN OR HOW THE HANDLE HAD GOTTEN TO THAT POS. AN IMMEDIATE EXAMINATION OF THE ACFT SHOWED THE RIGHT MAIN AND NOSE GEAR RETRACTED/COLLAPSED(?) AND THE PROP TIPS BENT BACKWARD, CONSISTENT WITH THE FACT THAT THE ENG HAD BEEN IDLING WHEN THE PROP TIPS CONTACTED THE TURF. LITTLE IF ANY OTHER DAMAGE WAS APPARENT. THE SOFT GND FACILITATED TRACKING THE COURSE OF THE ACFT BACK TO T/D. GND TRACKS SHOWED SOME RIPPED SOD WHERE THE MAINS TOUCHED, BUT NOTHING UNUSUAL UNTIL MUCH LATER. GRADUAL SETTLING WAS SUPPORTED BY THE LARGE # AND SLOWLY INCREASING DEPTH OF SUCCESSIVE SWATHS CUT BY PROP BLADES. BOTH CFII AND I COMMENTED ABOUT BEING SOMEWHAT FATIGUED BY THE DAY'S WORK. THE RELATIVE UNFAMILIARITY OF BOTH WITH THE PARTICULARS OF THIS ACFT MAY HAVE CONTRIBUTED, AS WELL THE RUSHED PRELNDG PROCS ASSOCIATED WITH SIMULATED ENG FAILURE. THOUGH AFTERWARD, NEITHER COULD POINT TO A PARTICULAR ACTION/INACTION CONTRIBUTING TO THE INCIDENT. THE EXAMINATION OF THE ACFT, TO DETERMINED IF HIDDEN DAMAGE AND IF MECHANICAL FAILURE CONTRIBUTED TO INCIDENT, IS CONTINUING. ON THE DAY AFTER THE INCIDENT, WHILE RAISING THE ACFT BACK ONTO ITS GEAR, THE LEFT MAIN, NOTED BY THE MECH SUPERVISING THE OPERATION AS BEING LOCKED OVER CENTER, COLLAPSED. ANY # OF THEORIES HAVE BEEN CONSIDERED: 1) FAILURE TO EXTEND GEAR INITIALLY. COUNTER ARGUMENT: NO RECOLLECTION OF GEAR HORN BY EITHER CFII OR RPTR, BOTH RECALLED SEEING 3 GREEN GEAR POS LIGHTS, AUTO GEAR EXTENSION BELOW A CERTAIN AIRSPD AND UNEVENTFUL INITIAL ROLLOUT. 2) INADVERTENT RAISING OF GEAR SELECTOR ON SHORT FINAL OR AFTER T/D. COUNTER ARGUMENT: BETTER THAN THEORY #1, BUT STILL DOESN'T ACCOUNT FOR AIRSPD SWITCH ON THE AUTO GEAR EXTENSION. NO PARTICULARLY VIGOROUS BUMPS WERE RECALLED. 3) SOME COMBINATION WITH #2 WITH A MECHANICAL FAILURE, PERHAPS FROM THE EARLIER FIRM LNDG OR A PRE-EXISTING CONDITION. COUNTER ARGUMENT: WILL HAVE TO WAIT FOR MECH'S ASSESSMENT. SEEMS MOST PLAUSIBLE TO RPTR. PREVENTIVE RECOMMENDATIONS: THESE ARE ONLY CONJECTURAL UNTIL MECH'S ANALYSIS IS COMPLETE. IF A BOUNCE RAISING THE ACFT OFF THE SQUAT SWITCH ENOUGH TO ALLOW THE RETRACTION SEQUENCE TO START WAS INVOLVED, A SHORT (.5-1 SEC) TIME DELAY RELAY IN THE SQUAT SWITCH CIRCUIT COULD ELIMINATE TRANSIENT ACTIVATION W/O MUCH EFFECT ON NORMAL DEP RETRACTION. SOLID STATE TIME DELAY RELAYS ARE CHEAP AND RELIABLE. CERTAINLY, THE RPTR INTENDS TO DO MORE DRY RUN (STATIONARY) EMER PROC PRACTICE. JUST GOING THROUGH THE MOTIONS OF THE SIMULATED EMER COULD REDUCE THE LIKELIHOOD OF MOVING THE WRONG SWITCH, WHETHER OR NOT THAT WAS INVOLVED IN THIS CASE. FATIGUE/NORMAL WORK STRESS MAY HAVE BEEN FACTORS. THE RPTR INTENDS TO DECLINE SIMULATED EMER PROCS IN FUTURE UNLESS WELL-RESTED, AT LEAST UNTIL MORE FAMILIAR WITH THE ACFT.

Data retrieved from NASA's ASRS site as of July 2007 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.