THE LNDG GEAR OD A GLASAIR III COLLAPSED DURING LNDG AFTER A SECOND TEST FLT WHEREIN THE LNDG GEAR EXTENSION RETRACTION SYS WAS BEING TEST FLOWN AFTER MAINT.

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THIS INCIDENT INVOLVES A LNDG GEAR INCIDENT WITH A GLASAIR III EXPERIMENTAL ACFT. I WAS BRINGING THE ACFT BACK HOME AFTER HAVING IT PAINTED AND A NUMBER OF MODIFICATIONS AND AN ANNUAL INSPECTION DONE ON IT IN ANOTHER STATE. ON THE MORNING OF MAR/XA/99; I HAD AN A&P FROM THE LOCAL FBO REPLACE THE GEAR STRUT SEALS TO CURE A LEAKING GEAR STRUT. I TOOK OFF SOON AFTER THE WORK WAS COMPLETED; AND FOUND THAT NOTHING HAPPENED WHEN I TRIED TO RAISE THE GEAR RIGHT AFTER TKOF. SO I PROMPTLY LANDED AND RETURNED TO THE MAINT HANGAR. THE MECH PUT THE PLANE BACK UP ON JACKS; AND AFTER ADJUSTING THE SQUAT SWITCH ON THE R-HAND SIDE GEAR LEG; THE GEAR APPEARED TO OPERATE NORMALLY IN A FULL RETRACTION TEST. SO I TOOK OFF A SECOND TIME; AND AGAIN; NOTHING HAPPENED WHEN I PUT THE GEAR SWITCH IN THE 'UP' POS. I WENT THROUGH THE EMER MANUAL GEAR PROCS; WHICH WAS UNSUCCESSFUL IN RETRACTING THE GEAR. SO I RETURNED THE VARIOUS SWITCHES BACK TO THEIR NORMAL LNDG POS AND LANDED. PRIOR TO LNDG; I VERIFIED WITH THE WING MIRROR THAT THE GEAR WAS DOWN. THE INITIAL PART OF THE LNDG ROLLOUT WAS NORMAL; WITH ALL 3 GEAR DOWN. APPROX 1/2 WAY THROUGH THE LNDG ROLLOUT (I'M ESTIMATING 750 FT DOWN THE RWY); THE L MAIN GEAR SLOWLY FOLDED UP. THE L WINGTIP SETTLED AND BEGAN TO SCRAPE ALONG THE RWY; AND THE PLANE VEERED OFF THE RWY TO THE L. AS THIS WAS HAPPENING; I IMMEDIATELY SHUT OFF THE ENG AND THE PROP STOPPED IN THE HORIZ POS. AS THE PLANE ENTERED THE MUDDY GND AND MELTING SNOW BANK TO THE SIDE OF THE RWY; THE NOSEWHEEL AND THE R MAIN GEAR LEG WERE STILL EXTENDED. THE L WINGTIP HIT AND BROKE 1 LNDG LIGHT; AND AS THE PLANE CAME INTO DEEPER SNOW; THE NOSEWHEEL ALSO FOLDED INTO ITS RETRACTED POS. SEVERAL SECONDS LATER; THE PLANE CAME TO REST ON THE L WINGTIP; THE LOWER NOSE COWLING; AND THE EXTENDED R MAIN GEAR. THERE WAS NO FIRE AND NO INJURIES. BECAUSE THE ACFT DID NOT HAVE SUBSTANTIAL DAMAGE; AN NTSB RPT WAS NOT REQUIRED. AFTER DISCUSSING THE POSSIBLE CAUSES OF THE GEAR PROBS WITH A COMPANY THAT SPECIALIZES IN BUILDING AND MODIFYING GLASAIRS; THE MOST LIKELY EXPLANATION IS THAT I INADVERTENTLY CREATED A 'PRESSURE LOCK' BY TRYING TO PUMP THE GEAR UP MANUALLY. AS I UNDERSTAND IT; THE NORMAL AUTOMATIC GEAR-DOWN HYD PRESSURE SERVES TO LOCK THE GEAR DOWN BY PRESSURIZING THE 'DOWN' SIDE OF THE HYD CYLINDERS. SO WHILE THE GEAR WAS PHYSICALLY EXTENDED DURING THE LNDG; MY MANUAL PUMPING ACTION WHILE ATTEMPTING TO RETRACT MAY HAVE CREATED EVEN HIGHER PRESSURE ON THE 'UP' SIDE OF THE CYLINDERS -- THEREBY OVERCOMING THE LOCKING ACTION PROVIDED BY THE NORMAL HYD PUMP PRESSURE. PRIOR TO PURCHASING THIS ACFT LAST SUMMER; I HAD APPROX 1900 HRS TOTAL TIME. I THEN TOOK 15 HRS OF GND SCHOOL AND 10 HRS OF FLT TRAINING FROM AN APPROVED INSTRUCTOR IN THIS ACFT IN ORDER TO FULFILL AN INSURANCE REQUIREMENT. HOWEVER; I DO NOT RECALL EVER HEARING IN TRAINING NOR SEEING IN THE MANUAL THAT THE EMER GEAR PROC IN THIS TYPE OF ACFT IS ONLY USEFUL FOR GETTING THE GEAR DOWN. AND NOT ONLY IS THE MANUAL PROC INCAPABLE OF RETRACTING THE GEAR; ATTEMPTING IT COULD CAUSE A PRESSURE LOCK THAT MAKES FOR UNSTABLE LNDG GEAR DURING THE LNDG PHASE. I WILL LET THE INSTRUCTOR KNOW THAT HE MAY WISH TO LET FUTURE STUDENTS KNOW ABOUT THIS CONDITION. AND I MAY ALSO POST A 'DO NOT ATTEMPT MANUAL GEAR RETRACTION' MESSAGE BY THE MANUAL HYD SELECTOR SWITCH (ALTHOUGH AFTER THIS; I DOUBT I WILL EVER FORGET IT!).