Narrative:

During the descent phase of a VFR flight from cameron park to san jose international airport, I received instructions from bay approach to maintain at or above 2500 ft MSL upon reaching embassy suites visual check point. At the time, or very shortly after, my landing gear popped open. My M20C aircraft is equipped with a manually operated landing gear with a bar located between the left and right pilot's seat. This distraction caused me to miss my altitude restr. The distraction was significant in nature, requiring my complete attention to determine what happened, the cause of the event, and the corrective action, including possible damage to aircraft which may have required special handling. My altitude was above 2500 ft at the time of the event. The distraction caused me to dip below the assigned altitude restr by 200 ft. I noticed another aircraft at my same altitude 2000 ft distance at my 12 O'clock position. I reported this to bay, then realized I was below 2500 ft. No evasive action was necessary. Immediately following this, bay handed me to san jose tower, and did not mention my altitude variance. The gear problem was determined to be caused by the loose end of the seat belt positioned between the 'bar' lock and 'bar' seat, resulting in an incomplete uplock position. No damage detected as a result of the event.

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Original NASA ASRS Text

Title: AN M20 PLT DSNDS BELOW HIS RESTR ALT WHEN HE IS DISTRACTED BY THE LNDG GEAR SUDDENLY AND UNEXPECTEDLY EXTENDING.

Narrative: DURING THE DSCNT PHASE OF A VFR FLT FROM CAMERON PARK TO SAN JOSE INTL ARPT, I RECEIVED INSTRUCTIONS FROM BAY APCH TO MAINTAIN AT OR ABOVE 2500 FT MSL UPON REACHING EMBASSY SUITES VISUAL CHK POINT. AT THE TIME, OR VERY SHORTLY AFTER, MY LNDG GEAR POPPED OPEN. MY M20C ACFT IS EQUIPPED WITH A MANUALLY OPERATED LNDG GEAR WITH A BAR LOCATED BTWN THE L AND R PLT'S SEAT. THIS DISTR CAUSED ME TO MISS MY ALT RESTR. THE DISTR WAS SIGNIFICANT IN NATURE, REQUIRING MY COMPLETE ATTN TO DETERMINE WHAT HAPPENED, THE CAUSE OF THE EVENT, AND THE CORRECTIVE ACTION, INCLUDING POSSIBLE DAMAGE TO ACFT WHICH MAY HAVE REQUIRED SPECIAL HANDLING. MY ALT WAS ABOVE 2500 FT AT THE TIME OF THE EVENT. THE DISTR CAUSED ME TO DIP BELOW THE ASSIGNED ALT RESTR BY 200 FT. I NOTICED ANOTHER ACFT AT MY SAME ALT 2000 FT DISTANCE AT MY 12 O'CLOCK POS. I RPTED THIS TO BAY, THEN REALIZED I WAS BELOW 2500 FT. NO EVASIVE ACTION WAS NECESSARY. IMMEDIATELY FOLLOWING THIS, BAY HANDED ME TO SAN JOSE TWR, AND DID NOT MENTION MY ALT VARIANCE. THE GEAR PROB WAS DETERMINED TO BE CAUSED BY THE LOOSE END OF THE SEAT BELT POSITIONED BTWN THE 'BAR' LOCK AND 'BAR' SEAT, RESULTING IN AN INCOMPLETE UPLOCK POS. NO DAMAGE DETECTED AS A RESULT OF THE EVENT.

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.