Narrative:

At cruise at 5500 ft MSL heading southeast; we saw a biplane in a vertical (90 degree) climb go through our altitude approximately 300 ft off our left nose. We are a low wing aircraft; so I didn't see it until it was nearly at our altitude. It appeared to be doing a 'tail slide.' we took a small turn to ensure avoidance. It did not appear to see us or maneuver away. It continued maneuver to 50-100 ft above our altitude; then descended on its tail; where we lost sight. Had the airplane been 300 ft to the west; it would have undoubtedly hit us; as we would never have seen it; and he obviously wasn't clearing above; either.

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Original NASA ASRS Text

Title: A PA24 PILOT REPORTS A NMAC WITH A BIPLANE SE OF SNS AT 5500 FT VFR. BIPLANE APPARENTLY DID NO CLEARING TURN.

Narrative: AT CRUISE AT 5500 FT MSL HEADING SE; WE SAW A BIPLANE IN A VERT (90 DEG) CLB GO THROUGH OUR ALT APPROX 300 FT OFF OUR L NOSE. WE ARE A LOW WING ACFT; SO I DIDN'T SEE IT UNTIL IT WAS NEARLY AT OUR ALT. IT APPEARED TO BE DOING A 'TAIL SLIDE.' WE TOOK A SMALL TURN TO ENSURE AVOIDANCE. IT DID NOT APPEAR TO SEE US OR MANEUVER AWAY. IT CONTINUED MANEUVER TO 50-100 FT ABOVE OUR ALT; THEN DSNDED ON ITS TAIL; WHERE WE LOST SIGHT. HAD THE AIRPLANE BEEN 300 FT TO THE W; IT WOULD HAVE UNDOUBTEDLY HIT US; AS WE WOULD NEVER HAVE SEEN IT; AND HE OBVIOUSLY WASN'T CLRING ABOVE; EITHER.

Data retrieved from NASA's ASRS site as of May 2009 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.