M20 PLT ON A TEST FLT EXPERIENCES A NMAC WITH A HIGH WING ACFT.

Narrative

WHILE CONDUCTING A TEST FLT TO CAPTURE PRESSURE ALT/VACUUM PRESSURE DATA TO RECERTIFY MY ACFT'S STANDBY VACUUM SYS; I WAS INVOLVED IN AN NMAC WITH A LARGE HIGH-WING ACFT. I DEPARTED ZZZ1 AT XA00 AM; JUN/XA/08 WITH UNRESTR VISIBILITY. DEPARTED ZZZ1 TO THE SE; CLBING UP TO 10000 FT; OVER-FLYING ZZZ2. I WAS IN CONTACT WITH ZZZ2 CTAF FREQUENTLY MAKING POS CALLS. THE FLT TEST DATA I WAS CAPTURING INCLUDED RPM/MP SETTINGS FOR MINIMUM VACUUM HG FOR PRESSURE ALTS AT: 10000 FT; 8000 FT; 6000 FT; 4000 FT; AND 2000 FT. I COMPLETED RECORDING MY FIRST DATA POINT AT 10000 FT; 12 NM S OF ZZZ2 AND 3 NM W OF ZZZ; PERFORMED A WBOUND TURN TO THE N AND WAS ON A HDG OF 330 DEGS; WHEN I STARTED MY GRADUAL DSCNT FROM 10000 FT DOWN TO 8000 FT TO COLLECT MY NEXT DATA POINT. GLANCING OUT OF THE COPLT SIDE WINDOW; I SAW A LARGE HIGH-WING ACFT IN A HIGH ANGLE-OF-ATTACK; BANKING AWAY FROM MY ACFT. THE ACFT PASSED OUT OF MY VIEW WITHIN A BLINK OF AN EYE. I WAS ABLE TO DISCERN THAT THE ACFT WAS A LARGE HIGH-WING PAX ACFT THE SIZE OF EITHER A CESSNA GRAND CARAVAN OR A DEHAVILLAND TWIN OTTER. THE ACFT'S COLOR WAS RED/ORANGE ON WHITE. THE ACFT CLBED PAST MY PLANE WITHIN 150 FT. ZZZ IS DESIGNATED AS 'EXTREMELY HVY PARACHUTE JUMPING ACTIVITY;' WITH JUMPING ACTIVITY OVER THE E OF THE ARPT. MY GUESS; IS THAT THE ACFT WHICH MISSED ME BY 150 FT; IS/WAS ENGAGED IN SKYDIVING ACTIVITY AT ZZZ. DUE TO THE FACT THAT MY MOONEY IS A LOW-WING ACFT; LIMITS MY ABILITY TO SPOT CLBING ACFT FROM BELOW. DUE TO THE SPDS AT WHICH THE ACFTS PASSED; THERE WAS NO REACTION TIME ON MY PART. IN HINDSIGHT; I SHOULD HAVE BEEN IN RADIO CONTACT WITH CTR; FOR RADAR TFC SVCS. THE SAME HOLDS TRUE FOR THE LARGE HIGH-WING ACFT.