SMA OPERATING NON TWR ARPT TRAFFIC PATTERN ENCOUNTERS SMA ENTERING TRAFFIC PATTERN NON STANDARD.

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I HAVE PURCHASED AN SMA AND I AGREED THAT I SHOULD FLY FROM THE BACK SEAT; DO SOME AEROBATICS AND PRACTICE SOME LNDGS. WE HAD ACCOMPLISHED 4 STOP AND GO LNDGS AND SUBSEQUENT TKOFS. ON CLBOUT I DEPARTED RWY 20 AND AT 500' BEGAN MY LEFT TURN TO XWIND. I HAD LOWERED THE NOSE TO LOOK FOR TFC. I LOOKED RIGHT FOR TFC; THEN LEFT AS I BEGAN MY TURN. THE INSTR BUMPED THE STICK BACK; THEN PULLED THE NOSE HIGH. I FOLLOWED HIS LINE OF SIGHT JUST IN TIME TO SEE A LOW WING SMA DISAPPEAR UNDER OUR ACFT. MAX PITCH ATTITUDE MAY HAVE REACHED 40 DEGS. AFTER THE TFC PASSED UNDER US FROM RIGHT TO LEFT WE CLBED TO THE PROPER PATTERN ALT. THE ACFT NEVER GOT WITHIN 300' OF EACH OTHER; HOWEVER THEY WOULD HAVE PASSED WITHIN 100' IF EVASIVE ACTION HAD NOT BEEN TAKEN. THE LOW WING SMA WAS NEW TFC. THE LOW WING SMA WOULD HAVE PASSED VERY CLOSE UNDER US; EVEN W/O EVASIVE ACTION; SO HIS MAX ALT UPON ENTERING DOWNWIND COULD NOT HAVE BEEN MORE THAN 700' AND I WOULD ESTIMATE HE WAS CLOSER TO 600'. (REFERRING TO THE NDB 2 APCH CHART MAY GIVE SOME INSIGHT AS TO WHY AN ACFT WOULD BE AT THIS ALT AT THIS POINT.) WE WERE FLYING A PROPER PATTERN WITH PROPER FLT AND RADIO PROCS. THERE IS NO WAY THAT AN ACFT COULD HAVE BEEN IN THE LOCATION THE LOW WING SMA WAS IN IF THE PLT WOULD HAVE EXECUTED A PROPER 45 DEG ENTRY TO DOWNWIND AT THE PROPER ALT. AS ANYONE CAN SEE THE NOSE UP ; WING UP POS OF A BIPLANE MAKES SEEING AN ACFT ENTERING DOWNWIND STRAIGHT IN DIFFICULT. HOWEVER; WE LOWERED THE NOSE AND LEVELED LOOKING FOR JUST THIS OCCURRENCE. IT CAN ALSO BE NOTED FROM THE ABOVE DIAGRAM THAT THE LOW WING SMA WAS ON A VERY CLOSE IN DOWNWIND.