MD80 APCHS UNITED STATES BORDER AT 300 KTS BELOW 10000 FT IN CYUL AIRSPACE.

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WE HAD JUST DEPARTED YUL AND WERE ON A HDG OF 200 DEGS. WE HAD BEEN CLRED TO FL230 BEFORE WE HAD REACHED 3000 FT AFL. PASSING 3000 FT AFL; I DECREASED THE RATE OF CLB TO PERMIT OUR AIRSPD TO INCREASE TO 320 KTS; PERMISSIBLE UNDER CANADIAN AIR REGS. AS WE WERE CLBING THROUGH 10000 FT MSL; IT SUDDENLY DAWNED ON ME THAT I WAS NOT CERTAIN WHERE WE WERE RELATIVE TO THE UNITED STATES/CANADIAN BORDER. I OBSERVED OUR DME TO BE APPROX 35 MI S OF THE YUL VOR; THEN LOOKED AT THE HIGH CHART TO OBSERVE THAT WE HAD NOT REACHED 10000 FT MSL UNTIL WE WERE VERY CLOSE TO THE UNITED STATES BORDER; WHICH I ESTIMATED TO BE ONLY 3- 4 MI AWAY. IT IS POSSIBLE THAT WE DID NOT REACH 10000 FT MSL UNTIL S OF THE BORDER; BUT I DO NOT THINK SO. THE POINT IS THAT FOR CANADIAN ARPTS NEAR THE UNITED STATES BORDER; SUCH AS MONTREAL OR VANCOUVER; CREWS SHOULD BE AWARE OF THIS PITFALL. THAT THIS WOULD BE AN ISSUE NEVER OCCURRED TO EITHER THE CAPT OR ME. I WOULD RECOMMEND THAT CONSIDERATION BE GIVEN TO ADDING A SMALL NOTE ON THE MONTREAL AND VANCOUVER COMPANY PAGES UNDER THE EXISTING CLB AIRSPD NOTE STATING FOR CREWS TO BE AWARE ON DEPS TO ENSURE THAT THEY USE CAUTION NOT TO EXCEED 250 KIAS BELOW 10000 FT MSL WHEN FLYING S INTO UNITED STATES AIRSPACE.