ACR ON VISUAL APCH PASSED THROUGH AREA OF HANG GLIDER ACTIVITY. ARPT ATIS CONTAINED INFO PERTAINING TO LOCATION AND ALTS OF GLIDER OPS. RPTR ESTIMATED MISSING HANG GLIDERS BY ONE HALF MI AT SAME ALT.

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FLYING ON PMD; LYNXX ARR FOR BURBANK. ACFT HAD SYS PROB APPROX 10000 FT ON DSCNT. DEALT WITH. BURBANK ATIS DIFFICULT TO RECEIVE (STARTED TRYING APPROX CA-AZ BORDER). SIT TOO BUSY TO ALLOW TO GO COMPLETELY OFF-LINE TO GET ATIS. FINALLY; NEAR JANNY; HAD ALL PIECES. BUR WAS USING RWYS 8 AND 15. SOCAL APCH GAVE US CHOICE OF RWY; CAPT PICKED RWY 15. SOCAL GAVE US VECTOR STRAIGHT TO ARPT. VISIBILITY TOO POOR TO SEE '4 STACKS' UNTIL AFTER XING LAST RIDGE LINE. CAPT HAD FIM 080 DEG RADIAL (4 STACKS VISUAL) SET UP ON FMS. VECTOR TOOK US S OF THAT LINE; APCH JANNY DIRECT BUR. ATIS ALSO SAID HANG GLIDERS ON THE VNY 010-025 DEG RADIAL; 9 MI; SURFACE TO 6000 FT. TO ME; THIS DIDN'T SEEM A PROB; AS I FORGOT VNY RWY 34 IS NW; NOT A N LINE. AFTER WE CROSSED THE RIDGELINE; DSNDING THROUGH 4500 FT AND S OF FIM 080 DEG RADIAL; SOMEONE (WE HAD 2 JUMPSEATERS ALSO) CALLED OUT 'HANG GLIDERS.' WE SAW 1; THEN BING; BING; BING; 4 OF THEM IN A THERMAL AT 10 O'CLOCK; UNCOMFORTABLY CLOSE (1/2 MI?). WE MADE A SLIGHT DEV TO THE R AND DO NOT KNOW IF THERE WERE MORE THAN 4. JUST BEFORE THIS; WE HAD SEEN THE '4 STACKS' AND HAD BEEN SWITCHED TO BUR TWR. ON ABOUT 3 MI FINAL; WE HEARD A HANG GLIDER CALLING THE TWR; SAYING AN AIRPLANE (US) HAD GONE THROUGH THE MIDDLE OF THE AREA. TWR SAID THEY COULDN'T UNDERSTAND THE RADIO; ALTHOUGH WE HEARD IT LOUD AND CLR. AFTER LNDG; WE REVIEWED OUR CHARTS AND SAW IT WAS VIRTUALLY IMPOSSIBLE TO PINPOINT THE ATIS SITE ON OUR CHARTS IN ORDER TO BE AWARE AND STAY AWAY FROM (FOR EXAMPLE; THE 4 STACKS VISUAL DOESN'T DEPICT VNY; AND THE CHARTS THAT SHOW VNY HAVE A COMPASS ROSE SO SMALL IT WAS HARD TO MEASURE; MUCH LESS ON DSCNT AT A HIGH WORKLOAD TIME). WE DON'T CARRY SECTIONALS FOR THE WHOLE WORLD; EITHER. (WITH A SECTIONAL -- WHICH WE DIDN'T HAVE -- ON THE GND; IT COULD HAVE BEEN PLOTTED AND VISUALIZED.) IT ALSO WAS NOT LISTED ON OUR NOTAMS FOR PREFLT. CAPT CALLED TWR VIA TELEPHONE AND THEY SAID; TOO BAD; THEY HAVE NO CTL OVER IT; THE AREA IS NOT A RESTR AREA. SUGGESTIONS: 1) HAVE IN NOTAMS (AT LEAST INDICATING OCCASIONAL OP) SO WE WOULD HAVE BEEN AWARE DURING PREFLT. 2) HAVE ATIS INDICATE LOCATION WITH RESPECT TO BURBANK. 3) HAVE ATC AVOID VECTORING INTO KNOWN HANG GLIDER; PARACHUTE; ETC; AREAS. SOMEDAY SOMEONE IS GOING TO GET HURT.