NMAC IN PROX OF MIL ARPT.

Narrative

I HAD AN ASSIGNMENT FOR AERIAL MAPPING AT LANGLEY ARPT ON A LINE APPROX N TO S FROM APPROX 350 DEGS AT 3 MI TO 270 DEGS OVER THE END OF THE W END OF THE E/W RWY AT 2000 FT. I HAD CALLED AHEAD TO NORFOLK APCH CTL (ON THE TELEPHONE BEFORE DEP) TO LET THEM KNOW THAT WE WOULD BE WORKING IN LANGLEY AIRSPACE. OVER HARCOM VOR I CONTACTED ORF APCH CTL AND THEY TURNED ME OVER TO LANGLEY. I REQUESTED TO FLY THE ABOVE LINE AT 2000 FT AND RECEIVED PERMISSION TO DO SO. THERE WERE SHADOWS ON THE GND BECAUSE OF HIGH CLOUDS AND I REQUESTED TO HOLD OVER THE JOB SITE AT 2000 FT WHILE THE CLOUDS MOVED OFF. WE CONTINUED TO HOLD BECAUSE IT LOOKED LIKE WE WERE GOING TO BE ABLE TO GET THE JOB DONE. AT SOME POINT IN TIME WHILE HOLDING; 2 JETS CAME AT US FROM W TO E AT 2000 FT. I PULLED UP TO 2300 FT AND THE JETS MISSED US. I SAW THEM ONLY MOMENTS BEFORE; JUST IN TIME TO PULL UP. THEY NEVER MOVED UNTIL I PULLED UP WHICH MAKES ME BELIEVE THAT THEY DID NOT SEE ME UNTIL I PULLED UP. MAYBE ABOUT 15-30 MINS WE LEFT BECAUSE THE CLOUD'S SHADOWS CONTINUED TO GO IN AND OUT. WE CAME BACK LATER IN THE DAY AND FINISHED THE JOB. I LEARNED TODAY FROM CAPT WHO WAS INVESTIGATING THE OCCURRENCE THAT THERE WERE 2 DOWNWIND ALTS FOR THE JETS; 1 AT 1500 FT; WHICH I KNOW IS STANDARD FOR THEM; AND 1 AT 2000 FT; WHICH IS NONSTANDARD. I LEARNED THAT I NEED TO DO BETTER PREFLT PLANNING AND CHKING PATTERNED ALTS SO THAT IF THE CTLR GIVES ME A REQUESTED ALT; THAT I WILL KNOW I'M OPERATING AT AN ALT WHERE OTHER AIRPLANES WILL BE OPERATING.