A GIV CREW ENCOUNTERED MODERATE TO SEVERE TURB AFTER DEPARTING BWI AND LOST THEIR YAW DAMPER AND AUTOPLT. THEY CLBED WITHOUT CLRNC BECAUSE ACFT CTL WAS IN DOUBT.

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AFTER DEPARTING BWI WE WERE WBOUND ON RADAR VECTORS AND AT AN ASSIGNED ALT OF 17000 FT. WE HAD BEEN EXPERIENCING CONTINUOUS MODERATE TURB AND HAD REQUESTED HIGHER TO CLR THE TOPS OF THE CLOUDS THAT WE WERE FLYING IN. THE INTENSITY OF THE TURB INCREASED AND WE ADVISED CTR AGAIN THAT WE WERE 'GETTING POUNDED' AND WE REALLY NEEDED TO CLB. ZDC ADVISED THAT THEY WERE UNABLE; BUT THEY GAVE US A HDG CHANGE FOR A CLB AND SAID IT WOULD BE ABOUT 1 MIN. ALMOST IMMEDIATELY AFTER THIS XMISSION WE ENCOUNTERED MODERATE/SEVERE TURB AND LOST OUR YAW DAMPER; PITCH TRIM; AUTOPLT AND AIR DATA COMPUTERS. WITH THE LOSS OF THE YAW DAMPER WE STRUGGLED TO MAINTAIN CTL OF THE ACFT IN THE TURB -- WE IMMEDIATELY NOTIFIED ZDC THAT WE WERE CLBING OUT OF THE TURB AND THAT WE HAD EXPERIENCED FAILURE OF OUR YAW DAMPER SYS AND COMPUTERS. WASHINGTON CLRED US TO FL220 AND DIRECT TO IHD VOR. I ADVISED THAT WE WOULD BE 'STRAIGHT AHEAD' WHILE WE SORTED THROUGH OUR MULTIPLE FAILURES AND THAT WE WERE CLBING TO FL220. THE RIDE IMPROVED CONSIDERABLY DURING THE CLB. WE WERE ABLE TO REGAIN THE USE OF THE YAW DAMPER ALONG WITH THE OTHER FAILED EQUIP AND WE THEN PROCEEDED ON COURSE TO OUR DEST.