What was found
AT 4000 FT INBOUND TO ORD AUTOPILOT B ENGAGED. RIGHT SIXPACK PANEL PUSHED TO TEST, AFTER LIGHTS WENT OUT, AUTO PILOT B DISENGAGED AND FLT CONT LIGHT ILLUMINATED LEFT SIX PACK. FLT CONT B LOW PRESSURE LIGHT ON. YAW DAMPENER SWITCH MOVED OFF, STANDBY RUDDER LIGHT ON. HYDRAULIC PRESS INDICATION WAS ONLY A TWO DIGIT NUMBER. THE FLIGHT DECLARED AN EMERGENCY. AFTER THREE MINUTES, ALL RETURNED TO NORMAL. NORMAL LANDING. FOUND B SYSTEM SUPPLY LINE NOT SECURED AND LOCKED. SECURED AND LOCKED B SYSTEM SUPPLY LINE PER AMM 29-11-41 OPS AND LK CKS GOOD. THE AIRCRAFT WAS GROUNDED.