Three separate incidents of aileron stiffness and jamming on Bombardier CL600-2B19 regional jets are being investigated by the NTSB. What makes the incidents unusual–besides the fact that they involve the same airplane model–is that they all occurred on the same day (May 8), with the same carrier (Comair) and all three aircraft had departed in a heavy rain storm from the same airport (Cincinnati/Northern Kentucky). All three airplanes were operating on autopilot and received either an LWD (left wing down) or RWD (right wing down) warning. When the pilots of each aircraft disengaged the autopilot, the aileron controls were stiff and appeared to be binding. In one case, while applying “light to moderate” roll input, the pilot said he felt a snap and the aileron control then operated normally. In the second case, the pilot declared an emergency and diverted. The third airplane made an uneventful landing at its intended destination. All three aircraft were in compliance with an AD (resulting from a similar incident in June 2000) requiring the installation of splash shields. >From AIN