Narrative:

The flight went smoothly until the approach phase. For this leg; the captain was the pilot flying. The weather at ZZZ was 4 miles visibility; rain with 4300 ft. Overcast. We were told by approach to descend to 3;000 feet and told to join the localizer. We descended to 3;000 feet on the autopilot; and; shortly thereafter; had captured the localizer but not the glideslope. The controller then cleared us for the ILS 17 approach. Shortly after being 'cleared for the approach'; I felt the airplane pitch up sharply and noticed that our pitch had indeed increased; the airspeed was decreasing and the altimeter was showing a fast climb. I said 'airspeed' and glanced over to see what the captain was going to do about it. He ended up disconnecting the autopilot and returned the airplane to straight and level at 4;200 feet we then started to descend back down to 3;000 feet.. We continued the approach while hand flying and landed without further incident. After landing; we discussed the 'event' and I was told that the autopilot had attempted to climb up to and capture a false glideslope instead of holding the assigned altitude of 3;000 feet; and capturing it from below.I think that the autopilot tried to climb up to and capture a false glideslope but also did not hold the altitude that we dialed in.

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Original NASA ASRS Text

Title: A CRJ-700 air crew after being 'cleared for the approach' felt the airplane pitch up sharply. The Captain disconnected the autopilot and continued the approach while hand flying and landed without further incident. The crew was told that the autopilot had attempted to climb up to and capture a false Glideslope.

Narrative: The flight went smoothly until the approach phase. For this leg; the Captain was the Pilot Flying. The weather at ZZZ was 4 miles visibility; Rain with 4300 ft. overcast. We were told by Approach to descend to 3;000 feet and told to join the Localizer. We descended to 3;000 feet on the autopilot; and; shortly thereafter; had captured the Localizer but not the glideslope. The controller then cleared us for the ILS 17 Approach. Shortly after being 'cleared for the approach'; I felt the airplane pitch up sharply and noticed that our pitch had indeed increased; the airspeed was decreasing and the altimeter was showing a fast climb. I said 'Airspeed' and glanced over to see what the captain was going to do about it. He ended up disconnecting the autopilot and returned the airplane to straight and level at 4;200 feet we then started to descend back down to 3;000 feet.. We continued the approach while hand flying and landed without further incident. After Landing; we discussed the 'event' and I was told that the autopilot had attempted to climb up to and capture a false Glideslope instead of holding the assigned altitude of 3;000 feet; and capturing it from below.I think that the autopilot tried to climb up to and capture a false Glideslope but also did not hold the altitude that we dialed in.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.