A crj-200 climbed about 100 feet uncommanded as the autopilot was capturing the localizer on an ILS ...

Narrative:

We were being vectored to join the final for an ILS prm 9R. We had been cleared for the approach and I had armed approach mode on the fcp. We had just captured the localizer and I noticed the aircraft had started an uncommanded climb; reaching approximately 7;100 feet and the flight director had become intermittent; flashing off and on on both sides. I disconnected the autopilot and returned to our assigned altitude of 7;000 feet. I called for the first officer to remove the flight director and flew the remainder of the approach raw data for a normal approach and landing. The flight director or possibly the glide slope had become intermittent and caused the aircraft to climb approximately 100 feet from our assigned altitude. I decided rather than try to re-engage the autopilot; the best course of action would be to hand fly the approach. After arriving; we contacted maintenance and wrote up the flight director.

Original NASA ASRS Text

Title: A CRJ-200 climbed about 100 feet uncommanded as the autopilot was capturing the localizer on an ILS PRM so the Captain disconnected the autopilot and hand flew the approach.

Narrative: We were being vectored to join the final for an ILS PRM 9R. We had been cleared for the approach and I had armed approach mode on the FCP. We had just captured the localizer and I noticed the aircraft had started an uncommanded climb; reaching approximately 7;100 feet and the Flight Director had become intermittent; flashing OFF and ON on both sides. I disconnected the autopilot and returned to our assigned altitude of 7;000 feet. I called for the First Officer to remove the Flight Director and flew the remainder of the approach raw data for a normal approach and landing. The Flight Director or possibly the glide slope had become intermittent and caused the aircraft to climb approximately 100 feet from our assigned altitude. I decided rather than try to re-engage the autopilot; the best course of action would be to hand fly the approach. After arriving; we contacted Maintenance and wrote up the Flight Director.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1085151
Time
Date	201305
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Regional Jet 200 ER/LR (CRJ200)
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Altitude Hold/Capture
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy

A crj-200 climbed about 100 feet uncommanded as the autopilot was capturing the localizer on an ILS prm so the captain disconnected the autopilot and hand flew the approach.