Cessna 750 suffered inappropriate altitude deviations when capturing the glide slope at teb.

Attributes
ACN	830210
Time
Date	200904
Local Time Of Day	1201-1800
Place
Locale Reference	TEB.Airport
State Reference	NJ
Aircraft 1
Make Model Name	Citation X (C750)
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Commercial
Experience	Flight Crew Last 90 Days 80 Flight Crew Total 6800 Flight Crew Type 2300
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

Upon capture of localizer and at the OM on approach to runway 19 teb; I watched the captain flying on autopilot. He called for final flaps and as I set them; the aircraft pitched up and gained 500 ft and was following GS commands. I told the captain and he immediately started a descent with the autopilot off; but maintained the GS commands. We were talking with the tower before this uncommanded pitch up and had been cleared to land. We did not come in conflict with any other aircraft and the captain was taken by surprise as the aircraft gained and lost 500 ft on the GS. A normal landing was made and no one from ATC called us.

Original NASA ASRS Text

Title: Cessna 750 suffered inappropriate altitude deviations when capturing the glide slope at TEB.

Narrative: Upon capture of LOC and at the OM on approach to Runway 19 TEB; I watched the Captain flying on autopilot. He called for final flaps and as I set them; the aircraft pitched up and gained 500 FT and was following GS commands. I told the Captain and he immediately started a descent with the autopilot off; but maintained the GS commands. We were talking with the Tower before this uncommanded pitch up and had been cleared to land. We did not come in conflict with any other aircraft and the Captain was taken by surprise as the aircraft gained and lost 500 FT on the GS. A normal landing was made and no one from ATC called us.

Data retrieved from NASA's ASRS site as of April 2012 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.