An air carrier at 2300 ft on an intercept heading for the buf ILS runway 23 pitched up to 30 degrees...

Narrative:

We were approaching the buf runway 23 localizer (ibuf 111.3) from the northwest given a descent to 2300 ft; and cleared for the approach. As we approached the level-off; the autopilot captured an erroneous glideslope indication and started an aggressive climb. We added thrust and leveled the wings to correct our loss of airspeed. The autopliot directed a pitch up of approximately 18-20 degrees. We gained 1400 ft of altitude. A go-around was not performed as we were still in a position to salvage and fly a normal; stabilized approach (VMC). There was a NOTAM indicating the glideslope was unusable more than 5 degrees right of the localizer. I believe we were inside this cone at the time of the incident. Being 4+ miles away from the final fix; 100 ft above glideslope intercept altitude; and cleared for the approach I selected app mode; not realizing how the autopilot would respond to the notamed glideslope problem. I need to pay closer attention to exactly what the NOTAM implies and delay app mode until I'm sure of localizer capture.callback conversation with reporter revealed the following info: the reporter's factual data was provided after a review of the aircraft's foqa data. The approach was briefed with the acknowledgment that the flight was approaching from the north and the glideslope may not be accurate until near the localizer's capture. The reporter saw the localizer coming in and the glideslope moving down then rapidly up toward the flight director's top edge up. The reporter did not see glideslope capture annunciated on the mode annunciator but in order for the autopilot to pitch up a glideslope capture would have had to have occurred prior to the pitch up from 5 degrees to 33 degrees. At the time of the event the aircraft was configured at flap 5. The airspeed decreased from the flaps 5 maneuver speed of 190 kts to 120 kts very rapidly with thrust set at 95% and full nose down. The glideslope anomaly was not reported to ATC because the crew believe the event was caused by the aircraft.

Original NASA ASRS Text

Title: An air carrier at 2300 ft on an intercept heading for the BUF ILS Runway 23 pitched up to 30 degrees and climbed 1400 ft as it approached the ILS glideslope from the north. The aircraft was at flaps 5 degrees and 190 kt but slowed to 120 kts during the 20 second event.

Narrative: We were approaching the BUF Runway 23 localizer (IBUF 111.3) from the northwest given a descent to 2300 ft; and cleared for the approach. As we approached the level-off; the autopilot captured an erroneous glideslope indication and started an aggressive climb. We added thrust and leveled the wings to correct our loss of airspeed. The autopliot directed a pitch up of approximately 18-20 degrees. We gained 1400 ft of altitude. A go-around was not performed as we were still in a position to salvage and fly a normal; stabilized approach (VMC). There was a NOTAM indicating the glideslope was unusable more than 5 degrees right of the localizer. I believe we were inside this cone at the time of the incident. Being 4+ miles away from the final fix; 100 ft above glideslope intercept altitude; and cleared for the approach I selected APP mode; not realizing how the autopilot would respond to the NOTAMED glideslope problem. I need to pay closer attention to exactly what the NOTAM implies and delay APP mode until I'm sure of LOC capture.Callback conversation with reporter revealed the following info: The reporter's factual data was provided after a review of the aircraft's FOQA data. The approach was briefed with the acknowledgment that the flight was approaching from the north and the glideslope may not be accurate until near the localizer's capture. The reporter saw the localizer coming in and the glideslope moving down then rapidly up toward the flight director's top edge up. The reporter did not see glideslope capture annunciated on the mode annunciator but in order for the autopilot to pitch up a glideslope capture would have had to have occurred prior to the pitch up from 5 degrees to 33 degrees. At the time of the event the aircraft was configured at flap 5. The airspeed decreased from the flaps 5 maneuver speed of 190 kts to 120 kts very rapidly with thrust set at 95% and full nose down. The glideslope anomaly was not reported to ATC because the crew believe the event was caused by the aircraft.

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.

Attributes
ACN	820250
Time
Date	200901
Local Time Of Day	1801-2400
Place
Locale Reference	BUF.Airport
State Reference	NY
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Other Instrument Precision
Flight Plan	IFR
Person 1
Function	Pilot Flying First Officer
Experience	Flight Crew Last 90 Days 209 Flight Crew Type 2100
Person 2
Function	Pilot Flying Captain
Experience	Flight Crew Last 90 Days 184
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Loss Of Aircraft Control

An air carrier at 2300 ft on an intercept heading for the buf ILS runway 23 pitched up to 30 degrees and climbed 1400 ft as it approached the ILS glideslope from the north. The aircraft was at flaps 5 degrees and 190 kt but slowed to 120 kts during the 20 second event.