Narrative:

We knew the WX at phl would be poor on arrival. We did everything according to our company procedures. The captain was flying the aircraft on autoplt until he coupled the ILS at about 1500' AGL at which time he turned the aircraft over to me. Upon G/south intercept I noticed a small amount of stick pumping, or elevator pumping, which I commented on, but it was not unusual. After the initial pumping the autoplt did a good job. All the indicator lights armed, including the go around at 500'. At about 200' on the radio altitude the aircraft pitched down. The GPWS went off, giving us a pull up. I came ahead with the throttles activating the go around mode, which arrested the sink. At that time the captain took the controls, disconnected the autoplt and aggressively rotated the aircraft. A flight ahead of us had complained about the ILS signal and executed a missed approach, followed by a comment by the controller that maybe an aircraft had taxied into the protected area. We were offered another approach with the controller saying their equipment was normal. Not knowing whether it was our equipment or phl's, we declined and proceeded to ewr where the WX was CAT I. We coupled for the approach to check our equipment. At 500' AGL we again experienced an aggressive pitch down. I disconnected the autoplt and made a normal landing. A couple of things that might save this from happening again, or at least prepare crews, would be to include this type of equipment failure in training sessions in the simulator. We have never covered an equipment failure on a CAT ii approach. Also, some type of a functional check on G/south couplers in better WX could be required. On many aircraft the only time the coupler gets used is when the WX is on the deck. A requirement for testing the equipment would also give crews more practice with the procedures.

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Original NASA ASRS Text

Title: ACR LGT AUTO LAND FAILED AT 200' PITCHING ACFT NOSE DOWN. FLT CREW EXECTUED GO AROUND.

Narrative: WE KNEW THE WX AT PHL WOULD BE POOR ON ARR. WE DID EVERYTHING ACCORDING TO OUR COMPANY PROCS. THE CAPT WAS FLYING THE ACFT ON AUTOPLT UNTIL HE COUPLED THE ILS AT ABOUT 1500' AGL AT WHICH TIME HE TURNED THE ACFT OVER TO ME. UPON G/S INTERCEPT I NOTICED A SMALL AMOUNT OF STICK PUMPING, OR ELEVATOR PUMPING, WHICH I COMMENTED ON, BUT IT WAS NOT UNUSUAL. AFTER THE INITIAL PUMPING THE AUTOPLT DID A GOOD JOB. ALL THE INDICATOR LIGHTS ARMED, INCLUDING THE GO AROUND AT 500'. AT ABOUT 200' ON THE RADIO ALT THE ACFT PITCHED DOWN. THE GPWS WENT OFF, GIVING US A PULL UP. I CAME AHEAD WITH THE THROTTLES ACTIVATING THE GO AROUND MODE, WHICH ARRESTED THE SINK. AT THAT TIME THE CAPT TOOK THE CONTROLS, DISCONNECTED THE AUTOPLT AND AGGRESSIVELY ROTATED THE ACFT. A FLT AHEAD OF US HAD COMPLAINED ABOUT THE ILS SIGNAL AND EXECUTED A MISSED APCH, FOLLOWED BY A COMMENT BY THE CTLR THAT MAYBE AN ACFT HAD TAXIED INTO THE PROTECTED AREA. WE WERE OFFERED ANOTHER APCH WITH THE CTLR SAYING THEIR EQUIP WAS NORMAL. NOT KNOWING WHETHER IT WAS OUR EQUIP OR PHL'S, WE DECLINED AND PROCEEDED TO EWR WHERE THE WX WAS CAT I. WE COUPLED FOR THE APCH TO CHK OUR EQUIP. AT 500' AGL WE AGAIN EXPERIENCED AN AGGRESSIVE PITCH DOWN. I DISCONNECTED THE AUTOPLT AND MADE A NORMAL LNDG. A COUPLE OF THINGS THAT MIGHT SAVE THIS FROM HAPPENING AGAIN, OR AT LEAST PREPARE CREWS, WOULD BE TO INCLUDE THIS TYPE OF EQUIP FAILURE IN TRNING SESSIONS IN THE SIMULATOR. WE HAVE NEVER COVERED AN EQUIP FAILURE ON A CAT II APCH. ALSO, SOME TYPE OF A FUNCTIONAL CHK ON G/S COUPLERS IN BETTER WX COULD BE REQUIRED. ON MANY ACFT THE ONLY TIME THE COUPLER GETS USED IS WHEN THE WX IS ON THE DECK. A REQUIREMENT FOR TESTING THE EQUIP WOULD ALSO GIVE CREWS MORE PRACTICE WITH THE PROCS.

Data retrieved from NASA's ASRS site as of August 2007 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.