Narrative:

B727 CAT ii coupled approach at dtw. ATIS called 100 ft ceiling and RVR 2000 ft. Autoplt made a hard pitch down at 250 ft. GPWS sink rate sounded. I clicked off autoplt and started go around. Runway came in sight and I elected to land as safest course. I have had repeated problems with B727 autoplts during coupled approachs. Coupled approachs are rarely made and almost never during VFR to check the autoplt. I suggest autoplt coupled approach check every 60 days like the MD80. Callback #1 conversation with reporter revealed the following information: the reporter was the captain on this approach to dtw runway 3L, a CAT ii and III runway. The autoplt was coupled and tracking perfectly down to 250 ft. The first officer was managing the autoplt and the captain was prepared to take over and land. When the autoplt pitched down, the first officer jammed the throttles forward, punched off the autoplt and pitched up. At pitch down, the nose went from about 3 degree nose up to about 10 degree nose down, 'bam, full forward.' the captain believes that he would have been 'dead meat' if the autoplt had not been punched off. The GPWS sounded and the captain saw 1200 FPM descent at 200 ft altitude. The autoplt may not have desensitized when passing the OM, but the captain does not know what air carrier maintenance found wrong with the autoplt. The WX included a 9 KT tailwind component. The air carrier's limit is 10 KTS tailwind. The air carrier's pilot union's safety officer is very pleased with the reporter's suggestion of requiring a flight check of the autoplt coupler as is done in the 2 man aircraft. Callback #2 conversation with reporter revealed the following information: a second call back was made to the reporting captain. This captain is experienced on the B727, having 7000 hours in the aircraft. When asked, he stated that the stabilizer out of trim light never came on, the autoplt was performing flawlessly down to 250 ft AGL when it made its pitch over maneuver. The first officer was flying but the first officer's response was inadequate during this event. The first officer responded to the pitch over with the programmed power up and did not disconnect the autoplt, thereby allowing the autoplt to make the programmed 5 degree pitch up maneuver. This 5 degree pitch up is from the aircraft's pitch angle when the power is applied. In this case the pitch was a minus or negative 10 degrees. (The normal deck angle during approach is 2-3 degrees nose up.) the resultant 5 degree pitch up instituted by the autoplt gave the aircraft a pitch down deck angle of minus 5 degrees. The first officer had been trained to do what he did, add the power up application and allow the autoplt to rotate the aircraft. The captain, realizing that this maneuver 'wasn't going to do the job,' disconnected the autoplt, grabbed the yoke and rotated to the required manual go around deck angle of about 8-10 degrees. He estimates the aircraft got to about 75 ft AGL. The aircraft is certified to have the autoplt coupled to 80 ft AGL but not more than 50 ft below the directional ht for the approach. The captain stated that he hadn't made a coupled approach in the B727 in over a year, as most of the B727 guys just hand fly this non gee whiz aircraft. He feels quite strongly about the need to 'certify' these autoplt approach couplers periodically. When asked, he replied strongly about the training syndrome as presented by the air carrier. He wants more emphasis placed upon the 5 degree mode or deck angle change from an unusual pitch attitude, not the standard 2-3 degree pitch attitude. He also stated that the crew must be alert to the need for an autoplt disconnect in cases such as this event. It scared the 'bejesus' out of him, seeing the approach lights from such a low altitude. He doesn't feel that this was a windshear or ground traffic problem. The event was written up in the logbook but he did not check back with maintenance to see what they found, if anything.

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Original NASA ASRS Text

Title: PROBABLE ACFT EQUIP PROB AUTOPLT PITCHED DOWN WHILE ON A COUPLED APCH.

Narrative: B727 CAT II COUPLED APCH AT DTW. ATIS CALLED 100 FT CEILING AND RVR 2000 FT. AUTOPLT MADE A HARD PITCH DOWN AT 250 FT. GPWS SINK RATE SOUNDED. I CLICKED OFF AUTOPLT AND STARTED GAR. RWY CAME IN SIGHT AND I ELECTED TO LAND AS SAFEST COURSE. I HAVE HAD REPEATED PROBS WITH B727 AUTOPLTS DURING COUPLED APCHS. COUPLED APCHS ARE RARELY MADE AND ALMOST NEVER DURING VFR TO CHK THE AUTOPLT. I SUGGEST AUTOPLT COUPLED APCH CHK EVERY 60 DAYS LIKE THE MD80. CALLBACK #1 CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE CAPT ON THIS APCH TO DTW RWY 3L, A CAT II AND III RWY. THE AUTOPLT WAS COUPLED AND TRACKING PERFECTLY DOWN TO 250 FT. THE FO WAS MANAGING THE AUTOPLT AND THE CAPT WAS PREPARED TO TAKE OVER AND LAND. WHEN THE AUTOPLT PITCHED DOWN, THE FO JAMMED THE THROTTLES FORWARD, PUNCHED OFF THE AUTOPLT AND PITCHED UP. AT PITCH DOWN, THE NOSE WENT FROM ABOUT 3 DEG NOSE UP TO ABOUT 10 DEG NOSE DOWN, 'BAM, FULL FORWARD.' THE CAPT BELIEVES THAT HE WOULD HAVE BEEN 'DEAD MEAT' IF THE AUTOPLT HAD NOT BEEN PUNCHED OFF. THE GPWS SOUNDED AND THE CAPT SAW 1200 FPM DSCNT AT 200 FT ALT. THE AUTOPLT MAY NOT HAVE DESENSITIZED WHEN PASSING THE OM, BUT THE CAPT DOES NOT KNOW WHAT ACR MAINT FOUND WRONG WITH THE AUTOPLT. THE WX INCLUDED A 9 KT TAILWIND COMPONENT. THE ACR'S LIMIT IS 10 KTS TAILWIND. THE ACR'S PLT UNION'S SAFETY OFFICER IS VERY PLEASED WITH THE RPTR'S SUGGESTION OF REQUIRING A FLT CHK OF THE AUTOPLT COUPLER AS IS DONE IN THE 2 MAN ACFT. CALLBACK #2 CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: A SECOND CALL BACK WAS MADE TO THE RPTING CAPT. THIS CAPT IS EXPERIENCED ON THE B727, HAVING 7000 HRS IN THE ACFT. WHEN ASKED, HE STATED THAT THE STABILIZER OUT OF TRIM LIGHT NEVER CAME ON, THE AUTOPLT WAS PERFORMING FLAWLESSLY DOWN TO 250 FT AGL WHEN IT MADE ITS PITCH OVER MANEUVER. THE FO WAS FLYING BUT THE FO'S RESPONSE WAS INADEQUATE DURING THIS EVENT. THE FO RESPONDED TO THE PITCH OVER WITH THE PROGRAMMED PWR UP AND DID NOT DISCONNECT THE AUTOPLT, THEREBY ALLOWING THE AUTOPLT TO MAKE THE PROGRAMMED 5 DEG PITCH UP MANEUVER. THIS 5 DEG PITCH UP IS FROM THE ACFT'S PITCH ANGLE WHEN THE PWR IS APPLIED. IN THIS CASE THE PITCH WAS A MINUS OR NEGATIVE 10 DEGS. (THE NORMAL DECK ANGLE DURING APCH IS 2-3 DEGS NOSE UP.) THE RESULTANT 5 DEG PITCH UP INSTITUTED BY THE AUTOPLT GAVE THE ACFT A PITCH DOWN DECK ANGLE OF MINUS 5 DEGS. THE FO HAD BEEN TRAINED TO DO WHAT HE DID, ADD THE PWR UP APPLICATION AND ALLOW THE AUTOPLT TO ROTATE THE ACFT. THE CAPT, REALIZING THAT THIS MANEUVER 'WASN'T GOING TO DO THE JOB,' DISCONNECTED THE AUTOPLT, GRABBED THE YOKE AND ROTATED TO THE REQUIRED MANUAL GAR DECK ANGLE OF ABOUT 8-10 DEGS. HE ESTIMATES THE ACFT GOT TO ABOUT 75 FT AGL. THE ACFT IS CERTIFIED TO HAVE THE AUTOPLT COUPLED TO 80 FT AGL BUT NOT MORE THAN 50 FT BELOW THE DIRECTIONAL HT FOR THE APCH. THE CAPT STATED THAT HE HADN'T MADE A COUPLED APCH IN THE B727 IN OVER A YEAR, AS MOST OF THE B727 GUYS JUST HAND FLY THIS NON GEE WHIZ ACFT. HE FEELS QUITE STRONGLY ABOUT THE NEED TO 'CERTIFY' THESE AUTOPLT APCH COUPLERS PERIODICALLY. WHEN ASKED, HE REPLIED STRONGLY ABOUT THE TRAINING SYNDROME AS PRESENTED BY THE ACR. HE WANTS MORE EMPHASIS PLACED UPON THE 5 DEG MODE OR DECK ANGLE CHANGE FROM AN UNUSUAL PITCH ATTITUDE, NOT THE STANDARD 2-3 DEG PITCH ATTITUDE. HE ALSO STATED THAT THE CREW MUST BE ALERT TO THE NEED FOR AN AUTOPLT DISCONNECT IN CASES SUCH AS THIS EVENT. IT SCARED THE 'BEJESUS' OUT OF HIM, SEEING THE APCH LIGHTS FROM SUCH A LOW ALT. HE DOESN'T FEEL THAT THIS WAS A WINDSHEAR OR GND TFC PROB. THE EVENT WAS WRITTEN UP IN THE LOGBOOK BUT HE DID NOT CHK BACK WITH MAINT TO SEE WHAT THEY FOUND, IF ANYTHING.

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