Narrative:

On our trip to dallas the previous day, maintenance asked us to use autothrottle #2 for the flight and to provide some feedback on how it operated. The first officer was flying. Uneventful flight. We were returning home at FL450 on an IFR flight plan which took us to bkw VOR, and then the jasen 2 arrival into iad airport. We had agreed to use autothrottle #1 on this sector to provide additional feedback to maintenance. After passing bkw, we were cleared to cross puttz intersection at FL240. The first officer selected FL240 in the altitude selector and gave me vertical navigation direct on the FMS to FL240. I selected VNAV, it captured providing a GS depiction next to the eadi on the PF display. We were in VMC conditions at dusk. Passing FL350, we both felt (and could see the attitude change) the aircraft smoothly pitch over. The rate of descent increased quickly. I noted the rate of descent at about 6000 FPM and the mach accelerating past mach .84 (300 KIAS and mach .80 was programmed for descent). There was still a lot of thrust being provided for the regime of flight and I reduced the automation sequence one level by disconnecting the autothrottle, and reducing power to idle thrust. I then selected vertical speed mode and selected 3000 FPM rate of descent. The aircraft responded and the maximum mach observed was mach .86 (mmo is mach .88). We leveled off 17 mi before puttz. We then selected autothrottle #2, and re-engaged the autothrottle system. At puttz, ZDC cleared us to cross doccs at 250 KIAS and 11000 ft. The first officer selected 11000 ft in the altitude selector, and gave me vertical direct to 11000 ft at doccs. I selected VNAV. The appropriate lights illuminated, and I saw the GS depiction appear next to the eadi. We spoke for a few mins about what had just happened with the autothrottles hanging up and the pitch attitude change. ZDC called and asked us if we were going to be able to make doccs at 250 KIAS and 11000 ft? We only had 3 mins to go to doccs. The aircraft had not commenced the descent and we were still at FL240. I selected flight level change and smoothly extended the spoilers. The first officer apologized saying we had some technical difficulties, and would not be able to comply with the restr. Center asked us to expedite descent as best we could, losing altitude first and then back on the speed to 250 KTS. From that point on, I only used flight level change and vertical speed for the remainder of the descent. There were no traffic conflicts at any time from our perspective, nor were there any TA's or RA's from the TCASII. We again apologized to the center when he handed us off to dulles approach. As we stepped down in altitude while being vectored, we noticed several times in leveloff that the right autothrottle would advance significantly over what the left was doing. For instance, the first officer noted on 1 occasion that as we leveled off with automatic speed selected at 200 KIAS, the target EPR was 1.15. The left autothrottle initially went to 1.20 while the right autothrottle went up to 1.46. As this was happening, I input some right rudder to counter the asymmetric condition that would have occurred. The right autothrottle then came back to its target and was fine. The approach and landing were uneventful. In the first event where the aircraft pitched down, I resisted the temptation to just get rid of the autoplt and autothrottle. Instead, I tried to reduce some automation, and use other functions to rectify the problem. It worked. In this scenario I thought that I was out of the woods once I corrected the first problem, selected autothrottle #2, only to get led down the garden path with a second problem. This aircraft has had a very good history of operation with the autothrottles, FMS's, and flight guidance controller interface. We had a long debrief with maintenance, and we were fortunate that our avionics technician was there. During the debrief, our avionics technician said that they had installed a 'loaner' flight guidance computer in the aircraft. I have also taken the precaution to call the next captain flying this aircraft and tell him what happened to us. Supplemental information from acn 428523: during this time a passenger had arrived on the flight deck and was observing the cockpitprocs. Both the captain and I were distraction and did not notice that the aircraft did not capture the VNAV and depart FL240. This is a very smooth autoplt and autothrottle equipped aircraft so very little sensation is evidenced in this flight regime. Contributing factors: distraction on the flight deck. Overreliance on the FMS VNAV feature which takes several seconds to process a command. PF being relatively new to aircraft and to a fully automated FMS management environment.

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Original NASA ASRS Text

Title: A GIV FLT DOESN'T ABIDE BY THE ALT XING RESTR AT DOCCS INTXN ON THE JASEN ARR PROC.

Narrative: ON OUR TRIP TO DALLAS THE PREVIOUS DAY, MAINT ASKED US TO USE AUTOTHROTTLE #2 FOR THE FLT AND TO PROVIDE SOME FEEDBACK ON HOW IT OPERATED. THE FO WAS FLYING. UNEVENTFUL FLT. WE WERE RETURNING HOME AT FL450 ON AN IFR FLT PLAN WHICH TOOK US TO BKW VOR, AND THEN THE JASEN 2 ARR INTO IAD ARPT. WE HAD AGREED TO USE AUTOTHROTTLE #1 ON THIS SECTOR TO PROVIDE ADDITIONAL FEEDBACK TO MAINT. AFTER PASSING BKW, WE WERE CLRED TO CROSS PUTTZ INTXN AT FL240. THE FO SELECTED FL240 IN THE ALT SELECTOR AND GAVE ME VERT NAV DIRECT ON THE FMS TO FL240. I SELECTED VNAV, IT CAPTURED PROVIDING A GS DEPICTION NEXT TO THE EADI ON THE PF DISPLAY. WE WERE IN VMC CONDITIONS AT DUSK. PASSING FL350, WE BOTH FELT (AND COULD SEE THE ATTITUDE CHANGE) THE ACFT SMOOTHLY PITCH OVER. THE RATE OF DSCNT INCREASED QUICKLY. I NOTED THE RATE OF DSCNT AT ABOUT 6000 FPM AND THE MACH ACCELERATING PAST MACH .84 (300 KIAS AND MACH .80 WAS PROGRAMMED FOR DSCNT). THERE WAS STILL A LOT OF THRUST BEING PROVIDED FOR THE REGIME OF FLT AND I REDUCED THE AUTOMATION SEQUENCE ONE LEVEL BY DISCONNECTING THE AUTOTHROTTLE, AND REDUCING PWR TO IDLE THRUST. I THEN SELECTED VERT SPD MODE AND SELECTED 3000 FPM RATE OF DSCNT. THE ACFT RESPONDED AND THE MAX MACH OBSERVED WAS MACH .86 (MMO IS MACH .88). WE LEVELED OFF 17 MI BEFORE PUTTZ. WE THEN SELECTED AUTOTHROTTLE #2, AND RE-ENGAGED THE AUTOTHROTTLE SYS. AT PUTTZ, ZDC CLRED US TO CROSS DOCCS AT 250 KIAS AND 11000 FT. THE FO SELECTED 11000 FT IN THE ALT SELECTOR, AND GAVE ME VERT DIRECT TO 11000 FT AT DOCCS. I SELECTED VNAV. THE APPROPRIATE LIGHTS ILLUMINATED, AND I SAW THE GS DEPICTION APPEAR NEXT TO THE EADI. WE SPOKE FOR A FEW MINS ABOUT WHAT HAD JUST HAPPENED WITH THE AUTOTHROTTLES HANGING UP AND THE PITCH ATTITUDE CHANGE. ZDC CALLED AND ASKED US IF WE WERE GOING TO BE ABLE TO MAKE DOCCS AT 250 KIAS AND 11000 FT? WE ONLY HAD 3 MINS TO GO TO DOCCS. THE ACFT HAD NOT COMMENCED THE DSCNT AND WE WERE STILL AT FL240. I SELECTED FLT LEVEL CHANGE AND SMOOTHLY EXTENDED THE SPOILERS. THE FO APOLOGIZED SAYING WE HAD SOME TECHNICAL DIFFICULTIES, AND WOULD NOT BE ABLE TO COMPLY WITH THE RESTR. CTR ASKED US TO EXPEDITE DSCNT AS BEST WE COULD, LOSING ALT FIRST AND THEN BACK ON THE SPD TO 250 KTS. FROM THAT POINT ON, I ONLY USED FLT LEVEL CHANGE AND VERT SPD FOR THE REMAINDER OF THE DSCNT. THERE WERE NO TFC CONFLICTS AT ANY TIME FROM OUR PERSPECTIVE, NOR WERE THERE ANY TA'S OR RA'S FROM THE TCASII. WE AGAIN APOLOGIZED TO THE CTR WHEN HE HANDED US OFF TO DULLES APCH. AS WE STEPPED DOWN IN ALT WHILE BEING VECTORED, WE NOTICED SEVERAL TIMES IN LEVELOFF THAT THE R AUTOTHROTTLE WOULD ADVANCE SIGNIFICANTLY OVER WHAT THE L WAS DOING. FOR INSTANCE, THE FO NOTED ON 1 OCCASION THAT AS WE LEVELED OFF WITH AUTO SPD SELECTED AT 200 KIAS, THE TARGET EPR WAS 1.15. THE L AUTOTHROTTLE INITIALLY WENT TO 1.20 WHILE THE R AUTOTHROTTLE WENT UP TO 1.46. AS THIS WAS HAPPENING, I INPUT SOME R RUDDER TO COUNTER THE ASYMMETRIC CONDITION THAT WOULD HAVE OCCURRED. THE R AUTOTHROTTLE THEN CAME BACK TO ITS TARGET AND WAS FINE. THE APCH AND LNDG WERE UNEVENTFUL. IN THE FIRST EVENT WHERE THE ACFT PITCHED DOWN, I RESISTED THE TEMPTATION TO JUST GET RID OF THE AUTOPLT AND AUTOTHROTTLE. INSTEAD, I TRIED TO REDUCE SOME AUTOMATION, AND USE OTHER FUNCTIONS TO RECTIFY THE PROB. IT WORKED. IN THIS SCENARIO I THOUGHT THAT I WAS OUT OF THE WOODS ONCE I CORRECTED THE FIRST PROB, SELECTED AUTOTHROTTLE #2, ONLY TO GET LED DOWN THE GARDEN PATH WITH A SECOND PROB. THIS ACFT HAS HAD A VERY GOOD HISTORY OF OP WITH THE AUTOTHROTTLES, FMS'S, AND FLT GUIDANCE CTLR INTERFACE. WE HAD A LONG DEBRIEF WITH MAINT, AND WE WERE FORTUNATE THAT OUR AVIONICS TECHNICIAN WAS THERE. DURING THE DEBRIEF, OUR AVIONICS TECHNICIAN SAID THAT THEY HAD INSTALLED A 'LOANER' FLT GUIDANCE COMPUTER IN THE ACFT. I HAVE ALSO TAKEN THE PRECAUTION TO CALL THE NEXT CAPT FLYING THIS ACFT AND TELL HIM WHAT HAPPENED TO US. SUPPLEMENTAL INFO FROM ACN 428523: DURING THIS TIME A PAX HAD ARRIVED ON THE FLT DECK AND WAS OBSERVING THE COCKPITPROCS. BOTH THE CAPT AND I WERE DISTR AND DID NOT NOTICE THAT THE ACFT DID NOT CAPTURE THE VNAV AND DEPART FL240. THIS IS A VERY SMOOTH AUTOPLT AND AUTOTHROTTLE EQUIPPED ACFT SO VERY LITTLE SENSATION IS EVIDENCED IN THIS FLT REGIME. CONTRIBUTING FACTORS: DISTR ON THE FLT DECK. OVERRELIANCE ON THE FMS VNAV FEATURE WHICH TAKES SEVERAL SECONDS TO PROCESS A COMMAND. PF BEING RELATIVELY NEW TO ACFT AND TO A FULLY AUTOMATED FMS MGMNT ENVIRONMENT.

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.