Narrative:

Descending through approximately 8000 ft, cleared to 3000 ft. We had originally been told to expect an ILS runway 19R, but as we approached iad, approach control issued a change to ILS runway 1L. While on vectors around WX bordering the approach course to runway 1L, we were issued a change to the ILS runway 1R. I elected to have the first officer continue flying the airplane while I entered the changes in the FMS. He was expediting the descent with the use of speed brakes while I was heads-down with the approach setup. I pointed out to him that he had selected full speed brakes with the autoplt engaged. In the A320, only half speed brakes are available with the autoplt engaged. The first officer then disengaged the autoplt and turned over FCU control to me. With the speed brake selector at full, when the autoplt was disengaged the speed brakes fully deployed. Our speed was decreasing so I called out 'check speed.' as our speed was decaying below vls (lowest selectable speed) I suggested configuring to flaps 1 degree to lower the vls. He called for flaps 1 degree and I checked speed, then extended the flaps. As expected, the vls decreased, but our speed continued to decay. As our speed started decaying into the alpha prot speed range, and with the aircraft pitch approximately 10 degrees up, I commanded the first officer to pitch down, repeated the command, the commanded him to pitch down to the flight director needles. The aircraft pitched up another 1 to 1 1/2 degrees, so I took control of the aircraft, pitched down to the flight director commanded pitch, and retracted the speed brakes. The speed rapidly recovered to normal. I engaged the autoplt, commanded the first officer to take control, and I completed the approach setup and briefing. The rest of the flight was uneventful. During debriefing, the first officer demonstrated that he understood the speed brake system and the need to utilize the flight director system to alleviate workload. He commented that, he thought he inadvertently selected full speed brakes, and had not considered that additional speed brake deployment was to be expected when the autoplt was disengaged. The rapid change in assigned approachs, along with deviating around the thunderstorms in the area caused him to momentarily lose situational awareness and failure to follow the flight director commands. The design of the A320's speed brake system contributed to this event. With the exception of the actual speed brake lever, there is no indication available to the pilots of just how much the speed brakes are extended. Partial or full speed brake selection is only annunciated with a 'speed brake' message on the ewd (engine warning display) in green text. When the speed brakes are inadvertently selected to full with the autoplt engaged, there is no indication that the lever is commanding more than is allowable. When the autoplt is disengaged, the speed brakes will deploy to full with no additional annunciation. I suggest that the system should flash 'speed brake' in orange (as it does with speed brake deployed with engines greater than idle speed) whenever the speed brake is selected beyond half with the autoplt engaged. Additionally, if speed brakes are selected with the autoplt engaged, the system should be inhibited to half speed brakes even if the autoplt is disengaged. There is already logic built into the system for automatic retraction with toga power and a requirement to retract the speed brakes to reset the system. A similar software change could require selecting full retraction before full extension is allowed after inhibition due to full extension selected with autoplt engaged. An appropriate message on the ewd would also need to be added to the system.

Related reports:

Google
 

Original NASA ASRS Text

Title: AN A320 FLT CREW GETS INTO A LOW SPD REGIME WHEN THE FO FAILS TO FOLLOW PROCS FOR THE ACFT CONFIGN SELECTED DURING A DSCNT INTO IAD, VA.

Narrative: DSNDING THROUGH APPROX 8000 FT, CLRED TO 3000 FT. WE HAD ORIGINALLY BEEN TOLD TO EXPECT AN ILS RWY 19R, BUT AS WE APCHED IAD, APCH CTL ISSUED A CHANGE TO ILS RWY 1L. WHILE ON VECTORS AROUND WX BORDERING THE APCH COURSE TO RWY 1L, WE WERE ISSUED A CHANGE TO THE ILS RWY 1R. I ELECTED TO HAVE THE FO CONTINUE FLYING THE AIRPLANE WHILE I ENTERED THE CHANGES IN THE FMS. HE WAS EXPEDITING THE DSCNT WITH THE USE OF SPD BRAKES WHILE I WAS HEADS-DOWN WITH THE APCH SETUP. I POINTED OUT TO HIM THAT HE HAD SELECTED FULL SPD BRAKES WITH THE AUTOPLT ENGAGED. IN THE A320, ONLY HALF SPD BRAKES ARE AVAILABLE WITH THE AUTOPLT ENGAGED. THE FO THEN DISENGAGED THE AUTOPLT AND TURNED OVER FCU CTL TO ME. WITH THE SPD BRAKE SELECTOR AT FULL, WHEN THE AUTOPLT WAS DISENGAGED THE SPD BRAKES FULLY DEPLOYED. OUR SPD WAS DECREASING SO I CALLED OUT 'CHK SPD.' AS OUR SPD WAS DECAYING BELOW VLS (LOWEST SELECTABLE SPD) I SUGGESTED CONFIGURING TO FLAPS 1 DEG TO LOWER THE VLS. HE CALLED FOR FLAPS 1 DEG AND I CHKED SPD, THEN EXTENDED THE FLAPS. AS EXPECTED, THE VLS DECREASED, BUT OUR SPD CONTINUED TO DECAY. AS OUR SPD STARTED DECAYING INTO THE ALPHA PROT SPD RANGE, AND WITH THE ACFT PITCH APPROX 10 DEGS UP, I COMMANDED THE FO TO PITCH DOWN, REPEATED THE COMMAND, THE COMMANDED HIM TO PITCH DOWN TO THE FLT DIRECTOR NEEDLES. THE ACFT PITCHED UP ANOTHER 1 TO 1 1/2 DEGS, SO I TOOK CTL OF THE ACFT, PITCHED DOWN TO THE FLT DIRECTOR COMMANDED PITCH, AND RETRACTED THE SPD BRAKES. THE SPD RAPIDLY RECOVERED TO NORMAL. I ENGAGED THE AUTOPLT, COMMANDED THE FO TO TAKE CTL, AND I COMPLETED THE APCH SETUP AND BRIEFING. THE REST OF THE FLT WAS UNEVENTFUL. DURING DEBRIEFING, THE FO DEMONSTRATED THAT HE UNDERSTOOD THE SPD BRAKE SYS AND THE NEED TO UTILIZE THE FLT DIRECTOR SYS TO ALLEVIATE WORKLOAD. HE COMMENTED THAT, HE THOUGHT HE INADVERTENTLY SELECTED FULL SPD BRAKES, AND HAD NOT CONSIDERED THAT ADDITIONAL SPD BRAKE DEPLOYMENT WAS TO BE EXPECTED WHEN THE AUTOPLT WAS DISENGAGED. THE RAPID CHANGE IN ASSIGNED APCHS, ALONG WITH DEVIATING AROUND THE TSTMS IN THE AREA CAUSED HIM TO MOMENTARILY LOSE SITUATIONAL AWARENESS AND FAILURE TO FOLLOW THE FLT DIRECTOR COMMANDS. THE DESIGN OF THE A320'S SPD BRAKE SYS CONTRIBUTED TO THIS EVENT. WITH THE EXCEPTION OF THE ACTUAL SPD BRAKE LEVER, THERE IS NO INDICATION AVAILABLE TO THE PLTS OF JUST HOW MUCH THE SPD BRAKES ARE EXTENDED. PARTIAL OR FULL SPD BRAKE SELECTION IS ONLY ANNUNCIATED WITH A 'SPD BRAKE' MESSAGE ON THE EWD (ENG WARNING DISPLAY) IN GREEN TEXT. WHEN THE SPD BRAKES ARE INADVERTENTLY SELECTED TO FULL WITH THE AUTOPLT ENGAGED, THERE IS NO INDICATION THAT THE LEVER IS COMMANDING MORE THAN IS ALLOWABLE. WHEN THE AUTOPLT IS DISENGAGED, THE SPD BRAKES WILL DEPLOY TO FULL WITH NO ADDITIONAL ANNUNCIATION. I SUGGEST THAT THE SYS SHOULD FLASH 'SPD BRAKE' IN ORANGE (AS IT DOES WITH SPD BRAKE DEPLOYED WITH ENGS GREATER THAN IDLE SPD) WHENEVER THE SPD BRAKE IS SELECTED BEYOND HALF WITH THE AUTOPLT ENGAGED. ADDITIONALLY, IF SPD BRAKES ARE SELECTED WITH THE AUTOPLT ENGAGED, THE SYS SHOULD BE INHIBITED TO HALF SPD BRAKES EVEN IF THE AUTOPLT IS DISENGAGED. THERE IS ALREADY LOGIC BUILT INTO THE SYS FOR AUTOMATIC RETRACTION WITH TOGA PWR AND A REQUIREMENT TO RETRACT THE SPD BRAKES TO RESET THE SYS. A SIMILAR SOFTWARE CHANGE COULD REQUIRE SELECTING FULL RETRACTION BEFORE FULL EXTENSION IS ALLOWED AFTER INHIBITION DUE TO FULL EXTENSION SELECTED WITH AUTOPLT ENGAGED. AN APPROPRIATE MESSAGE ON THE EWD WOULD ALSO NEED TO BE ADDED TO THE SYS.

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.