Narrative:

During approach to atl on macey 2 arrival, we were vectored off of arrival and cleared to descend to 5000 ft MSL. Captain (PF) set up the MCP for descent via vertical speed. I verified that 5000 ft was set in altitude window. Captain kept adjusting vertical speed rate. As we neared 5000 ft, I realized that the altitude was no longer 'armed' in the FMA panel. I told the captain 'we're not going to capture 5000 ft. It's not armed.' the captain turned the autoplt off, however she did not arrest the descent rate sufficiently and we went below 5000 ft. I then told her she needed to climb back to 5000 ft. However, all she did was shallow the descent rate and we continued to slowly descend. Approach called about this time and reclred us to 4500 ft which I acknowledged and we leveled at 4500 ft. From this point, we were cleared to fly a heading (I believe it was 210 degrees) maintain 4500 ft and cleared for the ILS to runway 26R at atl, maintain 180 KTS until ajaay and switch tower. After verifying that ILS was armed (the autoplt was back on at this point), I looked down to tune the VHF to tower frequency and to put ground in the standby window. When I looked back up we were right of the localizer (to the north) and the heading was going further right. The FMA was in heading select instead of localizer capture. Tower called about this time to ask if we had a problem. As I tried to figure out what had happened, tower told us to go missed approach and to turn to 090 degrees and climb to 3500 ft. What I believe happened was that the captain was setting up the MCP for the missed approach after we had localizer capture and accidentally activated heading select, which caused the airplane to begin a turn northward. Some other points were distraction by the previous altitude problem (due to inaction). We never had a conflict with other traffic and the rest of the flight was uneventful. Supplemental information from acn 599314: vectored to 'intercept runway 26R localizer on heading 210 degrees, maintain 5000 ft until freal, cleared ILS runway 26R approach.' armed ILS at that time. 210 degree heading took us inside of freal. Adjusted heading to relocate us just outside of freal. Had localizer capture and GS capture. At the time copilot was told to switch to tower (he did not make callouts), I noticed raw data did not agree with primary flight display. Tried rearming ILS (would not rearm). Tower asked if we were having problems (we were high and right of course, north of field). 2 factors contributed: copilot not backing up instrument callouts due to distraction of being told to switch frequency, and I most likely disarmed ILS when I adjusted heading for better intercept.

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Original NASA ASRS Text

Title: AN MD88 FLT STRAYS AWAY FROM THE APCH COURSE FOR RWY 26R DURING THE PIC'S ATTEMPT FOR A CAPTURED APCH 13 NM NE OF ATL, GA.

Narrative: DURING APCH TO ATL ON MACEY 2 ARR, WE WERE VECTORED OFF OF ARR AND CLRED TO DSND TO 5000 FT MSL. CAPT (PF) SET UP THE MCP FOR DSCNT VIA VERT SPD. I VERIFIED THAT 5000 FT WAS SET IN ALT WINDOW. CAPT KEPT ADJUSTING VERT SPD RATE. AS WE NEARED 5000 FT, I REALIZED THAT THE ALT WAS NO LONGER 'ARMED' IN THE FMA PANEL. I TOLD THE CAPT 'WE'RE NOT GOING TO CAPTURE 5000 FT. IT'S NOT ARMED.' THE CAPT TURNED THE AUTOPLT OFF, HOWEVER SHE DID NOT ARREST THE DSCNT RATE SUFFICIENTLY AND WE WENT BELOW 5000 FT. I THEN TOLD HER SHE NEEDED TO CLB BACK TO 5000 FT. HOWEVER, ALL SHE DID WAS SHALLOW THE DSCNT RATE AND WE CONTINUED TO SLOWLY DSND. APCH CALLED ABOUT THIS TIME AND RECLRED US TO 4500 FT WHICH I ACKNOWLEDGED AND WE LEVELED AT 4500 FT. FROM THIS POINT, WE WERE CLRED TO FLY A HDG (I BELIEVE IT WAS 210 DEGS) MAINTAIN 4500 FT AND CLRED FOR THE ILS TO RWY 26R AT ATL, MAINTAIN 180 KTS UNTIL AJAAY AND SWITCH TWR. AFTER VERIFYING THAT ILS WAS ARMED (THE AUTOPLT WAS BACK ON AT THIS POINT), I LOOKED DOWN TO TUNE THE VHF TO TWR FREQ AND TO PUT GND IN THE STANDBY WINDOW. WHEN I LOOKED BACK UP WE WERE R OF THE LOC (TO THE N) AND THE HDG WAS GOING FURTHER R. THE FMA WAS IN HDG SELECT INSTEAD OF LOC CAPTURE. TWR CALLED ABOUT THIS TIME TO ASK IF WE HAD A PROB. AS I TRIED TO FIGURE OUT WHAT HAD HAPPENED, TWR TOLD US TO GO MISSED APCH AND TO TURN TO 090 DEGS AND CLB TO 3500 FT. WHAT I BELIEVE HAPPENED WAS THAT THE CAPT WAS SETTING UP THE MCP FOR THE MISSED APCH AFTER WE HAD LOC CAPTURE AND ACCIDENTALLY ACTIVATED HDG SELECT, WHICH CAUSED THE AIRPLANE TO BEGIN A TURN NORTHWARD. SOME OTHER POINTS WERE DISTR BY THE PREVIOUS ALT PROB (DUE TO INACTION). WE NEVER HAD A CONFLICT WITH OTHER TFC AND THE REST OF THE FLT WAS UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 599314: VECTORED TO 'INTERCEPT RWY 26R LOC ON HDG 210 DEGS, MAINTAIN 5000 FT UNTIL FREAL, CLRED ILS RWY 26R APCH.' ARMED ILS AT THAT TIME. 210 DEG HDG TOOK US INSIDE OF FREAL. ADJUSTED HDG TO RELOCATE US JUST OUTSIDE OF FREAL. HAD LOC CAPTURE AND GS CAPTURE. AT THE TIME COPLT WAS TOLD TO SWITCH TO TWR (HE DID NOT MAKE CALLOUTS), I NOTICED RAW DATA DID NOT AGREE WITH PRIMARY FLT DISPLAY. TRIED REARMING ILS (WOULD NOT REARM). TWR ASKED IF WE WERE HAVING PROBS (WE WERE HIGH AND R OF COURSE, N OF FIELD). 2 FACTORS CONTRIBUTED: COPLT NOT BACKING UP INST CALLOUTS DUE TO DISTR OF BEING TOLD TO SWITCH FREQ, AND I MOST LIKELY DISARMED ILS WHEN I ADJUSTED HDG FOR BETTER INTERCEPT.

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.