B737 CREW HAD ALT AND SPD DEV.

Narrative

AFTER INTERCEPTING THE LOC TO RWY 4R AT ORD; WE WERE TOLD BY APCH CTL TO 'CROSS DEGAN AT 8000 FT AT 250 KTS; CLRED FOR THE APCH.' WE WERE ABOUT 10 MI SW OF DEGAN AT 10000 FT; 250 KTS. THE COPLT WAS RELATIVELY NEW AND ARMED THE APCH COUPLER ON THE MCP. AFTER CAPTURING THE GS; THE ACFT DSNDED AND I WAS INVOLVED WITH SEATING THE PAX AND GETTING ATIS WHEN I LOOKED AT THE INST PANEL AND SAW '264 KTS' ON THE AIRSPD INDICATOR. THE ACFT CONTINUED DSNDING AND I IMMEDIATELY TOLD THE COPLT TO DISCONNECT THE AUTOPLT AND FLY THE ACFT MANUALLY WITH SPD BRAKES DEPLOYED. AS THIS WAS DONE; IT TOOK SEVERAL SECONDS; THE ACFT WAS SLOWED. HOWEVER; DURING THIS PROCESS OF ADVISING THE COPLT HOW TO CORRECT PROPERLY; WE IN MANUAL FLT; DSNDED TO 7700 FT MSL 1 1/2 MI SW OF DEGAN INTXN. WE CORRECTED SLOWLY BACK TO 8000 FT AND CROSSED DEGAN AT THE ASSIGNED ALT BASED ON THE FMC MAP DISPLAY. SINCE WE WERE BOTH IN MANUAL ON OUR NAV/ILS FOR APPROX 5-10 MINS AND SINCE THE APCH WAS STARTED APPROX 42 MI SW OF ORD; WE HAD NO RADIO UPDATES. THE DISPLAY COULD HAVE DEVELOPED AN ERROR. ALTHOUGH WE NEVER DEVIATED MORE THAN 1 DOT FROM THE GS AT 23 DME; THAT COULD EASILY BE 300-400 FT; WHICH CAUSED US TO NOT COMPLY WITH THE RESTR OF 8000 FT AT DEGAN INTXN. I SHOULD HAVE BEEN A BIT MORE CAUTIOUS WITH THE FO BY EVALUATING THE EXPERIENCE LEVEL THIS PERSON HAD AND BY SUGGESTING THAT DRAG WAS GOING TO BE NEEDED TO COMPLY WITH THE AIRSPD RESTRS IF THE AUTOPLT AND APCH COUPLER WERE TO BE USED. I ASSUMED TOO MUCH AND ONCE THE DEVS BEGAN; SEVERAL OTHER PARAMETERS WERE IN JEOPARDY WHICH I TALKED ABOUT WHEN I SHOULD HAVE TAKEN CTL OF THE ACFT AS THE CAPT. ALTHOUGH SAFETY WAS NOT JEOPARDIZED; I THINK I WENT A LITTLE TOO FAR IN INSTRUCTING THE COPLT SO SOME POSITIVE LEARNING COULD OCCUR. NONETHELESS; THE COPLT FINALLY GOT THE APCH WITHIN LIMITS AND A DEBRIEF WAS CONDUCTED AFTER THE FLT. SUPPLEMENTAL INFO FROM ACN 443890: AT 11000 FT MSL; ON THE LOC FOR RWY 4R AT ORD; APCHING RAHNN; ORD APCH CLRED ACR FOR THE ILS 4R APCH. WE WERE INSTRUCTED TO MAINTAIN 250 KTS; AND 8000 FT OR ABOVE UNTIL DEGAN. WE WERE AT 250 KTS; 1 1/2 DOTS BELOW GS WHEN CLRED FOR THE APCH; AND I ARMED THE APCH MODE. THE ACFT CAPTURED THE GS; CLEAN AT 250 KTS. PASSING THROUGH 10000 FT ON GS; THE ACFT HAD ACCELERATED TO 263 KTS; AND THE CAPT PROMPTED ME TO DEPLOY THE SPD BRAKES. THE ACFT DECELERATED BACK TO 250 KTS BY 9300 FT. WE EXTENDED THE LNDG GEAR TO FURTHER AID IN AIRSPD CTL. WITH THE SPD BRAKES EXTENDED; AND LNDG GEAR DOWN; THE AUTOPLT FOLLOWED APCH MODE/GS INDICATIONS TO DSND THE ACFT TO 7700 FT ABOUT 1 NM PRIOR TO DEGAN. THE CAPT ANNOUNCED THE ALTDEV AND I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLE; AND CORRECTED EXPEDITIOUSLY BACK UP TO 8000 FT. I FLEW THE REMAINDER OF THE APCH MANUALLY (WITH FLT DIRECTOR; WITHOUT AUTOPLT OR AUTOTHROTTLE). I FEEL THAT THE ALT AND AIRSPD DEVS WERE PLT ERROR ON MY PART (IE; LESS EXPERIENCE WITH EXTREMELY FAST GS'S). DURING POSTFLT; THE CAPT DEBRIEFED THE ENTIRE APCH AND OFFERED FURTHER TECHNIQUES FOR THIS TYPE OF APCH.