Narrative:

On approach to ord in VMC; on a vector (essentially right base for runway 22R) the approach controller said they 'lost the winds' for lahso for runway 22R. ATIS winds were 310 degrees at 7 KTS gusting to 16 KTS (?). Soon after that; he switched us to tower. Tower cleared us to land with 'lahso runway 27L' instructions. I asked the captain if he wanted me to read back and accept the lahso. He said yes. I had used ACARS to pull up the landing data which showed brakes 'maximum' or 'off' as the full length braking options and winds with 0 headwind/10 (?) KT direct crosswind. At 1000 ft; I stated 'instruments crosschecked; GS approaching 1 DOT low.' at 500 ft; I stated '1 DOT low' around 100-200 ft (I'm not sure) I stated 'GS approaching 2 dots low' after which point we got an audible GS warning from the GPWS. It was at that point I realized flying the GS 1 DOT low had been the plan. I'm a little dense sometimes and hadn't realized that was the captain's way to assure complying with the lahso instruction. The captain landed; used maximum braking; complied with lahso and made the A1 turnoff. I now believe the winds had shifted to 320 degrees or more northerly and that there had been a tailwind on approach which would have prevented us from accepting a lahso. I also believe the tower controller knew this but didn't advise us -- how else would the approach controller have known? I was hesitant to call for a go around below 200 ft when we got the warning because of: 1) he's the captain and had a plan; 2) we were VMC in good WX. 3) a go around with intersecting runway departure paths might be less safe than being low on GS; 4) landing on the runway was assured. I also think that requesting a wind check might have forced the controllers hand by requiring him to tell us the current winds (which I suspect were beyond lahso limits). I was too preoccupied with being below GS and having a 'not so good' gut feeling to request a wind check.

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Original NASA ASRS Text

Title: B757-200 FO IS CONCERNED THAT THE CAPTAIN AND ATC CONSPIRED TO ALLOW AN INAPPROPRIATE LAHSO AT ORD.

Narrative: ON APCH TO ORD IN VMC; ON A VECTOR (ESSENTIALLY R BASE FOR RWY 22R) THE APCH CTLR SAID THEY 'LOST THE WINDS' FOR LAHSO FOR RWY 22R. ATIS WINDS WERE 310 DEGS AT 7 KTS GUSTING TO 16 KTS (?). SOON AFTER THAT; HE SWITCHED US TO TWR. TWR CLRED US TO LAND WITH 'LAHSO RWY 27L' INSTRUCTIONS. I ASKED THE CAPT IF HE WANTED ME TO READ BACK AND ACCEPT THE LAHSO. HE SAID YES. I HAD USED ACARS TO PULL UP THE LNDG DATA WHICH SHOWED BRAKES 'MAX' OR 'OFF' AS THE FULL LENGTH BRAKING OPTIONS AND WINDS WITH 0 HEADWIND/10 (?) KT DIRECT XWIND. AT 1000 FT; I STATED 'INSTS XCHKED; GS APCHING 1 DOT LOW.' AT 500 FT; I STATED '1 DOT LOW' AROUND 100-200 FT (I'M NOT SURE) I STATED 'GS APCHING 2 DOTS LOW' AFTER WHICH POINT WE GOT AN AUDIBLE GS WARNING FROM THE GPWS. IT WAS AT THAT POINT I REALIZED FLYING THE GS 1 DOT LOW HAD BEEN THE PLAN. I'M A LITTLE DENSE SOMETIMES AND HADN'T REALIZED THAT WAS THE CAPT'S WAY TO ASSURE COMPLYING WITH THE LAHSO INSTRUCTION. THE CAPT LANDED; USED MAX BRAKING; COMPLIED WITH LAHSO AND MADE THE A1 TURNOFF. I NOW BELIEVE THE WINDS HAD SHIFTED TO 320 DEGS OR MORE NORTHERLY AND THAT THERE HAD BEEN A TAILWIND ON APCH WHICH WOULD HAVE PREVENTED US FROM ACCEPTING A LAHSO. I ALSO BELIEVE THE TWR CTLR KNEW THIS BUT DIDN'T ADVISE US -- HOW ELSE WOULD THE APCH CTLR HAVE KNOWN? I WAS HESITANT TO CALL FOR A GAR BELOW 200 FT WHEN WE GOT THE WARNING BECAUSE OF: 1) HE'S THE CAPT AND HAD A PLAN; 2) WE WERE VMC IN GOOD WX. 3) A GAR WITH INTERSECTING RWY DEP PATHS MIGHT BE LESS SAFE THAN BEING LOW ON GS; 4) LNDG ON THE RWY WAS ASSURED. I ALSO THINK THAT REQUESTING A WIND CHK MIGHT HAVE FORCED THE CTLRS HAND BY REQUIRING HIM TO TELL US THE CURRENT WINDS (WHICH I SUSPECT WERE BEYOND LAHSO LIMITS). I WAS TOO PREOCCUPIED WITH BEING BELOW GS AND HAVING A 'NOT SO GOOD' GUT FEELING TO REQUEST A WIND CHK.

Data retrieved from NASA's ASRS site as of May 2009 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.