Narrative:

Arriving into ord on the oxi 1 arrival, we were assigned runway 22R by approach, and vectored accordingly for a left downwind. I (PF) immediately began slowing the aircraft by extending the gear and flaps to 30 degrees. Shortly after we began slowing, we were vectored by approach towards the runway 22R FAF and given a crossing altitude, which was slightly above normal GS intercept altitude there. Referencing the ehsi 'green arc,' it was clear that we would arrive over the FAF slightly high, so we extended flaps to 40 degrees to increase our rate of descent. We were then cleared for a visual approach to runway 22R. At the established confign and rate of descent, we anticipated reaching the GS and target speed inside the FAF, but before 1500 ft AGL. At approximately the FAF, the runway 22R GS 'came alive' and we were well on track to meet established stabilized approach criteria early. As we continued to capture the GS, the GS indication on the ehsi quickly passed through center, and went to full scale top (below GS). Due to the conflicting information between the ILS GS and our ehsi green arc, I stopped my descent to re-evaluate our situational awareness. During this pause in descent, we once again went high on the actual (not indicated) GS, and then all ILS indications (GS and CDI) completely disappeared on our ehsi, we later assumed because of interference from a preceding B777 clearing the runway. Once we confirmed our position relative to the terrain, we attempted to recover the approach. Now with the runway and VASI clearly in sight, it appeared that re-establishing the GS would be possible before the 500 ft limit. Around 1000 ft, the GS once again came alive, and we felt confident we could meet stabilized approach criteria. At 500 ft AGL, we were still slightly outside stabilized approach parameters, but the aircraft trend showed us reaching it momentarily. I asked the captain 'shall I continue?' and the response was, 'yes, continue.' I believe we met all stabilized approach criteria around 400 ft AGL. A normal flaps 40 degree landing resulted, followed by a normal taxi to the gate. After completing our parking checklist, the captain and I re-evaluated our decision to continue the approach. We both agreed that executing a missed approach/go around would have been better, and the correct option. Contributing factors to this event were: being 'set up' by ord approach to get high, clearance for a visual approach in MVFR conditions, possible ILS interference from a preceding aircraft, conflicting approach guidance information resulting in re-evaluating our situational awareness, and our attempt to recover a poorly set up approach. Factors which led us to continue the approach were: a visual confirmation of terrain clearance and the runway, full aircraft confign allowing a good prediction of approach results, and the joint belief that we would meet stabilized approach limits. While no part of the final approach segment felt 'uncomfortable' to either pilot, the fact of the matter was that we were not able to meet stabilized approach criteria by 500 ft AGL.

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Original NASA ASRS Text

Title: B737 FLT CREW HAS AN UNSTABILIZED APCH INTO ORD.

Narrative: ARRIVING INTO ORD ON THE OXI 1 ARR, WE WERE ASSIGNED RWY 22R BY APCH, AND VECTORED ACCORDINGLY FOR A L DOWNWIND. I (PF) IMMEDIATELY BEGAN SLOWING THE ACFT BY EXTENDING THE GEAR AND FLAPS TO 30 DEGS. SHORTLY AFTER WE BEGAN SLOWING, WE WERE VECTORED BY APCH TOWARDS THE RWY 22R FAF AND GIVEN A XING ALT, WHICH WAS SLIGHTLY ABOVE NORMAL GS INTERCEPT ALT THERE. REFING THE EHSI 'GREEN ARC,' IT WAS CLR THAT WE WOULD ARRIVE OVER THE FAF SLIGHTLY HIGH, SO WE EXTENDED FLAPS TO 40 DEGS TO INCREASE OUR RATE OF DSCNT. WE WERE THEN CLRED FOR A VISUAL APCH TO RWY 22R. AT THE ESTABLISHED CONFIGN AND RATE OF DSCNT, WE ANTICIPATED REACHING THE GS AND TARGET SPD INSIDE THE FAF, BUT BEFORE 1500 FT AGL. AT APPROX THE FAF, THE RWY 22R GS 'CAME ALIVE' AND WE WERE WELL ON TRACK TO MEET ESTABLISHED STABILIZED APCH CRITERIA EARLY. AS WE CONTINUED TO CAPTURE THE GS, THE GS INDICATION ON THE EHSI QUICKLY PASSED THROUGH CTR, AND WENT TO FULL SCALE TOP (BELOW GS). DUE TO THE CONFLICTING INFO BTWN THE ILS GS AND OUR EHSI GREEN ARC, I STOPPED MY DSCNT TO RE-EVALUATE OUR SITUATIONAL AWARENESS. DURING THIS PAUSE IN DSCNT, WE ONCE AGAIN WENT HIGH ON THE ACTUAL (NOT INDICATED) GS, AND THEN ALL ILS INDICATIONS (GS AND CDI) COMPLETELY DISAPPEARED ON OUR EHSI, WE LATER ASSUMED BECAUSE OF INTERFERENCE FROM A PRECEDING B777 CLRING THE RWY. ONCE WE CONFIRMED OUR POS RELATIVE TO THE TERRAIN, WE ATTEMPTED TO RECOVER THE APCH. NOW WITH THE RWY AND VASI CLRLY IN SIGHT, IT APPEARED THAT RE-ESTABLISHING THE GS WOULD BE POSSIBLE BEFORE THE 500 FT LIMIT. AROUND 1000 FT, THE GS ONCE AGAIN CAME ALIVE, AND WE FELT CONFIDENT WE COULD MEET STABILIZED APCH CRITERIA. AT 500 FT AGL, WE WERE STILL SLIGHTLY OUTSIDE STABILIZED APCH PARAMETERS, BUT THE ACFT TREND SHOWED US REACHING IT MOMENTARILY. I ASKED THE CAPT 'SHALL I CONTINUE?' AND THE RESPONSE WAS, 'YES, CONTINUE.' I BELIEVE WE MET ALL STABILIZED APCH CRITERIA AROUND 400 FT AGL. A NORMAL FLAPS 40 DEG LNDG RESULTED, FOLLOWED BY A NORMAL TAXI TO THE GATE. AFTER COMPLETING OUR PARKING CHKLIST, THE CAPT AND I RE-EVALUATED OUR DECISION TO CONTINUE THE APCH. WE BOTH AGREED THAT EXECUTING A MISSED APCH/GAR WOULD HAVE BEEN BETTER, AND THE CORRECT OPTION. CONTRIBUTING FACTORS TO THIS EVENT WERE: BEING 'SET UP' BY ORD APCH TO GET HIGH, CLRNC FOR A VISUAL APCH IN MVFR CONDITIONS, POSSIBLE ILS INTERFERENCE FROM A PRECEDING ACFT, CONFLICTING APCH GUIDANCE INFO RESULTING IN RE-EVALUATING OUR SITUATIONAL AWARENESS, AND OUR ATTEMPT TO RECOVER A POORLY SET UP APCH. FACTORS WHICH LED US TO CONTINUE THE APCH WERE: A VISUAL CONFIRMATION OF TERRAIN CLRNC AND THE RWY, FULL ACFT CONFIGN ALLOWING A GOOD PREDICTION OF APCH RESULTS, AND THE JOINT BELIEF THAT WE WOULD MEET STABILIZED APCH LIMITS. WHILE NO PART OF THE FINAL APCH SEGMENT FELT 'UNCOMFORTABLE' TO EITHER PLT, THE FACT OF THE MATTER WAS THAT WE WERE NOT ABLE TO MEET STABILIZED APCH CRITERIA BY 500 FT AGL.

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.