B737-800 FLC MISCALCULATE FMS PROGRAMMING AND UNDERSHOOT INTERMEDIATE XING RESTRS ON KORRY ONE STAR.

Date: 2002-01 · Aircraft: B737-800 · Phase: descent

Anomalies: deviation-altitude-undershoot|deviation-altitude-crossing-restriction-not-met|deviation-discrepancy-procedural-published-material-policy

Synopsis

B737-800 FLC MISCALCULATE FMS PROGRAMMING AND UNDERSHOOT INTERMEDIATE XING RESTRS ON KORRY ONE STAR.

Narrative

ENRTE FROM ATL TO LGA WE WERE STEPPED DOWN FROM OUR CRUISE ALT SEVERAL TIMES. THE LAST CRUISE ALT WAS FL190. I WAS IN THE R SEAT CONDUCTING AN OE FOR THE CAPT IN THE L SEAT. THE CAPT WAS USING THE 'CRUISE DSCNT' VNAV MODE TO ACCOMPLISH DSCNT TO THE NEW ALTS. WHILE DSNDING IN THIS 'CRUISE DSCNT' VNAV MODE; WE WERE CLRED TO DSND VIA THE KORRY ONE ARR. THE CAPT SET 10000 FT IN THE MODE CTL PANEL TO ENABLE THE ACFT TO DSND AND CROSS KORRY AT 10000 FT MSL. I REVIEWED THE ALT CONSTRAINTS AND WAYPOINTS LOADED IN THE FMS AND THAT THE ACFT WAS IN A VNAV PATH DSCNT. I BELIEVED THAT THE FMS WAS PROPERLY PROGRAMMED TO COMPLY WITH THE STAR; HOWEVER; I DID NOT NOTE THAT WE WERE STILL IN CRUISE DSCNT MODE. THE LEGS PAGE SHOWED THE PROPER WAYPOINTS AND ALT CONSTRAINTS AND THE FMA INDICATED A VNAV PATH DSCNT. WHEN THE FMS TRANSITIONED (AT FL190) FROM THE CRUISE DSCNT MODE TO THE APPROPRIATE PATH MODE; WE WERE APPROX 2300 FT HIGH TO CROSS BRAND AT 11000 FT. WE HAD STRONG TAILWINDS (75-100 KTS) AND THE B737-800 HAS A RESTR PROHIBITING SPD BRAKE EXTENSION AT INDICATED AIRSPDS ABOVE 300 KTS. WE WERE DSNDING AT ABOUT 320 KIAS AT THIS POINT. I IMMEDIATELY NOTIFIED ATC THAT WE WOULD BE UNABLE TO MEET THE ALT CONSTRAINTS ON THE ARR AND ASKED FOR A VECTOR IF NECESSARY. AT THE SAME TIME; WE BEGAN TO SLOW TO ALLOW SPD BRAKE EXTENSION AT 300 KIAS. THE CTLR REMARKED THAT 'YOU'D BETTER PUSH IT ON OVER...THAT'S WHY WE GAVE YOU 19000 FT WAY BACK THERE...' OR SOMETHING TO THAT EFFECT; WE ADVISED THAT WE WOULD CROSS KORRY AT 10000 FT. IF THE SPD BRAKE RESTR HAD NOT PROHIBITED THEIR USE AT 320 KIAS; WE COULD HAVE MADE THE CONSTRAINTS IN SPITE OF BEING HIGH EARLY ON THE PROFILE. THE SUBTLE DIFFERENCE BTWN HOW VNAV CRUISE DSCNT AND VNAV PATH DSCNT IS ANNUNCIATED CONTRIBUTED TO MY FAILING TO RECOGNIZE OUR DEV HIGH OFF THE DESIRED PATH EARLY IN THE DSCNT. SUPPLEMENTAL INFO FROM ACN 535230: I SELECTED FL190 ON FMC CRUISE PAGE. THE EFIS MAP SHOWED A NEW TOP OF DSCNT POS FOR FL190; HOWEVER; CRUISE DSCNT MODE TOOK PRECEDENCE AND WHEN WE CROSSED THE TOP OF DSCNT POINT WE WERE APPROX 2300 FT HIGH ON THE PROFILE TO CROSS BRAND AT 11000 FT AND KORRY AT 10000 FT. WITHOUT THE SPD BRAKE RESTR ALL ALTS WOULD HAVE BEEN MET. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ACKNOWLEDGED THAT HE DID NOT PROPERLY PLAN FOR THE NEW STAR PROC AND THAT THIS IOE CHK RIDE WAS ALSO A DISTR. IN ORDER TO 'GET AHEAD' OF THE FMS; IT WAS DISCUSSED THAT THE CREW WOULD ADD ANTI-ICE; ON AND ADD ANOTHER 30 KTS TAILWIND TO 'FURTHER TRICK' THE FMS TO ENSURE THAT THEY WERE ABLE TO MEET THE TIGHTLY POSITIONED XING RESTRS.

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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.