Narrative:

Passing 10000 ft; crp departure told us to turn right and intercept the lisse arrival crp transition to hou. I engaged the autoplt and saw from the VOR that we were on an intercept heading. I then programmed the FMC for an intercept course and typed the course 028 degrees; into the intercept course box and made sure the course changed from small numbers to large numbers. I asked the first officer to verify the intercept and he said it was correct. I executed the command and then selected my HSI switch to navigation. The first officer put his HSI switch to navigation as well. I remember thinking how we used to get some immediate intercepts and occasional overshoots with prior FMC software and recalled how I hadn't seen that for several yrs. Things seemed to be working fine since we first went to revised software several yrs ago. In retrospect; I should have had the first officer keep the HSI switch in VOR with crp tuned to xchk the intercept. I believe we were climbing through about 17000 ft when ZHU asked if we had been cleared the lisse with the crp transition. The first officer switched back to VOR and it showed we had passed through the crp 028 degree radial. During the turn back to course; hou gave us a 20 degree vector to the left for the intercept. There was no traffic in the area and the controller didn't seem the least bit upset. After we were on the intercept heading I re-entered the LNAV intercept and got the same display showing left of course when we were actually about 3 mi right of course. The first officer again backed me up and both of us were baffled by what the box was doing. We only engaged LNAV again after we were on course to lisse.

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Original NASA ASRS Text

Title: IN NAV MODE; B737-500 FLIES THROUGH PROGRAMMED INTERCEPT COURSE ON LISSE STAR CRP TRANSITION TO HOU.

Narrative: PASSING 10000 FT; CRP DEP TOLD US TO TURN R AND INTERCEPT THE LISSE ARR CRP TRANSITION TO HOU. I ENGAGED THE AUTOPLT AND SAW FROM THE VOR THAT WE WERE ON AN INTERCEPT HDG. I THEN PROGRAMMED THE FMC FOR AN INTERCEPT COURSE AND TYPED THE COURSE 028 DEGS; INTO THE INTERCEPT COURSE BOX AND MADE SURE THE COURSE CHANGED FROM SMALL NUMBERS TO LARGE NUMBERS. I ASKED THE FO TO VERIFY THE INTERCEPT AND HE SAID IT WAS CORRECT. I EXECUTED THE COMMAND AND THEN SELECTED MY HSI SWITCH TO NAV. THE FO PUT HIS HSI SWITCH TO NAV AS WELL. I REMEMBER THINKING HOW WE USED TO GET SOME IMMEDIATE INTERCEPTS AND OCCASIONAL OVERSHOOTS WITH PRIOR FMC SOFTWARE AND RECALLED HOW I HADN'T SEEN THAT FOR SEVERAL YRS. THINGS SEEMED TO BE WORKING FINE SINCE WE FIRST WENT TO REVISED SOFTWARE SEVERAL YRS AGO. IN RETROSPECT; I SHOULD HAVE HAD THE FO KEEP THE HSI SWITCH IN VOR WITH CRP TUNED TO XCHK THE INTERCEPT. I BELIEVE WE WERE CLBING THROUGH ABOUT 17000 FT WHEN ZHU ASKED IF WE HAD BEEN CLRED THE LISSE WITH THE CRP TRANSITION. THE FO SWITCHED BACK TO VOR AND IT SHOWED WE HAD PASSED THROUGH THE CRP 028 DEG RADIAL. DURING THE TURN BACK TO COURSE; HOU GAVE US A 20 DEG VECTOR TO THE L FOR THE INTERCEPT. THERE WAS NO TFC IN THE AREA AND THE CTLR DIDN'T SEEM THE LEAST BIT UPSET. AFTER WE WERE ON THE INTERCEPT HDG I RE-ENTERED THE LNAV INTERCEPT AND GOT THE SAME DISPLAY SHOWING L OF COURSE WHEN WE WERE ACTUALLY ABOUT 3 MI R OF COURSE. THE FO AGAIN BACKED ME UP AND BOTH OF US WERE BAFFLED BY WHAT THE BOX WAS DOING. WE ONLY ENGAGED LNAV AGAIN AFTER WE WERE ON COURSE TO LISSE.

Data retrieved from NASA's ASRS site as of January 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.