I think we all know the FMC has issues like the wind page, failure to calculate T/D on some flight plans, etc. I ran across a situation on a KBOS-KTPA flight this morning. Once the STAR and Approach for KTPA was entered into the FMC it would not calculate a T/D. The end of the STAR was FL360 and the beginning of the ILS approach for 01L was at 3000 ASL. Just a mere loss of 33000 feet in about 6 miles. So I used the erase work around to get a T/D. I thought I would enter a headwind of 200 MPH and see if that changed the ETA at KTPA. No change which was expected since the Wind Page is useless. When I went back to the Progress Page the T/D was gone. I figured I must screwed something up. So I went thru the routine again. The T/D had disappeared once more. The 752 is a laugh a minute.

Michael Cubine