Originally Posted by
firstmrj
oceancrosser,
Thanks for the reply,
I agree that we are totally free to use speedbrake.
I just wonder why the FMS’s algorithm draw such unachievable path without extra drag (speedbrake) path in spite of the below assumptions in the FCOM.
“The path to the first constraint is based on:
• idle thrust
• speedbrakes retracted
• FMC cruise wind
• wind entries on the DESCENT FORECAST page
• predicted use of anti-ice
• applicable target speed”
Besides, in my previous types, i.e. B737CL, B737NG and A320, I could follow VNAV PATH down to FAF in most situations when no short cut or no detour from STAR.
However in case of B767 it seems I have to elect not to use VNAV descent or to use VNAV with help of speedbrakes in the deceleration portion.
That last sentence sums it up. The 757/767 FMC/VNAV is archaic. You need to manage these airplanes accordingly. VNAV works ok during descent until you get into manuevering/speed control in the STAR. So you may/will need different modes. Also keep in mind that the weight span of the 767 is far greater than the other jets you have flown. A very light 767 is a different beast from one at MTOW (or MLW at that).
Last edited by oceancrosser; 20th Jun 2020 at 10:31.