Heavy Jet Descent Profile
I was asked a question recently which I couldn’t answer so I thought I would ask here.
Big jet descent profile – for maximum range (least trip fuel).
For max range (minimum trip fuel), does a jet (any heavy jet really), reduce power to idle then descend at the best L/D speed (called best glide speed in bugsmashers). Would you maintain altitude until you achieved that best L/D speed then start descending, or start descending straight away given the cruise IAS at high alt would be fairly close to the best L/D – or is there a best L/D mach number above FL260. Is this the technique to get minimum trip fuel used assuming for the purposes of the question, no altitude or speed requirements and a straight in approach. Obviously, there is a reduction in speed as you get closer for flap/gear etc.
How does this compare with the typical descent profile in real world operations. Is it normally at a predetermined RoD of close to Mmo/Vmo like in the old days.