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Descent Profile

Started by Bluestar, Fri, 13 Jan 2023 02:08


I noticed that the descent profile was .81/290.  The flight was cruising at 290 KIAS and .844M.  When the descent started the aircraft slowed to .81 which slowed the aircraft to 280 KIAS.  It held the .81M until 290 KIAS.  I would have expected the the aircraft to have remained at 290 KIAS from TOD. 

I did not save a situation file at TOD, but this post is related to the situation file.

Grace and Peace,


Hardy Heinlin

That's correct. If you have set .81/290 for the DES and you are above the Mach/IAS transition altitude, your initial DES speed will be the Mach number, not the IAS. During the DES at a constant Mach, the IAS will increase, and when it has increased to the programmed command IAS, it will switch from Mach mode to IAS mode. Not vice versa.

If you want to maintain the CRZ speed after T/D, the DES page should contain that CRZ Mach (with or without a paired IAS) or just that CRZ IAS alone without a paired Mach.