Temperature will be increasing as we descend in the troposphere.
CAS
EAS TAS
MN
Altitude
At constant CAS
As altitude decreases
Speed TAS
& MN decrease
Or:
CAS is a measure of dynamic pressure = ˝ ρV2
Where ρ = air density (increasing in descent) and V = TAS (decreasing to keep CAS constant)
LSS is increasing as temperature increases.
MN = TAS/LSS = Decreasing/Increasing = Decreasing