Q226) Given:
TAS = 485 kt,
OAT = ISA +10°C,
FL 410.
Calculate the Mach Number?
A) 0.90
B) 0.85
C) 0.87
D) 0.825 (mark scheme answer)
-> Using the CR-3 Circular Computer and the formulas I get approximately 0.85 (C).
Using formula I get the following:
OAT at FL410 = 206.8k (assuming LR of 1.98 per 1000') +10 = 216.8k
LSS= 38.94xSquare root of temp - 38.94x14.72 = 573.38
Mach # = TAS/LSS - 485/573.38 = 0.845
So I would have said B as well