Formula for TAS?

[Cron]

Given FL, OAT and Mach is there a formula for TAS? Thanks in advance.

[SFI145]

Mach Number (M) = TAS/CS
CS = sound speed= 38.967854*sqrt(T+273.15) where T is the OAT in celsius.
TAS is true airspeed in knots.

[Intruder]

Rules of thumb:

TAS = IAS + 2% per 1,000' altitude

TAS (miles/minute) = IMN * 10

Examples:

100 KIAS, 5,000' MSL: TAS = 100 + 10% = 110 KT

Mach 0.8: TAS = 8 NM/min = 480 knots

[compressor stall]

Even quicker rule of thumb...

3*altitude in 1000's plus IAS.

so at 170 indicated at 24K it's 170+(24*3) = 242 kts

CS

[keithl]

Another one, similar to CStall's:
IAS+ (IAS as Miles/min*thousands of ft)
Using the same figures as CStall
170+ (3*24) =242

Using a different example:
300 kts at 15000ft gives
300+ (5*15) = 375

[Lemurian]

Mach number and OAT are sufficient for TAS computation.
1)M*6
2)add or substract 1 Kt per degree C differential from OAT=-35
(add if warmer,substract if colder)
For ins tance, M=.75 and OAT=-45
TAS=75*6-10=440kt
This method is amazingly accurate.
Cheerio!