TAT and SAT on E6B?

[funkydreadlocks]

Hey guys,

does anyone know how to calculate SAT (OAT) from the TAT and TAS with the E6B flight computer? I've been looking everywhere to no avail.

Eg

The TAT indicated at 460kt (TAS) is -25°C. Use the navigation computer to find SAT.

cheers!

[ericthepilot]

@ what Flight Level ?

[funkydreadlocks]

that's the question, no flight level given

[Da-20 monkey]

Hi,

On a CRP5 computer there is a blue arc on the front to get the temperature rise (ram rise) for a given TAS. This option probably doesn't exist on a E6B.


Ram Rise (TAT- SAT) by itself is actually only dependant on Mach number. You cannot make a really exact calculation in your example, because to know your mach number, you need to know the SAT in the first place.

However, this formula gives a good estimation based on TAS:

TAT= SAT + (TAS/100)²

With this formula the ram rise is 21 degrees, according to the blue arc on a CRP5 the rise is about 22,5 degrees. So the SAT will be around - 46 degrees with the formula.





The ,correct' formula is this one, by the way:

TAT= SAT(1+0,2M²)

[funkydreadlocks]

Thanks a lot.

I know the question is crap but that's what is given to me, word to word. The solution uses the CRP5 to answer it, unfortunately, I'm lacking one.

The ,correct' formula is this one, by the way:

TAT= SAT(1+0,2M²)

I know about this formula but ironically I need the SAT to calculate Mach speed. I avoided buying a CRP5 because of the high price and got an E6B instead (less than a third of the price), sure it would do the job since all the guys in the US seem to use it with no problem.

I find myself in an annoying situation. I'll end up spending more. I'll try using the other formula you suggested, thanks a lot!

[RichardH]

The E6B is fine for the US and for PPL level over here, it does most but certainly not all of the ATPL.

If you are doing ATPL exams in UK/EASA then you should really INVEST in a CRP-5 or equivalent. Buying any other is a false economy as you have just discovered.

I have lost count of the number of students turning up on brush-up courses without the correct tools for the job then wonder why they can't answer a particular ATPL level question.

Reminder to US students that programmable calculators are NOT allowed in exams here in UK. The Casio scientific calculator seems to be the de-facto standard. Most theory schools will either provide the equipment or at least give a recommendation.

On my ancient E6B ram rise not possible but as previous post it's simple with a CRP-5. I too get around -47.