Had a question regarding the variation from ISA at FL 340 of the temperature on a route between A & B.
The temperature showed 52. This was the temperature that the key off to the side for showed is the ISA for FL340. However, they also stated to "Assume a standard 2 degrees Celcius lapse rate."
I wasn't sure if that was just a red herring.
Anyway, I'm thinking that there is no difference between what temp is standard at FL340 and what the route at that level is showing. I'm expecting "Nil" to be one of the options.
The options were:
A. -1 C
B. +9 C
C. +1 C
D. -9 C
Any ideas?

Hi Melb3049,
I would have to read the RSWT to see what the temps are.

Any chance you can post them?

Regards,
Mister W

Mr.W. It was in an exam so I don't have anything to post. The reported temp at 34000 was 52. Isn't that the same temp as ISA at 34000? Maybe I'm missing something here.

Doing some math it seems that if you do 34 x 2 = 68. Then subtract that from 15c, then it would be
15
-68
= minus 53
They had the options as I previously posted. The temp on the route for FL340 was 52. Therefore I guess +1 was the correct answer.

Hi Melb3049,

Your calculation sounds right. Might have to ask the good people at BoM that one!

So in the exam question, these two temps matched?
FL -- ISA YMML/YSSY YSSY/YBBN YMML/YPAD YMML/YMHB
YPAD/YPOD/YMHB
450 -- 56 2604859 2503761 2805659 2705557 2905659 2805457
390 -- 56 2405360 2203757 2705260 2606861 2805960 2706961
340 -- 52 2404952 2003849 2706050 2506551 2806450 2606651
300 -- 44 2404439 2002939 2805039 2504941 2905639 2605341
240 -- 33 2403123 2202322 2804123 2703825 2904523 2803925
180 -- 21 2502312 2302111 2803412 2803013 3003812 2803114

Regards, Mr W.

Yes. Exactly.

So I'm thinking. Nil or zero deviation has to be an option. It wasn't though. I guessed correctly it seems as I picked +1. Interpretation of RSWT did not appear on my KDR.