ISA Deviation Question at Altitude

[BodhiWes]

Hi, I'm having trouble calculating this question.

If you are flying at 38,000 with a SAT of -50C and the tropopause was actually at 44,000 where SAT was -65C what is the deviation from ISA?

a) ISA +6C
b) ISA -6C
c) ISA +23C
d) ISA +15C

The book says the answer is a) ISA +6C. How is this calculated?

Thanks.

[NotDirty!]

The ISA starts at 15 C at sea level, decreasing 1.98 C for every 1000 ft above, up to 36,000 ft. Above that it is a constant -56.5 C. So ISA at 38,000 is -56.5; actual SAT is -50; -50- (-56.5) = 6.5 C. So the deviation is 6.5 degrees warmer than ISA, aka ISA+6

[455tt]

Good job NotDirty, you beat me to it.

To the OP: does the book not provide any references for its questions?

[BodhiWes]

Thank you for your answer.

So, the information regarding the trop is at 44,000' and the SAT is -65C is negligible? In other words, why do you ignore this part of the question?

There are not any references to the questions. Thankfully, I have been getting a lot of help from this forum.

Thanks so much.

[455tt]

High level performance charts are typically laid out on the basis of ISA temperature deviation. So you work this out first, then look to the chart.

In this question the fact that the Tropopause is higher and colder than ISA is certainly interesting to note, but not essential to working out the ISA temperature deviation in terms of your actual in-flight altitude, so it would not be needed to answer the question.

Most ATPL question banks in Canada will have references. If you are studying from a source having only questions with no references this is not the ideal since you will be lacking the background theory. Have you considered obtaining a standard Canadian ATPL text, there are many good ones available and this would be helpful to your study.

[BodhiWes]

The book I'm using is from Aerocourse. I just passed the SARON studying from it and am now studying for the SAMRA. I don't know if I can say this book has really helped me but rather the hours of studying has been the determining factor. What book(s) do you recommend for the SAMRA? I have the Aerocourse study guide, and Aviation & Meteorology books which I am currently studying from but I have noticed other books from Sharpler Edge Solutions, and . 2020.

[455tt]

Aha - now everything makes sense.

AeroCourse is really 2 products, their questions workbook, plus their seminar. If you use their workbook only, without purchasing their seminar, then, if you want to know and understand the material, you must research the background subjects, using alternate sources, or asking for help here, since as you correctly note, there are no references provided, which can be time consuming.

The other sources you mention are fine for the SAMRA although the Sharper Edge will be cheaper (but less thorough).

Since you have already passed the SARON, you will probably be fine to carry on to the end as you have been doing. Source and review the TC ATPL Study and Reference Guide would be useful. And a good read through the TC AIM will also be helpful.

The RCAF Weather Manual is an outstanding reference for high level met theory on the SAMRA.

To do really well on the SAMRA, you need to "think outside of the box" and apply theory to practical scenarios.

Doing all of this extra work is more time consuming than question answer recognition, but you will be more knowledgeable in the end.

[BodhiWes]

Right on, thanks for the help. I really appreciate it.

[chematrix]

I'm study for my IATRA. Which books do you recommend me?
I'm using Canadian ATPL aero course book and I saw that question regarding ISA deviations.
I'd appreciate if you have any tips for my for the IATRA.

Thanks guys