I recently failed nav and am resitting on Wednesday. I got about 4 fuel calcs and got most of them wrong as I wasn’t sure whether to apply the Caap rules such as charter 45 mins and 10 percent or the half an hour for private. In one question, it didn’t specify charter or private so I didn’t use any variable or fixed reserves, however some questions would say you have a private flight but didn’t say the reserve in the question, so I wasn’t sure whether to use it or not. Do you only use what it specifies or if it says private/charter without specifying do you just use the caap rules? Thanks.

Also got confused with a question, it was
A 20s 135e
B 35s 135e

What would the difference in lmt be if time at A is 0450
Thanks so much in advance

Welcome to the world of CASA examinations. Now, we can't see the actual questions you faced so we have to fill in the gaps a bit from your report.

(a) Reserves.

Keep in mind that you are sitting the CPL exam, so there will be a presumption that you are looking at commercial operations. That is to say, if the question doesn't explicitly say what the conditions are, then you should be presuming that the CAAP requirements for CHTR will apply. Be decisive in your approach to the question's solution. Pilots can't afford to be wishy washy in their decision making processes.

(b) BOD

Have a sit back and consider what the question is asking.

Normally we enter the AIP BOD/EOD charts at the date for the latitude and then read off the LMT value.

In this case, you don't have the date, but the examiner has given you the answer anyway so you don't need the date. So, enter at an LMT of 0450 and run across to 20S. As you are intersecting the curve, you will have two possible answers for the date - around 12 Nov or 15 Dec - neither of which dates is important for the answer.

Next, from the intersections with the curve, run down to 35S and read off, respectively around 0419 and 0410. These numbers give you differences between the latitudes of 31 and 40 minutes.

As to which answer the question is after, we would need some more information from you regarding what the question actually said.

Hang in there - it will get easier the more work you do.

Read through Bob's books, again, run the test questions, front the exam and get back on the horse !

Hi, thanks so much for replying. Ok that’s good to know about fuel, if no flight type is specified, I’ll use charter 10% and 45 mins fixed.

That’s all the question said I’m pretty sure. From memory:

The time in LMT at A is 0450, what will the time in LMT be at B is A is 20S 135E and B is 35S 135E. I think it may have also been on a date somewhere in December because this influenced my decision (this was also a type in).

In the exam I put 0550 as I thought that the 15 degree difference would equal an hour later. However this was wrong. I then thought the answer would be 0450 as I read somewhere that if they’re on the same meridian, it should be the same LMT (I’m fully aware this could be wrong, as evidenced I’m extremely confused about this question).

I hadn’t even considered the way you worked it out. I’ll give that a shot.

Thanks, fingers crossed I can get it next time, this is my last CASA and first fail so at least the others are fine haha.

I think it may have also been on a date somewhere in December

That resolves which date is the one the examiner is after and your answer follows.

In the exam I put 0550 as I thought that the 15 degree difference would equal an hour later

That is confusing longitude (time differences as the Earth ambles around its daily journey) and latitude.

I then thought the answer would be 0450 as I read somewhere that if they’re on the same meridian

The question told you they were on the same meridian (135E)

it should be the same LMT

No, can't be that as the sun BOD/EOD times are very strongly latitude dependent as the AIP graphs show. You did look up the AIP graphs, I trust ?

This suggests that you are confusing the significance of latitude and longitude. Suggest you have a good look through Bob's notes on time and daylight calculations.

We will all be looking forward to hearing some good news later on in the week ....

I just re-read your original question and I may have headed off before on a wild goose chase. I note that you didn't mention BOD and I jumped in and ran off assuming that we were talking BOD (what's the old story about never assume because it often means making an ass of u and me ?

I am rather certain that the question was intended to be a BOD question. However, if there was no mention of BOD, then the question MAY have been an ultra simple waster of time question in that all it was looking for was for you to recognise that the clock time associated with earth rotation is the same on all points of a meridian. If this were the case, then the answer would be the same LMT for all latitudes. I can't see that being the case but I should note the possibility, having now noted my missing no reference to BOD in your stating of the question.

I think that’s correct, I remember classmates saying that they’d put 0450 as an answer and thought they’d gotten it right. I just couldn’t understand it but after reading your reply I think that confirms it’s the answer. I think I understand this now as like you said the LMT on a meridian would be the same at any point on that meridian. Say then for example would this mean that if the question were to instead change in longitude and not latitude and say
A - 20s 135e (it’s 0450)
B - 20s 150e what’s the time in LMT

Then you would use 15 degrees (60 minutes)
So the time at B would be 0550 as it’s an hour ahead/further east?

Sorry to pester with simple annoying questions, but I really want to nail my understanding of time as I screwed up last exam. I really appreciate your time in helping.

So long as you are thinking and pondering about things, you'll do just fine.

Ref your last posed question, indeed, latitude becomes irrelevant and the LMT depends on longitude. If the dLong is whatever, then you simply run the 15 deg/hour relationship.

I'm still amazed that an exam question would be wasted on something so simple and fundamental but there you go.

So long as you are up to speed with the BOD/EOD charts as well ....

And, keep in mind, there are no silly questions when you are learning something .. but it is a bit silly not to ask the question if you don't understand what's going on and what's behind the story.

So, mea culpa maxima for the earlier haring off on the wild goose chase ....

I know, fingers crossed I get that question again haha, everyone seemed to get that one or at least very similar. Yep BOD EOD charts should be fine. Fair enough, thanks so much again, will let you know how the exam goes Wednesday haha. And no that’s all good, I really appreciate the help

Passed with 95%!! Thanks so much for your help again .

Well done ! I'm sure everyone is happy for your successful result.

John