PPL Confuser Discrepancy with AFE

[skyhighbird]

Guys,

I was told by a few 'helpful' people to ask this question here (so please dont have a go at me for posting this twice. So hopefully you can help guys:

Guys,

A while back I wrote a post regarding how the AFE (CAA Lasors recommended) practice test was nothing like the questions in the Confuser. But the confuser is as close to the real thing as possible. Laughable.

Anyway, that was for Air Law and I am happy to say I passed it. NOw I am doing Meteorology anf lo and behold, I see another discrepancy - not just in the way they ask the questions but the answer. So here is the example:

Q23

At 1400z, the surface wind was 22025kt. The likely Wind velocity at 2000ft agl would be:

a)26040
b)24035
c)22020
d)23030

I answered A. Because according to Pratt's AFE book, wind veers 30' and windspeed 50%.

So 220+30=250. And 25kt+50% = 37.5kt.

So now we have a problem. The answer (according to the assumptions in AFE) is slap bang in the middle of answer A)26040 and B)24035. So I rounded up.

However the answer is B. Not because of rounding down but becasue the assumption is that wind veers 25' giving a direction of 245'.

So naturally the Confuser answer should be B) 24035.

So guys. What should I do? Should I go with the 25' assumption or keep with Pratt's 30' assumption? Or should I just chuck away all my PPL books that cost me around a hundred quid and just learn the Confuser because the AFE books give "wrong" information?

[Keith.Williams.]

The AFE statement represents the "conventional wisdom" on this matter.

The author of the PPL confuser probably constructed his explanation to match the CAA answer to the question.

But the question has since been amended.

In its current form neither the 30 degrees (AFE) nor the 25 degrees (PPL CONFUSER) nor the 50% speed increase will get you exactly the CAA answer.

But they will all get you an answer that is closer to the CAA answer than to any of the other options.

Looking further ahead, don't expect any book to be 100% correct. They won't be.

[Gertrude the Wombat]

In real life of course this is b*ll*cks.

In real life the wind changes direction "a bit" and changes speed "a bit".

Plus, you know what the wind is at 2000' because you looked up the forecast before you took off, didn't you.

So in reality you're working the calculation the other way, from the pretty good forecast to work out what it's going to be on the ground, to decide whether and how to land.

If conditions are that marginal that you need a more accurate estimate than the above then you're maybe cutting it too fine - you may not wish to attempt to land there, you may prefer to divert to somewhere with one or more of:

(a) someone on the ground with a radio who will tell you what the surface wind is (and remember you can ask for it any time, you don't need to wait for them to tell you after you've called "final", for example on approaching an airfield you can ask for the surface wind in order to help decide which runway to ask for)

(b) a longer runway

(c) a runway more into wind.

[LH2]

Well, Gertrude has beat me to it. I obviously agree with what he says and therefore the answer is e) Any and, on a bad day, all of the above.

The bloke writing the questions should really get a life.

[White Otter]

Something I've noticed is that in the AFE Met book it says the SALR is 1.5 degree per thousand feet but I've seen elsewhere its 1.8 degrees. Which one is it?

And one more thing in aircraft general it mentions the turn coordinator (page 124 if anybody is looking) and says "the instrument face is normally vague about what indication represents a Rate One turn, unfortunately it is almost certainly not when the model aircraft's wing is on the left or right mark". Now I've seen the exact opposite and my instructor has confirmed that the mark is a Rate One turn. Is it? :ugh:

For reference if its difficult to understand what I'm talking about with the turn coordinator heres the wiki link showing a Rate One turn (or is it???):
link (http://en.wikipedia.org/wiki/Turn_coordinator)

[Gertrude the Wombat]

(or is it???)
Hope so! - that's what my instructors have been telling me for the last umpteen hours and that's how I propose to use the instrument on my IMCR test!

[FREDAcheck]

Plus, you know what the wind is at 2000' because you looked up the forecast before you took off, didn't you.I'm sure that was tongue in cheek, but just to be sure, the F214 spot wind forecast of up to 9 hours earlier won't be terribly accurate either, of course. But if the spot wind forecast at 2000 feet is consistent with the surface wind (i.e. the wind at height is a bit to the right and a bit faster) then it gives some confidence in the area forecasts.

[Gertrude the Wombat]

the F214 spot wind forecast of up to 9 hours earlier won't be terribly accurate either
It's usually not bad. It's sometimes spot on - use it to fly dead reckoning, then fail to spot the next check point because it's immediately under the aircraft, for example.
(i.e. the wind at height is a bit to the right and a bit faster)
Yes indeed. "A bit" was precisely my point!

[skyhighbird]

Guys,

thank you for your replies however it still didn't clear up the discrepancy I was asking about.

In the CAA exam - what do I use? Do I use 30 degrees or this mysterious 25 degrees?

YOu only have to get 5 questions wrong to fail in the Met exam so it be a shame to get one wrong becasue it is out of your hands?

Is the general consensus that the confuser is wrong and that 30 should have been used?

I'm actually quite worried.

Kieth Williams - I didn't quite understand by what you meant. Yes both do get you near the right answer. But in this particular case, using 25 degrees or 30 degrees gets you to 2 possible answers. So in exam conditions, what do I do in this case? Pray!

[S-Works]

As the confuser questions are based on CAA style rather than actual CAA questions I would not work yourself up to much about it.

Both of the methods yo describe are rule of thumbs as it is not an exact science.

[Whopity]

my instructor has confirmed that the mark is a Rate One turn. Is it?The turn coordinator only indicates a Rate 1 turn if the aircraft is in balance; so unless the ball is in the middle its not a Rate 1 turn. If you understand how a Turn Coordinator works you will know why.

[Fark'n'ell]

The bloke writing the questions should really get a life.

He should be hung, drawn and quartered.
Where I live you can get 360/15 on the ground and 230/20 at 2000. Have'nt these dickheads who write the questions not heard of a sea breeze.

[Keith.Williams.]

Skyhighbird.

As I said in my previous post, neither of the methods will get exactly the correct answer in the real question. But they will both get you an answer that will enable you to select the correct answer (because it will be the closest one to your answer).


Fark'n'ell.

I think that you will find that "the dickheads" have heard of sea breezes. That is why the real question specifies an inland airfiled at 1400.

[Gertrude the Wombat]

YOu only have to get 5 questions wrong to fail in the Met exam so it be a shame to get one wrong becasue it is out of your hands?
I'm afraid that the allowance of questions that you can get wrong will indeed be at least partially used up by b*ll*cks of this sort.

Personally I aim at getting every question right, then I pass the exam because the number of b*ll*cks questions is actually sufficiently small that it doesn't use up your entire allowance.

[skyhighbird]

Keith,

Thnk you for your reply but I'm afraid I will have to annoy you once more.

In this specific example I gave - using the 2 DIFFERENT asssumptions does not give you the right answer (you are correct) but it gets you close to the 2 different answers dependant on what assumption you used!

Using Pratts 30 degrees gets you close to answer A

Using Confuser's 25 degrees gets you close to answer B

And B is the correct answer in the Confuser.

So if I get the same type of question again and 2 possible answers come about using either 25 degrees or 30 degrees what should I do!

I agree with the wombat - always aim for 100%.

Sorry keith for badgering you again for info.

I hope the ATPLs are not like this.

[Keith.Williams.]

But the question that you have quoted isn't the real question.

If and when you see the real question either method will get you a number that is closer to the CAA answer than it is to any of the other options.

If you plan to move on to the ATPL exams then all I can say is "You aint seen nothing yet". If you get exctly the correct answer in General Nav you should be seriously worried. You have probably done so by accident.

[skyhighbird]

"If and when you see the real question either method will get you a number that is closer to the CAA answer than it is to any of the other options"

NowI get ya!!! Thanks Keith.

Just that in the last 2 years since I have been on ppune, the confuser is considered gospel. So when I come upon something like this, I start to question my own ability!