Uh? Where does it say the altimeter is set to zero?

I just ran the question through my E6B and it came up with the answer that I gave.

The question does not ask what the altimeter would display it asks the pressure altitude. In which case I am pretty sure that both the question and my answer add up....

What does QFE mean?

I think you need to read the question.

bose-x, I did!

The question as stated is 'what is the pressure altitude at an aerodrome where the QFE is 992mb.' The only possible answer (at 30ft per mb) is 630ft.

I just put the question through my E6B on my iPhone and the ASA CX2 pathfinder and the answer came up as 1598ft.

So one of us is not reading the question correctly.....

The question:

An aerodrome elevation is 968ft and the QFE is 992mb, what is the aerodrome pressure altitude?

A 1598ft
B 338ft
C 720ft
D 1270ft

Or one of us doesn't really understand altimetry! ;)

Clearly, which also apparently means none of the software developers who have written the software I have plugged it into have an understanding either.....

Let's try phrasing the question slightly differently.

If the outside air pressure is 992mb, how high are we above 1013mb?

Your right bose-x, its much easier if you draw it out as a diagram..

http://img255.imageshack.us/img255/9...gramap1.th.jpg


This looks right to me.. maybe an easier way to view it?

Yep, looks right to me. Perhaps my old fashioned view of Altimetry as opposed to Islander2's works?

bose-x, I'll give you a clue.

Your E6B and CX2 are suffering from garbage in == garbage out!

You are misreading aerodrome QFE as aerodrome QNH.

As you wish mate. My E6B has to 2 entries for a pressure altitude question.

Pressure - Pressure is 992
Altitude - 968ft

My simple understanding is that if you are 968 ft and the pressure at 968 ft is 992 if you add 21mb to that then the pressure altitude is 1598 ft. You have added 630 feet by taking it to 1013 which gives you the pressure altitude. Pressure altitude being a common datum rather than QNH.

The question does not say anything about an altimeter it just asks what the pressure altitude is based on the figures given.

I just plugged in the 2 figures from the question and out popped an answer of 1598ft which was the same as my original old fashioned calculation and as answer A on the quiz.

I clearly do not understand how you are working it out. But please feel free to edify us.

I thought I had!

All you need to do is answer my rephrasing of the question:
... and then explain why you think that's a different question from the one posed.

I say again, your answer is based on the the 992mb pressure being at sea level ... whereas the question says that it is the pressure at aerodrome level.

You have lost me completely.....

Ah well, I'll bail out then. It only remains for me to wish Dave luck in his exams ... you can still pass even if you get the altimetry questions wrong!

I understand it like this.


Your stood at an aerodrome which is 968ft above mean sea level. You have an altimeter in your hand. In order for it to read 0 then you must set 992mb.
Now, the question is asking for the aerodrome pressure altitude.

"pressure altitude is the indicated altitude when the altimeter is set to an agreed baseline pressure setting" In our case, this is 1013mb.

So, were stood at the aerodrome and it wants the aerodrome pressure altitude. So to set 1013 from 992 we need to go up 21mb. 21mb at 30ft per second is 630ft.

Now are we to believe because we have been given the QFE the altitude is 0, well yes.. Hmm interesting, whilst typing this out i actually understand what Islander is talking about...

How the hell does PPL quiz get 338mb? That wouldn't be pressure altitude, that would be mean sea level altitude right?

Explain why?

It wants the pressure altitude at the aerodrome.

So it wants the altitude when you set the altimeter from QFE of 992mb to 1013mb..

Dave, I'm heartened, you've got it!

Their answer of 338ft is a nonsense. That is actually the height of the 1013mb pressure level above MSL (QNH is 1024.27mb), which is a meaningless number.