Posted: Sat Jul 25, 2009 10:06 pm Post subject: Quadrantal rule
Question: you are in level flight ( outside controlled airspace) on a heading of 095. Due to wind your mag track is 087. The QNH is 994mbs. If you wish to comply with the quadrantal rule, you should fly at:
A an indicated 5000ft with 1013 set
B an indicated 5500ft with 1013 set
C an indicated 3000ft with 1013 set
D an indicated 3500ft with 994 set
I know that for a mag track of 087 is less than 090 so it has to be an odd FL and I also know that you must fly above the transistion level with 1013mb set on the altimeter.So that leaves A and C. I know also that 1mb =30ft more or less but I dont know if I should use the 994mb to work out the FL or the 1013mb. Please help.
Joined: Jul 20, 2004 Posts: 3702 Location: Birmingham, UK
Posted: Sat Jul 25, 2009 10:33 pm Post subject:
You are on the right track with ODDs as the QR is based on magnetic track so as you say this rules out B and D... but always draw a little picture to visualise this next bit...
The significance of the QNH being 994 is that this would mean a 570' difference between sea level pressure and the 1013 datum, therefore if you are flying along at 3,000' with the QNH set and you change your altimeter to 1013, it is now going to indicate 3,570' (you haven't moved it's just the indication that is different).
Therefore "today", FL30 is not available, and neither is FL35. So the first available FL would be FL40, and that's no good because it's an even one. So what do you reckon the answer is?
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