View Full Version : NZ ATPL Met Question
Sqwark2000
4th Sep 2002, 08:22
Studying this today, had a look at a sample question, which went something like this.
"Over a large body of water (ocean) the wind at 4000' is 260/30, what will the wind velocity likely be immediately above the water (surface wind)"
Now ****** me if I couldn't find anything to do with this type of question. The question doesn't mention time of day, so can't be about backing/veering with sunrise/set etc, and I have seen any sort of formula to calculate such a thing.
The four multiguess answers were half n half backing and veering with a small increase /decrease in speed and the other half with a largish speed change.
Can anyone help?
PS Does anyone have any other Sample papers for ATPL Met other than the one avaialble from ASL? Would appreciate your help.
Cheers
S2K:confused:
cracked pot
4th Sep 2002, 08:38
S2K,
I think you will find the answer is 270/20 (In the southern hemisphere). Veered by 10° and slowed to 2/3. Due to coriolis force being reduced by surface friction. Good luck with the study, I'm doing Aus met in about 2 weeks.
cracked
Split Flap
4th Sep 2002, 09:26
I think I remember some thing like that when I was studying it.
I think cracked pot has "cracked it"
NoseGear
5th Sep 2002, 04:47
Cracked it is right, due to the friction of the wind over a paticular type of surface the formula goes like this.
Over land (more friction) the speed is 1/3 of freestream speed and the wind backs by 30 degrees. (230/10)
Over water (less friction) the speed is 2/3 of freestream and the wind only backs by 10 degrees. (250/20)
Think Surface BACK to altitude.
Hope this helps
Nosey
In the N Hemisphere the wind "Backs and Slacks" as you get lower and in the evenings (all else being equal). in the S hemisphere it "Veers and Slacks"............etc
cracked pot
5th Sep 2002, 06:39
Nosey, you are right if you are in the Northern Hemisphere.
Over land (more friction) the speed is 1/3 of freestream speed and the wind backs by 30 degrees. (230/10)
Over water (less friction) the speed is 2/3 of freestream and the wind only backs by 10 degrees. (250/20)
In the southern hemisphere the surface wind is VEERED with respet to the gradient wind (ie changes direction in a clockwise sense).
Therefore over land in the southern hemisphere direction would be 290°, over water 270°.
The thepry behind this is best explained with a diagram - message me if you want one and I'll scan a copy.
cracked
NoseGear
7th Sep 2002, 04:18
Thanks for the offer cp, but I've got all the ATPL subjects.
I zigged when I should have zagged then, but the theory is correct. It is surface BACK to altitude when starting on the ground, so veering is the same effect when going from altitude to surface as Hobo mentioned. Of course the answer is 290 and 270 degrees. At least I got the speed right?
:o :o
Nosey:D
ZK-DAN
9th Sep 2002, 04:43
Afternoon!
I've just finished all my CPL/BGT and IFR subjects and am about to get into the flying. I'm quite keen to get in to the (NZ)ATPL's fairly quickly. The flying school I'm at (Nelson Aviation College) recommends PPSC for ATPL theory. Has anyone out there used them before and if so do you want to sell the notes to a struggling trainee pilot (me!)? Any other recommendations for the ATPL's?
Also anyone keen to get rid of a pre-loved headset? I have a mate on the same course as me who needs one.
Cheers
DAn :D
The moral of the story is that if you are ditching in the ocean without a GPS you'll be so glad you studied Met. to this degree of knowledge.