Pressure pattern navigation/Bellamy's drift
 

I apologise to the Powers in the Towers if this is classed as cross posting, but I drew a deafening silence in Tech Log.

I have recently read an article on the above including the idiots guide and a formula for calculating drift based on barometric pressures. The article was fairly superficial and mentioned 'shortcomings' to this technique upon which it failed to elaborate.

I wonder of any of you clever fellows has any more in depth information or background to share on this subject. Perhaps there may be some of you old enough to have tried it for real ;)




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Hi CB.

I have a March 1993 copy of an African aviation magazine called Airnews, which contains an in-depth article by Barry Schiff on the subject. Hang on a bit longer, and if I can figure out how to work this scanner thingy here I'll e-mail it to you.

JJ

Struggling with your e-mail CB. Just confirm you have a space between Code and Blue, or is that an underscore?

I'd be interested in seeing that article too Jumbo Jockey. Would've shot off an E-mail but it wasn't listed in your profile.


Cheers,


Grade 3

P.S. my E-mail should be in my profile

Jumbo

Thanks for the attempt to email. I have contacted you on the email address you gave.

Code Blue, PPN was covered in Tech Log quite some time ago, just in case you haven't performed a search yet.

Used to do it on V bombers. The biggest problem is determination of the real height versus the altimeter height. We were blessed with a bombing computer and a very accurate Radar Altimeter. Thus we could accurately determine the Altimeter height error. At 27 ft = 1 mb you can determine the pressure gradient over a given distance. By using a geostrophic wind scale you can determine the wind and thence the drift. Can't remember the formula.

Good reference: AP3340 Handbook of Aviation Meteorology (1960). That covers the principles if not the method.

Thanks for the replies.
As suggested a search - when server loads permit :) yielded the following 2 threads:
www.pprune.org/ubb/NonCGI/Forum3/HTML/000151.html
www.pprune.org/ubb/NonCGI/Forum3/HTML/001257.html
of which the first is by far the more detailed. The original source ref for most of the detail is The Complete Air Navigator by AVM D C T Bennett.

With regard to altitude measurement, is GPS accurate enough to substitute for radar altimetry? The newer alts I gather only read up to 5000' whereas the in-flight procedures talk of alts up around 20000' - not that my narrow bodied 'light metal', will flying up there :).




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