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richatom
6th Feb 2008, 10:36
Can anybody explain how a passive stormscope determines the distance to a lightning cell?

hellsbrink
6th Feb 2008, 11:12
http://www.seaerospace.com/bfg/wx1000pg.pdf


Oi fink it makes sense....

Miraz
6th Feb 2008, 11:56
Unreliably...:hmm:

hellsbrink
6th Feb 2008, 12:27
What is truly reliable nowadays?

Down Three Greens
6th Feb 2008, 13:05
....measures the time between the flash and the bang? :E

Sorry couldn't resist!

Pugilistic Animus
6th Feb 2008, 21:46
I heard that stormscope and other spherics systems work kind of like a souped up adf receiver with some fourier transform logic to pin point better----but the conservatism required with stormscope is higher than with wxr.


the old advantage [no longer really applies] was that it could be used on the ground to get a panoramic view of cell locations [ and lightning goes with TS's all the time] as opposed to heavy rain...the best for GA/corporate is to have both:ok:

galaxy flyer
6th Feb 2008, 22:09
We have them in our corporate planes, in 3 years, not amused. Unless a real boomer, doesn't correspond with the radar picture. Also, lots of lightning symbols where there is no weather, radar or out the windscreen.

GF

rkivel
15th Feb 2008, 01:02
It depends on the model The WX-7, 8, 9,10,11, &12 only measured the amplitude of the 50 Khz component of the lightning strike. With the WX-1000 the used not just amplitude but also 5 different parts of the 50 Khz like pulse rise time, pulse witdth etc with the more modern Stormscopes like The WX-950 and WX-500 they take measurements if at least 11 different frequencies. As the processors have become smaller and faster the technology has allowed a more accurate ranging.

bill_s
15th Feb 2008, 03:08
From what I read, the original Stormscope determined lightning az via ADF techniques, and dist by strength of the signal. Being that lightning strokes can vary over a huge range in strength, more refined methods are used in current equipment that claim to be independent of stroke strength. One patent, useful only in the air, measures the time difference between the direct path to the stroke and the path reflected from the earth. Simple geometry, but best over water and maybe problematical over mountains.

I wouldn't bet my life on this info, but if I saw a great concentration of strokes in a particular direction, I wouldn't want to be the first one to fly there.

Does anyone know of research into the distance accuracy of the various systems?

wiggy
15th Feb 2008, 12:31
If you are not a pilot it's not a dumb question - most, if not all large aircraft do indeed have weather radars, the scanner assembly sits inside the nose and there are displays on the flight deck. The more modern kit colour codes the display, Green returns on the screen means there's no big problem, probably just lots of moisture, might be a bit bumpy, way up to Red or even purple which is an area you really, really want to avoid by a large margin.

(edited to try to avoid confusion over who's question I was answering)

fullyspooled
15th Feb 2008, 12:55
I got the wrong end of the stick here - post removed.

fullyspooled
15th Feb 2008, 13:38
Wiggy, apologies. Your edit explains the reference to a dumb question, and the reason for the simplistic reply. Sorry.

wiggy
15th Feb 2008, 13:46
Sorry chaps- fullyspooled, I promise will write out 100 times
" I must remember to address my posts more carefully...":(

PK.... Glad we sorted that out and hope you are suitably enlightened on both the StormScope and Weather Radars....

Off for a lie down.

IO540
17th Feb 2008, 11:54
I fly behing a WX500 displaying on a KMD550 MFD.

The azimuth data appears accurate.

The range data appears overly conservative, often showing say 20nm when the bad stuff is at about 50nm.

I know of pilots who fly in IMC, with embedded CBs, and they find it good enough for that. I assume these pilots do not fly with passengers ;) But I can see this strategy works if you want to avoid flying into a really nasty active CB.

IRRenewal
17th Feb 2008, 12:46
Flew an A/C once with one of those things in it. Showed a cell 25 nm behind us. Funny thing was that it was there (right behind us) whichever heading we were on. It disappeared when we switched the anti-collision beacon off.

I personally don't rate them as the most useful bit of kit on board.

IO540
17th Feb 2008, 15:41
That was a bodged installation, IRRenewal.

The only odd effects I have seen are huge bands right across the screen caused by airliner radar taxiing in front of you, and the occassional single "strike" which appears in the middle of clear air.

Any consistent grouped returns have always been real seriously bad turbulence - the sort of stuff which will bang one's head on the ceiling.

It's not an expensive thing - of the order of a few Łk which is cheap on the scale of most avionics.