Tstorm avoidance

Thanks to all of you for sharing your experience. I have just
recently installed a Stormscope but don't have enough experience using
it yet to know how much to trust it. A couple of times I have flown
with Tstorm activity within range, the azimuth appears off by as much
as 30 degrees - plan to bring it in next week to be checked.

Thanks to all of you for sharing your experience. I do have a new
stormscope installed but haven't yet used it enough to know to what
extent I can trust it. A couple of recent flights when Tstorms were
within range show a possible 30 degree azimuth error (compared with
where I thought the activity was via radar before takeoff), so I plan
to bring it back to the shop next week.

Tom Sixkiller ) wrote:

"Michael" wrote in message
om...

Face it - if you're going to fly IMC when there are T-storms around,
you need some sort of weather avoidance gear. Relying on ATC is not a
realistic option.

It's not an option PERIOD.

HUH? "Not a realistic option" "not an option PERIOD" ???

What am I missing that I interpret those two phrases as more similar than
different?

I shudder to think Michael is in the same skies as myself the rest of us.

I do not understand how you could judge someone's abilities based on your
subtle differences in interpretation.

To me, newsgroup proclamations such as yours speak more about your ego than
anything else.


--
Peter












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"Nathan Young" wrote in message
...
On Wed, 2 Jun 2004 22:52:16 -0700, "Tom Sixkiller"
wrote:


"Michael" wrote in message
. com...

Face it - if you're going to fly IMC when there are T-storms around,
you need some sort of weather avoidance gear. Relying on ATC is not a
realistic option.

It's not an option PERIOD.

I shudder to think Michael is in the same skies as myself the rest of us.

Why? Michael flies a Twin Comanche equipped with Stormscope. Seems
like a pretty capable setup for dodging tstorms.

Equipment is neither knowledge, nor judgment.

Re-read his original and how he interprets how ATC handles such requests.

"Peter R." wrote in message
...
Tom Sixkiller ) wrote:

"Michael" wrote in message
om...

Face it - if you're going to fly IMC when there are T-storms around,
you need some sort of weather avoidance gear. Relying on ATC is not a
realistic option.

It's not an option PERIOD.

HUH? "Not a realistic option" "not an option PERIOD" ???

What am I missing that I interpret those two phrases as more similar than
different?

I shudder to think Michael is in the same skies as myself the rest of
us.

I do not understand how you could judge someone's abilities based on your
subtle differences in interpretation.

To me, newsgroup proclamations such as yours speak more about your ego
than
anything else.

It speaks of what Michael has written in the past, plus his interpretation
of the ATC process.

Re-read his original.

Tom Sixkiller ) wrote:

It speaks of what Michael has written in the past, plus his interpretation
of the ATC process.

Re-read his original.

I did and I just don't see what you see. In fact, his interpretation of
ATC during t-storms pretty much coincides with my IFR experiences in the
northeast US.

In his original post in this thread, what *specific advice* rubs your fur
the wrong way? Show me what I am missing.

I have been reading these groups for the last three years or so and
during that time I have concluded that I would pay top dollar for some of
Michael's time as an instrument instructor. Too bad I don't live closer to
his home airport.

Experience is the best teacher and to me his posts continually demonstrate
that he has quality instrument experience.


--
Peter












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(PaulH) wrote
Thanks to all of you for sharing your experience. I do have a new
stormscope installed but haven't yet used it enough to know to what
extent I can trust it. A couple of recent flights when Tstorms were
within range show a possible 30 degree azimuth error (compared with
where I thought the activity was via radar before takeoff), so I plan
to bring it back to the shop next week.

Actually, you can do a decent job of checking azimuth error using a
spark plug tester, or really any small unshielded engine with
electronic ignition. Put it about 5 feet from the antenna, and run
it. The sparks will show up.

An electric power saw or power drill can also work, but it will need
to be closer - say 2 ft - which limits the accuracy of your
determination. Still, a 30 degree azimuth error is pretty obvious.

Keep in mind that the antenna is mounted to the fuselage, and thus the
azimuth information you get is relative to your heading, not your
track. This can be a significant difference in a slow airplane,
though 30 degrees of crab would be very unusual.

Despite what you have been told by the less than knowledgeable, the
Stormscope can usually be used to estimate range as well as azimuth,
though not so accurately as RADAR.

First off, it is incorrect to say that the Stormscope (or competing
brand - my experience is that the Strikefinder is so similar as to
make no difference in operation) looks simply at intensity. There is
more to it. It also looks at spectral spread using digital signal
processing. I won't go into the physics of it unless someone insists,
but the general principle is that a strong distant storm shows up as a
longer duration (broader) peak than a close weak one, ON AVERAGE.
Thus if you fly a constant heading and let the dots collect, the
average position of the dots is a fair estimate of range. Any
individual dot is suspect.

Since you probably don't care about stuff over 100 miles away (that
weather will likely change by the time you get there) you should only
be using the 200 mile range (if your device even has it - some don't)
as a general indicator that something is out there. Turn to a less
sensitive range (50 or 100 miles) for avoidance. This rejects the
weakest peaks out of hand, and the stronger the peaks are the better
the range estimate.

In any case, you need only use that method for activity at your 12
o'clock. For stuff off to the side, you can do a little math. You
might recall those wingtip bearing change problems from your
instrument written. Nobody actually uses that method to establish
position anymore, but it's actually quite useful for Stormscope
interpretation.

Let's say you've been watching a cell (which shows up as strikes along
a radial line) and in the time you've been watching it (say 10
minutes), it's gone from being at your 2 o'clock to your 2:30 o'clock.
That's 15 degrees in 10 minutes, or 1.5 degrees a minute. Now, let's
say you're cruising 90 kts - that's about 1.5 nm a minute. So at what
distance is 1 degree of bearing change equal to a nautical mile?
Approximately 60 nm. So that cell is about 60 nm away (that number is
about as accurate as your estimate of time, speed, and angular drift),
and you can accept that turn of 90 degrees to your right for the next
10 minutes with no worries. This is really all basic geometry.

Now all of this goes out the window when you're dealing with lines
rather than individual cells. As a general rule, spherics is not a
way to penetrate lines - it is a way to avoid scattered cells.
However, if you know something of the geometry of the lines and
clusters you are dealing with (maybe you looked at Nexrad before
takeoff or have it in the cockpit) you can often get a good enough
picture to slip between lines and/or clusters.

Michael

Michael wrote:

(PaulH) wrote

Thanks to all of you for sharing your experience. I do have a new
stormscope installed but haven't yet used it enough to know to what
extent I can trust it. A couple of recent flights when Tstorms were
within range show a possible 30 degree azimuth error (compared with
where I thought the activity was via radar before takeoff), so I plan
to bring it back to the shop next week.


Actually, you can do a decent job of checking azimuth error using a
spark plug tester, or really any small unshielded engine with
electronic ignition. Put it about 5 feet from the antenna, and run
it. The sparks will show up.

An electric power saw or power drill can also work, but it will need
to be closer - say 2 ft - which limits the accuracy of your
determination. Still, a 30 degree azimuth error is pretty obvious.

Keep in mind that the antenna is mounted to the fuselage, and thus the
azimuth information you get is relative to your heading, not your
track. This can be a significant difference in a slow airplane,
though 30 degrees of crab would be very unusual.

Despite what you have been told by the less than knowledgeable, the
Stormscope can usually be used to estimate range as well as azimuth,
though not so accurately as RADAR.

First off, it is incorrect to say that the Stormscope (or competing
brand - my experience is that the Strikefinder is so similar as to
make no difference in operation) looks simply at intensity. There is
more to it. It also looks at spectral spread using digital signal
processing. I won't go into the physics of it unless someone insists,
but the general principle is that a strong distant storm shows up as a
longer duration (broader) peak than a close weak one, ON AVERAGE.

I insist.

Matt

Sometimes ATC can go too far to the other extreme and vector you around
even the smallest rain showers. Just the other day we were flying looking
for some actual IMC conditions. There were pockets of rain (level 1 and
2), and ATC kept vectoring us around it.



"Dan Luke" wrote in news:10bsid5r2ecpg78
@news.supernews.com:

"PaulH" wrote:
I have a fairly new IFR rating and am wondering how
much help to expect from ATC on Tstorm avoidance.

It is not something you can rely upon. Their equipment is not designed
for it and it and individual controllers vary widely in their ability
and inclination to help you. Be especially wary in or near Class B
airspace - they have a lot of aircraft to separate and your t'storm
problems may be way down on their priority list.

Will they suggest re-routing or do you have to request
it based on visual, FSS, or stormscope location?

Get some weather display gear in your airplane and *tell* ATC where you
need to go. If you are going to fly IFR when there are many CBs about,
this is a must.

The best thunderstorm avoidance tool is see-and-avoid, but if you can't
see them with your eyes because you're in IMC, you'd better have a
gizmo
that can see them for you.

Matt Whiting wrote:
It also looks at spectral spread using digital signal
processing. I won't go into the physics of it unless someone insists,
but the general principle is that a strong distant storm shows up as a
longer duration (broader) peak than a close weak one, ON AVERAGE.

I insist.

I'll take a shot at it. A lighting strike is essentially an
instantaneous electromagnetic pulse. What a mathematician would call a
"delta function". As such, it is composed of a wide spectrum of
frequencies (perhaps it's better to think of it as wavelengths).

Different wavelengths travel at different speeds. This is why, for
example, white light is broken up into a spectrum by a prism.

Here's an analogy which may help explain what's going on. Let's say you
have 10 cars starting out from the same spot, but each going at
different speeds (60, 61, 62, ... up to 69 MPH). If you stand right at
that spot, you see them all pass you at the same time. If you stand a
mile away, the fastest one will pass you first, then the next fastest,
and so on. They have spread out. If you stand 2 miles away, they will
have spread out even more by the time they get past you.

This is what's happening with a lightning strike. Right at the strike
point, you've got all these different wavelengths of electromagnetic
energy syncronized into one big spike. A mile away, the shorter
wavelengths have gotten to you a little before the longer wavelengths
(or is it the other way around?). Two miles away, the spread is even
greater. The further you go away from the source, the more the various
wavelengths have spread out, just like the cars moving at different
speeds. This is called spectral dispersion.

In the acoustic world, this is why a nearby lightning strike has a
thunder clap that sounds like one big "zzzaappp", while further away it
sounds like a rumble that goes on for a while.

So, the theory is that if you look at the width (in time) of a pulse and
compare it to its strength, you should get some idea of how much
spectral dispersion it has undergone, and thus be able to estimate how
far away it came from. It's not very precise, but it's good enough for
a strike finder.

To give any better explanation would require me to exercise neural
pathways which have lain dormant for many years, and are probably best
left that way.