Why are TE probes so long?

[Duane Eisenbeiss]

"Mark James Boyd" > wrote in message
news:4095c4f4$1@darkstar...
> Why are these things so long? If they were 2" instead of
> a foot long would it really matter that much? Is the airflow
> really disturbed enough to make a difference?
>
> Mark Boyd
> Avenal, California, USA

Ans 1 - See Ans 3
Ans 2 - Yes
Ans 3 - Yes. It is a matter of the very small pressure change measured by
the TE versus the disturbed air.

Duane

[Mark James Boyd]

I pulled a swivelling tailwheel off a G-103 today and was (gratefully)
reminded to not hit the long TE probe when standing up.

Why are these things so long? If they were 2" instead of
a foot long would it really matter that much? Is the airflow
really disturbed enough to make a difference?

The pitot on many power planes is maybe 2-4" long.
What's the deal here?

Has anyone tried a shorter TE probe? What's the difference
in error? Can it be compensated?
--

------------+
Mark Boyd
Avenal, California, USA

[Mike Borgelt]

On 2 May 2004 21:05:08 -0800, (Mark James Boyd)
wrote:

>I pulled a swivelling tailwheel off a G-103 today and was (gratefully)
>reminded to not hit the long TE probe when standing up.
>
>Why are these things so long? If they were 2" instead of
>a foot long would it really matter that much? Is the airflow
>really disturbed enough to make a difference?
>
>The pitot on many power planes is maybe 2-4" long.
>What's the deal here?
>
>Has anyone tried a shorter TE probe? What's the difference
>in error? Can it be compensated?


You want to keep the probe out of the flow field around the fin/stab.
This flow can exaggerate pitch and slip changes and the LE of the tail
surfaces have stagnation points so small changes in slip and pitch
may cause small changes in pressure over small time periods which may
in fact be large rates of change of pressure and rate of chnage of
pressure is what varios measure.

While you are at it clean the bugs off the probe before flying -
everyone cleans the wing leading edges but how many clean the probe?

Mike Borgelt

[Hank Nixon]

(Mark James Boyd) wrote in message news:<4095c4f4$1@darkstar>...
> I pulled a swivelling tailwheel off a G-103 today and was (gratefully)
> reminded to not hit the long TE probe when standing up.
>
> Why are these things so long? If they were 2" instead of
> a foot long would it really matter that much? Is the airflow
> really disturbed enough to make a difference?
>
> The pitot on many power planes is maybe 2-4" long.
> What's the deal here?
>
> Has anyone tried a shorter TE probe? What's the difference
> in error? Can it be compensated?


Reply: There is a measurable pressure change which varies with speed
and angle of attack in front of every surface flowing through the air.
Experience has shown that TE sensors need to be at least 1/2 chord
length in front of the fin to avoid negative effects.
Easier to learn not to bend probe than try to make TE system work with
stubby probe.
Good Luck UH

[d b]

I'm sure somebody may correct me, but as I recall, the TE probe produces
a signal equal and opposite of the pitot (total pressure). Unless you have
separated flow, or flow inside the boundary layer, the total pressure doesn't
change anywhere around the plane. It would seem to me to be a case
where angular changes (due to deflected airflow) would be the cause
of the shift in the TE pressure. The shape and angle of the TE probe is
not as forgiving as the pitot end.



In article >,
wrote:
(Hank Nixon) wrote:
>
>>Experience has shown that TE sensors need to be at least 1/2 chord
>>length in front of the fin to avoid negative effects.
>
>In addition to the disturbance from the tail surfaces, there
>can be disturbances from the wing. You usually want your
>probe above an imaginary line connecting the leading edge of
>the horizontal stabilizer to the wing. Length (and turning
>the tip up) helps get the probe into that undisturbed air.
>Todd Pattist - "WH" Ventus C
>(Remove DONTSPAMME from address to email reply.)

[tango4]

TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
magnitude.

Ian

[d b]

Why is it, then, that you can calibrate a TE probe by driving down the road
with it sticking out of the window, hooked up backwards to an airspeed
indicator (static is pressure, TE is static port) and it reads the
same as a pitot probe with a normal hook up?



In article >, "tango4"
> wrote:
>TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
>magnitude.
>
>Ian
>
>

[Derrick Steed]

D B wrote:
>Why is it, then, that you can calibrate a TE probe by driving down the road
>with it sticking out of the window, hooked up backwards to an airspeed
>indicator (static is pressure, TE is static port) and it reads the
>same as a pitot probe with a normal hook up?



>In article , "tango4"
>wrote:
>>TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
>>magnitude.
>>
>>Ian
>>
>>

1. ASI has two connections: static and pitot (= total pressure = static + dynamic)

2. TE probe provides static - dynamic pressure

3. ASI measures difference between ptot (dynamic + static = total pressure) and static

4. connect TE probe to static on ASI, pitot on ASI to free air (= static pressure = ambient pressure inside your car

5. therefore ASI reads dynamic pressure (linearly proportional to airspeed below 0.3 M)

But, bear in mind that unless you hold you TE probe at least about 10 feet from you car the reading will be off quite a bit, and you should also worry about the ambient pressure inside the car. Not a good way to calibrate a TE probe. Even thought of investing in a wind tunnel?

Rgds,

Derrick.

[Hank Nixon]

"tango4" > wrote in message >...
> TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
> magnitude.
>
> Ian

Not So
Properly functioning TE probe is equal in magnitude to pitot and
opposite in sign.
In fact you could connect airspeed static to probe and airspeed
"pitot" to airfarme static and get the same reading as conventional
hookup. This is actually a fairly useful test tool.
UH

[Derrick Steed]

Hank Nixon wrote:
>>"tango4" wrote in message news:...
>> TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
>> magnitude.
>>
>> Ian
>
>Not So
>Properly functioning TE probe is equal in magnitude to pitot and
>opposite in sign.
>In fact you could connect airspeed static to probe and airspeed
>"pitot" to airfarme static and get the same reading as conventional
>hookup. This is actually a fairly useful test tool.
>UH

So, you are saying:

1. (TE pressure) = - (pitot pressure) yes?

But at the pitot the pressure = (static pressure) + (dynamic pressure head)

So according to your statement (TE pressure) = - [(static pressure) + (dynamic pressure head)]

OK, lets agree that the pressure sensed at the static port is (static pressure) = (ambient atmospheric pressure)

Then, connecting up an ASI in reverse:

(A) Pressure on static entry to ASI (connected to TE probe) = - [(static pressure) + (dynamic pressure head)]

(B) Pressure on pitot entry to ASI (connected to static vent) = (static pressure)

The ASI effectively subtracts the pressure on the static entry from the pressure on the pitot entry (normally this would result in it measuring the value of the dynamic pressure head which is proportional to airspeed - well, for us it is a fairly accurate measure of it)

So, we have on the ASI a reading proportional to (pressure on pitot entry) - (pressure on static entry)

Taking values from above this is
(pitot entry) - (static entry) = (B) - (A)
= (static pressure) - [(static pressure) + (dynamic pressure head)]
= - (dynamic pressure head)

This would probably damage your ASI if it was so.

Whereas, if the TE pressure = (static pressure) - (dynamic pressure head)
Then (pitot entry) - (static entry) = (static pressure) - [(static pressure) - (dynamic pressure head)]
= (dynamic pressure head)


Rgds,

Derrick.

[Robert Ehrlich]

d b wrote:
>
> I'm sure somebody may correct me, but as I recall, the TE probe produces
> a signal equal and opposite of the pitot (total pressure).

Not exactly, total pressure is static + dynamic, TE is static - dynamic.

[John Giddy]

Derrick Steed wrote:
> So, you are saying:
>
> 1. (TE pressure) = - (pitot pressure) yes?
>
> But at the pitot the pressure = (static pressure) + (dynamic
pressure
> head)
>
> So according to your statement (TE pressure) = - [(static pressure)
+
> (dynamic pressure head)]
>
> OK, lets agree that the pressure sensed at the static port is
(static
> pressure) = (ambient atmospheric pressure)
>
> Then, connecting up an ASI in reverse:
>
> (A) Pressure on static entry to ASI (connected to TE probe) = -
> [(static pressure) + (dynamic pressure head)]
>
> (B) Pressure on pitot entry to ASI (connected to static vent) =
> (static pressure)
>
> The ASI effectively subtracts the pressure on the static entry from
> the pressure on the pitot entry (normally this would result in it
> measuring the value of the dynamic pressure head which is
> proportional to airspeed - well, for us it is a fairly accurate
> measure of it)
>
> So, we have on the ASI a reading proportional to (pressure on pitot
> entry) - (pressure on static entry)
>
> Taking values from above this is
> (pitot entry) - (static entry) = (B) - (A)
> = (static pressure) - [(static pressure) + (dynamic pressure head)]
> = - (dynamic pressure head)

Should be: "=(static pressure) - [-(static pressure) - (dynamic
pressure head)]"
= 2(static pressure) + (dynamic pressure head)

Still the wrong result. I think, when people refer to TE probes
providing minus the pitot pressure, they are talking "gauge pressure"
not "absolute pressure"
i.e. the pressure difference from static, such as is measured by most
pressure gauges. (e.g. the gauge on your service station tyre
inflation device)
Cheers, John G.

[d b]

In article >, Robert Ehrlich > wrote:
>d b wrote:
>>
>> I'm sure somebody may correct me, but as I recall, the TE probe produces
>> a signal equal and opposite of the pitot (total pressure).
>
>Not exactly, total pressure is static + dynamic, TE is static - dynamic.


Let's put it this way. The indicator reads the difference in pressure between
the hole called P and the hole called S. When I hook the hole called P to a
pitot tube and the hole called S to a perfect static source, I get a number,
let's say 70.

Now I hook a TE probe to the hole called S and the perfect static source to
the hole called P. The indicator again reads 70. Obviously, the TE probe is
the exact opposite of the pitot tube.

It is agreed that the pitot is the total energy static + dynamic
The obvious conclusion is that the TE probe is - (static + dynamic)

It is NOT static - dynamic, it IS -(static+dynamic)

Kinda sucks, doesn't it?

[Craig Funston]

Yikes, my head hurts!

Static pressure is simply that. The static pressure of the ambient
air around you. A good aircraft static system should give you the
same value for any given ambient pressure (ie altitude) no matter how
fast your glider is going.

Dynamic pressure is the pressure due to velocity and it varies by the
square of the velocity (ie twice the velocity = four times the
pressure). The ASI measures the difference between the dynamic
(pitot) pressure and the static pressure to give velocity.

Keep in mind that the static pressure at the pitot and at the static
port are the same and cancel each other out in the equation (unless
like most of us you have a horrible static system).

The difference between the pressure at the TE probe and static
pressure should be the same as the dynamic pressure but of opposite
sign. Again static pressure at both locations is the same so it
cancels.

I have driven many miles with an automobile test rig consisting of a
pitot, a static and a TE probe connected to a pair of side by side
U-tube water manometers. The manometers share the same static and one
uses the pitot signal while the other uses the TE signal. A properly
calibrated TE probe will cause exactly the same pressure difference as
the pitot, just with the opposite sign. The mounting bracket for the
probes hung out way in front of the car to get clean air for the
testing. I must say it got quite a few stares.

In practice I usually build TE probes to overcompensate slightly to
make up for poor static systems. The probes are easy for the user to
tame down slightly and they can be tailored by the individual pilot to
match their preference and sailplane.

[Michael McNulty]

"Craig Funston" > wrote in message
om...
> Yikes, my head hurts!
<snip>

> Dynamic pressure is the pressure due to velocity and it varies by the
> square of the velocity (ie twice the velocity = four times the
> pressure). The ASI measures the difference between the dynamic
> (pitot) pressure and the static pressure to give velocity.
>

No. The ASI measures the dynamic pressure as the difference between the
total pressure and the static pressure. The pitot measures total pressure.

[John Giddy]

d b wrote:
> In article >, Robert Ehrlich
> > wrote:
>> d b wrote:
>>>
>>> I'm sure somebody may correct me, but as I recall, the TE probe
>>> produces a signal equal and opposite of the pitot (total
pressure).
>>
>> Not exactly, total pressure is static + dynamic, TE is static -
>> dynamic.
>
>
> Let's put it this way. The indicator reads the difference in
pressure
> between
> the hole called P and the hole called S. When I hook the hole called
> P to a
> pitot tube and the hole called S to a perfect static source, I get a
> number,
> let's say 70.
>
> Now I hook a TE probe to the hole called S and the perfect static
> source to
> the hole called P. The indicator again reads 70. Obviously, the TE
> probe is
> the exact opposite of the pitot tube.
>
> It is agreed that the pitot is the total energy static + dynamic
> The obvious conclusion is that the TE probe is - (static +
dynamic)
>
> It is NOT static - dynamic, it IS -(static+dynamic)
>
> Kinda sucks, doesn't it?

Yes it IS (static - dynamic). Go study your fluid dynamics again
Cheers, John G.

[d b]

Perhaps it isn't obvious. The airspeed indicator is a DELTA pressure guage.
It is not an absolute pressure guage. If the indicator reads the same delta
pressure, the two devices have to be producing the same delta pressure.
One sucking, the other blowing.


In article >, "John Giddy"
> wrote:
>d b wrote:
>> In article >, Robert Ehrlich
>> > wrote:
>>> d b wrote:
>>>>
>>>> I'm sure somebody may correct me, but as I recall, the TE probe
>>>> produces a signal equal and opposite of the pitot (total
>pressure).
>>>
>>> Not exactly, total pressure is static + dynamic, TE is static -
>>> dynamic.
>>
>>
>> Let's put it this way. The indicator reads the difference in
>pressure
>> between
>> the hole called P and the hole called S. When I hook the hole called
>> P to a
>> pitot tube and the hole called S to a perfect static source, I get a
>> number,
>> let's say 70.
>>
>> Now I hook a TE probe to the hole called S and the perfect static
>> source to
>> the hole called P. The indicator again reads 70. Obviously, the TE
>> probe is
>> the exact opposite of the pitot tube.
>>
>> It is agreed that the pitot is the total energy static + dynamic
>> The obvious conclusion is that the TE probe is - (static +
>dynamic)
>>
>> It is NOT static - dynamic, it IS -(static+dynamic)
>>
>> Kinda sucks, doesn't it?
>
>Yes it IS (static - dynamic). Go study your fluid dynamics again
>Cheers, John G.
>
>

[Robert Ehrlich]

d b wrote:
>
> In article >, Robert Ehrlich > wrote:
> >d b wrote:
> >>
> >> I'm sure somebody may correct me, but as I recall, the TE probe produces
> >> a signal equal and opposite of the pitot (total pressure).
> >
> >Not exactly, total pressure is static + dynamic, TE is static - dynamic.
>
> Let's put it this way. The indicator reads the difference in pressure between
> the hole called P and the hole called S. When I hook the hole called P to a
> pitot tube and the hole called S to a perfect static source, I get a number,
> let's say 70.
>
> Now I hook a TE probe to the hole called S and the perfect static to
> the hole called P. The indicator again reads 70. Obviously, the TE probe is
> the exact opposite of the pitot tube.
>
> It is agreed that the pitot is the total energy static + dynamic
> The obvious conclusion is that the TE probe is - (static + dynamic)
>
> It is NOT static - dynamic, it IS -(static+dynamic)
>
> Kinda sucks, doesn't it?

No, the reading of your indicator is P - S, converted into whatever speed
unit you like. If P is connected to a pitot tube and S to a perfect static
source, P - S is total - static = (static + dynamic) - dynamic) = dynamic).
When P is connected to a perfect static source and S to a TE probe,
P -S = static - (static - dynamic) = dynamic again, so the reading are the
same.

[Eggert Ehmke]

(Craig Funston) schrieb:

>I have driven many miles with an automobile test rig consisting of a
>pitot, a static and a TE probe connected to a pair of side by side
>U-tube water manometers. The manometers share the same static and one
>uses the pitot signal while the other uses the TE signal. A properly
>calibrated TE probe will cause exactly the same pressure difference as
>the pitot, just with the opposite sign.

I understand we need the TE probe to generate the difference
static-dynamic because classical instruments are pure mechanical and
need the TE information to compensate the vario. But given electronic
devices/computers, do we really need the TE probe at all? The
information is given, when static and dynamic pressure are known. The
rest can be calculated. Wrong?
Eggert

[Derrick Steed]

>>I have driven many miles with an automobile test rig consisting of a
>>pitot, a static and a TE probe connected to a pair of side by side
>>U-tube water manometers. The manometers share the same static and one
>>uses the pitot signal while the other uses the TE signal. A properly
>>calibrated TE probe will cause exactly the same pressure difference as
>>the pitot, just with the opposite sign.
>
>I understand we need the TE probe to generate the difference
>static-dynamic because classical instruments are pure mechanical and
>need the TE information to compensate the vario. But given electronic
>devices/computers, do we really need the TE probe at all? The
>information is given, when static and dynamic pressure are known. The
>rest can be calculated. Wrong?
>Eggert

Eggert, right. You are correct and some electronic instruments do just that
- they take the pitot and the static (instead of static and TE) and subtract
them electronically, and it's not just mechanical instruments which use TE,
the B50 has three inputs: pitot, TE, and static.

A TE probe isn't the only way of compensating for airspeed changes, ancient
glider pilots used diaphrams to achieve the same thing.

I sent some notes to Eckhard yesterday relating to how you might try and
achieve the calculation in Cumulus.

Rgds,

Derrick.

[Robert Ehrlich]

Robert Ehrlich wrote:
> ...
> P - S is total - static = (static + dynamic) - dynamic) = dynamic).
> ...

correcting myself, should read:

.... P - S is total - static = (static + dynamic) - static = dynamic.

[Eggert Ehmke]

Hank Nixon wrote:

> Easier to learn not to bend probe than try to make TE system work with
> stubby probe.

Last year, our Astir lost its TE probe due to a rough landing. We did not
find it and invented a replace from an old glider that was out of service.
We had to bend it to make it fit to the Astir. After this had worked fine
for several weeks, we found the original probe laying in the grass just
beside another landed glider, in perfect shape. So we could replace it
again! But the bended probe had done a good job.
Eggert

[Mike Borgelt]

On 5 May 2004 16:53:06 GMT, Derrick Steed
> wrote:

>>>I have driven many miles with an automobile test rig consisting of a
>>>pitot, a static and a TE probe connected to a pair of side by side
>>>U-tube water manometers. The manometers share the same static and one
>>>uses the pitot signal while the other uses the TE signal. A properly
>>>calibrated TE probe will cause exactly the same pressure difference as
>>>the pitot, just with the opposite sign.
>>
>>I understand we need the TE probe to generate the difference
>>static-dynamic because classical instruments are pure mechanical and
>>need the TE information to compensate the vario. But given electronic
>>devices/computers, do we really need the TE probe at all? The
>>information is given, when static and dynamic pressure are known. The
>>rest can be calculated. Wrong?
>>Eggert
>
>Eggert, right. You are correct and some electronic instruments do just that
>- they take the pitot and the static (instead of static and TE) and subtract
>them electronically, and it's not just mechanical instruments which use TE,
>the B50 has three inputs: pitot, TE, and static.
>
>A TE probe isn't the only way of compensating for airspeed changes, ancient
>glider pilots used diaphrams to achieve the same thing.
>
>I sent some notes to Eckhard yesterday relating to how you might try and
>achieve the calculation in Cumulus.
>
>Rgds,
>
>Derrick.
>
>
The B50 does not do electronic TE from the pitot/static. The TE probe
provides TE for the vario and the pitot/static measures airspeed for
the TAS/speed to fly/relative netto computation.

The reason for this is that is is *much* easier to get satisfactory TE
this way for the users.

The diaphragm compensator was one of the giant setbacks to the cause
of good glider instruments. Read any of the stuff by Moffat et al from
the 1960's and you will be treated to many stories of trying to get
good TE(and mostly failing). They only work properly at one altitude
too.

Althaus's revival of the venturi type probe in about 1969 was a great
improvement and they provide correct compenation at all altitudes.

It seems to me most TE probes are somewhat shorter than this thread!

:-)

Mike Borgelt
Borgelt Instruments

[Eric Greenwell]

d b wrote:

> Perhaps it isn't obvious. The airspeed indicator is a DELTA pressure guage.
> It is not an absolute pressure guage. If the indicator reads the same delta
> pressure, the two devices have to be producing the same delta pressure.
> One sucking, the other blowing.

Or, if you have a good static system, one that neither blows nor sucks,
but just sits there!
--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Eric Greenwell]

Todd Pattist wrote:

> Eggert Ehmke > wrote:
>
>
>>I understand we need the TE probe to generate the difference
>>static-dynamic because classical instruments are pure mechanical and
>>need the TE information to compensate the vario. But given electronic
>>devices/computers, do we really need the TE probe at all? The
>>information is given, when static and dynamic pressure are known. The
>>rest can be calculated. Wrong?
>
>
> Not "wrong" but incomplete. The static pressure (from the
> static sensor) and the total pressure (static plus dynamic
> from the pitot tube) are large numbers. You would need to
> calculate the dynamic pressure which is a small number by
> subtracting the two large numbers to be able to calculate
> the TE pressure that you want. Since the large numbers
> come from two different sensors (static and pitot) they have
> different errors, and the difference shows those errors. It
> is simpler/cheaper and you get better data by using a single
> TE sensor at a single point where the errors tend to cancel
> out.

Or you could use the semiconductor equivalent of the airspeed gauge
(delta pressure sensor), connect it to the pitot and static, and measure
the dynamic pressure directly. This avoids the need to subtract two
large numbers. Even if the pressure is measured accurately, the quality
of the reading depends on the quality of the pitot/static system. This
quality is generally easier to ensure on a TE probe than a sailplane.

Nonetheless, using a Cambridge 302 on my ASH 26 E with a probe and with
electronic TE, I couldn't tell the difference. I stayed with the
electronic TE because it is much less affected while the engine is
running, since the pitot and static are not in the prop wash.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Craig Funston]

>
> No. The ASI measures the dynamic pressure as the difference between the
> total pressure and the static pressure. The pitot measures total pressure.

Thanks, I mispoke. It's what I was thinking as I wrote, but not what I wrote.

[Derrick Steed]

Mike Borgelt wrote:
>On 5 May 2004 16:53:06 GMT, Derrick Steed
>wrote:

>>>>I have driven many miles with an automobile test rig consisting of a
>>>>pitot, a static and a TE probe connected to a pair of side by side
>>>>U-tube water manometers. The manometers share the same static and one
>>>>uses the pitot signal while the other uses the TE signal. A properly
>>>>calibrated TE probe will cause exactly the same pressure difference as
>>>>the pitot, just with the opposite sign.
>>>
>>>I understand we need the TE probe to generate the difference
>>>static-dynamic because classical instruments are pure mechanical and
>>>need the TE information to compensate the vario. But given electronic
>>>devices/computers, do we really need the TE probe at all? The
>>>information is given, when static and dynamic pressure are known. The
>>>rest can be calculated. Wrong?
>>>Eggert
>>
>>Eggert, right. You are correct and some electronic instruments do just
that
>>- they take the pitot and the static (instead of static and TE) and
subtract
>>them electronically, and it's not just mechanical instruments which use
TE,
>>the B50 has three inputs: pitot, TE, and static.
>>
>>A TE probe isn't the only way of compensating for airspeed changes,
ancient
>>glider pilots used diaphrams to achieve the same thing.
>>
>>I sent some notes to Eckhard yesterday relating to how you might try and
>>achieve the calculation in Cumulus.
>>
>>Rgds,
>>
>>Derrick.
>>
>>
>The B50 does not do electronic TE from the pitot/static. The TE probe
>provides TE for the vario and the pitot/static measures airspeed for
>the TAS/speed to fly/relative netto computation.
>
>The reason for this is that is is *much* easier to get satisfactory TE
>this way for the users.
>
>The diaphragm compensator was one of the giant setbacks to the cause
>of good glider instruments. Read any of the stuff by Moffat et al from
>the 1960's and you will be treated to many stories of trying to get
>good TE(and mostly failing). They only work properly at one altitude
>too.
>
>Althaus's revival of the venturi type probe in about 1969 was a great
>improvement and they provide correct compenation at all altitudes.
>
>It seems to me most TE probes are somewhat shorter than this thread!
>
>:-)
>
>Mike Borgelt
>Borgelt Instruments

I should correct the impression given above - I wasn't trying to imply the
B50 did it electronically, but I did, although it seemed obvious to me when
I wrote my bit that if it took the TE input then it used it as just that in
the conventional way.

I cherish memories of a british army nationals pilot that I crewed for back
in '69 and '70 trying to repair his diaphram compensator with a sheet of
latex material cut from a male contractive - I think he might have got a lot
more pleasure from using it in the conventional manner.

I think the thread on high energy pull ups with or without water was longer
- there was just as misconception, bogus physics, and appalling arithmetic
there too!

Still, it's a good laugh innit?

Rgds,

Derrick.

[Eggert Ehmke]

Todd Pattist > schrieb:

>Not "wrong" but incomplete. The static pressure (from the
>static sensor) and the total pressure (static plus dynamic
>from the pitot tube) are large numbers. You would need to
>calculate the dynamic pressure which is a small number by
>subtracting the two large numbers to be able to calculate
>the TE pressure that you want. Since the large numbers
>come from two different sensors (static and pitot) they have
>different errors, and the difference shows those errors. It
>is simpler/cheaper and you get better data by using a single
>TE sensor at a single point where the errors tend to cancel
>out.

But the TE probe also gives a large value (static-dynamic) as the
pitot gives (static+dynamic). So we have a third probe that has it's
own error. It may still be the case that the TE probe gives the better
result because if is in clean air, what may not be the case for the
pitot.
Eggert

[Mike Borgelt]

On Thu, 06 May 2004 15:21:05 +0200, Asbjorn Hojmark
> wrote:


>Previously, I had an Avionic GS500 (designed by Stig Øye, who I'm
>sure you know), and it's by far the best variometer I've ever
>flown with. (It's not in production any more). In particular, the
>fact that on glides, it told you exactly what you were going to
>get if you started turning, worked extremely well. The GS500 was
>purely electronically compensated.
>

That feature is called relative netto . The B50 does that. You do not
need to have electronic TE to do this but you do need an airspeed
sensor.

>I might add that I fly almost entirely in flat old Denmark, so
>the variations with altitude has never hit me as a problem.

Altitude variations probably aren't a problem in Denmark. In
Australia, NZ and the western US they certainly are particularly when
the cruising speeds are higher and greater demands are placed on the
TE system.
>
>Oh, I have a B40, which also works fine, but it's of cause not as
>advanced as the GS500 was, and it uses a TE probe.

As designed. The B50 has the advanced features.

Mike Borgelt

[Mike Borgelt]

On 6 May 2004 06:35:06 GMT, Derrick Steed
> wrote:


>I should correct the impression given above - I wasn't trying to imply the
>B50 did it electronically, but I did, although it seemed obvious to me when
>I wrote my bit that if it took the TE input then it used it as just that in
>the conventional way.
>
>I cherish memories of a british army nationals pilot that I crewed for back
>in '69 and '70 trying to repair his diaphram compensator with a sheet of
>latex material cut from a male contractive - I think he might have got a lot
>more pleasure from using it in the conventional manner.
>
>I think the thread on high energy pull ups with or without water was longer
>- there was just as misconception, bogus physics, and appalling arithmetic
>there too!
>
>Still, it's a good laugh innit?
>
>Rgds,
>
>Derrick.
>
>

Sure is. Are you frightened too by the fact that we have a high tech
civilization that might as well be running on magic as far as most
people are concerned? I do know the quote about "any sufficiently
advanced technology is indistinguishable from magic". Arthur C. Clarke
wasn't it?

Mike

[Derrick Steed]

>On 6 May 2004 06:35:06 GMT, Derrick Steed
>wrote:
>
>
>>I should correct the impression given above - I wasn't trying to imply the
>>B50 did it electronically, but I did, although it seemed obvious to me
when
>>I wrote my bit that if it took the TE input then it used it as just that
in
>>the conventional way.
>>
>>I cherish memories of a british army nationals pilot that I crewed for
back
>>in '69 and '70 trying to repair his diaphram compensator with a sheet of
>>latex material cut from a male contractive - I think he might have got a
lot
>>more pleasure from using it in the conventional manner.
>>
>>I think the thread on high energy pull ups with or without water was
longer
>>- there was just as misconception, bogus physics, and appalling arithmetic
>>there too!
>>
>>Still, it's a good laugh innit?
>>
>>Rgds,
>>
>>Derrick.
>>
>>
>
>Sure is. Are you frightened too by the fact that we have a high tech
>civilization that might as well be running on magic as far as most
>people are concerned? I do know the quote about "any sufficiently
>advanced technology is indistinguishable from magic". Arthur C. Clarke
>wasn't it?
>
>
>Mike
>
I remember the quote, I've read Arthur, it may also have been Isaac Asimov
(now there was an ego!) in his foundation series. The Arthur C. Clarke novel
which really sticks in my memory is "Childhoods end", the solution that the
aliens applied to prevent us from perpetuating all the cruelty we inflict on
other species on our planet was particularly aposite, GWB, Rumsfeld & co
could certainly do with a dose of it.

And yes, I am frightened by it - I get the feeling that once the princes of
this world get control of the information again (they had it back in the
middle ages, think about that), life will be a lot worse for all of us
because the technology _will_ be elevated to the status of magic with only
the wizards privy to the knowledge necessary to make sense of it. Or are we
already there?

I'm not a conspiracy theorist, I'm a stupid theorist: the world is
controlled by very intelligent, very arrogant, extremely over-confident
people who seem to be terminally stupid to the extent that they can't see
the consequences of all their complicated plans and intrigues, with the
consequence that the rest of us suffer as a result.

Rgds,

Derrick.

[ADP]

"Whenever you hear the word conspiracy, think stupidity." Don't remember
where I read that.
"Simple explanations are preferred to complicated ones." William of Ockham,
mid 19th century.
"The simplest explanation is always stupidity." Darwin Minor "Darwin's
Blade" - Dan Simmons, Harper Torch, 2000.

The point being, stupidity rules.

Allan



> I'm not a conspiracy theorist, I'm a stupid theorist: the world is
> controlled by very intelligent, very arrogant, extremely over-confident
> people who seem to be terminally stupid to the extent that they can't see
> the consequences of all their complicated plans and intrigues, with the
> consequence that the rest of us suffer as a result.
>
> Rgds,
>
> Derrick.

[Steve Bralla]

In article >, Derrick Steed
> writes:

>I do know the quote about "any sufficiently
>>advanced technology is indistinguishable from magic". Arthur C. Clarke
>>wasn't it?
>>
>>
>>Mike
>>
>I remember the quote, I've read Arthur, it may also have been Isaac Asimov
>(now there was an ego!) in his foundation series.


The quote is one of "Clarke's Laws". The other is something about "When a
scientist says something in his field of knowledge is possible he is most
probably right, and when he says something is impossible he is most probably
wrong". It's stated better than I have here.

I'm a big Clarke fan.
Steve

[Steve Bralla]

In article >, "ADP"
> writes:

>"The simplest explanation is always stupidity." Darwin Minor "Darwin's
>Blade" - Dan Simmons, Harper Torch, 2000.
>

Parts of "Darwin's Blade" take place at and above the Warner Springs
gliderport. If I remember Darwin flys a flapped (?) L-33 in the book, also a
"metal and canvas skinned" Twin Astir.

Steve

[Martin Gregorie]

On Fri, 07 May 2004 08:05:40 +1000, Mike Borgelt
> wrote:

>On 6 May 2004 06:35:06 GMT, Derrick Steed
> wrote:
>
>
>>I should correct the impression given above - I wasn't trying to imply the
>>B50 did it electronically, but I did, although it seemed obvious to me when
>>I wrote my bit that if it took the TE input then it used it as just that in
>>the conventional way.
>>
>>I cherish memories of a british army nationals pilot that I crewed for back
>>in '69 and '70 trying to repair his diaphram compensator with a sheet of
>>latex material cut from a male contractive - I think he might have got a lot
>>more pleasure from using it in the conventional manner.
>>
>>I think the thread on high energy pull ups with or without water was longer
>>- there was just as misconception, bogus physics, and appalling arithmetic
>>there too!
>>
>>Still, it's a good laugh innit?
>>
>>Rgds,
>>
>>Derrick.
>>
>>
>
>Sure is. Are you frightened too by the fact that we have a high tech
>civilization that might as well be running on magic as far as most
>people are concerned? I do know the quote about "any sufficiently
>advanced technology is indistinguishable from magic". Arthur C. Clarke
>wasn't it?
>

That's the man.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Nyal Williams]

At 11:00 08 May 2004, Martin Gregorie wrote:
>On Fri, 07 May 2004 08:05:40 +1000, Mike Borgelt
> wrote:
>
>>On 6 May 2004 06:35:06 GMT, Derrick Steed
>> wrote:
>>
>>
>>>I should correct the impression given above - I wasn't
>>>trying to imply the
>>>B50 did it electronically, but I did, although it seemed
>>>obvious to me when
>>>I wrote my bit that if it took the TE input then it
>>>used it as just that in
>>>the conventional way.
>>>
>>>I cherish memories of a british army nationals pilot
>>>that I crewed for back
>>>in '69 and '70 trying to repair his diaphram compensator
>>>with a sheet of
>>>latex material cut from a male contractive -
<<snip>>

Wot's that, some kinda salt peter?

[Derrick Steed]

Nyal Williams wrote:
>At 11:00 08 May 2004, Martin Gregorie wrote:
>>On Fri, 07 May 2004 08:05:40 +1000, Mike Borgelt
>> wrote:
>>
>>>On 6 May 2004 06:35:06 GMT, Derrick Steed
>>> wrote:
>>>
>>>
>>>>I should correct the impression given above - I wasn't
>>>>trying to imply the
>>>>B50 did it electronically, but I did, although it seemed
>>>>obvious to me when
>>>>I wrote my bit that if it took the TE input then it
>>>>used it as just that in
>>>>the conventional way.
>>>>
>>>>I cherish memories of a british army nationals pilot
>>>>that I crewed for back
>>>>in '69 and '70 trying to repair his diaphram compensator
>>>>with a sheet of
>>>>latex material cut from a male contractive -
>>
>
>Wot's that, some kinda salt peter?
>
Spooky, are you related to him?

Rgds,

Derrick.