varios not using a total energy probe

"Mike Borgelt" wrote in message
...
On 16 Apr 2004 03:27:43 -0700, (Robert) wrote:

Hello! Can someone tell me which compensated varios do not need a
total energy probe? (no electronic compensation) Thanks a lot! Robert

While some people report good results with pitot/static TE your
results may differ. I wonder if thy've tested two identical varios
capable of being on pitot/static or TE side by side on the same
sources then on the different sources side by side. I've done this
with TE probes mounted in different places on the ship and got
interesting results.The gear doors are a good location for a TE probe.

I have one pitot/static TE vario (With dedicated static ports.) and one TE
probe vario (B40)

Generally pitot and static probes/ports are much more sensitive to
sideslip than are good TE probes.(Good TE probe = Irving type two hole
probe )

True, it's easily observed.


You may have timing issues due to the distributed flow resistance and
capacitance of the sailplane plumbing.

Yep, the TE probe vario is about 0.25-0.5 sec slower than the pitot/static
vario at the onset of lift. Mike, do you think this is due to the long
tubing run to the fin mounted TE probe?


Remember for pitot/static TE you are measuring two large signals and
subtracting them. Minor timing differences in the signals and small
non linearities in the measurement show up as large unwanted
transients on your vario.

Hmm, they seem to track together most of the time but there are differences.
I trust the B40 the more.

Thanks for the comments, Mike.

Bill Daniels

On Wed, 21 Apr 2004 10:02:05 +1000, Mike Borgelt
wrote:

Generally pitot and static probes/ports are much more sensitive to
sideslip than are good TE probes.(Good TE probe = Irving type two hole
probe )

Mike, just a quick question:

My ASW-20 is fitted with a fin mounted Irving-type TE probe except
that it only has a single hole in place of the usual two holes. What
advantages would there be to swapping it for a two-hole version?


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

Earlier, Martin Gregorie wrote:

My ASW-20 is fitted with a fin mounted Irving-type TE probe except
that it only has a single hole in place of the usual two holes. What
advantages would there be to swapping it for a two-hole version?

This might be a bit of pedantry, but I believe that the one-hole probe
is generally what you'd call a "Nicks tube," for the late Oran Nicks
who developed the theory and practice of this simple yet relatively
effective TE probe design. And I think that the one with the slot or
two is generally a "Braunschweig tube." I don't know the name for the
two-hole probe design.

Here's an article by Dick Johnson on how he further developed and
validated a Nicks-pattern probe design and location for the PW-5:

http://www.ssa.org/Johnson/89-1998-04.pdf

That article cites Nicks' earlier (1976 and 1977) _Soaring_ articles
on TE probe design.

Elsewhere in this thread I've already posted a link to an article on
thge Les Sebald innovation of using a Nicks TE probe as a radio
antenna.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

On 21 Apr 2004 13:40:46 -0700, (Bob Kuykendall)
wrote:

Earlier, Martin Gregorie wrote:

My ASW-20 is fitted with a fin mounted Irving-type TE probe except
that it only has a single hole in place of the usual two holes. What
advantages would there be to swapping it for a two-hole version?

This might be a bit of pedantry, but I believe that the one-hole probe
is generally what you'd call a "Nicks tube," for the late Oran Nicks
who developed the theory and practice of this simple yet relatively
effective TE probe design. And I think that the one with the slot or
two is generally a "Braunschweig tube." I don't know the name for the
two-hole probe design.

Here's an article by Dick Johnson on how he further developed and
validated a Nicks-pattern probe design and location for the PW-5:

http://www.ssa.org/Johnson/89-1998-04.pdf

That article cites Nicks' earlier (1976 and 1977) _Soaring_ articles
on TE probe design.

Elsewhere in this thread I've already posted a link to an article on
thge Les Sebald innovation of using a Nicks TE probe as a radio
antenna.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

Thanks, Bob. That was an interesting read. Bookmarked for future
reference together with the dual use probe you mentioned.
--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

In message , Bob
Kuykendall writes
Earlier, Martin Gregorie wrote:

My ASW-20 is fitted with a fin mounted Irving-type TE probe except
that it only has a single hole in place of the usual two holes. What
advantages would there be to swapping it for a two-hole version?

This might be a bit of pedantry, but I believe that the one-hole probe
is generally what you'd call a "Nicks tube," for the late Oran Nicks
who developed the theory and practice of this simple yet relatively
effective TE probe design. And I think that the one with the slot or
two is generally a "Braunschweig tube." I don't know the name for the
two-hole probe design.

Here's an article by Dick Johnson on how he further developed and
validated a Nicks-pattern probe design and location for the PW-5:

http://www.ssa.org/Johnson/89-1998-04.pdf

Couldn't get this to down load. Can someone who can post it to me?

Regards

Robin
That article cites Nicks' earlier (1976 and 1977) _Soaring_ articles
on TE probe design.

Elsewhere in this thread I've already posted a link to an article on
thge Les Sebald innovation of using a Nicks TE probe as a radio
antenna.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

--
Robin Birch

On Wed, 21 Apr 2004 11:57:40 +0100, Martin Gregorie
wrote:

On Wed, 21 Apr 2004 10:02:05 +1000, Mike Borgelt
wrote:

Generally pitot and static probes/ports are much more sensitive to
sideslip than are good TE probes.(Good TE probe = Irving type two hole
probe )

Mike, just a quick question:

My ASW-20 is fitted with a fin mounted Irving-type TE probe except
that it only has a single hole in place of the usual two holes. What
advantages would there be to swapping it for a two-hole version?


Martin,

While I have seen wind tunnel data that suggests that the suction
around the rear 180 deg of the tube is constant there do seem to be
variations and the two hole probe may be less sensitive to sideslip.

Also:

Many years ago now just after the Irving probe design became available
I built one in 1/4" tube and one in 3/16" tube and a Nicks(single hole
type)in 3/16" as per Oran Nicks drawings. I then flew my Mini Nimbus
with a second ASI connected to probe and pitot. I checked the two
instruments against each other and applied static system corrections
to the readings of the normal ASI and reckoned I could get down to an
error band of +/- 4%.

I had had a feeling that the Nicks tube was under compensating and the
test showed it to be short of suction by 20% and a little more at low
speeds.

The Irving probe made per Irving was within my error band and the
3/16" Irving was a little short on suction getting worse at low speeds
leading me to conclude that there may be a Reynolds number effect for
the low airspeeds and smaller diameter tubes.

Interestingly Nicks recommended the hole 2 x tube diameters from the
end and Irving said 1.5

Current Irving type tubes have settled on about 1.67 as the hole
distance from the end and the holes are closer together than on the
original Irving design and 6mm or 1/4" tube is used.

Mike Borgelt

On Wed, 21 Apr 2004 00:39:14 GMT, "Bill Daniels"
wrote:


"Mike Borgelt" wrote in message
.. .
On 16 Apr 2004 03:27:43 -0700, (Robert) wrote:

Hello! Can someone tell me which compensated varios do not need a
total energy probe? (no electronic compensation) Thanks a lot! Robert

While some people report good results with pitot/static TE your
results may differ. I wonder if thy've tested two identical varios
capable of being on pitot/static or TE side by side on the same
sources then on the different sources side by side. I've done this
with TE probes mounted in different places on the ship and got
interesting results.The gear doors are a good location for a TE probe.

I have one pitot/static TE vario (With dedicated static ports.) and one TE
probe vario (B40)

Generally pitot and static probes/ports are much more sensitive to
sideslip than are good TE probes.(Good TE probe = Irving type two hole
probe )

True, it's easily observed.


You may have timing issues due to the distributed flow resistance and
capacitance of the sailplane plumbing.

Yep, the TE probe vario is about 0.25-0.5 sec slower than the pitot/static
vario at the onset of lift. Mike, do you think this is due to the long
tubing run to the fin mounted TE probe?

May be, particularly the capacity with small holes at the probe.
You may also be seeing the g effect when you enter lift. The probe is
about 1 meter above the instrument. Add g load due to entering lift
and the vertical pressure gradient in the glider plumbing in the fin
increases. As the pressure at the probe holes hasn't increased this
means the B40 sees increased pressure i.e. sink while the G is
increasing which will have to effect of slowing the response to lift.
This is one advantage of pitot static TE when using nose pitot and
fuselage nose statics. Also why a TE probe sticking out of the nose
ahead of the glider is better than a tail mounted probe.
There is also an effect of the rotation of the glider when pitching
with pressure sources a long way from the C of G.



What pitot/static positions are you using? I presume nose and sides
of the nose. Some people run pitot static TE off tail fin mounted
pitot static probes which are no better than a TE probe on the fin and
maybe worse fro the above reasons and the one below.

If you do pitot/static TE you want the pitot to be twice as far from
the C of G as the static port and on the same side. This avoids
pressure transients due to atmospheric pressure gradient during pitch
manouvers. Stig Oye pointed this out to me 20 years ago.

The B40 has electrically adjustable instrument time constant. See the
manual but VERRRY gently on the adjust please! Try about 20 degrees in
the faster direction if you like on the 180 deg trimpot. These are
factory set at the midway position and I haven't seen any reason to
change mine nor have I had people complain about the factory setting.


Mike Borgelt




Remember for pitot/static TE you are measuring two large signals and
subtracting them. Minor timing differences in the signals and small
non linearities in the measurement show up as large unwanted
transients on your vario.

Hmm, they seem to track together most of the time but there are differences.
I trust the B40 the more.

Thanks for the comments, Mike.

Bill Daniels

"Mike Borgelt" wrote in message

What pitot/static positions are you using? I presume nose and sides
of the nose. Some people run pitot static TE off tail fin mounted
pitot static probes which are no better than a TE probe on the fin and
maybe worse for the above reasons and the one below.

Two static ports on the side of the nose just forward of the instrument
panel. The pitot is in the nose vent.


If you do pitot/static TE you want the pitot to be twice as far from
the C of G as the static port and on the same side. This avoids
pressure transients due to atmospheric pressure gradient during pitch
manouvers. Stig Oye pointed this out to me 20 years ago.

Possibly the static ports are a bit further forward than half the distance
from the CG to the nose pitot.


The B40 has electrically adjustable instrument time constant. See the
manual but VERRRY gently on the adjust please! Try about 20 degrees in
the faster direction if you like on the 180 deg trimpot. These are
factory set at the midway position and I haven't seen any reason to
change mine nor have I had people complain about the factory setting.

I'll probably take your advice and leave it alone. I often fly in rough air
with the buoyancy/shear ratio in the single digits and 30+ knots of wind
shear in the convective boundary layer. I'd hate to lose the silky smooth
response. The onset of lift is pretty obvious with the stiff carbon wings
on the Nimbus. With softer wings, the vario delay wouldn't be noticeable.

That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?

Bill Daniels

On Fri, 23 Apr 2004 01:06:40 GMT, "Bill Daniels"
wrote:

rs ago.

Possibly the static ports are a bit further forward than half the distance
from the CG to the nose pitot.

Probably close enough. The maths is simple.

For a TE vario you want pressures so:
static - q
This can be generated as (2 x static) - pitot
pitot = static + q
If you pitch so at the static port you see decrease of delta p then at
the pitot you see 2 x delta p if the pitot is twice as far from the C
of G as the static port, put these in the TE equation and they cancel
hence no transient pressure.


The B40 has electrically adjustable instrument time constant. See the
manual but VERRRY gently on the adjust please! Try about 20 degrees in
the faster direction if you like on the 180 deg trimpot. These are
factory set at the midway position and I haven't seen any reason to
change mine nor have I had people complain about the factory setting.

I'll probably take your advice and leave it alone. I often fly in rough air
with the buoyancy/shear ratio in the single digits and 30+ knots of wind
shear in the convective boundary layer. I'd hate to lose the silky smooth
response. The onset of lift is pretty obvious with the stiff carbon wings
on the Nimbus. With softer wings, the vario delay wouldn't be noticeable.

The big thing about varios is to get used to the response. That's why
I'm not fan of much user changeable vario response in the cockpit.
Wil Schuemann said this about 30 years ago and was right.

That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?

I've seen it done and used this on the ASW20B I flew at Uvalde in 1986
at the Nationals.
Worked Ok but the Texans used germ warfare on the Aussies there.

Mike

Watch out for that chile... It catches the unwary.

Mike Borgelt wrote:\
That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?


I've seen it done and used this on the ASW20B I flew at Uvalde in 1986
at the Nationals.
Worked Ok but the Texans used germ warfare on the Aussies there.

Mike

--

Pete