Today's Message Index:
----------------------
1. 12:22 AM - Re: AeroElectric-List Digest: 14 Msgs - 06/11/12 (Franz Fux)
2. 08:48 AM - Pitot Tube Help (Jeff Luckey)
3. 09:05 AM - Re: Pitot Tube Help ()
4. 09:28 AM - Re: Pitot Tube Help (Jeff Luckey)
5. 02:41 PM - Re: Pitot Tube Help (Robert L. Nuckolls, III)
6. 03:10 PM - Re: Pitot Tube Help (BobsV35B@aol.com)
Message 1
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| Subject: | Re: AeroElectric-List Digest: 14 Msgs - 06/11/12 |
only intermittent access to e-mail until June 19th, in an urgent matter contact
info@lastfrontierheli.com
Message 2
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Off topic! (well it is electrically heated;) Looking to capitalize on the
Aerolectric Brain Trust to find an old pitot tube expert.
I have a pitot tube, Aero Instrument PH504, (AN 5811-1), which is looks like
a typical C-172 pitot tube (you know, "L" shaped with about a 4 in tube
attached to an airfoil cross-section vertical piece. When mounted under the
wing on a C-172 the tube part would be closest to the ground.)
However this one is designed for INVERTED mounting, apparently designed to
be mounted to a top surface of an airframe (where the tube part would be
furthest from the ground.)
I'm pretty sure that the air doesn't care which way the thing is mounted, as
long as the tube is parallel to the air stream. So my guess is that the
Inverted model has drain holes in different places.
Questions:
1. does drain hole position REALLY matter?
2. Multiple Choice: What will happen in flight if this device is
mounted the standard way (not inverted) and it picks-up a little moisture?
a. water in pitot lines
b. inaccurate airspeed indication
c. the end of life as we know it
d. smoking crater
TIA,
Jeff Luckey
Message 3
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| Subject: | Re: Pitot Tube Help |
Are you sure that hole is a drain and not a static port?
From: Jeff Luckey
Sent: Tuesday, June 12, 2012 10:46 AM
Subject: AeroElectric-List: Pitot Tube Help
Off topic! (well it is electrically heated;) Looking to capitalize on
the Aerolectric Brain Trust to find an old pitot tube expert
I have a pitot tube, Aero Instrument PH504, (AN 5811-1), which is looks
like a typical C-172 pitot tube (you know, =9CL=9D shaped
with about a 4 in tube attached to an airfoil cross-section vertical
piece. When mounted under the wing on a C-172 the tube part would be
closest to the ground.)
However this one is designed for INVERTED mounting, apparently designed
to be mounted to a top surface of an airframe (where the tube part would
be furthest from the ground.)
I=99m pretty sure that the air doesn=99t care which way the
thing is mounted, as long as the tube is parallel to the air stream. So
my guess is that the Inverted model has drain holes in different places.
Questions:
1.. does drain hole position REALLY matter?
2.. Multiple Choice: What will happen in flight if this device is
mounted the standard way (not inverted) and it picks-up a little
moisture?
1.. water in pitot lines
2.. inaccurate airspeed indication
3.. the end of life as we know it
4.. smoking crater
TIA,
Jeff Luckey
Message 4
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Yes, drawing that came with the unit indicates Drain Hole
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
berkut13@berkut13.com
Sent: Tuesday, June 12, 2012 09:03
Subject: Re: AeroElectric-List: Pitot Tube Help
Are you sure that hole is a drain and not a static port?
From: Jeff Luckey <mailto:JLuckey@pacbell.net>
Sent: Tuesday, June 12, 2012 10:46 AM
Subject: AeroElectric-List: Pitot Tube Help
Off topic! (well it is electrically heated;) Looking to capitalize on the
Aerolectric Brain Trust to find an old pitot tube expert.
I have a pitot tube, Aero Instrument PH504, (AN 5811-1), which is looks like
a typical C-172 pitot tube (you know, "L" shaped with about a 4 in tube
attached to an airfoil cross-section vertical piece. When mounted under the
wing on a C-172 the tube part would be closest to the ground.)
However this one is designed for INVERTED mounting, apparently designed to
be mounted to a top surface of an airframe (where the tube part would be
furthest from the ground.)
I'm pretty sure that the air doesn't care which way the thing is mounted, as
long as the tube is parallel to the air stream. So my guess is that the
Inverted model has drain holes in different places.
Questions:
1. does drain hole position REALLY matter?
2. Multiple Choice: What will happen in flight if this device is
mounted the standard way (not inverted) and it picks-up a little moisture?
a. water in pitot lines
b. inaccurate airspeed indication
c. the end of life as we know it
d. smoking crater
TIA,
Jeff Luckey
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matro
nics.com/Navigator?AeroElectric-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
No virus found in this message.
Checked by AVG - www.avg.com
Message 5
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From: Jeff Luckey
Sent: Tuesday, June 12, 2012 10:46 AM
Subject: AeroElectric-List: Pitot Tube Help
Off topic! (well it is electrically
heated;) Looking to capitalize on the
Aerolectric Brain Trust to find an old pitot tube expert=85
I have a pitot tube, Aero Instrument PH504, (AN
5811-1), which is looks like a typical C-172
pitot tube (you know, =93L=94 shaped with about a 4
in tube attached to an airfoil cross-section
vertical piece. When mounted under the wing on a
C-172 the tube part would be closest to the ground.)
However this one is designed for INVERTED
mounting, apparently designed to be mounted to a
top surface of an airframe (where the tube part
would be furthest from the ground.)
I=92m pretty sure that the air doesn=92t care which
way the thing is mounted, as long as the tube is
parallel to the air stream. So my guess is that
the Inverted model has drain holes in different places.
Questions:
does drain hole position REALLY matter?
* Multiple Choice: What will happen in flight
if this device is mounted the standard way (not
inverted) and it picks-up a little moisture?
* water in pitot lines
* inaccurate airspeed indication
* the end of life as we know it
* smoking crater
A modern pitot tube is a complex study in aerodynamics,
pneumatics, thermal dynamics and manufacturing. Contemporary
design goals for a 'qualified' pitot tube calls for testing
in an icing tunnel that is supposed to be sort of a worst case
icing condition.
http://tinyurl.com/7pmnqta
Emacs!
The idea is to melt any ice accumulation and provide a place
for the moisture to go besides into the pitot-static plumbing.
At the same time, many airplanes are fitted with accumulators
at the system's low-spot that include a drain for removing
any water.
Some years ago at HBC, we had a series of incidents involving
loss of pitot data on both sides at the same time at altitude
with no visible moisture (clouds or ice crystals). Both systems
recovered before the airplane landed and draining the accumulators
produced no observable moisture.
The pitot tubes installed were grand-fathered over from earlier
installations and not 'qualified' to the latest and greatest
de-icing specs. In fact, the tubes were originally installed
pointed up at about 45 degree angle and had been moved to the
bottom pointed downward thus placing the drain hole in the
wrong clocking.
New, latest and greatest tubes were installed. I'm not aware
of any recurring incidents . . . need to make some phone calls.
I'm a bit skeptical. I did some flight tests on the original
tubes to measure internal and temperatures. The areas all over
the tube remained well above freezing (LT1, LT3, LT4 curves
in http://tinyurl.com/74yr5q8 )
The idea that there was frozen blockage of passages inside the
tube didn't compute. So even if water did run down into the
plumbing, where did it come from? Thawed ice crystals? Your
guess is as good as mine. In any case, position of the drain
hole was certainly not a high order concern.
What I did come to understand was that unless your heated pitot
tube is mounted to a machine qualified for flight into known
icing, the ability to heat the tube is of limited usefulness.
Once the tube is overwhelmed the flight characteristics (airfoil
shapes) combined with added weight of ice make sort of pollutes
the value of knowing indicated airspeed. The recommended process
being to get to warmer altitudes without without changing anything
that would move you closer to the low-speed corner of a flight
envelope that is no longer defined.
What you have is probably a fine device for use outside of
icing conditions. Inside icing conditions becomes a toss-up
as to whether the flight qualities airplane or the instrumentation
get overwhelmed first.
Wire that heater up if it makes you feel any better but
know that having good IAS numbers is only part of the equation.
Got a real good lesson during my only in-flight instrument
approach in icing conditions. In this case, my instructor
was sitting there calmly waiting for me to figure it out all
the way down to the flare after having kept all the needles
centered up for over 15 minutes in the clouds.
The airplane fell out of the air and muffed what was
supposed to be a good "by the numbers" landing . . . numbers
that no longer represented the shape of the wing. Bottom
line is that ice presents worries that can be a lot more
hazardous than IAS numbers.
Bob . . .
Message 6
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| Subject: | Re: Pitot Tube Help |
Good Afternoon Bob,
We have had this same discussion before and I think we agreed to disagree,
but since you presented your side of the discussion, mind if I add mine?
Ice is where you find it.
Icing forecasts are not real reliable and if you never fly in conditions
where ice is a possibility, you deprive yourself of a lot of flexibility.
Some say that the way to handle ice is to avoid it.
My thought is that the way to handle ice is to keep a good way handy to get
out of the ice.
That has worked well for me over the last 62 years since I earned my
Instrument rating.
I do agree with you that we can fly adequately and safely without an
airspeed indicator, but faster airplanes do make speed control much easier
if we
have a good airspeed indication.
In my book, a couple hundred bucks spent to get a heated pitot tube is
money well spent.
Just this old guy's opinion!<G>
Happy Skies,
Old Bob
Downers Grove Illinois
Stearman N3977A
Beech V35B N20318
In a message dated 6/12/2012 4:44:10 P.M. Central Daylight Time,
nuckolls.bob@aeroelectric.com writes:
From: Jeff Luckey
Sent: Tuesday, June 12, 2012 10:46 AM
Subject: AeroElectric-List: Pitot Tube Help
Off topic! (well it is electrically heated;) Looking to capitalize on the
Aerolectric Brain Trust to find an old pitot tube expert
I have a pitot tube, Aero Instrument PH504, (AN 5811-1), which is looks
like a typical C-172 pitot tube (you know, =9CL=9D shaped with
about a 4 in tube
attached to an airfoil cross-section vertical piece. When mounted under
the wing on a C-172 the tube part would be closest to the ground.)
However this one is designed for INVERTED mounting, apparently designed to
be mounted to a top surface of an airframe (where the tube part would be
furthest from the ground.)
I=99m pretty sure that the air doesn=99t care which way the thi
ng is mounted,
as long as the tube is parallel to the air stream. So my guess is that
the Inverted model has drain holes in different places.
Questions:
does drain hole position REALLY matter?
* Multiple Choice: What will happen in flight if this device is
mounted the standard way (not inverted) and it picks-up a little moisture?
* water in pitot lines
* inaccurate airspeed indication
* the end of life as we know it
* smoking crater
A modern pitot tube is a complex study in aerodynamics,
pneumatics, thermal dynamics and manufacturing. Contemporary
design goals for a 'qualified' pitot tube calls for testing
in an icing tunnel that is supposed to be sort of a worst case
icing condition.
_http://tinyurl.com/7pmnqta
_ (http://tinyurl.com/7pmnqta)
The idea is to melt any ice accumulation and provide a place
for the moisture to go besides into the pitot-static plumbing.
At the same time, many airplanes are fitted with accumulators
at the system's low-spot that include a drain for removing
any water.
Some years ago at HBC, we had a series of incidents involving
loss of pitot data on both sides at the same time at altitude
with no visible moisture (clouds or ice crystals). Both systems
recovered before the airplane landed and draining the accumulators
produced no observable moisture.
The pitot tubes installed were grand-fathered over from earlier
installations and not 'qualified' to the latest and greatest
de-icing specs. In fact, the tubes were originally installed
pointed up at about 45 degree angle and had been moved to the
bottom pointed downward thus placing the drain hole in the
wrong clocking.
New, latest and greatest tubes were installed. I'm not aware
of any recurring incidents . . . need to make some phone calls.
I'm a bit skeptical. I did some flight tests on the original
tubes to measure internal and temperatures. The areas all over
the tube remained well above freezing (LT1, LT3, LT4 curves
in _http://tinyurl.com/74yr5q8 _ (http://tinyurl.com/74yr5q8) )
The idea that there was frozen blockage of passages inside the
tube didn't compute. So even if water did run down into the
plumbing, where did it come from? Thawed ice crystals? Your
guess is as good as mine. In any case, position of the drain
hole was certainly not a high order concern.
What I did come to understand was that unless your heated pitot
tube is mounted to a machine qualified for flight into known
icing, the ability to heat the tube is of limited usefulness.
Once the tube is overwhelmed the flight characteristics (airfoil
shapes) combined with added weight of ice make sort of pollutes
the value of knowing indicated airspeed. The recommended process
being to get to warmer altitudes without without changing anything
that would move you closer to the low-speed corner of a flight
envelope that is no longer defined.
What you have is probably a fine device for use outside of
icing conditions. Inside icing conditions becomes a toss-up
as to whether the flight qualities airplane or the instrumentation
get overwhelmed first.
Wire that heater up if it makes you feel any better but
know that having good IAS numbers is only part of the equation.
Got a real good lesson during my only in-flight instrument
approach in icing conditions. In this case, my instructor
was sitting there calmly waiting for me to figure it out all
the way down to the flare after having kept all the needles
centered up for over 15 minutes in the clouds.
The airplane fell out of the air and muffed what was
supposed to be a good "by the numbers" landing . . . numbers
that no longer represented the shape of the wing. Bottom
line is that ice presents worries that can be a lot more
hazardous than IAS numbers.
Bob . . .
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