Hercules Engines

From: "Jim Knoyle"
Date: 1/17/2004 8:00 PM Central Standard Time
Message-id:


"B2431" wrote in message
...
From: "Jim Knoyle"
Date: 1/17/2004 3:48 PM Central Standard Time
Message-id:


"Tarver Engineering" wrote in message
...

"Jim Knoyle" wrote in message
...

"Tarver Engineering" wrote in message
...

"Jim Knoyle" wrote in message
...

Hey, Splaps. Next time you are ever near a DADC or it's diagram,
check out what they have at the other end of the tubing connected
to the fitting labeled *TOTAL*. Only ONE pitot tube!

Yep, the term Total means they added two sensors.

Nope, the pitot tube detects static pressure + impact pressure.
Read the book(s).

I have been writing that to you for years, Knoyle. That is why you
seem
such an idiot when you insist a pitot port is a pitot tube.

Total means there is more than one sensor, nothing more.

You really don't understand how that one little opening on the end
of that pointy thing up front can detect static pressure (altitude)
as well as impact pressure (airspeed), do you. That's sad!


The hole on the front only detects pitot pressure. If there are holes on
the
side are for detecting static pressure.


No, sorry Dan, you'll have to refer to a more modern air data computer.
When the label at the top of the ADC switched from pitot to total, the
definition for Total Pressure (Pt) was given as:
"This is a pressure input (from the aircraft pitot probe) which varies
both with altitude and aircraft speed. (Range 3.11 to 42.50 in. Hg.)"
*This was a direct quote from a Honeywell HG280D DADC guide*
The book goes on to explain how the delta Ps is removed to arrive at
a more accurate airspeed. The Ps, whether obtained from the static
port(s) on the probe or flush mounted ports on the fuselage, is fed
through another fitting on the DADC (labeled static) and is something
else entirely. It does factor in to the math.

JK

OK, I see where you are coming from. The pitot pressure DOES vary by altitude.
To compensate for that when measuring airspeed you use static pressure to give
you altitude. Some aircraft detect static pressure from holes on the side of
the pitot tube and others have the static ports located elswhere.

I would be interested in seeing a schematic of your aircraft's pitot-static
systems including DADC. I have never worked on DADC. I did work on the CADC
abomination on the F-4E.

Dan, U.S. Air Force, retired

(B2431) wrote:



OK, I see where you are coming from. The pitot pressure DOES vary by altitude.
To compensate for that when measuring airspeed you use static pressure to give
you altitude. Some aircraft detect static pressure from holes on the side of
the pitot tube and others have the static ports located elswhere.



But you need BOTH Dan, you cannot measure airspeed AND altitude
unless you have BOTH pitot pressure AND static pressure...
--

-Gord.

"Jim Knoyle" wrote:




No, sorry Dan, you'll have to refer to a more modern air data computer.
When the label at the top of the ADC switched from pitot to total, the
definition for Total Pressure (Pt) was given as:
"This is a pressure input (from the aircraft pitot probe) which varies
both with altitude and aircraft speed. (Range 3.11 to 42.50 in. Hg.)"
*This was a direct quote from a Honeywell HG280D DADC guide*
The book goes on to explain how the delta Ps is removed to arrive at
a more accurate airspeed. The Ps, whether obtained from the static
port(s) on the probe or flush mounted ports on the fuselage, is fed
through another fitting on the DADC (labeled static) and is something
else entirely. It does factor in to the math.

JK

Hang on here a second now Jim, you still need two samples. As Dan
says you need 'static pressure' to read the altitude from and you
need 'pitot pressure' (ram air pressure) as well as the static
pressure to derive the airspeed reading from. Sounds like you're
saying that you can read 'both' from just the 'ram air pressure'
alone. Or did I misunderstand you?

I'm sure that you know that lots of pitot tubes have both a
static port (flush mount on the side) and a 'ram air port' the
hole in the front to collect 'pitot pressure'.
--

-Gord.

From: "Gord Beaman" )
Date: 1/18/2004 12:48 AM Central Standard Time
Message-id:

(B2431) wrote:



OK, I see where you are coming from. The pitot pressure DOES vary by
altitude.
To compensate for that when measuring airspeed you use static pressure to
give
you altitude. Some aircraft detect static pressure from holes on the side of
the pitot tube and others have the static ports located elswhere.



But you need BOTH Dan, you cannot measure airspeed AND altitude
unless you have BOTH pitot pressure AND static pressure...
--

-Gord.

That's what I said.

Dan, U. S. Air Force, retired

"B2431" wrote in message
...
From: "Jim Knoyle"
Date: 1/17/2004 8:00 PM Central Standard Time
Message-id:


"B2431" wrote in message
...
From: "Jim Knoyle"
Date: 1/17/2004 3:48 PM Central Standard Time
Message-id:


[ snip ]

The hole on the front only detects pitot pressure. If there are holes
on
the
side are for detecting static pressure.


No, sorry Dan, you'll have to refer to a more modern air data computer.
When the label at the top of the ADC switched from pitot to total, the
definition for Total Pressure (Pt) was given as:
"This is a pressure input (from the aircraft pitot probe) which varies
both with altitude and aircraft speed. (Range 3.11 to 42.50 in. Hg.)"
*This was a direct quote from a Honeywell HG280D DADC guide*
The book goes on to explain how the delta Ps is removed to arrive at
a more accurate airspeed. The Ps, whether obtained from the static
port(s) on the probe or flush mounted ports on the fuselage, is fed
through another fitting on the DADC (labeled static) and is something
else entirely. It does factor in to the math.

JK

OK, I see where you are coming from. The pitot pressure DOES vary by
altitude.
To compensate for that when measuring airspeed you use static pressure to
give
you altitude. Some aircraft detect static pressure from holes on the side
of
the pitot tube and others have the static ports located elswhere.

In another recent part of this thread that didn't get cross-posted from
a.d.a.
(is that cheering I hear? ) I mention how the 727, 757 & DC10 use the
flush mounted static ports whereas the 737, 747 & 767 use the combined
pitot/static probe. Since Tarver seems to infer that the combined
pitot/static
probe is somehow better, I couldn't resist getting in a jab as to how the
777
uses the seperate pitot tubes on the nose and the flush mounted static ports
on the fuselage. Seems the Boeing Engineers ignore his mud bee warnings.
They do use analog/digital conversion right at the probe or port and run
wiring instead of plumbing. Sounds like a good idea to me.

I would be interested in seeing a schematic of your aircraft's
pitot-static
systems including DADC. I have never worked on DADC. I did work on the
CADC
abomination on the F-4E.

In this long running sparring with Tarver, I've placed a couple diagrams on
"his" page: http://home.att.net/~j.knoyle/the_ta...hronicles.html
The DC10 plumbing diagram at the bottom of this came from the DADC book
mentioned above: http://home.att.net/~j.knoyle/mechtest.html
There is a 767 plumbing diagram at the bottom of this page:
http://home.att.net/~j.knoyle/pitot.html
Somewhere I came across this great 777 presentation:
http://euler.ecs.umass.edu/ece655/Boeing777.ppt

JK

"Gord Beaman" wrote in message
...
"Jim Knoyle" wrote:




No, sorry Dan, you'll have to refer to a more modern air data computer.
When the label at the top of the ADC switched from pitot to total, the
definition for Total Pressure (Pt) was given as:
"This is a pressure input (from the aircraft pitot probe) which varies
both with altitude and aircraft speed. (Range 3.11 to 42.50 in. Hg.)"
*This was a direct quote from a Honeywell HG280D DADC guide*
The book goes on to explain how the delta Ps is removed to arrive at
a more accurate airspeed. The Ps, whether obtained from the static
port(s) on the probe or flush mounted ports on the fuselage, is fed
through another fitting on the DADC (labeled static) and is something
else entirely. It does factor in to the math.

JK

Hang on here a second now Jim, you still need two samples. As Dan
says you need 'static pressure' to read the altitude from and you
need 'pitot pressure' (ram air pressure) as well as the static
pressure to derive the airspeed reading from. Sounds like you're
saying that you can read 'both' from just the 'ram air pressure'
alone. Or did I misunderstand you?

Darn, Gord, I thought it sounded clear to me... still do.
It must be getting late. The book (and I) says that the
Ps component of Total Pressure must be taken into account.
The Ps from the other DADC fitting (labeled static) is used
to accomplish this. That's what I meant by "it does factor in..."
Can't tell (the value of) one without the other.

I'm sure that you know that lots of pitot tubes have both a
static port (flush mount on the side) and a 'ram air port' the
hole in the front to collect 'pitot pressure'.

The combined pitot/static probe which I referred to by
"The Ps, whether obtained from the static port(s) on the probe
or flush mounted ports on the fuselage."

We all agree, we just don't know it. Sorry if I confused
the issue.

JK

"Gord Beaman" wrote in message
...
"Jim Knoyle" wrote:

Hang on here a second now Jim, you still need two samples. As Dan
says you need 'static pressure' to read the altitude from and you
need 'pitot pressure' (ram air pressure) as well as the static
pressure to derive the airspeed reading from. Sounds like you're
saying that you can read 'both' from just the 'ram air pressure'
alone. Or did I misunderstand you?

Jim has finally figued out what a pitot tube is, but somehow he still wants
to be correct in his archive troll. It is a great paradox.

"Jim Knoyle" wrote:


The combined pitot/static probe which I referred to by
"The Ps, whether obtained from the static port(s) on the probe
or flush mounted ports on the fuselage."

We all agree, we just don't know it. Sorry if I confused
the issue.

JK

Yes fine Jim...I think I read too much into your "This is a
pressure input...("rather than pressure 'inputs') sorry...yes we
all agree but don't know that we agree!
(I also know that John will disagree...and I didn't even read his
reply right below your post yet...)
--

-Gord.

"Tarver Engineering" wrote:


"Gord Beaman" wrote in message
.. .
"Jim Knoyle" wrote:

Hang on here a second now Jim, you still need two samples. As Dan
says you need 'static pressure' to read the altitude from and you
need 'pitot pressure' (ram air pressure) as well as the static
pressure to derive the airspeed reading from. Sounds like you're
saying that you can read 'both' from just the 'ram air pressure'
alone. Or did I misunderstand you?

Jim has finally figued out what a pitot tube is, but somehow he still wants
to be correct in his archive troll. It is a great paradox.


I know...ain't life a bitch John

--

-Gord.

"Gord Beaman" wrote in message
...
"Tarver Engineering" wrote:


"Gord Beaman" wrote in message
.. .
"Jim Knoyle" wrote:

Hang on here a second now Jim, you still need two samples. As Dan
says you need 'static pressure' to read the altitude from and you
need 'pitot pressure' (ram air pressure) as well as the static
pressure to derive the airspeed reading from. Sounds like you're
saying that you can read 'both' from just the 'ram air pressure'
alone. Or did I misunderstand you?

Jim has finally figued out what a pitot tube is, but somehow he still
wants
to be correct in his archive troll. It is a great paradox.


I know...ain't life a bitch John

I have to free a few from the tarbaby, if I am to let Ed have what he wants.