Is a static port a precision thing?

"Michael Horowitz" wrote in message
...
Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a
static port of a precision size? - Mike

Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a
static port of a precision size? - Mike

The only requirements for a static port is the hole(s) be flush to the aircraft
such that there is no air forced in or sucked out by the local airflow in
flight. You don't want the hole too small or you will get lag when changing
altitude. You may not ever notice the lag, but it's there. You don't want it
too big or critters my think you built them a home.

The static ports on big aircraft such as C-130s have a salt shaker appearance
and have half a dozen or so holes around .032". Helicopters like the H-1 and
H-60 don't have static ports. They leave the static holes on the ASI, VVI and
altimiter open to cockpit pressure.

Aircraft Spruce sells a single hole port.

You want a smooth surface within a few inches of the port.

That's as complicated as they get


Good luck with your project.

Dan, U. S. Air Force, retired

On Sun, 10 Aug 2003 23:45:26 +0000, B2431 wrote:


Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a static
port of a precision size? - Mike

The only requirements for a static port is the hole(s) be flush to the
aircraft such that there is no air forced in or sucked out by the local
airflow in flight. You don't want the hole too small or you will get lag
when changing altitude. You may not ever notice the lag, but it's there.
You don't want it too big or critters my think you built them a home.

The static ports on big aircraft such as C-130s have a salt shaker
appearance and have half a dozen or so holes around .032". Helicopters
like the H-1 and H-60 don't have static ports. They leave the static
holes on the ASI, VVI and altimiter open to cockpit pressure.

Aircraft Spruce sells a single hole port.

You want a smooth surface within a few inches of the port.

That's as complicated as they get


Good luck with your project.

Dan, U. S. Air Force, retired

The location of the static port(s) is also very important. Ideally they
would be located such that they would be subjected to the ambient
pressure. I.e. the pressure that is present a long ways away from the
aircraft. But the pressure changes as the air goes around the aircraft.
So it is pretty much impossible to find a single location where the
pressure at the aircraft's skin is the same as the ambient pressure for
all airspeeds.

So the designer has to find a compromise location for the static port that
works as good as possible over the aircraft's flight envelope. The errors
in the pressure sensed at the static ports (position error) drive the vast
majority of the airspeed error that you will note in the POH, and of
course the static source error causes altimeter error too. This can be
significant - the Canadian S-2s that I used to fly had about 80 ft of
altimeter error in the landing configuration at the recommended approach
speed. This is a big deal when you are shooting an ILS down to 200 ft
AGL, using the barometric altimeter to define the decision height.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/

Being qualified in both the UH-1H/V and UH-60A, also currently flying the
UH-1, I beg to differ about the static port.

When the UH-1 went to roof mounted pitot system the static ports were
removed from the sides of the aircraft and are part of the pitot tube now.

The UH-60A with the wedge mounted pitot tubes are the same way.

It has been a long time since I flew the CH-47 and I am pretty sure they are
the same way except the static port hole is in the bottom of the nose
mounted tube.

Just my two cents and I am going to check with the flight instrument guys
the next time I am over at the flight facility.

Fred
"B2431" wrote in message
...

Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a
static port of a precision size? - Mike

The only requirements for a static port is the hole(s) be flush to the
aircraft
such that there is no air forced in or sucked out by the local airflow in
flight. You don't want the hole too small or you will get lag when
changing
altitude. You may not ever notice the lag, but it's there. You don't want
it
too big or critters my think you built them a home.

The static ports on big aircraft such as C-130s have a salt shaker
appearance
and have half a dozen or so holes around .032". Helicopters like the H-1
and
H-60 don't have static ports. They leave the static holes on the ASI, VVI
and
altimiter open to cockpit pressure.

Aircraft Spruce sells a single hole port.

You want a smooth surface within a few inches of the port.

That's as complicated as they get


Good luck with your project.

Dan, U. S. Air Force, retired

On USAF UH-1P and UH-60A they were as I described when I worked on them.
The UH-60A may have changed over the years. I was in the first USAF unit to get
them.

Dan, U. S. Air Force, retired




Being qualified in both the UH-1H/V and UH-60A, also currently flying the
UH-1, I beg to differ about the static port.

When the UH-1 went to roof mounted pitot system the static ports were
removed from the sides of the aircraft and are part of the pitot tube now.

The UH-60A with the wedge mounted pitot tubes are the same way.

It has been a long time since I flew the CH-47 and I am pretty sure they are
the same way except the static port hole is in the bottom of the nose
mounted tube.

Just my two cents and I am going to check with the flight instrument guys
the next time I am over at the flight facility.

Fred
"B2431" wrote in message
...

Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a
static port of a precision size? - Mike

The only requirements for a static port is the hole(s) be flush to the
aircraft
such that there is no air forced in or sucked out by the local airflow in
flight. You don't want the hole too small or you will get lag when
changing
altitude. You may not ever notice the lag, but it's there. You don't want
it
too big or critters my think you built them a home.

The static ports on big aircraft such as C-130s have a salt shaker
appearance
and have half a dozen or so holes around .032". Helicopters like the H-1
and
H-60 don't have static ports. They leave the static holes on the ASI, VVI
and
altimiter open to cockpit pressure.

Aircraft Spruce sells a single hole port.

You want a smooth surface within a few inches of the port.

That's as complicated as they get


Good luck with your project.

Dan, U. S. Air Force, retired

Why can't the military keep things simple?

Fred

"B2431" wrote in message
...
On USAF UH-1P and UH-60A they were as I described when I worked on them.
The UH-60A may have changed over the years. I was in the first USAF unit
to get
them.

Dan, U. S. Air Force, retired




Being qualified in both the UH-1H/V and UH-60A, also currently flying the
UH-1, I beg to differ about the static port.

When the UH-1 went to roof mounted pitot system the static ports were
removed from the sides of the aircraft and are part of the pitot tube
now.

The UH-60A with the wedge mounted pitot tubes are the same way.

It has been a long time since I flew the CH-47 and I am pretty sure they
are
the same way except the static port hole is in the bottom of the nose
mounted tube.

Just my two cents and I am going to check with the flight instrument guys
the next time I am over at the flight facility.

Fred
"B2431" wrote in message
...

Folks - When I bought my Tcraft, all that existed of the static port
was a length of rubber tubing running parallel to the ram air port
(which was there). Do I need to terminate that piece of hose in a
static port of a precision size? - Mike

The only requirements for a static port is the hole(s) be flush to the
aircraft
such that there is no air forced in or sucked out by the local airflow
in
flight. You don't want the hole too small or you will get lag when
changing
altitude. You may not ever notice the lag, but it's there. You don't
want
it
too big or critters my think you built them a home.

The static ports on big aircraft such as C-130s have a salt shaker
appearance
and have half a dozen or so holes around .032". Helicopters like the
H-1
and
H-60 don't have static ports. They leave the static holes on the ASI,
VVI
and
altimiter open to cockpit pressure.

Aircraft Spruce sells a single hole port.

You want a smooth surface within a few inches of the port.

That's as complicated as they get


Good luck with your project.

Dan, U. S. Air Force, retired

"Frederick Wilson" wrote:

Why can't the military keep things simple?

Fred
+++++++++++++++++++++++++++++

Duh...
Because there is no money in it.


Barnyard BOb - follow the money

Take a look at the Puzzle Palace aka the Pentagon. There are people there who
have no concept of reality.

Next, take a look at the aquistion process. There are no procedures for asking
contractors to keep things simple.

When we first aquired the UH-60A the Sikorski reps and brochures said that the
helicopter had been designed with "maintenance in mind." Despite the pretty
pictures in the brochures and the friendly reps no one ever said that meant
they intended to make life easy for us. My favourite example was the pitch bias
actuator. The PBA was a little box about 8 inches long, 2 inches thick and 4
inches wide. The PBA was mounted in the middle of the mixing unit and was a
bear to replace. It was perpetually failing and was ultimately eliminated with
no noticable change in handling.

Dan, U. S. Air Force, retired