Do ventures work very well?????
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Do ventures work very well?????
I was wondering how much suction you guys indicate from the ventures? I only show 2 on the suction gauge in flight. Any suggestions or comments are welcome.
God forbid we should ever be twenty years without a rebellion. ***Thomas Jefferson***
You guys ought to get together 2 inches plus 7 inches = 9 inches devided by 2 = 4.5 inches near the norm. quoted below in 43.13-1b(12-38 ). I believe it is possible to prematurely wear out gyros with to much vacuum and low vacuum causes delayed sluggish instrument reations.
Take a look at the specs for the RC Allen AI shown on this web page, they note a range of 4 to 6 inches.
http://www.pacificavionics.com/product_ ... ct=RCA22-7
9/27/01 AC 43.13-1B CHG 1
Par 12-38 Page 12-15
12-38. PNEUMATIC GYROS.
a. Venturi Systems. The early gyro instruments
were all operated by air flowing out
of a jet over buckets cut into the periphery of
the gyro rotor. A venturi was mounted on the
outside of the aircraft to produce a low pressure,
or vacuum, which evacuated the instrument
case, and air flowed into the instrument
through a paper filter and then through a nozzle
onto the rotor.
(1) Venturi systems have the advantage
of being extremely simple and requiring no
power from the engine, nor from any of the
other aircraft systems; but they do have the
disadvantage of being susceptible to ice, and
when they are most needed, they may become
unusable.
(2) There are two sizes of venturi tubes:
those which produce four inches of suction are
used to drive the attitude gyros, and smaller
tubes, which produce two inches of suction,
are used for the turn and slip indicator. Some
installations use two of the larger venturi tubes
connected in parallel to the two attitude gyros,
and the turn and slip indicator is connected to
one of these instruments with a needle valve
between them. A suction gage is temporarily
connected to the turn and slip indicator, and
the aircraft is flown so the needle valve can be
adjusted to the required suction at the instrument
when the aircraft is operated at its cruise
speed. (See figure 12-1.)
FIGURE 12-1. Venturi system for providing airflow through gyro instruments.
Aircraft Technical Book Company
http://www.actechbooks.com
800-780-4115
Take a look at the specs for the RC Allen AI shown on this web page, they note a range of 4 to 6 inches.
http://www.pacificavionics.com/product_ ... ct=RCA22-7
9/27/01 AC 43.13-1B CHG 1
Par 12-38 Page 12-15
12-38. PNEUMATIC GYROS.
a. Venturi Systems. The early gyro instruments
were all operated by air flowing out
of a jet over buckets cut into the periphery of
the gyro rotor. A venturi was mounted on the
outside of the aircraft to produce a low pressure,
or vacuum, which evacuated the instrument
case, and air flowed into the instrument
through a paper filter and then through a nozzle
onto the rotor.
(1) Venturi systems have the advantage
of being extremely simple and requiring no
power from the engine, nor from any of the
other aircraft systems; but they do have the
disadvantage of being susceptible to ice, and
when they are most needed, they may become
unusable.
(2) There are two sizes of venturi tubes:
those which produce four inches of suction are
used to drive the attitude gyros, and smaller
tubes, which produce two inches of suction,
are used for the turn and slip indicator. Some
installations use two of the larger venturi tubes
connected in parallel to the two attitude gyros,
and the turn and slip indicator is connected to
one of these instruments with a needle valve
between them. A suction gage is temporarily
connected to the turn and slip indicator, and
the aircraft is flown so the needle valve can be
adjusted to the required suction at the instrument
when the aircraft is operated at its cruise
speed. (See figure 12-1.)
FIGURE 12-1. Venturi system for providing airflow through gyro instruments.
Aircraft Technical Book Company
http://www.actechbooks.com
800-780-4115
John E. Barrett
aka. Johneb
Sent from my "Cray Super Computer"
aka. Johneb
Sent from my "Cray Super Computer"