Most 2" and 4" venturis that I have encountered in vacuum gyro systems were
mounted on the side of the cowling in a region of reasonably smooth,
parallel airflow. The venturis were identified by suction capacity when
exposed to an airstream of around 100 MPH. In order to install a functional
turn-and-bank indicator in a Piper J-3 Cub, I found that the normal 2"
venturi would not generate enough suction to do the job, at 70 MPH. I ended
up installing a 4" venturi and a vacuum bleed valve, which allowed me to
adjust the suction to a functional level.
This was done to allow us to provide a primary panel in the Cub, at a time
when the FAA required primary panel experience when pursuing a Private
License.
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Chris Barker" <ftog@xxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Tuesday, December 15, 2009 12:09 AM
Subject: Re: [OM] IMG: 1929 Gulf Hawk Seen in 1972
>I must admit that I had never realised that the venturi below aircraft like
>that was a "relief" tube. I had always thought it to be a pitot system.
>I'll try to remember to look when I next visit Duxford, which is just to
>the south of me.
>
> Chris
>
> On 15 Dec 2009, at 06:04, Jim Nichols wrote:
>
>>
>> Yes, those were a real challenge to control properly. Thanks for
>> looking.
>> When I saw the venturi beneath the cockpit, I couldn't help but think of
>> the
>> earlier thread.
>
> --
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