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Venturi as a Vacuum Source
By Evan McCombs, Technical Counselor

It seems that all of  the sport planes that are built today have a full gyro panel installed.  The venturi is the most trouble free, reliable and economical source of vacuum that is available.  The super venturi will easily operate all 3 gyro instruments, turn coordinator, heading indicator and attitude indicator.

Now, I'm not suggesting that you mount a high drag, ugly super venturi on the side of your new glass slipper homebuilt.  However, mounting a super Ventrui on the engine mount inside the engine compartment and ducting air from the rear baffle or mounting the venturi below the engine and ducting air from a cowling inlet may provide a low drag hidden alternative.  This same engine compartment mounted venturi could be used as a stand-by vacuum source for your homebuilt with a vacuum pump.

Introducing heat (from the cabin heat system) into the venturi air stream flow or a heated shroud around the venturi would be a good idea to prevent ice from forming inside the venturi.

Testing this vacuum system and heating system would be necessary to be sure that the required amount of vacuum is available during all regimes of flying.  Experimenting with the kind of system is what homebuilding is all about.