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Thread: IFR airplane requirements

  1. #1
    Richgj3's Avatar
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    IFR airplane requirements

    Can an airplane with no vacuum pump which uses a Venturi to provide vacuum to the AI and DG be IFR certified, assuming all other requirements are met? I think it would be crazy to do it but I canít seem to find the reg. Obviously one can have no vacuum/pressure pump and still be certified when there are no instruments requiring it, as in all electric.

    Rich

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    behindpropellers's Avatar
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    Quote Originally Posted by Richgj3 View Post
    Can an airplane with no vacuum pump which uses a Venturi to provide vacuum to the AI and DG be IFR certified, assuming all other requirements are met? I think it would be crazy to do it but I can’t seem to find the reg. Obviously one can have no vacuum/pressure pump and still be certified when there are no instruments requiring it, as in all electric.

    Rich
    Took my instrument check ride in the airplane you describe and also put about 25 hours on it in the clouds.

    Tim

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    Richgj3's Avatar
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    Tim

    Thanks. I owned an old 172 like that once and I know it works, but I was curious. I’m probably going to end up with a nice 170B that has everything it needs for IFR but has Venturi, no vacuum pump. I don’t intend to fly IFR but nice to know it could be certified if one wanted to be legally caught in a cloud.

    Rich

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    behindpropellers's Avatar
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    Quote Originally Posted by Richgj3 View Post
    Tim

    Thanks. I owned an old 172 like that once and I know it works, but I was curious. I’m probably going to end up with a nice 170B that has everything it needs for IFR but has Venturi, no vacuum pump. I don’t intend to fly IFR but nice to know it could be certified if one wanted to be legally caught in a cloud.

    Rich
    Rich,

    Yep. 1957 172. Learned on those ancient instruments...


    Tim

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    Quote Originally Posted by behindpropellers View Post
    Rich,

    Yep. 1957 172. Learned on those ancient instruments...


    Tim
    Yup, there are times flying with a 6 pack warrants a 6 pack after the flight.
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    BC12D-4-85's Avatar
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    Venturis can't be trusted in the cold if there's enough moisture in the cockpit. Wet boots or clothing and whatever will cause moisture to get sucked into the venturi and can freeze...blocks the venturi port. Then no way to thaw and vacuum reduced or lost. Been there more than once but had an electric T&B as backup.

    Gary
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    Good reason to put a good EFIS in as a not required instrument, read the faa allows you to use the cheaper $1100. version of the G5 that experimental pilots are allowed to use as primary instruments.
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    The cost of electronic gages is less than mechanical now, would be silly to install a venturi system today. If itís already there, ok, but you loose a couple mph from the drag.


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    behindpropellers's Avatar
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    Quote Originally Posted by dgapilot View Post
    The cost of electronic gages is less than mechanical now, would be silly to install a venturi system today. If it’s already there, ok, but you loose a couple mph from the drag.


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    Perhaps a good re-use of a venturi is a relief tube, then.

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    When you lower the pressure, you lower the temperature, possibly to freezing. On a King Air the relief tube has a trigger that opens a valve so you arenít dumping pressurization out the tube all the time. Years ago working for a company with King Airs, it was common practice with a new guy for the left seater to use the relief tube. He would let go of the trigger before he finished up. Then when the new guy feels the need, he starts the flow, but the outlet was frozen! The tube fills up and he would have to try and stop the flow before he was finished. Not a pretty sight!

    In short, I donít think it would be a good solution.


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    SJ's Avatar
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    My C-170 was certified IFR with no pitot heat and a venturi system.
    "Often Mistaken, but Never in Doubt"
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    Take a look at the Garmin announcements tomorrow - Wednesday. And then break out the credit card for upgrades to your 6 pack, with some very capable new gauges.

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    Certification has more to do with the manufacturer than with the equipment. My Decathlon has full gyros, a glide slope receiver, and a sweep second hand clock. It would take a lot op extra paperwork to make it legal to fly in the clouds. My J3, on the other hand,can legally be flown IFR if it has the right instruments and a pitot static check.

  14. #14
    SJ's Avatar
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    Quote Originally Posted by Farmboy View Post
    Take a look at the Garmin announcements tomorrow - Wednesday. And then break out the credit card for upgrades to your 6 pack, with some very capable new gauges.
    Yep

    Sent from my Pixel using SuperCub.Org mobile app
    "Often Mistaken, but Never in Doubt"
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    Quote Originally Posted by dgapilot View Post
    When you lower the pressure, you lower the temperature, possibly to freezing. On a King Air the relief tube has a trigger that opens a valve so you aren’t dumping pressurization out the tube all the time. Years ago working for a company with King Airs, it was common practice with a new guy for the left seater to use the relief tube. He would let go of the trigger before he finished up. Then when the new guy feels the need, he starts the flow, but the outlet was frozen! The tube fills up and he would have to try and stop the flow before he was finished. Not a pretty sight!

    In short, I don’t think it would be a good solution.


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    P-2V had a heater on the relief tube. Placard next to relief tube said something like “Depress relief tube heat switch for ten seconds prior to urination.

    Turned out it took twenty seconds.....it was an old relief tube heater.....or the mechanics switched placards.

    MTV

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    BC12D-4-85's Avatar
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    Quote Originally Posted by behindpropellers View Post
    Perhaps a good re-use of a venturi is a relief tube, then.
    Depends on what's downstream on the fuselage for door openings or leaks. I dumped a squeeze water bottle full of P out the boot cowl vent on a Scout and the rear passenger shared the golden shower.

    Gary

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    Quote Originally Posted by Eddie747 View Post
    Good reason to put a good EFIS in as a not required instrument, read the faa allows you to use the cheaper $1100. version of the G5 that experimental pilots are allowed to use as primary instruments.
    Read FAA policy statement PS-ACE-23-08
    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/6A24902AE5F1AEAC86257EC1005B2FBC?OpenDocument&High light=ps-ace-23-08
    Cessna Skywagon-- accept no substitute!
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