PILOT SPIN
Pilot Zone => Pilot Zone => Topic started by: Jaybird180 on February 19, 2016, 03:15:32 PM
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Some antique aircraft have something other than a pitot tube to measure airspeed, but I can't remember the name of the system. It looks like a venturii. Help me out with the name.
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Some antique aircraft have something other than a pitot tube to measure airspeed, but I can't remember the name of the system. It looks like a venturii. Help me out with the name.
The thing that looks like a venturi is, in fact, a venturi. It uses Bernoulli's Theorem to "power" vacuum gyros:
(http://www.heraldnet.com/apps/pbcsi.dll/bilde?Site=DH&Date=20130911&Category=BLOG5206&ArtNo=130919972&Ref=AR&MaxW=800&MaxH=800&q=90)
Is that what you mean?
The only thing other than a pitot tube I can think of to measure airspeed is a spring-loaded paddle arrangement, like this:
(http://www.homebuiltairplanes.com/forums/attachments/light-stuff-area/32158-design-plane-thread-tiger-moth-airspeed-indicator-closeup.jpg)
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Venturi was used on what airplanes?
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Venturi was used on what airplanes?
Many, many older ones of all description.
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You mean the Venturi wasn't used to measure airspeed but instead powered gyros???? How and why would a designer choose that setup?
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You mean the Venturi wasn't used to measure airspeed but instead powered gyros? ??? How and why would a designer choose that setup?
Because a venturi generates a natural vacuum when there is airflow through it. No moving parts to fail like a vacuum pump, no power needed.
The problem with them is that there's no airflow through them on the ground, so your gyro instruments are not spun up until you're moving.
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Because a venturi generates a natural vacuum when there is airflow through it. No moving parts to fail like a vacuum pump, no power needed.
The problem with them is that there's no airflow through them on the ground, so your gyro instruments are not spun up until you're moving.
Ah! But then no pump failure. So why do we need gyros on the ground?
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Ah! But then no pump failure. So why do we need gyros on the ground?
Well...it's much easier to set your DG when you don't have to worry about compass dip and such.
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"Venturi tube - A specially shaped tube attached to the outside of an aircraft to produce suction to allow proper operation of gyro instruments."
PHAK, page G33
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Well...it's much easier to set your DG when you don't have to worry about compass dip and such.
Since I've never operated a Venturi powered DG, can they be set just before takeoff while lined up in runway heading? Would it be accurate enough even for a 0-0 takeoff?
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The thing that looks like a venturi is, in fact, a venturi. It uses Bernoulli's Theorem to "power" vacuum gyros:
(http://www.heraldnet.com/apps/pbcsi.dll/bilde?Site=DH&Date=20130911&Category=BLOG5206&ArtNo=130919972&Ref=AR&MaxW=800&MaxH=800&q=90)
Is that what you mean?
[/img]
That looks like a shot/jigger to me.
(and it's only 8:30 in the morning).
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Since I've never operated a Venturi powered DG, can they be set just before takeoff while lined up in runway heading?
No
Would it be accurate enough even for a 0-0 takeoff?
Why would you ever do a 0/0 takeoff?
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Why would you ever do a 0/0 takeoff?
PIC prerogative for Part 91. Not the thread to argue the merits/ demerits of a 0-0 takeoff. IMO.
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No
Why would you ever do a 0/0 takeoff?
So it is good enough for a 200' ceiling? Probably yes. Again, why aren't they popular anymore.
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So it is good enough for a 200' ceiling? Probably yes. Again, why aren't they popular anymore.
If something happens on take off and the field is truly 0/0 what are your options. At 200' with some visibility you might stand a chance.