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Re: [OM] Sailplane Instruments - for Chris B.

Subject: Re: [OM] Sailplane Instruments - for Chris B.
From: ChrisB <ftog@xxxxxxxxxxxxxx>
Date: Sun, 31 May 2015 15:16:56 +0100
Jim

Thanks, I’ll look it up.  There’s no point in wasting all your knowledge and 
experience, surely?

I didn’t know the name, “variometer”, but that device sounds like a VSI’s 
function, effectively.  It compares, mechanically, the ambient pressure now and 
that some seconds ago; it’s a lag instrument.  I teach my students not to use 
it when trying to assess whether or not they are flying level.  The altimeter 
(or even air speed) gives a more immediate indication of climb or descent.

I use the VSI only when established on an instrument approach.

Chris
> On 31 May 2015, at 14:53, Jim Nichols <jhnichols@xxxxxxxxxxxxx> wrote:
> 
> You can learn about the Winter Variometer via a Google Search.  They are made 
> in Germany, in several forms.  If I understand correctly, one side of the 
> internal aneroid  is vented to static pressure directly and the other is 
> vented through a bottle of a specified size.  This means that one side is 
> damped, while the other reacts quickly, providing a needle indication of the 
> change in pressure.
> 
> I used the same principle to locate the shock wave position in the diffuser 
> of a large supersonic wind tunnel.  We designed and installed a small "tank" 
> that contained a sensitive pressure transducer, with one side of the 
> transducer connected directly to a static orifice in the diffuser wall, and 
> the other side vented to the tank, which was itself vented to a diffuser wall 
> orifice.  We placed a row of these devices down one side of the diffuser, and 
> connected them to a display that reacted to the pressure difference measured 
> by each device.  Once flow was established, the signals ahead of the shock 
> were steady, while those downstream were very active.  We could actually 
> observe the shock movement during the process of establishing supersonic flow 
> in the test section.
> 
> Too much said about another life...........................

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