Jan, I suspect that almost anywhere not in the prop wash and not close to
the tip would do. You end up by adjusting the pressure sensor head to sound
off at a chosen speed above the stall anyway and I guess that adjustment
would be valid anywhere in the central wing section. I suspect that the 52"
bit is the shortest length (to make retrofit as easy as possible) that is
reliably clear of prop effect.
Regards, david Joyce, G-XSDJ
----- Original Message -----
From: "Jan de Jong" <jan_de_jong@casema.nl>
Sent: Tuesday, November 01, 2011 4:19 PM
Subject: Re: Europa-List: Stall warner-retrofit installation-classic (- Mod
61 B - Classic)
> Manfred,
> For what it's worth - my opinion.
>>
>> * *
>>
>> * 1/.) I know the instruction on Mod 61B-Classic says that the hole of
>> the stall warner should be 52 (1321 mm) out from the aircraft
>> centreline, so far so good!/*
>>
>> */ I actually would like to know whether this point 52 is obligatory
>> or could it be 70?? And if it must be 52 what is the reason for
>> this exact point?? Does 70 from the aircraft/*
>>
>> */ centerline not work accurately? And why not? (Because I installed
>> already an empty tube to the 70 point at the beginning when
>> manufacturing the wing!!)/*
>>
> Wing section at 70" has slightly lower angle of attack than wing section
> at 52" and stalls a little later, but I think it will work perfectly
> well. Actually, on new build the postion is at least 70" out on the wing
> (past the flaps I remember) and in addition XS wing twist could be
> greater than Classic wing twist (?).
>>
>> *//*
>>
>> */2.) I understand that a vacuum appears on a special point _below_
>> the leading edge if in stall configuration. /*
>>
>> */ But to my past knowledge in air-pneumatics on the leading wing
>> edges there should still appear a pressure instead of a vacuum when
>> the wing comes to the stall. I looked /*
>>
>> */ into many /*good aeronautical text books containing the theory of
>> stall characteristics but I always found a pressure there!?//
>>
>> */ I would like to understand the airflow = pressure or vacuum = on
>> the leading wing edge in stall configuration on our type of wing./*
>>
>> */ Could someone give me some hints, where I could see/read the
>> theoretical background on this subject? Perhaps on the internet?/*
>>
> At high angle of attack stagnation point (pressure = dynamic pressure)
> moves to underside of wing. Somewhere just below leading edge pressure
> drops to below static pressure.
> Stagnation point: see attached.
> Interesting book including stall warner explanation:
> http://www.av8n.com/how/
>>
>> *//*
>>
>> */3.) In the retrofit installation instruction (Mod 61b Classic) it
>> calls at page 5 for a _W39 probe_ to be installed at a special angle
>> as per the hole template!/*
>>
>> */ What kind of probe is that? Is it just a small brass or aluminium
>> tube of 3 mm inside diameter, or is it a special manufactured probe
>> with a sophisticated inside/*
>>
>> */ configuration? Is it a must buying it, or could I manufacture it
>> myself?/*
>>
> Must be just an installation aid - on new build the probe is nothing but
> a 5052 aluminium tube.
> Inside diameter 3 or 4 mm, 1 mm is enough. Will allow tuning the hole
> position up/down somewhat later.
>
> Regards,
> Jan de Jong,
> filling the canoe of #461
>
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