The Europa stall warner, as supplied by the factory is not a leading edge
vane but a hole drilled in the leading-edge of the wing which detects
changes in pressure.
---From our own experience of this particular stall warner there is no
discernible difference in the warning given whether the flats are up or
down. We recently conducted our annual test flight and both with the flaps
up and down the warning buzzer sounded five knots prior to the stall.
The stall warner is activated by a pressure switch which is manually
adjusted when the stall warner is initially setup. We were lucky, and no
adjustment was ever necessary, but it is my opinion that there is such a
dramatic change in pressure when the wing is on point of stalling that the
very coarse adjustment would be required to make any difference. I may be
wrong in this assumption and if anyone knows differently perhaps they would
say.
For my money a five knot warning is more than adequate and with Europa this
seems to be true whether the flats are up or down. Whether this is a factor
relating to the Europa factory stall warner or to the design of the Europa
classic wing I do not know.
----- Original Message -----
From: <RiteAngle3@aol.com>
Subject: Europa-List: Re: Stall Warning device errors
>
> In a message dated 12/13/03 11:57:10 PM Pacific Standard Time,
> europa-list-digest@matronics.com writes:
> Stall warners do not degrade the aerodynamics
> and can easily be set to give a warning at any desired speed/AOA.
> Stall warning devices such as the leading edge vane can only give
warning
> at one fixed flap setting correctly. This is why they are so much of a
> nuisance. They must be set to go off when the stagnation point of the
airflow
> changes and moves the vane upward, closing a micro switch which make the
light or
> horn go off. This must be at the lowest AOA which a stall can occur,
otherwise
> it would not give stall protection with the wing in that configuration.
> For a stall warning to be accurate and reliable it must have some sort
of
> method of correcting for flap position.
> To certify an aircraft in the US, the stall warning must go off a minimum
of
> 5 kts above the stall. This is in the flaps up configuration, which is
why
> the stall warners are so inaccurate on all light production aircraft with
the
> flaps down, especially aircraft with very effective flaps.
>
> You can set your stall warning for flaps extended on your experimental
> aircraft, but then you wouldn't have adequate stall warning protection
with the
> flaps up.
>
> Elbie
> Old CFI
> EM aviation
> www.riteangle.com
>
>
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