A fascinating insight into the reasoning behind the recommendation for
the optimum flap setting can be found on page three of this early
factory newsletter, dated March 1994.
This did of course relate to the first prototype, G-YURO, which was
powered by the 80 horse 912 driving a fixed pitch Warp Drive prop.
Happy days. The enthusiasm and excitement was palpable. Isn't it time
somebody developed a new homebuild?
Nigel
On 30/07/2013 10:23, Frans Veldman wrote:
>
> On 07/29/2013 11:25 AM, GRAHAM SINGLETON wrote:
>
>> don't use 30 degree flap, Europa tested it and found you are starting to
>> lose aileron control at the low speeds achieved in ground effect.
> I have some trouble believing this (and even when it is true it is
> questionable whether this is still a valid reason for the XS with the
> increased aileron span and with more powerfull engines).
>
> With higher flap settings you are getting more drag than additional
> lift. With 10% more flap (30 degree instead of 27) you will get maybe
> just 5% more lift. If the ailerons are inadequate for this tiny bit of
> extra lift I think they would have difficulties handling 27 degrees as
> well. Furthermore, in the XS the ailerons are substantially increased in
> lenght, significantly more than 5%, and should have much more control
> power at low speeds! Even if control problems were the limiting factor,
> than it is questionable whether the same limit would still be needed for
> the XS.
>
> I thought that the limitation in flap was because of the 80hp engine
> used for the certification, which might have lacked sufficient power to
> exercise a go around with full flaps under full load (which is, if I
> remember correctly, a certification requirement. For the same reason the
> older Cessna's have 40 degree flaps, where the newer ones have 30 degree
> which was instantly rewarded with a 30Kg higher MTOW without any
> structural changes).
>
> Furthermore, in the tri gear the fact that you have the option to use 30
> degree flaps doesn't mean that you will have to use this all the time.
> There are situations where more flap would be welcome, and there might
> be situations where using less flap would be better. I can't see the
> benefit of the 26 degree limit. Of course for the mono you have no other
> option than to land with full flaps, so maybe in this case the
> limitation is justified.
>
> I know folks having drilled a new hole in the lugs on the flap control
> tube, so that the actuator can drive the flap further (and faster). No
> control difficulties are observed even in quite a few nasty situations
> with 30 knots wind and lots of turbulence. Instead the short field
> capabilities are somewhat improved.
>
> Regards,
> Frans
>
>
|