- Admin : Ce message ci dessous (en noir gras désormais) était hors sujet (dans un sujet qui concernait le moyen de joindre un internaute américain).
Il a été extrait du sujet où il n'aurait pas dû figurer, pour former un sujet spécifique ici.
Merci de poster aux bons endroits, ou de créer des sujets spécifiques, sinon ça demande beaucoup de manipulations fastidieuses pour rattraper ...
La question initiale d'un certain bob le 1e avril 2015, était :
I am not sure, but if it does not have an elevator then possibly it is flown with variable wing incidence??
Much the same as a PPC uses variable difference between engine and wing??? or wing flaps? Not enough is shown on drawings provided.... Not sure I would invest in that!!!
et le message de "jplandez" est ci-après :
(il était utile de mettre les choses dans leur contexte)
J'ai trouve ca :
https://beta.groups.yahoo.com/neo/group ... pics/15218
Y'a des images, des documents et des vidéos,
A défaut de comprendre comment ça marche, on voit comment c'est fait.
- Et la réponse à "bob" est faite par "rimak58" le 3 mai 2015 :
Hi Bob
You are right to point out the questions concerning control of the Spratt103 around his different axis.
First: I guess, that most of the pictures and videos you find on the Spratt103 site were made before and around 2003, because the French "fiche d'identification" which is contained in the files when you buy the plans is dated June 25th, 2003.
And now let's discuss the "control-system" of the Spratt103:
If you are watching the following pictures and videos, you will find on almost all of them that the angle of attack is varied by a mechanism that I would call "tube-driven-system":
http://www.spratt103.com/images2/photos/image2.jpg
http://www.spratt103.com/images2/photos ... rget02.jpg
http://www.spratt103.com/images2/photos ... _droit.jpg
https://www.youtube.com/watch?feature=p ... O9S60Np3ic
This means, that the two wings are mechanically connected. One wing cannot move without a countermovement of the other!
Digression: If I understand the drawings on page 21 in this document: http://speleotrove.com/wings/files/cont ... -part1.pdf , Bill Wolfe also used a system which mechanically connected the two wings from his Spratt 107. Keyword: "collective pitch control".
But in the recent Spratt103 plans which Geffray begun selling end 2013, that mechanism is replaced by cables. I will call that here "cable-driven-system". It is possible, that 10 or 15 years ago Geffray already "tested" such a configuration. Perhaps here:
http://www.reaa.ru/yabbfiles/Attachment ... HiRes-.jpg (see also the prop
But most of the pictures we find, are showing what I call "tube-driven-wings".
Now: what could be the difference between these two systems?
The actual Spratt103-wings (at least the wing on my plans and a finished wing that I saw) are not weightbalanced. That's why flutter could eventually become a problem because you use cables which logically only are "stable" in the "pull-direction". Following the position of your stick, you give each of the two wings more or less space to move independently. And the pilot has no reasonable possibility to "block" them*.
That's not the case with the "tube-driven-system", where the two wings are mechanically connected. Here, flutter eventually doesn't appear or can be avoided via the stick before it really starts.
I don't know the different effects which are possible with the "cable-driven" system. And I have no idea how that works in gusts or - even more important - in turbulences. But I think there are several potentially dangerous positions, combinations and procedures conceivable. I also don't know if both systems were really completely testet and especially what kind of tests were carried out in or before 2003 for the Spratt103.
Add to that the fact that for ultralight aircrafts the French authorities just ask the designer to "confirm", that all the tests they asked for, have been realized successfully. (By the way: this also applies to calculations, load tests and so on). So a single signature is sufficient to get the paper, (which is called "fiche d'identification") that you need in France to market an ultralight aircraft or his plans. That's why never confuse such a French "fiche d'identification" for an ultralight aircraft with a real ICAO or EASA certification!
* Don't let yourself be fooled by the picture where the wings are seeming to be "blocked": http://www.reaa.ru/yabbfiles/Attachment ... HiRes-.jpg The stick on the photo is in a "parking position", hold by a bungee cord. In the air, the stick is not (or rarely) at this position.
PS : Il est demandé aux modérateurs et aux adhérents de mettre des balises URL* autour des liens hypertextes qui posent problème
(*voir en haut de la fenêtre de rédaction des messages)