FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1933
1933 - 0198.PDF
SUPPLEMENT TO FLIGHT 42 THE AIRCRAFT ENGINEER JULY 27, 1933 •ZRf g&4G££ggst8X££Bgge£S22&£. jgssa&fzaay jr*>*>sj-j/sp*- I UidBr .e^/^ /^/fi^ £>£&££re& /V<?7"/T. CGJJrtf/l/? o/^c/r^r/^H 0 >«vf <<VP yy^/y •?,*- Z/f/=- s-A-qtt /v^en SfC.Z- Company requested models from New York University with the idea of checking them in its own tunnel. This was done and the results of New York University as to lift and drag coefficients were substantiated. The B/J Company had always been extremely interested in slots and flaps and naturally the Zap development fell into sympathetic hands. We had always felt that the success of slow flying, regardless of how it was obtained, whether with slots and flaps, boundary layer control, or any other means, was depen dent upon adequate control at the reduced low speeds. When it was found that an adequate slow speed lateral control device was in existence and at the same time did not impair the utilisation of the whole span of the wing to obtain maximum lift increases, our enthusiasm for the Zap combination of flap and ailerons was intensified. In previous designs of a simple flap, as stated before, it was known that tho maximum-lift coefficients did not exceed 0.0044, and when the split flap presented possi bilities of 0.0065, an explanation of the theory became necessary. It might be of interest to certain individuals to theorise a little on what actually takes place in a split flapped airfoil. With a normal wing, when the simple flap constitutes an actual break in the contour of the upper surface, the increase in lift is primarily due to change in camber, and there is no reaction due to increase of chord or change in flow over the top surfaces other than that which would normally be ex pected from increasing the camber. With a split-type flap, where the contour of the upper surface of the airfoil is preserved intact, the increase in lift can be divided into three possible heads: first, increase in camber of the bottom surface, which naturally stimu lates the flow over the top surface; second, the preser vation of the upper surface with the same chord and possibly an increase with certain types of flap move ment; and third, a change in flow over the upper sur face brought about by the fact that the split trailing edge and undisturbed upper contour creates a combina tion which causes a further increase in flow over the wing. In the stereopticon pictures which will be shown later the flow reactions back of a simple flap veisus the split flap will be seen, and also the effects of moving the trailing edge of the flap forward along the chord. Whether the additional increase in flow over the top of the wing referred to is due to the presence oi an area of depression at the trailing edge of the wing caused by the split flap or whether it is due to the dis placing of the reversal flow away from the trailing edge so that the bottom surface flow unites with the upper surface flow with less detrimental vortices is a matter for the theoretical aerodynamicists to thrash out. It is a fact, however, that as the flap is moved forward so that the phenomena, whatever it might be, is taken away from its influence at the trailing edge, there an appreciable loss in maximum lift and is best the trailing edge of the flap is approximately below we trailing edge of the wing, as is the case of the arrangement. Some very interesting data on lit crease devices has been prepared and publishes Mr. Richard M. Mock, a copy of which is attache' With this explanation, our next question was the aeroplane did not require greater changes in horizontal stabiliser to take care of flap up and nap down positions. In Fig. 2 is shown the change in centre of pressure brought about by the use of this parti'" a flap movement on an airfoil and the consequent c moving the trailing edge of the flap fore and aft- an aeroplane with flaps the centre of pressure » and effect of changes in angle of downwash must taken into consideration, and in most cases With Zap it has a favourable reaction. In Figs. 3, o. • and 3c, pitching moments of a conventional nava plane equipped with Zap flaps and ailerons are she 15 hen Zap in to why th< 754 6
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
