FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1935
1935 - 0453.PDF
FEBRIARY 28, 1935- THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT 226c large tail-less flying boat having a Pterodactyl wing plus tubs a combination of two experimental features. In S ,U courge of the tests we have discovered a few interesting facts about porpoising and its amelioration, but not enough warrant laying down rules for success. Here is another case where systematic changes as opposed to ad hoc tests are desirable, and it is hoped to have time in the near future to start such a series. So far, we have had very little opportunity to compare the results predicted from models with full-scale behaviour, but where this has been done the agreement between model and full-scale is good. " Seaworthiness tests in a train of waves demand a similar technique to porpoising, and dynamic models are necessary. A wave-maker has been installed in the R.A.E. tank and experiments in this direction have been commenced. "Another interesting use of dynamic models was in an experiment made in connection with a proposal for impact tests on hulls. By photographing in slow motion the im pact of a model in which various alterations were made, e.g., the air structure removed and lift applied by weights, moment of inertia altered, no lift applied, etc., it was possible to say what type of test was desirable in order to give approximately the right motion after impact. Future Research "A few words should be said with regard to the work contemplated. Several designers have expressed the view that the unstable yawing moments on certain types of hulls should be investigated. At the same time yawing moments at low speeds are required for water rudder tests, and we are therefore designing a balance to measure yawing moments. The same apparatus will measure rolling moments more satisfactorily than the present crude arrangement and further systematic tests on lateral stabilisers will be made. Experiments on changes in hull design in order to im prove efficiency have commenced. Some of the changes contemplated are in the direction of unorthodox hull forms, but the effect of altering standard types will also be tried. The study of porpoising is going forward by both analytical and experimental methods. The analysis depends on the evaluation of the stability derivatives, and this is in hand. The most profitable field for experiment is an investigation on dynamic models in which the effect of systematic changes in hull design are correlated with their effects on stability. " In all the foregoing discussion I have made no refer ence to development tests, though a large proportion of the tank time is devoted to these. The reasons are obvious, as the results are, in general, confidential and applicable only to the particular design under test. The research methods described are frequently used ultimately in routine tests, as in the case of porpoising where a large proportion of new designs are constructed as dynamic models in order to assess their stability." CONTROL SURFACE FLAPS for TRIM and BALANCE Generally referred to in America as " Tabs," these Flaps are called " Trimmers" when used Instead of Adjustable Tailplanes, and as " Balances " when their Function is to Reduce Hinge Moments of Control Surfaces ALTHOUGH trimming tailplanes are still used on f-^ the majority of British aircraft, there is a tendency in the most modern designs to adopt the small trailing-edge flap which has become popular with American designers of recent years. The following article will probably be of interest to British designers. It is taken, with due acknowledgment, from the Journal of the Aeronautical Sciences, which is the American " opposite number " to our Journal of the Royal Aeronautical Society. It is published by the Institute of the Aeronautical Sciences, Inc.—which corresponds to our R.Ae.S.—and now appears six times per annum. The author of the article is Mr. A. E. ™rd- of the Curtiss Aeroplane and Motor Co., Inc. llt7 tlle Past few years (savs Mr. Lombard) the Ppncation of small flaps to the movable control surfaces aeroplanes has become extensive. That these flaps give quick, Hght and highly effective control is shown by the diJ °n the Curtiss-Wright "Condor" a 90 deg. ono£ rn\0f the elevator flap control wheel changes the on ?h !nf' tnm of the aeroplane as much as 28 turns On StabIhser adiustment control. n tiLaei°P,es of more than one engine the control flap 5 the rudder has proved to be of when flying fuselage, and the rudder with its control flap has sufficient power to hold the aeroplane on a straight course with one engine out of commission. When used to give control in lieu of an adjustable stabiliser or vertical fin the control flap may be called a " trimmer," and when used to reduce the hinge moments of a control surface the term " balance " is appropriate. In the following notes the theoretical formulae for the effect of these flaps are presented as well as the results of wind tunnel tests on several types of trimmers and balances. Nomenclature a, = stabiliser angle, see Fig. 1. S = elevator angle, see Fig. 1. i = control flap angle, see Fig. 1. ct elevator chord aft of hinge, which includes chord of inset flap.* See Fig. 1. cf flap chord aft of hinge.* See Fig. 1. c, = overall chord of tail.* See Fig. 1. S, = elevator area aft of hinge including area of inset flap.* Sf = flap area aft of hinge.* ilot great assistance to the esponsibl f mg Wath °ne en&ne dead- and is Iargely a n be d C- °r *^e ^ac* tnat modern twin engine aeroplanes or eva, ?ned satisfactorilv with a single vertical tail. 929-1Tcoo hAthe ori&ina] Curtiss "Condor," built in 'reams fr' d two fins and rudders, located in the slip-0 be mai T- two ProPellers to enable straight flight ui lt with -ed °n °ne enSine- The new " Condor " is n a single vertical tail mounted rigidlv on the See Eqs. (1 and 2). See Eqs. (1 and 2). E, = c,/ct. pt, yc. A, = parameters—elevator. y/, A/ = parameters—control flap. q = dynamic pressure (= pV-lz). CL = Uit/qS. CHf — (Elevator hinge moment) jqcfSf. * In the case of the tests with the external flaps, see Fig. 8, the elevator chord and area, c,. and S«, do not include the chord and area of the flap. Also, in this case ct and Sf represent the total chord and area of the flap rather than just the chord and area aft of the hinge.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
