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determined from mous deflection measure and trailing edg
3. Chord component.–Usually, the chord of the wing will not
be horizontal but will be inclined so the load laid on the wing will also load the drag system. The angle of inclination will be such as to produce the correct chord component
as determined from the stress analysis. 4. Deflections.-Numerous deflection measurements should be
taken along the span either at the leading and trailing edges or at the front and rear spars. The points of support should be observed also to see whether or not they move under load. Measurements should be made at each increment of load and these values should later be plotted in curve form in the manufacturer's report, to show the elastic behavior of the wing under load.
C. Rigidity.–At present, the Federal Aviation Agency has no
established criteria for permissible bending deflection in wings. D. Test report.—The manufacturer's report should include all
items peculiar to his particular test, such as computations showing the chord component of the test loads and curves of deflections along the span. The bending deflections should be separated from the torsional deflections and separate curves should be plotted for each.
CONTROL SURFACE TESTS Tail surface and aileron tests.A. Test loads.1. Kinds of tests.—Tests on tail surfaces and ailerons may be
either limit load tests or ultimate tests. In either case, the
loading distribution itself (not the total load) is the same. 2. Load distribution-tail surfaces.—The horizontal and vertical
tail surfaces should be tested for both of the conditions illustrated in figs. 1-XI, and 1-XII. The magnitude of the load in each case depends upon which of the specified condi
tions is critical. 3. Ailerons.-Ailerons should be tested for the load distribu
tion shown in fig. 1-XV. 4. Balance area.—The ordinate of the loading curve at the hinge
line is constant over the span. It is not affected by the chord of the movable surface. The unit loading on the balance area, if any, is the same as at the hinge line as shown in
figs. 1-XII and 1-XV. B. Test methods (see figs. 2–XIII and 2-XIV.) 1. Horns.—Control surface tests should include the horn of the
arm to which the control system is attached. Control surface horns should be rigidly held by tubes or straps instead of flexible cables, unless the test is purely a control system test. Cable usually stretches excessively, and the resultant angular deflection of the control surface may disturb the position of the loading bags or possibly cause them to tumble
onto the floor. 2. Mounting.—The control surfaces may be mounted on the
glider provided that cables are eliminated and that the fuselage or wing is either supported rigidly or its movement at the attachment fittings of the control surfaces is accurately measured. If the surfaces are mounted on a jig, the jig should be so constructed as to simulate the attachment conditions applying in the glider.
Support pulley from roof or on floor trestles
Vertical thru elastic
axis at wing tip
- Approx4 -
LEVEL for reading scales
Figure 2–VII. Setup for torsional test of wing.