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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.

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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.

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Figure 2-V. Setup for test of complete wing and its attachment to the fuselage.

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Figuro 2-VI. Typical wing test setup using a Axture in lieu of fuselage.

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Support pulley from roof or on floor trestles

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. (A)
Wooden forms cut to airfoil contour

Vertical thru elastic

axis at wing tip
Fuselage supported rigidly in flying position

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BOLT

FELT
WOODEN BEAMS

T PADDING

Support and
anchor tail
of fuselage
to prevent
movement

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LEVEL for reading scales

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Figure 2–VII. Setup for torsional test of wing.

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