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identification number of report; serial and model number of
of critical test conditions and loadings.
3. Description of test setup, with reference to drawing numbers. Flap tests.A. Test methods and loads.
Wing flaps should usually be tested on a jig because of the difficulty of mounting a complete wing and flap assembly in the inverted position. In all cases, however, the test should include the supporting brackets and their means of attachment to the wing. The test will be similar to that for an aileron or elevator except that the load distribution over the surface will usually be uniform instead of decreasing toward the trailing edge, as is the case for the ailerons, rudder and the elevator. If it is necessary or advisable to test the flap supports as installed in the wing, that may be done, without inverting the wing, by running cables from the flap hinges up
and over pulleys to a loading platform. B. Test report. In all cases the manufacturer making a test is
required to submit a complete report covering details of tests.
tion of critical test conditions and loadings.
3. Description of test setup, with reference to drawing numbers. Control system tests.A. Test loads.1. Operating test.—The controls should be operated from the
pilot's seat when the system is sustaining the “limit” loads
specified in Chap. 1. 2. Strength tests.—The test loads used in a limit load test or an
ultimate test are premised either on the control surface design loads or on the control system design loads depending on the particular limiting conditions. This is explained in Chap. 1.
B. Test methods.-
conducted only upon a fully installed system in the actual
secured at the normal point of contact with the pilot's
are usually satisfactory methods of accomplishing this. STABILIZER RIB
REAR SHEAR WEB
Figure 2-XIII. Typical test of a control surface hinge bracket and its attachment to wing.
(b) The control system for the main surfaces may be secured
as in (a) and the load applied to the control surface horns or other outer extremities of the system by the use
of cables leading over pulleys to a loading platform. 2. Application. The test loads should be applied, if practicable,
under conditions which produce the most critical loads in the system. For instance, push-pull tubes should be loaded in compression rather than tension. Also, brackets and fittings should be loaded under the most critical conditions if there exists a variation in strength or loading throughout
the range of movement of the control system. 3. Operation test.—The purpose of the operating test is to deter
mine that the controls and their attachment fittings are free from binding, jamming or excessive friction or deflection at
the specified operating test loads. 4. Ultimate load test.—The purpose of a control system ultimate
test is to ascertain that all parts of the system have sufficient strength and rigidity for service. Ultimate load tests should be conducted when the combination of stress analyses and limit load tests are not considered satisfactory criteria of strength. During the ultimate load test the loads should be carried to the limit load values and then removed to make sure that no undue permanent deflections up to the limit load values are within the elastic limit of the materials used
in detail parts of the system. C. Rigidity.-Extra-flexible cable as used in control systems
sometimes will stretch a relatively large amount when subjected to its limit or ultimate loads even though of adequate size and prestretched. Although not particularly desirable this does not impair the airworthiness of a system unless the deflec
tion is excessive. D. Test report.—In all cases the manufacturer making a test is
required to submit a complete report covering details of tests. The report should include photographs or drawings of the test setup and the test specimen; photographs of failed parts or sections; records of deflections and readings taken; date of test; identification number of report; serial and model number of glider and signature of responsible witnesses and/or test personnel. In addition, the following points should be covered when applicable: 1. Substantiation by references or computations of the selection
of critical test conditions and loadings. 2. Loading schedule used in the test. 3. Description of test setup, with reference to drawing numbers.
1. The test loads for a fuselage usually comprise the torsion and
bending loads corresponding to the ultimate" or "limit" loads for the tail surface structure. The horizontal tail surfaces, being symmetrically placed, introduce straight bending loads in the fuselage structure which during the tests are resisted by the wing reactions and the weights forward of the center of gravity. The loads from the vertical tail cause a bending moment which during the tests is resisted by the wing reactions. For the landing conditions the fuselage will be loaded by inertia loads and the landing
gear (wheel or skid) reactions. 2. Two separate tests should be conducted, one for each type of
loading. For the bending test the loads are so chosen and placed, if possible, as to represent the most severe loading condition or conditions for all parts of the fuselage. If the upper part of the fuselage appears to be weak, it should be tested for upward acting tail loads. Usually, however, the downward acting loads are critical. For the torsion test there is only one condition to consider, that is, the fin and
rudder load. Test methods.1. General.—The general structural test procedure outlined
elsewhere can also apply to fuselage tests. 2. Bending test. For the bending test the fuselage is mounted
in a horizontal position and is held in place only by its wing attachment fittings. It is either right side up or upside down depending upon the loading conditions. Tail surface loads are applied through the stabilizer attachment fittings and loads representing weights in the fuselage, if used, are laid inside or suspended at their proper locations along the
fuselage. 3. Torsion test.—For the torsion test the fuselage is mounted
on its side, with the longitudinal axis horizontal, and held only by the wing attachment fittings. If the fin is in place on the fuselage, the test load is laid directly on it, distributed so as to locate the center of pressure of the load in its proper place. Otherwise, some means of applying the correct torsion, shear and bending loads through the fin attachment fittings must be devised. Unless the fin is of cantilever construction it will be necessary for this test to have both the
fin and stabilizer mounted on the fuselage. See fig. 2–XII. 4. Towing and launching loads.—Chap. 1 states that it is un
necessary to investigate launching and towing loads aft of the front spar. However, in testing for these conditions, loads must be applied at points aft of the rear spar to resist