Learning to fly in the U.S. Army

by E. N. Fales

Several small Crescent adjustable wrenches.

Several pliers with wire-cutting attachment.

Pins for manipulating turnbuckles.

1 steel tape.

1 foot rule, 6 ft. long.

1 small brass hammer.

A small work bench equipped with a 3-in. or 4-in. vise.

The fuselage which is to be trued is mounted on the horse with the wedges between the top horse rails and the lower longerons. These horses or trestles should be so arranged that about three-fourths of the fuselage toward the tail sticks out unsupported. In this way it will take, as near as possible, its normal flying position. It is always desirable, in fact quite necessary, especially when checking a fuselage for the first time, to have the airplane’s specifications as well as a detailed drawing of the fuselage and an assembly of the airplane as a whole available. The reason for this, of course, is quite obvious.

The engine bearers and the top longerons are the basic parts from which the fuselage as a whole is lined up. Consequently the first thing which is done, when inspecting the fuselage for alignment, is to test the truth of these parts. This is done by sighting the top longerons lengthwise to see if they are bowed downward, upward, inward or outward. As near as possible the fuselage is made level on the trestles. The steel blocks or cubes referred to in the tool list above are placed on the longerons and the straight edge and level placed on these, first crosswise and then lengthwise. A string is stretched over the top of the fuselage touching the top cross braces and brought as close as possible to the center of these pieces. This string should stretch from the rudder post as far forward as possible. Then the cross wires or diagonal brace wires are sighted to see how close their intersections agree with this center-line string. Furthermore, the level is placed on the engine bearers and they are tested for cross level and longitudinal level. If the engine is mounted in place, but one point on the bearers will be available for this purpose, but the check should nevertheless be made. It may also be found that the longitudinal level of the engine bearers can be tested from underneath by placing the steel cubes mentioned above on the top of the level and then holding the level up against the bottom of the bearers. As a rule, if the fuselage is warped it should be possible to detect this with the eye, but when engine bearers are out of line this can only be detected with certainty by the use of the level.

Let it be assumed that the fuselage is out of true. The first parts to tackle are, of course, the engine bearers. If they should not be in line they must first be brought so, and afterward kept in this condition. The diagonal wires at the front of the fuselage should be adjusted to make this correction. If the bearers are badly out of line it will, perhaps, be wisest to remove the engine, or at least loosen it up from the bearers before doing any adjusting for the reason that it may become strained by serious pulling on the bearers. After the bearers are in place, it will be safe to bolt the engine fast again.