Learning to fly in the U.S. Army

by E. N. Fales

Additional Flight Defects.—In addition to the foregoing the following conditions may also exist which cause trouble when flying as well as when landing:

Airplane Climbs Badly.—Such a condition, apart from engine or propeller trouble, is probably due to excess resistance somewhere.

Flight Speed Poor.—This condition apart from engine or propeller trouble, is probably due to (1) distorted surfaces, (2) wrong angle of incidence, or (3) dirt or mud, resulting in excessive skin friction and weight.

Inefficient Control.—This is probably due to (1) wrong setting of the control surfaces, (2) distortion of control surfaces, or (3) control cables being badly tensioned.

Will Not Taxi Straight.—If the airplane is uncontrollable on the ground it is probably due to (1) alignment of the undercarriage being wrong, (2) unequal tension of shock absorbers, (3) tires unequally inflated, (4) axle bent, (5) tight wheel and axle, (6) loose spokes causing wheel to wobble.

CHAPTER IX
TRUING UP THE FUSELAGE

Before an airplane is assembled for the first time after leaving the factory, and especially after it has made its first few “breaking-in” flights, the fuselage or basic framework should be carefully examined and checked up. This is done in order to determine whether or not the fuselage became distorted from rough usage during shipment (which is always likely) or from taking sets due to the flying stresses to which it was subjected for the first time during the “breaking-in” flights. It frequently happens that rough landings and “stunt” flying cause distortions of the fuselage frame and other parts of the airplane so that it is very necessary to make a careful inspection immediately after to ascertain not only what twists, bows and stretching of vital parts have resulted, but also to detect fittings, wires, etc., which may have been pulled loose or broken. The extreme importance of having your airplane adjusted correctly and carefully, and to know that it is in the proper condition can not be reiterated too often. And, since the fuselage is the foundation from which, so to speak, the entire apparatus is built up, it is doubly important that it should always be in correct adjustment.

When the fuselage is built in the factory it is placed on a long table whose surface is perfectly horizontal and which has metal strips inlaid. This table in reality is a big face plate especially arranged, as described, for fuselage truing in the factory. The fuselage, of course, has had none of its coverings applied when it is placed on the table, nor are the accessories such as controls and engine in place. On this table then the builders begin to do the necessary adjusting and this is no simple or quick job. Working from a perfectly smooth horizontal surface it is, of course, easy to detect warpings, twists, etc., of the framework. These are first remedied by tightening or loosening of cross wires, etc., as the case may be. Then, when the fuselage is reasonably square and level, lengthwise and crosswise, as determined by the eye, check measurements are taken by rule, trams and level and final adjustments made to bring the various parts in final proper relation to one another. For instance, the rudder post must be perfectly vertical, as determined by a plumb line, when the engine bearers or the top longerons are level. The various fittings such as those for horizontal and vertical stabilizers and the engine sections and side panels must all conform accurately to one another so that the airplane as a whole, when it is assembled, will not contain any inherent defects such as tail planes with slightly distorted angles of incidence, left main panels ahead of right or over or under right main panels, fittings so located that an initial strain must be imposed upon them by forcing them together, etc.

After the fuselage has been lined up in the factory as described briefly above, it is permitted to set for a week or so and then it is checked up again and such additional slight corrections made which would be necessitated by the sets which had occurred. The additional fittings required are then applied and the fuselage finally covered and sent away to have the engine and instruments applied.

When checking and truing a fuselage on the flying field after the airplane has been assembled and flown the process is not quite so simple as when the fuselage is checked up and trued in the factory, largely owing to the lack of ideal factory facilities and also because so many fittings, coverings, etc., are in the way which one must always be cautious about removing. In general, the method of procedure may be outlined as follows, but it must be obvious that one can not in a series of written notes touch upon all the possible queries and combinations of fuselage distortions which may occur and the ways for detecting and correcting them. A certain amount of experience in the field accompanied with some fixed habits of inspection, and everlasting curiosity about the perfections of your machine, and a willingness and readiness always to pitch in and help correct the defects found, will soon develop in you the ability to diagnose easily and quickly and remedy intelligently whatever trouble you may run across.