With the engine bearers temporarily disposed of, the fuselage proper is tackled. Here the first thing to do is to get the top surfaces of the longerons level crosswise. Use the spirit level and the two steel cubes mentioned in the tool list for this purpose. Start at the front of the fuselage in the cock pit. Adjust the internal diagonal wires until the level bubble is in its proper place. Then measure these first two sets of diagonal wires, getting them of equal length. Continue this process throughout the length of the fuselage until the rear end is reached, always working from the front.
Lastly, before proceeding to the next operation, try the engine bearers for level again. If out, make the proper adjustments.
If the centers of the crosswise struts are not marked, this should first be done before going further. Then stretch a string from No. 1 strut, or as far forward as possible to the center of the rudder post. All center points on the cross struts, if the fuselage is true lengthwise, should lie exactly on this string. If not, adjust the horizontal diagonal wires, top and bottom, working from the front, until the center-line points all agree. Always check by measuring diagonal wires which are mates. These should be of equal length. If not, some wire in the series may be overstressed. In order to pull the center points on the cross struts over, always stop to analyze the situation carefully, determining which are the long diagonals and which the short ones from the way the fuselage is bowed. Then shorten the long ones and ease off on the short ones, being careful never to overstress any of the wires.
The last thing to do is to bring the longerons or the center line of the fuselage into level lengthwise. For this purpose a long straight-edge, the two cubes, and a spirit level are of advantage, although simply stretching a string closely over the top of the longeron may suffice. Then as in the case of removing a crosswise bow in the fuselage, here too, we manipulate the outside up and down diagonal wires in bringing the top longerons into their proper level position lengthwise, always working from the front.
After all this is done it is well to make some overall checks with steel tape or trams to see how various fittings located according to the drawings, agree with one another. Since there is a right and a left side, distance between fittings on these sides may be compared. And, finally, the engine bearers should be tried again. In short no opportunity should be neglected to prove the truth of the fuselage as a whole and in detail.
It might be pointed out that an excellent time to check the fuselage is when engine is being removed or changed. In fact this time in general is a good one to give the airplane as a whole, a careful inspection.
After all the necessary corrections have been made and all the parts of the fuselage brought into correct relation with one another, the turnbuckles are safety wired and then served with tape to act as a final protection. The linen covering is reapplied if it had previously to be removed and the level, empennage wires, panels etc., are placed in position and aligned as pointed out in the notes on assembly and alignment.
CHAPTER X
HANDLING OF AIRPLANES IN THE FIELD AND AT THE BASES PREVIOUS TO AND AFTER FLIGHTS
No unimportant part of the operation and maintenance of airplanes is their handling in the field, and at the various bases previous to, between, and after flights. This phase of the entire subject contemplates the transportation of airplanes in knockdown condition either by railway or truck, their unloading and unpacking, to a certain extent their assembly, their storage in hangars and sheds, their storage and disposition in the open, their disassembling and packing for transportation, etc.
The Unloading and Unpacking of Airplanes.—The personnel required to unload an airplane properly boxed and crated from a railway car, is 15 men and two non-commissioned officers. The tools needed for this purpose are: