Learning to fly in the U.S. Army

by E. N. Fales

FAULTS IN FLIGHT, DUE TO IMPROPER ALIGNMENT AND HOW TO CORRECT THEM

An airplane pilot may experience difficulty with the flying qualities of his machine. Consequently he should know something about the conditions which are responsible for the various kinds of unsatisfactory flying qualities which are more or less characteristic of airplanes.

In the chapter on “Principles of Flight” the reader has been made acquainted with such terms as stability, instability, longitudinal stability, etc. For the purposes of rigging, however, it will be well to review these terms again.

Stability is a condition whereby an object disturbed has a natural tendency to return to its first and normal position. Example: a weight suspended by a cord.

Instability is a condition whereby an object disturbed has a natural tendency to move as far as possible away from its first position, with no tendency to return. Example: a stick balanced vertically on your finger.

Neutral stability is a condition whereby an object disturbed has no tendency to move farther than displaced by the force of the disturbance, and no tendency to return to its first position.

Now in order that an airplane may be reasonably controllable, it is necessary for it to possess some degree of stability longitudinally, laterally and indirectionally.

Longitudinal stability is its stability about an axis transverse to the direction of normal horizontal flight, and without which it would pitch and toss.

Lateral stability is its stability about its longitudinal axis, and without which it would roll sideways.

Directional stability is its stability about its vertical axis, and without which it would have no tendency to keep its course.

Whenever an airplane does not fly properly, aside from conditions arising from engine or propeller trouble, either its longitudinal, lateral, or directional stability is affected. When its longitudinal stability is affected we call this condition longitudinal instability; likewise, regarding lateral stability and directional stability, referring to these conditions respectively as lateral and as directional instability. The effect of alignment errors will be treated under the foregoing respective heads.

Alignment Errors, Longitudinal.—

1. The Stagger May Be Wrong.—The top surface or wing may have drifted back a little owing to some of the wires, probably the incidence wires, having elongated their loops or having pulled the fittings into the wood. If the top surface is not staggered forward to the correct amount, then consequently the whole of its lift is too far back, and it will then have a tendency to lift up the tail of the machine too much. The airplane will then be said to be nose-heavy. A ¼-in. error in the stagger will make a very considerable difference in the longitudinal stability.

2. The Angle at Which the Main Surfaces Are Set Relative to the Fuselage May Be Wrong.—This will have a bad effect especially in the case of an airplane with a lifting tail plane or horizontal stabilizer. If the angle of incidence is too great, the machine will have a tendency to fly “tail-high.” If the angle is too small the airplane may have a tendency to fly “tail-down.”

3. The Fuselage May Have Become Warped Upward or Downward.—This would give the tail plane or horizontal stabilizer an incorrect angle of incidence. If it has too much angle, it will lift too much, and the airplane will be “nose-heavy.” If it has too little angle, it will not lift enough and the airplane will be “tail-heavy.”

4. The Tail Plane May Be Mounted upon the Fuselage at a Wrong Angle of Incidence.—If this condition exists, it must be corrected by making a change at the fittings. If nose-heavy, the tail plane should be given a smaller angle of incidence. If tail-heavy, it should be given a greater angle of incidence; but care should be taken not to give it too great an angle, because the longitudinal stability entirely depends upon the tail plane being set at a smaller angle of incidence than is the main surface, and if that difference is decreased too much, the airplane will become uncontrollable longitudinally. Sometimes the tail plane is mounted on the airplane at the same angle as the main surface, but it actually engages the air at a lesser angle, owing to the air being deflected downward by the main surfaces.

Alignment Errors, Lateral.—The machine manifests a tendency to fly one wing down. The reason for such a condition is a difference in the lifts of the right and left wings, assuming the motor torque is already taken care of by washout. That may be caused as follows:

1. The Angle of Incidence of One Wing May Be Wrong.—If it is too great, it will produce more lift than on the other side of the airplane; and if too small, it will produce less lift than on the other side—with the result, in either case, the airplane will try to fly one wing down.

2. Distorted Surfaces.—If some part of the surface is distorted, the lift will not be the same on both sides of the airplane, which, of course, will again cause it to fly one wing down.

3. The Ailerons May Be Set Slightly Wrong.—This may be due to one control cable being longer than the other, or one of the aileron horns being bent or twisted. This condition can easily be detected by setting the aileron control—in neutral and checking up the position of the ailerons.

Alignment Errors, Directional.—If there is more resistance on one side of the airplane than on the other the airplane will, of course, tend to turn to the side having the most resistance. This may be caused by the following conditions:

1. The Angle of Incidence of the Right and Left Surfaces May Be Unequal.—The greater the angle of incidence, the greater the resistance. The less the angle, the less the resistance.

2. If the Alignment of the Fuselage, Vertical Stabilizer, the Struts or Stream-line Wires Is Not Absolutely Correct.—That is to say, if they are turned a little to the right or left instead of being in line with the direction of flight—then they will act as a rudder and cause the airplane to turn off its course.

3. If Any Part of the Surface Is Disturbed It Will Cause the Airplane to Turn off Its Course.—If, owing to the leading edge, spars, or trailing edge becoming bent, curvature is spoiled, that will result in changing the amount of resistance on one side of the airplane, which will then develop a tendency to turn off its course.

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.

For satisfactory fuselage checking and truing let us say in the field shop, a certain minimum equipment of tools is necessary. This equipment is:

At least two sawhorses about 3 to 4 ft. high for mounting the fuselage in flying position.

Several wooden wedges (show taper) for easy adjustment of fuselage for cross and lengthwise level.

About 25 yd. of strong linen line for checking center lines.

2 carpenter levels about 2 to 3 ft. long.

4 perfectly formed steel cubes about 1¼ to 1½ in. in size.

1 plumb bob.

1 small screw jack.

1 pair of wood clamps.

1 straight edge about 12 ft. long.

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.

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:

1	ax.
2	crowbars.
6	lengths of iron pipe about 2 in. in diameter, 3 ft. long.
6	lengths of iron pipe about 2 in. in diameter, 4 ft. long.
100	ft. manila rope, 1 in. in diameter.

A regular flat-bed moving truck or ordinary truck with a flat-bed trailer should be provided for handling the machine from the car to the field erecting shop.

Airplanes are usually shipped in automobile cars with end doors or gondola cars. After opening doors of cars, examine and inspect all crates and boxes carefully to see that they are all there in accordance with the bill of loading or shipping memorandum, as well as to see that they are in good condition. If any boxes are found damaged, they should not be removed from the car without first reporting the fact to the receiving officer.

Next, all cleats and bracing should be removed. The crate containing the fuselage and engine should, if possible, be unloaded first. The heavy end where the engine is fixed should be lifted up, have 2-in. pipe rollers put underneath and manipulated into the truck which has been backed up against the car door so that this heavy end, when finally placed, will rest on the body of the truck as far forward as possible. Next lash the front end of the box securely to the truck.

Should it happen that the fuselage crate is so located in the car that the light end must of necessity emerge first through the door, then this end may be run on to a truck and the crate removed from the car with the heavy end adequately supported by sufficient help. Another truck is then backed up against the rear of the first one which has been moved into the clear, and the heavy end of the fuselage crate brought to rest as far forward as possible in the second truck. It is then secured and the first truck released.

After the box is properly lashed by means of the manila rope, a man should be placed on each side of it to watch and see that the lashings do not loosen and the box shift in transit. Trucks should be driven slowly, especially over rough ground, tracks, etc. In addition to the fuselage crate it may also be possible to load the panel crates on this same truck, but as a rule it is better to load these on a second truck. Common sense goes a long way in transporting aircrafts by motor trucks.

Unloading of the crates is done with the use of skids applied to the rear of the truck and secured so as to form a sort of an inclined plane down which to slide the boxes on the pipe rollers to the ground. These skids should be at least 4 in. by 4 in. by 6 ft. and made of strong wood. The rear end of the crate may be brought to the ground, rested there, and the truck moved forward slowly until the entire length rests on the ground. Care must be used not to jolt or drop this box at any stage whatsoever.

When uncrating the fuselage, remove the top and both ends of the box. Fold both sides of box flat down on ground and use same for assembling machine. The wing boxes should have the tops removed and planes lifted out in that manner.

Next, the airplane is assembled in accordance with instructions already given.

The Dismantling and Loading of Airplanes.—When airplanes are to be prepared for shipment by motor truck or railway, they should, of course, be taken down and crated similar to the way they were shipped from the factory. The order in which this is done should be as follows:

Remove propeller.

Unfasten control wires.

Unfasten main planes from fuselage and dismantle on ground.

Remove tail surfaces.

Unless machine is to be placed in box, landing gear and tail skid should remain attached to fuselage.

If the machine is crated it should be handled when shipped the same as described above. If, however, it is to be loaded without being crated, then the following procedure should be observed. Using two planks, 2 in. by 12 in. by 18 ft. long for runway from ground into car, load machine into car, engine first. Block wheels to prevent machine shifting. Secure fuselage, tail end, to the floor of the car by means of ropes passed over the fuselage and fastened to the floor with cleats. The wings should be crated against the sides of car and secured by wires, ropes or canvas strips. All boxes should be marked with name of organization, destination, weight, cubic contents, hoisting centers, number of box, “This Side Up,” etc. A shipping memorandum should always be made out and mailed to destination when shipment goes forth.

Storing of Airplanes and Parts at Bases and in Fields.—Airplanes when not in active flying duty are stored in hangars or sheds especially adapted to house them. Under certain conditions it is necessary to store them in the open. In each case particular precautions should be observed in order not to subject the machines to unnecessary wear and tear.

Since moisture is one of the airplanes’ worst enemies in that it deteriorates the weatherproofing and the fabric, distorts and otherwise injures the wooden parts of the machines and worst of all, rusts the metal parts, the first consideration for proper storage facilities should be the absence of moisture. Next, extreme heat and cold are a menace to airplanes. The temperature of the air surrounding them while in storage should be regulated as much as possible. Under shelter, especially when the machine is to be out of active service for 48 hr. or more, the entire machine should be raised off the ground a few inches so that the wheels are free and the flexible connections released. This is done by the points where the undercarriage struts meet the skids. Furthermore, the wings might well be supported and the weight thus taken off the landing wires, and hinge connections by placing padded trestles underneath the wing skids. Care should be exercised that dirt, grease, water, etc., does not accumulate in any part of the airplane.

Furthermore, all water should be drained from the radiator and gasoline from the gasoline tank. The propeller should be placed in a vertical position and covered with a weatherproof cloth. The engine cockpit and instruments should all be covered and the magneto should be enclosed in a thick layer of felt or cotton waste. If any fluid is apt to freeze, and oil will freeze in temperatures low enough, it should be carefully drained.

When spare parts such as wings, struts, fuselages, etc., are stored, the same general precautions outlined above should be observed. Spare planes particularly should be placed in such a manner that their weight is evenly supported. Never should planes of any kind be laid flat on the ground. They should always stand edgewise, with the leading edge down, supported several inches off the ground on blocks or boards evenly spaced. One plane must not be allowed to lean against another. In fact, the best way is to suspend planes by means of canvas slings hung from overhead. Within the loop of the slings there must be a batten about 2½ in. wide.

All parts of an airplane subject to attack by rust should be kept well coated with grease or oil. Periodically the entire machine should be wiped by means of clean, dry cheese cloth or selected cotton waste. Engines which are in stored planes or which have been set aside for future use should be turned over by hand daily.

It will sometimes be impossible for airplane sheds or hangars to be brought up to the front on service, hence, airplanes must be prepared to remain in the open. When this is the case they should be placed to the leeward of the highest hedge available, a clump of trees, a building, a bank, a knoll, or hill, etc. They should be sunk as low as possible by digging a trench for the wheels and undercarriage. The nose of the plane should, of course, first be run into the wind, and then the wings and the tail pegged down with ropes, particularly if there is any chance of a wind starting up. The engine, propeller, instruments, and cockpit should be covered over with a waterproof cloth and great care taken to protect the propeller from the sun, for it will surely warp if not cared for properly. At night in cold or wet weather the magneto should be packed round with waste and water in the radiator drained. While machines are stored in the open, the necessity of wiping them to keep them moisture and dirt free is all the more urgent and should be pursued with doubled energy.

CHAPTER XI
INSPECTION OF AIRPLANES

Mechanics in charge of airplanes, who are primarily responsible for their safety while in their care, should constantly think of new methods for insuring greater safety and reliability. They should invariably bring any fresh points they think of to the attention of their Flight Commander, in order that the rest of the Corps may benefit by them. They should always try to find out the cause of anything wrong, and inform the officer in charge of the machine of their opinion. They should bear in mind any particular incidents which may have happened to their machine while under their charge during each flight, and be on the lookout for signs of stresses that may have occurred to the machine in consequence of these incidents. For example, a steep spiral may cause side strains on the engine bearers; a flight in bad weather may cause bending stresses on the longitudinal members of the body, besides stretching the landing and flying wires. No part of a machine can be safely overlooked, and good mechanics will always be seeking for the possible cause of accidents and bringing them to the notice of the officer in charge of the machines.

During all inspections the following matters of detail deserve particular attention:

Look out for dirt, dust, rust, mud, oil on fabric. Cleanliness is the very first consideration.

Give the control cables particular attention. These should not be too tight, otherwise they will rub stiffly in the guides. The hand should be passed over them to detect kinks and broken strands. They should be especially well examined where they run over pulley. Don’t forget the aileron balance wire on the top plane.

See that all wires are well greased and oiled, and that they are all in the same tension. When examining wires, be sure to have machine on level ground as otherwise it may get twisted, throwing some wires into undue tension and slackening others. The best way, if time is available, is to jack the airplane up into “flying position.” If a slack wire is found, do not jump to the conclusion that it must be tensioned. Perhaps its opposite wire is too tight, in which case it should be slackened.

Carefully examine all wires and their connections near the propeller, and be sure that they are snaked around with safety wire, so that the latter may keep them out of the way of the propeller if they come adrift.

Carefully examine all surfaces, including the controlling surfaces, to see whether any distortions have occurred. If distortions can be corrected by adjustment of wires, well and good, but if not, matter should be reported.

Verify the angles of incidence, the dihedral angle, the stagger, and the overall measurements as often as possible (at least once a week) and correct as outlined in notes on assembly and adjustment of airplanes.

Constantly examine the alignment and fittings of the undercarriage, the condition of tires, shock absorbers and the skids. Verify the rigging position of the ailerons and elevators.

Constantly inspect the locking arrangements of the turnbuckles, bolts, etc.

Learn to become an expert at vetting, which means the ability to judge the alignment of the airplane and its parts by eye. Whenever you have the opportunity practice sighting one strut against another to see that they are parallel. Standing in front of the machine, which in such a case should be on level ground, sight the center section plane against the tail plane and see that the latter is in line. Sight the leading edge against the main spars, the rear spars, and the trailing edges, taking into consideration the “washin” and “washout.” You will be able to see the shadow of the spars through the fabric. By practising this sort of thing you will, after a time, become quite expert, and will be able to diagnose by eye faults in efficiency, stability and control.

The following order should be observed in the daily and weekly inspections:

Daily Inspection.—All struts and their sockets, longerons, skids, etc.

All outside wires and their attachments.

All control levers or wheels, control wires and cable and their attachments.

All splices for any signs of their drawing.

Lift and landing gear cables or wires for any signs of stretching.

All fabrics, whether on wings or other parts of the machine, for holes, cuts, weak or badly doped places, or signs of being soaked with gasoline, and to see if properly fastened to wings, etc.

All outside turnbuckles, to see that they have sufficient threads engaged, and that they are properly locked.

Axles, wheels, shock absorbers, and tires, pumping the latter up to the correct pressure.

The seats, both for passenger and pilot, seeing that they are fastened correctly.

Safety belts and their fastenings.

This examination should be carried out systematically in the following order:

(a) Lower wings, landing gear complete, tail planes with all wires attached to these tail skids and all attachments and rudder.

(b) Nacelle or fuselage, bolts of lower plane, all control levers and wires.

(c) Top wings, wing flaps or ailerons and wires.

Inspection after Each Flight.—The landing gear, tail skid and attachments and lift and drag wires for tautness.

The wheels, after a rough landing, for bent spokes, uncovering them if necessary.

After flying is finished for the day, wipe all oil off the planes as far as possible with a cloth or cotton waste.

Weekly Inspection.—Check over all dimensions, span, chord, gap, stagger of wings, angles of incidence or set angle of wings and tail, dihedral angle, alignment of fuselage, rudder, elevators, and the general truth of the machine.

Examine the points of crossing of all wires to see that there are no signs of wear, and that each wire is properly bound with insulating tape to prevent rubbing.

Examine all places where wires cross the strut to see if the plates require renewal.

Examine any control wires which are bound together, and see that they are correct. (Insulating tape should be used for this in preference to wires which are bound to slip and cause slack.)

Examine the wheels for bent or loose spokes, uncovering if necessary.

Examine all nuts and bolts of cotter-pin applications, lock washers, etc.

The following directions for inspection are given to the U. S. Inspectors of Airplanes:

Inspection of Cables.

Are there any kinks in the cable?

Are loops properly made?

Are thimbles used in eyes?

Are ends wrapped properly (when wrapped splice is used, wrap must be at least fifteen times the diameter of wire).

No splicing of the cable itself is permitted.

Has acid struck cable during soldering?

Are any of the strands broken?

Are unwrapped ends stream-lined and show the result of skilled workmanship?

For Roebling Hard Wire.

Are there any file cuts or flaws to weaken it?

Is loop well made?

Is ferrule put on correctly?

Are there any sharp bends or kinks?

Are wires too loose or tight in machine?

Fittings.

Is workmanship good?

Is material good?

Are holes drilled correctly to develop proper strength?

Are there any deep file cuts or flaws to weaken it?

Is rivet or fastening wire put in properly?

Are thimbles of large enough diameter?

Turnbuckles.

Any file cuts, tool marks, or flaws in shank or barrel?

Are there too many threads exposed?

Is turnbuckle of right strength and size to develop full strength of wire?

Are shanks bent?

Are threads on shank or in barrel well made?

Is barrel cracked?

Is turnbuckle properly wired?

Inspection of Linen.

All linen used in airplane construction should be of the following specifications:

Free from all knots or kinks.

Without sizing or filling.

As near white as possible.

Weight, between 3.5 and 4.5 oz. per square yard.

Strength as per Government Specifications.

Inspection of Wood.

All wood should be inspected before varnish is applied.

Is grain satisfactory?

Are there any sap or worm holes?

Are there any knots that look as if they would weaken the member?

Any brashiness?

Any holes drilled for bolts or screws that would weaken the member?

Any splits or checks?

Are laminations glued properly?

Are there any plugged holes?

Any signs of dry rot?

Inspection of Metal Fittings.

When fittings are copper plated and japanned the inspection should take place after the copper plating.

Have fittings been bent in assembling?

Does fitting show any defects that lessen its strength?

Are holes drilled properly. Do fittings fit?

Sheet aluminum should be inspected for defects such as cracks, bad dents, etc. Where openings occur in sheet aluminum the corners should be rounded, allowing a good-sized radius.

Directions for Work.

Before you start work on rigging you are advised as follows:

1. Do not hurry about the work. No rush jobs can be done in airplane rigging.

2. You are cautioned against leaving tools of any kind in any part of the airplane.

3. The bolts and their threads must not be burred in any way; for this reason, the use of pliers or pipe wrenches on bolts is very bad form.

4. Start all turnbuckles from both ends every time they are connected up.

5. Full threads must be had in every case to develop the full strength of a bolt and nut, with turnbuckles at least turn on for a distance equal to three times the thickness of the shank.

6. Lock with safety wires all turnbuckles and pins, and cotter-pin every nut.

7. Watch for kinking of wires and their rubbing around controls and wherever they may vibrate against one another.

8. All bolts and pins must have an easy tapping fit only; do not pound them into position.