The Aeroplane Speaks. Fifth Edition

icient and safe condition, it is necessary to possess a knowledge of the

y expressed by the result found by dividing the load by the number of su

re inches of cross-sectional area, and the total load it is called u

eformation prod

ollapse, by the maximum stress it will be called upon to endure. For instance, if a control wire be called upon to endure

form, probably of centreweights, but the dictionary entries, even from a hundred years ago do not list this as a word, but do l

ion tends to produce a crushing strain. Ex

ion tends to produce the strain of

of bending is a combination

which the top, centre, and bottom lines are of equal le

r than the centre line. That can be due only to the strain of elongation produced by the stress of tension. The wood between the centre li

the strain of crushing produced by the stress of compression. The wood between the centre and bottom lines is then in c

y surrounding it is under considerably less stress than the wood farther away. This being so, the wood in the centre may be holl

k from one end of a strut or spar to the other end. A point to remember is that the outsi

collapses under it, one part slides over

s and from which wires are taken. Such a wire, exerting a sideways pull upon a bolt, tri

unded of compression, tension, and shear

k is put under a bending stress, it will probably collapse to a stress of not more than about 50 lb. That is a very great difference, and, since weight is of the greatest importance, the design of an aeroplane is always such as to, as far as possible, keep the various wooden parts of its construction in direct

NS TO BE

nd struts must be

e will be more compression on one side of the centre of strength than on the other side. That is a step towards getting compression on one side and tension on the other side, in which case it may be forced to take a bending stress for which it is not de

ght of the nacelle, are arched upwards. If this was not done, it is possible that rough landings might result in the weight causing the spars to become slightly distorted downwards. That

e correct, as otherwise there will be bulging places on the outside, with the result that the stre

e fibres of the wood are doing by far the most work. If these get bruised or scored, then the strut or spar suffers in strength

knots, or shakes. Such blemishes produce weak places and, if a

Then again, a strut must bed well down all over its cross-sectional area as illustrated above; otherwise the stress of compression will not be evenly disposed about the centre of strength, and that may

not matter but for the fact that it does not expand and contract uniformly, but becomes unsymmetrical, i.e., distorted. I have alrea

attitude. That is only so when the spars of the bottom plane are parallel with those of the top plane. Also, the chord of the top plane must be parallel with the chord of the bottom plane. If that is not so,

e sockets or fittings, or even the spars upon which they are placed, sometimes vary in thickness owing to faulty manufacture. This must be offset by altering the length of the struts. The best way to proceed is to measure the distance between the top and bottom spars by the side of each strut, and if that distance, or "gap" as it is calle

. A bolt-hole should be of a size to enable the bolt to be pushed in, or, at any rate, not more than gently tapped in. Bolts should not be hammered in, as that may split the spar. On the other hand, a

be used in all-metal construction. This is to disperse the stress over a large area; otherwise the washer may be pulled into the wo

used in such a way that the nut cannot possibly unscrew at all. The split pin should be passed t

ad the whole head of the bolt. That might damage the woodwork inside the fabric-covered surface

adjusted to their proper tension. Eye-bolts must be a good fit in the barrel; that is to say, not slack and not very tight. Theoretically it is not necessary to screw the eye-bolt into the barrel

bore within it. The best method is to pass a piece of wire through the hole in its centre, and to use that as a lever. When the correct adjustment has been secured, the turnbuckle must be locked to prevent it from unscrewing. It is quite possible to lock it in su

should be carefully observ

ft. An easy practical way of learning to know

and the third piece of the right quality. Fix them in a vice, about an inch apart and in a vertical position, and with the

t, which will broaden at that point. In the case of the wire which is too hard, the band of light will broaden very little at the turn, but, if you look carefully, you will see som

earn to know really bad wire from good, and also learn to k

at is to say, it must be unki

e of regreasing them, as they are inside fabric-covered surfaces. They should be prevented from rusting by being painted with an anti-rust mixture. Great care should be taken to see that the wire is perfectly clean and dry

ould be of the same tension when the aeroplane is supported in such a way as to throw no stress upon them. If so

d by packing underneath the lower surfaces as well as by packing underneath the fuselage or nacelle. I

amework rigid. Anything more than that lowers the factor of safety, throws various parts of the framework into undu

earning the construction of the various types of aeroplanes, the work the various p

posite direction. For instance, an auxiliary lift wire may run from the bottom of a strut to a spar in the top plane at a

, will spoil the camber (curvature) of the surface, and result in changing both the lift and the drift at that part of

of the utmost importance. When this, and also accuracy in securing the vario

ting. These loops, even when made as perfectly as possible, have a tendency to elongate, thus spoiling the adjustment

e within reason. By that I mean it should not be so sm

the loop should

to prevent the ferrule from slipping up. At the sam

ld be undamaged, and it should not be

h twine until it has been inspected by whoever is in c

, then the cable should be re

time an aeroplane comes down from flight the rigger should carefully examine the cables, espe

is necessary to fetch a high pair of steps in order to examine it. Don't slack this

in rigging the aileron, rudder, and elevator properly, for t

the aeroplane is in flight, they are in a fair true lin

lifting surface, then they should be rigged to be

above the position in which it has been rigged. It is able to lift owing to a certain amount of slack in the control wire holding it-and one cannot adjust the control wire to have no slack, because that would cause it to bind against the pulleys and make the operation of it too hard for the pilot. It is therefore necessary to rig

is safe to rig it dow

in a fair line with the surface in front; or about 1/2 inch

be in their neutral positions. It is not sufficient to lash them

uch wires must be carefully adjusted. If they are distorted and there are no bracing wires wi

ring the stability of the aeroplane. Nothing can be accomplished in t

l bracing wires so that the ribs are parallel to the direction of flight. The ribs usually cause the fabric to make a ridge where they occur, and, if su

ork. They should not be tensioned above that unless the wires are, at their ends, bent to form loo

hesive tape. The wires must be rendered perfectly dry and clean, and the

lts, then their places should be marked before being bored and their positions confirmed by whoever

ables is quite an art, and upon it will depend to a large deg

od is as

s SMARTLY. Tension the control cables so that when the levers are smartly moved there is no perceptible snatch or lag. Be careful not to tension the cables more than necessary to take out the snatch. If tensioned too much they will (1) bind roun

itions, and move them to and fro about 1/8 inch either side of such positions. If the adjustment is correct, it s

ts it is necessary to place it in what is known as its "flying posit

e of the level. The slightest error will assume magnitude towards the extremities of the aeroplane. Great care should be taken to block up the aeroplane rigidly. In case it gets accidentally disturbed while the work is going on, it is well to constantly verify the flying position by running the straight-edge and spirit-level over the engine foundations. The straight-edge should be carefully tested befor

"flying position" is some special attitude laid down in the aeroplan

thod of finding the angle

a spirit-level. The set measurement will then be from the top of the straight-edge to the centre of the bottom surface of the main spar, or it may be from the top of the straight-edge to the lowest part of the leading edge. Care s

n the struts, because, in such places, the spars may have taken a slight permanent set up or down; not, perhaps, sufficiently bad to make any mat

g, it should then be

t, and this is done by slackening ALL the wires going to the top of the s

o the bottom of the strut, and tighten ALL the wires going to

just the angle by w

e stated in the aeroplane's specificat

his is as follows, and this method will, at the

t (which should be accurate to 1/16 inch or less) is then from the strings down to four points on the main and rear spars of the centre-section surface. These points should be just inside t

at is as shown in the above illustration, i.e., by weighting the strings down to the spars by means o

is of no great importance, provided it is divided equally between the left- and right-hand

of the aeroplane. As a rule such diagonal measurements are taken from the bottom socket of one strut to the to

should be at fixed distances from the butts of the spars, suc

than the butts of the spars. It is not practicable to do so, howev

f incidence, is by means of the dihedral board. It is a light handy thing to use, but l

its use is that it has to be placed on the spars in a position between the struts, and that is just where the spars may have a little permanent s

raise it above the flanges of the ribs (which cross over the spars), as they may vary in depth. A spirit-level is then placed on the board, and the wires must be adjusted to give the surface such an inclin

hedral angle, and at the same time t

with the spar, or a fixed measurement from the line to the spar taken at a specified distance from the butt. This opera

re that after the job is done t

advance of the bottom surface when the aeroplane is in fl

of the lower leading edge to the plumb-lines. It makes a difference whether the measurement is taken along a horizontal line (which can be found by using a straig

the wrong line, it may result in a difference of perh

agger have been secured, it is as well to confirm all of them, as,

llowing over-all check measu

A and B are marked on the main spar, and must in each case be the same distance from the butt of the spar. The rigger should not attempt to make A and B merely the sockets of the outer str

e or rudder-post. D and E are points marked on both top and bottom rear spars, and each must be t

fuselage being out of truth, but of course the rigger should have made quite sure that the fuselage was true before rigging the rest of the machine. Again, it may be due t

o make about three-quarters of it towards the tail stick out unsupported. In this way it will assume a condition as near as possible to flying conditions, and when it is in this position the set measurements should

is necessary to make sure that the spars are horizontal when the aeroplane is in flying position and the tail unsupported as e

must be very carefully aligned as

eels being off the ground when rigged. When in this position the axle must be horizontal and

e struts bed well do

tension. In the case of rubber shock absorbers, bot

LTS IN FLIGHT, STAB

ce) on one side of the aeroplane than there is on the other side. The aeroplane wil

urface may be wrong. The greater the angle of incidence, th

arman, the front outriggers, are not absolutely correct-that is to say, if they are turned a little to the left or to the right in

through the air with the least possible drift. If, owing perhaps to the leading edge, spars, or trailing edge becoming bent, the curvature is

ble reason for such a condition is a difference in the lif

n the other side of the aeroplane; and if too small, it will produce less lift than on the o

ts camber is spoiled, and the lift will not be the same on both sides o

LITY may be due to t

ir loops or having pulled the fittings into the wood. If the top surface is not staggered forward to the correct degree, then consequently the whole of it

l make a very considerable differe

not right, it will have a bad effect, especially i

e of the aeroplane and result in a tendency to fly "tail-down." If the angle is too small,

gle of incidence. If it has too much angle, it will lift too much, and the aeroplane will be "nose-he

to give it too great an angle, because the longitudinal stability entirely depends upon the tail-plane being set at a much smaller angle of incidence than is the main surface, and if that difference is decreased too much, the aeroplane will become uncontrollable longitudinally. Sometimes

e or propeller trouble, probably due to (1) distort

rouble, probably due to (1) distorted surfaces, (2) too great an angle o

ting of control surfaces, (2) distortion of control

n the ground, it is probably due to (1) alignment of underca