University of Virginia Library

5. CHAPTER V
MAINTENANCE

Cleanliness.—The fabric must be kept clean and free from oil, as that will rot it. To take out dirt or oily patches, try acetone. If that will not remedy matters, then try petrol, but use it sparingly, as otherwise it will take off an unnecessary amount of dope. If that will not remove the dirt, then hot water and soap will do so, but, in that case, be sure to use soap having no alkali in it, as otherwise it may injure the fabric. Use the water sparingly, or it may get inside the planes and rust the internal bracing wires, or cause some of the wooden framework to swell.

The wheels of the undercarriage have a way of throwing up mud on to the lower surface. This should, if possible, be taken off while wet. It should never be scraped off when dry, as that may injure the fabric. If dry, then it should be moistened before being removed.

Measures should be taken to prevent dirt from collecting upon any part of the aeroplane, as, otherwise, excessive skin-friction will be produced with resultant loss of flight speed. The wires, being greasy, collect dirt very easily.

Control Cables.—After every flight the rigger should pass his hand over the control cables and carefully examine them near pulleys. Removal of grease may be necessary to make a close inspection possible. If only one strand is broken the wire should be replaced. Do not forget the aileron balance wire on the top surface.

Once a day try the tension of the control cables by smartly moving the control levers about as explained elsewhere.

Wires.—All the wires should be kept well greased or oiled, and in the correct tension. When examining the wires, it is necessary to place the aeroplane on level ground, as otherwise it may be twisted, thus throwing some wires into

undue tension and slackening others. The best way, if there is time, is to pack the machine up into its "flying position."

If you see a slack wire, do not jump to the conclusion that it must be tensioned. Perhaps its opposition wire is too tight, in which case slacken it, and possibly you will find that will tighten the slack wire.

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

The wires inside the fuselage should be cleaned and regreased about once a fortnight.

Struts and Sockets.—These should be carefully examined to see if any splitting has occurred.

Distortion.—Carefully examine all surfaces, including the controlling surfaces, to see whether any distortion has occurred. If distortion can be corrected by the adjustment of wires, well and good; but if not, then some of the internal framework probably requires replacement.

Adjustments.—Verify the angles of incidence; dihedral, and stagger, and the rigging position of the controlling-surfaces, as often as possible.

Undercarriage.—Constantly examine the alignment and fittings of the undercarriage, and the condition of tyres and shock absorbers. The latter, when made of rubber, wear quickest underneath. Inspect axles and skids to see if there are any signs of them becoming bent. The wheels should be taken off occasionally and greased.

Locking Arrangements.—Constantly inspect the locking arrangements of turnbuckles, bolts, etc. Pay particular attention to the control cable connections, and to all moving parts in respect of the controls.

Lubrication.—Keep all moving parts, such as pulleys, control levers, and hinges of controlling surfaces, well greased.

Special Inspection.—Apart from constantly examining the aeroplane with reference to the above points I have made, I think that, in the case of an aeroplane in constant use

it is an excellent thing to make a special inspection of every part, say once a week. This will take from two to three hours, according to the type of aeroplane. In order to carry it out methodically, the rigger should have a list of every part down to the smallest split-pin. He can then check the parts as he examines them, and nothing will be passed over. This, I know from experience, greatly increases the confidence of the pilot, and tends to produce good work in the air.

Windy Weather.—The aeroplane, when on the ground, should face the wind; and it is advisable to lash the control lever fast, so that the controlling surfaces may not be blown about and possibly damaged.

"Vetting" by Eye.—This should be practiced at every opportunity, and, if persevered in, it is possible to become quite expert in diagnosing by eye faults in flight efficiency, stability and control.

The aeroplane should be standing upon level ground, or, better than that, packed up into its "flying position."

Now stand in front of it and line up the leading edge with the main spar, rear spar, and trailing edge. Their shadows can usually be seen through the fabric. Allowance must, of course, be made for wash-in and wash-out; otherwise, the parts I have specified should be parallel with each other.

Now line up the centre part of the main-plane with the tail-plane. The latter should be horizontal.

Next, sight each interplane front strut with its rear strut. They should be parallel.

Then, standing on one side of the aeroplane, sight all the front struts. The one nearest to you should cover all the others. This applies to the rear struts also.

Look for distortion of leading edges, main and rear spars, trailing edges, tail-plane and controlling surfaces.

This sort of thing, if practiced constantly, will not only develop an expert eye for diagnosis of faults, but will also greatly assist in impressing upon the memory the characteristics and possible troubles of the various types of aeroplanes.

Mishandling of the Ground.—This is the cause of a lot of unnecessary damage. The golden rule to observe is: Produce no Bending Stresses.

Nearly all the wood in an aeroplane is designed to take merely the stress of direct compression, and it cannot be bent safely. Therefore, in packing an aeroplane up from the ground, or in pulling or pushing it about, be careful to stress it in such a way as to produce, as far as possible, only direct compression stresses. For instance, if it is necessary to support the lifting surface, then the packing should be arranged to come directly under the struts so that they may take the stress in the form of compression for which they are designed. Such supports should be covered with soft packing in order to prevent the fabric from becoming damaged.

When pulling an aeroplane along, if possible, pull from the top of the undercarriage struts. If necessary to pull from elsewhere, then do so by grasping the interplane struts as low down as possible.

Never lay fabric-covered parts upon a concrete floor. Any slight movement will cause the fabric to scrape over the floor with resultant damage.

Struts, spars, etc., should never be left about the floor, as in such position they are likely to become scored. I have already explained the importance of protecting the outside fibres of the wood. Remember also that wood becomes distorted easily. This particularly applies to interplane struts. If there are no proper racks to stand them in, then the best plan is to lean them up against the wall in as near a vertical position as possible.

Time.—Learn to know the time necessary to complete any of the various rigging jobs. This is really important. Ignorance of this will lead to bitter disappointments in civil life; and, where Service flying is concerned, it will, to say the least of it, earn unpopularity with senior officers, and fail to develop respect and good work where men are concerned.

The Aeroplane Shed.—This should be kept as clean and orderly as possible. A clean, smart shed produces briskness, energy, and pride of work. A dirty, disorderly shed nearly always produces slackness and poor quality of work, lost tools and mislaid material.