ibly 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 floo