ontrol--A wire connecting a controlling surface with the pilot's
control lever, wheel, or rudder-bar.

Wire, Aileron Gap--A wire connecting top and bottom ailerons.

Wire, Aileron Balance--A wire connecting the right- and left-hand top
ailerons. Sometimes termed the "aileron compensating wire."

Wire, Snaking--A wire, usually of soft metal, wound spirally or tied
round another wire, and attached at each end to the framework. Used to
prevent the wire round which it is "snaked" from becoming, in the event
of its displacement, entangled with the propeller.

Wire, Locking--A wire used to prevent a turnbuckle barrel or other
fitting from losing its adjustment.

Wing--Strictly speaking, a wing is one of the surfaces of an
ornithopter. The term is, however, often applied to the lifting surface
of an aeroplane when such surface is divided into two parts, one being
the left-hand "wing," and the other the right-hand "wing."

Wind-Tunnel--A large tube used for experimenting with surfaces and
models, and through which a current of air is made to flow by artificial
means.

Work--Force X displacement.

Wind-Screen--A small transparent screen mounted in front of the pilot to
protect his face from the air pressure.

FOOTNOTES:

[1] Propeller Slip: As the propeller screws through the air, the
latter to a certain extent gives back to the thrust of the propellor
blades, just as the shingle on the beach slips back as you ascend it.
Such "give-back" is known as "slip," and anyone behind the propellor
will feel the slip as a strong draught of air.

[2] Helicopter. An air-screw revolving upon a vertical axis. If driven
with sufficient power, it will lift vertically, but having regard to the
mechanical difficulties of such construction, it is a most inefficient
way of securing lift compared with the arrangement of an inclined
surface driven by a propeller revolving about a horizontal axis.

[3] Pancakes: Pilot's slang for stalling an aeroplane and dropping
like a pancake.

[4] Morane parasol: A type of Morane monoplane in which the lifting
surfaces are raised above the pilot in order to afford him a good view
of the earth.

[5] Skin friction is that part of the drift due to the friction of the
air with roughnesses upon the surface of the aeroplane.

[6] Banking: When an aeroplane is turned to the left or the right
the centrifugal force of its momentum causes it to skid sideways and
outwards away from the centre of