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high wing, like the average Cessna:
High wing planes may have struts to
help keep the wings up, as well as
internal bracing. Both types are also
called cantilever, or semi-cantilever,
respectively.
Aeroplanes are single- or multi-engined,
with fixed or retractable
undercarriages, if they are
landplanes, skis if they land on snow,
and floats if they operate on water:
A monoplane has one pair of wings,
while a biplane has two (the Red
Baron's triplane had three. I forget
8 Canadian Private Pilot Studies
what Snoopy had). The shape of a
wing as viewed from above is known
as a planform, and could be rectangular,
tapered (from root to tip), elliptical,
delta or sweptback. Large, wide ones,
for example, are good for large
transport aircraft, and short, stubby
ones will be found on fast sports
aircraft. The aspect ratio of a wing is
the relationship between its length
and width, or span and chord. You
could have two wings of equal
surface area but different aspect
ratios, depending on what they were
designed for. The higher the ratio
(i.e. the longer the wing relative to its
width), the more lift you get, with
less induced drag and downwash (as
with gliders):
However, it does stall at a lower
angle.
An aeroplane's rated strength is a
measure of the load the wings can
carry without being damaged. Light
aircraft can take total loads in three
categories:
· Normal, 3.8 x the gross weight
· Utility, 4.4 x gross weight
· Acrobatic, 6 x gross weight
Naturally, there is a safety factor
involved, but the above should not
be exceeded.
Normal or utility categories do not
allow manoeuvres with high positive
and negative load factors. Bank
angles would normally be inside 60°.
Flight Controls
When airflow over them is high, the
controls have a positive feel. They
are less responsive at slow speeds,
which is a point to remember when
flying low and slow (also, because of
the nose high attitude, the control
surfaces may not have any airflow
over them at all, which is why some
aircraft have the tail at the top of the
fin). In fact, the effectiveness of any
control depends on its distance from
the Centre of Gravity, the size of the
control surface, its speed through
the air and the degree of movement.
Control surfaces in small aircraft are
usually activated by cables and
pulleys, or rods and tubes.
The elevator, rudder and ailerons are
attached by hinges to the tailplane
(or horizontal stabiliser), fin and
wing trailing edges, respectively (a
Canard is a horizontal stabiliser
mounted on the front, with the
advantage of a longer moment arm,
so they can be smaller).
The elevator controls pitching by
increasing the angle of attack above
or below the tailplane, according to
whether it is raised up or forced
down by movement of the control
column in the cockpit (if the column
is pushed forward, the elevator is
forced down into the airflow
underneath the stabiliser, the angle
Principles of Flight 9
of attack is increased, the tail rises
because more lift is created and the
nose goes down, the opposite if
pulled back). Sometimes, there is no
elevator, but the whole stabiliser is
moved, in which case it is a stabilator.
The rudder does much the same
thing, only sideways, making the
nose yaw, or move left and right. It is
controlled by the foot pedals –
whichever one goes forward moves
the rudder to that side, where more
lift is created and the fin is forced
sideways in the opposite direction, to
produce a flat turn with a skid (you
don't use the rudder to turn, but to
fine tune one initiated by the
ailerons, or stop it going the wrong
way – see Low and Slow, below).
The ailerons make the aircraft roll
around the nose. If you move the
control column to the left, the right
aileron goes down, increasing the
angle of attack on that side, and the
left one goes up, decreasing it,
causing a roll in the same direction.
To counteract Aileron Drag, which
comes from the downgoing aileron,
you might see frise or differential
ailerons used. With the former, the
downgoing aileron is streamlined.
The latter moves the down aileron
through a smaller angle.
In fact, the frise aileron's hinge is
offset, so a portion of the leading
edge of the downgoing aileron sticks
out into the airflow, to create a little
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