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guesstimating it, such as speed,
which may have to be increased
slightly with aircraft weight, reducing
your range, as you will be using more
power, and hence fuel, to attain it.
The biggest factor concerning your
range will be the wind, which will
reduce your groundspeed when on
the nose, causing you to use more
fuel. However, a slight increase in
airspeed, say 5-10%, will get you
there sooner with only a slight effect
on fuel consumption.
Maximum Endurance Speed
This gives you the most time in the
air for least amount of fuel, which is
useful when waiting for the weather
to clear, or when asked to hold clear
of a control zone, but, in practice, it
gives you little or no controllability,
so there will be a recommended
endurance speed in the flight manual,
which is a few knots above.
The endurance is longer the lower
you can fly (allowing for safety, of
course), and turbulence and flaps
will affect the speed considerably.
There is more drag with endurance
speed than there is with range speed,
which is higher.
Formula
Guess what? There's a formula for
drag, too, which, luckily is very
similar to that for lift:
D = CD½ rV2S
Drag will also increase with speed.
Load Factor
The total lift divided by the total
weight, the ratio being 1:1 in level
unaccelerated flight. In other words,
the weight carried by a wing
expressed in terms of "G".
When you turn, the aircraft tries to
continue in a straight line, and a
force is needed to point it towards
the centre of the turn – this would
be Centripetal Force, which must be
generated by extra lift from the
wings. In effect, the (upwards) lift
vector is reduced by the same
amount, which needs to be
compensated for. In a 60° banked
turn, therefore, the amount of lift
you need is doubled, so the load
factor becomes 2. This can also be
increased temporarily by sharp
manoeuvres or gusts and turbulence
(a gust with a speed of 66 feet per
second will change the angle of
attack at 200 kts by as much as 11°,
164 Canadian Professional Pilot Studies
which will either lift you very quickly
or cause a stall).
Here is a chart expressing angles of
bank against load factors:
Angle Factor
0° 1
15° 1.04
45° 1.41
60° 2
75° 4
Use this formula to calculate the
stalling speed for an angle of bank:
Vso in turn = Vso X ÅLF
Propellers
These are just aerofoils with a twist
in them (washout) to spread the lift
evenly over the whole length, as the
tips run faster than the center and
need less angle of attack (the word
pitch is sometimes used loosely to
describe this). The basic propeller is
averaged to cope with many flight
conditions, so is not perfect for
them all, particularly the takeoff. The
real problem is that you have to
make the engine run faster for more
performance from the prop, and
engines work best within a certain
speed range.
Officially, a propeller's function is to
convert crankshaft rotary movement
into thrust, by moving a large column
of air backwards, to propel the
aircraft forward. As a propeller is an
aerofoil, the thrust it creates is
equivalent to the lift produced by a
wing – it's just used differently.
A tractor (at the nose) will propel fast,
turbulent air over the lifting surfaces,
whereas a pusher (somewhere behind
the fuselage) provides better high
speed performance because it
doesn't produce so much drag. On
the other hand, the tractor bites into
clean air, while a pusher spins in air
that is already disturbed.
A rotating propeller creates various
forces which may be allowed for in
the design stages, including gyroscopic
precession (see Instruments), where
lifting the tail tends to make the nose
yaw to the left.
Torque results from the airframe
going the opposite way to the
direction of rotation:
The effect is to produce a roll, which
is countered by washout on the
upgoing wing.
The blade going down pulls more at
high angles of attack, resulting in
asymmetric thrust (also known as the P
factor). Where the propellers rotate
the same way on a multi-engined
aircraft (as with the PA 23), the
failure of one engine may cause
more problems than the other
because of this – in the case of the
Aztec, the downgoing blade is on the
right side, since the blades rotate
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