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further reducing your payload at
the start of a flight. It's actually
the Zero Fuel Weight, plus
reserve and alternate fuel.
· Payload capacity is the maximum
zero fuel weight, less the empty
weight, equipment necessary for
its operation and the operating
load, which includes the
minimum flight crew.
A couple of things to bear in mind
are that the Basic Weight and the
payload will not change during flight,
but the fuel load will. Another is that
the Maximum Permitted Takeoff Weight
will be the lowest of three weights,
the Maximum Takeoff Weight, the
Maximum Landing Weight (plus the
burnoff) and the Maximum Zero Fuel
Weight (plus fuel in the wing tanks).
Some aircraft have a proper cargo
fit, but problems arise where one
that normally carries passengers is
used without modification, which is
why you may need to be certificated
on your training forms as being
cleared to change the aircraft layout.
Naturally, in small aircraft where the
emergency exits are obvious, this
really only involves removing the
seats, because the aim is just to
substitute loads that use the same
fixtures and locations, but where you
get involved in removing galleys and
otherwise converting the cabin in
larger ones, the exercise becomes a
little more difficult (just because a
Flight Manual has freight limitations,
don’t assume modifications you
make are permitted—they may only
have been for basic certification).
Refer to Wake Turbulence for weight
classifications.
Standard Mass Values
In small aircraft, where the number
of seats does not allow proper
statistical analysis, you should
normally use the actual weight of
passengers and baggage.
However, certain circumstances
preclude this, and standard weights can
be used when things are happening
quickly and you cannot weigh things:
Summer Winter
182 lbs Males (>12) 188 lbs
135 lbs Females (>12) 141 lbs
75 lbs Children (2-11) 75 lbs
30 lbs Infants (0-<2) 30 lbs
These figures include an allowance
for carry-on baggage so, if there is
none, reduce them by 8 lbs. Use 8
lbs for clothing in Summer and 14
lbs in Winter.
Fuel and oil have standard weights,
too, although technically the weight
of fuel in the machine changes with
temperature (check the flight manual
for what the manufacturer thinks).
For exam purposes, take jet fuel as
being 6.5 lbs/US gal and oil as 7.5
lbs/US gal.
Distribution
Incorrect loading naturally affects
aircraft performance, and will
possibly prevent the thing from even
getting airborne. A Centre of Gravity
too far forward will make it more
difficult to raise the nose on take-off
(or landing), possibly overstress the
nosewheel as a result, and make the
flight less economical by excessive
use of trim tabs, which causes more
drag. There are certain advantages to
having the C of G towards the rear
(by making the tailplane contribute
Flight Planning 337
to total lift, or at least not detract
from it, which also reduces the
power required and hence fuel used),
but too much will make the aircraft
less stable, more fatiguing to fly and
cause similar drag and nosewheel
problems (but in reverse) as
excessive forward C of G. Also, if
you don’t have the elevator
movement to get yourself out of a
stall, you could end up in a flat spin
you can’t get out of.
In a helicopter, if the C of G is too
far aft or forward of its ideal
position, there is a danger of running
out of cyclic control in the opposite
direction – one too far forward, for
example, will mean you will not be
able to pull the cyclic back far
enough to cope with certain stages
of flight (as fuel is consumed, for
example, when the C of G generally
moves forward), as a lot of its range
will be taken up with the unusual
attitude, although a forward position
is needed to counteract flapback.
Not being able to flare in an
autorotation could well ruin your day
(in fact, if your engine fails and you
don't have enough cyclic movement
to counteract the nose down
tendency, the airflow will meet the
disc edge-on and not go up through
it, so you will not enter autorotation,
and the RPM will decrease even
more – ouch!). As well, lateral C of G
may be affected with some loads,
such as when hoisting.
Passenger seats occupy the whole
floor space evenly; this loadspreading
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Canadian Professional Pilot Studies2(83)
