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165
The Aeroplane Speaks. Fifth Edition
·
H. Barber
79
Perhaps
some
day
a
brilliant
inventor
will
design
an
aeroplane
of
reasonable
weight
and
drift
of
which
it
will
be
possible
for
the
pilot
to
vary
at
will
the
above-mentioned
opposing
essentials.
Then
we
shall
get
maximum
velocity,
or
maximum
margin
of
lift,
for
power
as
required.
Until
then
the
design
of
the
aeroplane
must
remain
a
compromise
between
Velocity
and
Climb.
[Footnote
14:
See
Newton's
laws
in
the
Glossary
at
the
end
of
the
book.]
[Footnote
15:
See
"Aerofoil"
in
the
Glossary.]
CHAPTER
II
STABILITY
AND
CONTROL
STABILITY
is
a
condition
whereby
an
object
disturbed
has
a
natural
tendency
to
return
to
its
first
and
normal
position.
Example:
a
weight
suspended
by
a
cord.
INSTABILITY
is
a
condition
whereby
an
object
disturbed
has
a
natural
tendency
to
move
as
far
as
possible
away
from
its
first
position,
with
no
tendency
to
return.
Example:
a
stick
balanced
vertically
upon
your
finger.
NEUTRAL
INSTABILITY
is
a
condition
whereby
an
object
disturbed
has
no
tendency
to
move
farther
than
displaced
by
the
force
of
the
disturbance,
and
no
tendency
to
return
to
its
first
position.
In
order
that
an
aeroplane
may
be
reasonably
controllable,
it
is
necessary
for
it
to
possess
some
degree
of
stability
longitudinally,
laterally,
and
directionally.
LONGITUDINAL
STABILITY
in
an
aeroplane
is
its
stability
about
an
axis
transverse
to
the
direction
of
normal
horizontal
flight,
and
without
which
it
would
pitch
and
toss.
LATERAL
STABILITY
is
its
stability
about
its
longitudinal
axis,
and
without
which
it
would
roll
sideways.
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