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165
The Aeroplane Speaks. Fifth Edition
·
H. Barber
94
It
is
due
to
the
combination
of
(1)
a
very
steep
spiral
descent
of
small
radius,
and
(2)
insufficiency
of
keel-surface
behind
the
vertical
axis,
or
the
jamming
of
the
rudder
and/or
elevator
into
a
position
by
which
the
aeroplane
is
forced
into
an
increasingly
steep
and
small
spiral.
Owing
to
the
small
radius
of
such
a
spiral,
the
mass
of
the
aeroplane
may
gain
a
rotary
momentum
greater,
in
effect,
than
the
air
pressure
of
the
keel-surface
or
controlling
surfaces
opposed
to
it;
and,
when
once
such
a
condition
occurs,
it
is
difficult
to
see
what
can
be
done
by
the
pilot
to
remedy
it.
The
sensible
pilot
will
not
go
beyond
reasonable
limits
of
steepness
and
radius
when
executing
spiral
descents.
In
this
connection
every
pilot
of
an
aeroplane
fitted
with
a
rotary
engine
should
bear
in
mind
the
gyroscopic
effect
of
such
engine.
In
the
case
of
such
an
engine
fitted
to
a
"pusher"
aeroplane,
its
effect
when
a
left-hand
turn
is
made
is
to
depress
the
nose
of
the
machine.
If
fitted
to
a
"tractor"
it
is
reversed,
so
the
effect
is
to
depress
the
nose
if
a
right-hand
turn
is
made.
The
sharper
the
turn,
the
greater
such
effect--an
effect
which
may
render
the
aeroplane
unmanageable
if
the
spiral
is
one
of
very
small
radius
and
the
engine
is
revolving
with
sufficient
speed
to
produce
a
material
gyroscopic
effect.
Such
gyroscopic
effect
should,
however,
slightly
assist
the
pilot
to
navigate
a
small
spiral
if
he
will
remember
to
(1)
make
right-hand
spirals
in
the
case
of
a
"pusher,"
(2)
make
left-hand
spirals
in
the
case
of
a
"tractor."
The
effect
will
then
be
to
keep
the
nose
up
and
prevent
a
nose-dive.
I
say
"slightly"
assist
because
the
engine
is,
of
course,
throttled
down
for
a
spiral
descent,
and
its
lesser
revolutions
will
produce
a
lesser
gyroscopic
effect.
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