曝光台 注意防骗
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The Circuit
This is not just a way of making sure
that everyone follows the same oneway
route around an airfield, but a
good exercise in precision flying.
The existence of the circuit is the
reason why airfields have to be
avoided by a minimum distance.
The traffic circuit is rectangular,
usually left-handed, and consists of 5
parts – the takeoff, crosswind leg,
downwind leg, base leg and landing:
The takeoff phase lasts until 500
feet, where you make a 90° turn
crosswind to level off at circuit
height (usually 1000 feet, but check,
in case they surprise you). Another
90° turn takes you downwind, and
you report being on the downwind
leg when approximately abeam the
tower. You also do your pre-landing
checks, leaving the landing gear for
the base leg, which is another 90°
turn at the end of downwind.
While in the circuit, keep a good
lookout and be very aware of your
position relative to other aircraft,
especially at Biggin Hill! Adjust your
spacing as necessary. Use the
downwind leg to plan your final
approach, according to conditions.
You generally leave the circuit
either straight ahead, or off the
crosswind or downwind legs (don't
climb until clear). You join on the
downwind or base legs, or maybe
directly on finals on a slow day. You
can also join at 45° to downwind, or
crossing over from the upwind side
at circuit height.
DO NOT TRY TO TURN BACK
TOWARDS THE FIELD IF THE
ENGINE FAILS IN THE
TAKEOFF PHASE – LAND
STRAIGHT AHEAD.
190 Canadian Professional Pilot Studies
READ THAT AGAIN.
AND AGAIN.
Straight and Level
This is the basis of all other flight
attitudes – many pilots regard doing
it well as a matter of professional
pride. This makes sense, because it is
where you will spend most of your
flying life.
Correct small amounts of yaw (less
than 10°) with rudder only – larger
amounts need aileron as well to
prevent rolling. In a similar vein,
small changes in altitude are less
than 100 feet, for which you can just
use the elevator. Larger amounts
need power as well.
After initiating a manoeuvre, it will
continue unless you centralise the
controls, so, having started a turn,
for example, return the controls to
where they started when you get to
the position you want.
Turns
A "proper" turn is one in which the
aircraft is in balance, and there are
no acceleration forces, unless you are
climbing and descending
deliberately. That is, there is a
constant rate of change of direction,
maintaining height, and the forces
acting on the machine are in
equilibrium. You turn by making the
aircraft bank in the required
direction with ailerons.
Having done that, some of the lift
force is applied to the turn, so the
lift vector is reduced. You must
therefore apply some backwards
control column movement to force
the tail down and the nose up, at the
cost of a little speed (if you want to
keep the same speed, you must also
apply some power). There will also
be a yawing moment applied the
opposite way to the turn, because
the upgoing wing has more aileron
in the airflow, and is producing more
drag to slew the nose round (adverse
aileron yaw). This will need a little
rudder movement to keep the ship
straight, although this can be allowed
for in modern designs by adjusting
the movement of the ailerons, or the
shape, like the Frise aileron, which
produces a counter drag from a lip
that appears underneath the wing
when it is moved upwards. You will
also need a slight force to stop the
machine turning, because the outside
wing will be moving faster and
producing more lift.
The greater the rate of turn, the
more the lift must be increased to
maintain height, and the more the
weight artificially increases to keep
the forces balanced, which is one
good reason for not being
overweight, because you never know
when you will need the power. At
3G, for example, the weight is the
equivalent of three times what it would
be in straight and level flight.
A turn will continue unless the
controls are centralised. The nose
drops because the lift vector moves
away from its opposition to gravity
(weight). You can either increase
speed or the angle of attack, but the
latter is preferable, although power is
required for steep turns (see below).
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