曝光台 注意防骗
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just as soon as the airplane begins its takeoff roll.
Instead, the pilot should confirm that both engines
are developing full-rated manifold pressure and
r.p.m., and that the fuel flows, fuel pressures, exhaust
gas temperatures (EGTs), and oil pressures are matched
in their normal ranges. A directed and purposeful scan
of the engine gauges can be accomplished well before
the airplane approaches rotation speed. If a crosswind is
present, the aileron displacement in the direction of the
crosswind may be reduced as the airplane accelerates.
The elevator/stabilator control should be held neutral
throughout.
Full rated takeoff power should be used for every takeoff.
Partial power takeoffs are not recommended.
There is no evidence to suggest that the life of modern
reciprocating engines is prolonged by partial power
takeoffs. Paradoxically, excessive heat and engine
wear can occur with partial power as the fuel metering
system will fail to deliver the slightly over-rich
mixture vital for engine cooling during takeoff.
There are several key airspeeds to be noted during the
takeoff and climb sequence in any twin. The first speed
to consider is VMC. If an engine fails below VMC while
the airplane is on the ground, the takeoff must be
rejected. Directional control can only be maintained by
promptly closing both throttles and using rudder and
brakes as required. If an engine fails below VMC while
airborne, directional control is not possible with the
remaining engine producing takeoff power. On takeoffs,
therefore, the airplane should never be airborne
before the airspeed reaches and exceeds VMC. Pilots
should use the manufacturer’s recommended rotation
speed (VR) or lift-off speed (VLOF). If no such speeds
are published, a minimum of VMC plus 5 knots should
be used for VR.
The rotation to a takeoff pitch attitude is done
smoothly. With a crosswind, the pilot should ensure
that the landing gear does not momentarily touch the
runway after the airplane has lifted off, as a side drift
will be present. The rotation may be accomplished
more positively and/or at a higher speed under these
conditions. However, the pilot should keep in mind
that the AFM/POH performance figures for acceleratestop
distance, takeoff ground roll, and distance to clear
an obstacle were calculated at the recommended VR
and/or VLOF speed.
After lift-off, the next consideration is to gain altitude
as rapidly as possible. After leaving the ground,
altitude gain is more important than achieving an
excess of airspeed. Experience has shown that
excessive speed cannot be effectively converted into
altitude in the event of an engine failure. Altitude
gives the pilot time to think and react. Therefore, the
airplane should be allowed to accelerate in a shallow
climb to attain VY, the best all-engine rate-of-climb
speed. VY should then be maintained until a safe
single-engine maneuvering altitude, considering
terrain and obstructions, is achieved.
To assist the pilot in takeoff and initial climb profile,
some AFM/POHs give a “50-foot” or “50-foot barrier”
speed to use as a target during rotation, lift-off, and
acceleration to VY.
Landing gear retraction should normally occur after a
positive rate of climb is established. Some
AFM/POHs direct the pilot to apply the wheel brakes
momentarily after lift-off to stop wheel rotation prior
to landing gear retraction. If flaps were extended for
takeoff, they should be retracted as recommended in
the AFM/POH.
Once a safe single-engine maneuvering altitude has
been reached, typically a minimum of 400-500 feet
AGL, the transition to an enroute climb speed should
be made. This speed is higher than VY and is usually
maintained to cruising altitude. Enroute climb speed
gives better visibility, increased engine cooling, and a
higher groundspeed. Takeoff power can be reduced, if
desired, as the transition to enroute climb speed is
made.
Some airplanes have a climb power setting published
in the AFM/POH as a recommendation (or sometimes
as a limitation), which should then be set for enroute
climb. If there is no climb power setting published, it is
customary, but not a requirement, to reduce manifold
pressure and r.p.m. somewhat for enroute climb. The
propellers are usually synchronized after the first
power reduction and the yaw damper, if installed,
engaged. The AFM/POH may also recommend leaning
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12-14
the mixtures during climb. The “climb” checklist
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AIRPLANE FLYING HANDBOOK 飞机飞行手册下(34)
