曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
towards the runway surface. Remember also that
because of ground effect, the vertical speed indicator
and the altimeter may not show a positive climb until
the airplane is 35 to 50 feet above the runway.
The climb pitch attitude should continue to be held and
the airplane allowed to accelerate to flap retraction
speed. However, the flaps should not be retracted until
Ch 15.qxd 5/7/04 10:22 AM Page 15-18
15-19
obstruction clearance altitude or 400 feet AGL has
been passed. Ground effect and landing gear drag
reduction results in rapid acceleration during this phase
of the takeoff and climb. Airspeed, altitude, climb rate,
attitude, and heading must be monitored carefully.
When the airplane settles down to a steady climb,
longitudinal stick forces can be trimmed out. If a turn
must be made during this phase of flight, no more than
15° to 20° of bank should be used. Because of spiral
instability, and because at this point an accurate trim
state on rudder and ailerons has not yet been achieved,
the bank angle should be carefully monitored throughout
the turn. If a power reduction must be made, pitch
attitude should be reduced simultaneously and the
airplane monitored carefully so as to preclude entry
into an inadvertent descent. When the airplane has
attained a steady climb at the appropriate en route
climb speed, it can be trimmed about all axes and the
autopilot engaged.
JET AIRPLANE APPROACH AND
LANDING
LANDING REQUIREMENTS
The FAA landing field length requirements for jet
airplanes are specified in 14 CFR part 25. It defines the
minimum field length (and therefore minimum
margins) that can be scheduled. The regulation
describes the landing profile as the distance required
from a point 50 feet above the runway threshold,
through the flare to touchdown, and then stopping
using the maximum stopping capability on a dry
runway surface. The actual demonstrated distance is
increased by 67 percent and published in the FAAapproved
Airplane Flight Manual as the FAR dry
runway landing distance. [Figure 15-22] For wet
runways, the FAR dry runway distance is increased by
an additional 15 percent. Thus the minimum dry
runway field length will be 1.67 times the actual
minimum air and ground distance needed and the wet
runway minimum landing field length will be 1.92
times the minimum dry air and ground distance
needed.
Certified landing field length requirements are
computed for the stop made with speed brakes
deployed and maximum wheel braking. Reverse thrust
is not used in establishing the certified FAR landing
distances. However, reversers should definitely be
used in service.
LANDING SPEEDS
As in the takeoff planning, there are certain speeds that
must be taken into consideration during any landing in
a jet airplane. The speeds are as follows.
• VSO—Stall speed in the landing configuration.
• VREF—1.3 times the stall speed in the landing
configuration.
• Approach climb—The speed which guarantees
adequate performance in a go-around situation
with an inoperative engine. The airplane’s weight
must be limited so that a twin-engine airplane
will have a 2.1 percent climb gradient capability.
(The approach climb gradient requirements for 3
and 4 engine airplanes are 2.4 percent and 2.7
percent respectively.) These criteria are based on
an airplane configured with approach flaps, landing
gear up, and takeoff thrust available from the
operative engine(s).
• Landing climb—The speed which guarantees
adequate performance in arresting the descent
and making a go-around from the final stages of
landing with the airplane in the full landing configuration
and maximum takeoff power available
on all engines.
The appropriate speeds should be pre-computed prior
to every landing, and posted where they are visible to
both pilots. The VREF speed, or threshold speed, is used
VREF = 1.3 VS
50 Ft. TD
Actual Distance 60% 40%
FAR (Dry) Runway Field Length Required
1.67 x Actual Distance
FAR (Wet) Runway Field Length Required
1.15 x FAR (Dry)
or
1.92 x Actual Distance
15%
Figure 15-22. FAR landing field length required.
Ch 15.qxd 5/7/04 10:22 AM Page 15-19
15-20
as a reference speed throughout the traffic pattern. For
example:
Downwind leg—VREF plus 20 knots.
Base leg—VREF plus 10 knots.
Final approach—VREF plus 5 knots.
50 feet over threshold—VREF.
The approach and landing sequence in a jet airplane
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
AIRPLANE FLYING HANDBOOK 飞机飞行手册下(84)
