2.
If the ram air input to the pitot is blocked and the drain hole is also blocked, pressure is trapped in the system and the airspeed indicator will react as an altimeter.
A. In level flight, the indicated airspeed will remain constant even with large power changes.
B. In a climb, the indicated airspeed will increase. If allowed to continue, the MACH warning alarm will eventually sound. Should the cockpit crew interpret this as a true MACH warning and the appropriate remedial action is followed, further problems, such as stick shaker, could occur.
C. If a descent, the indicated airspeed will decrease.
3. If the static ports are blocked, the results will be just the opposite of 2. above.
Descent/Approach
When icing is anticipated during descent, commence use of the engine and airfoil anti-ice systems well before reaching the expected icing level. If the engines are at low power, it may be necessary to increase power to a minimum of 1.2 EPR to maintain a minimum of 20 psi pneumatic pressure for the ice protection systems. Increased drag, such as use of speedbrakes, may be necessary to maintain an adequate rate of descent. Vertical speeds should be kept as high as practical to reduce the exposure and ice accretion time. For approach maneuvering, 11 degrees flaps may be used as an intermediate flap setting as slats extended to the mid-position will be less subject to ice accumulation.
Holding is normally flown in the minimum fuel consumption cruise configuration with slats and flaps retracted. Engine bleed air adequate to maintain anti-icing may require a higher drag configuration, much the same as descent, consequently causing a higher fuel consumption. When forced to hold in icing conditions, there is a concern for ice buildup on the underside of the flaps and the flap/slat extension mechanisms. If necessary, the landing gear may be extended to increase drag as the effects of ice accumulation on the landing gear would be less than on the flaps, slats, and speedbrakes.
If airfoil anti-ice is required for approach, tail de-ice should be initiated approximately 1 minute prior to extension of landing flaps, normally just prior to landing gear extension. Fuel heat should be turned on for 1 minute prior to final approach whenever the fuel temperature is 0°C (32°F) or below. Fuel heat switches should be off for final approach and go-around. If a landing is to be made on a runway contaminated with slush, standing water, or during heavy rain, the APU should be started and the left and right APU bus switches on prior to final approach. This will serve as a back-up electrical power source in case the engine-driven generators are lost due to slush or water ingestion by the engines and subsequent loss of engine RPM.
Landing
Refer to Landing On Wet Or Slippery Runways, this section.
Taxi-In
If the approach was made in icing conditions or if the runway was covered by slush or snow, retract the flaps and slats to 15/T.O. EXT. Damage to the flaps and slats could occur if residual ice is present and the flaps and slats are fully retracted. Slush in puddles or runway low spots may be deeper than the maximum allowed for operation and cause damage to flaps or other parts. A check after parking should be made for any damage or the necessity to de-ice the flaps and slats area. After a satisfactory check, flaps and slats should be moved to UP/RET.
Apply the same precautions for taxi-in as for taxi-out. Maintaining a safe taxi speed during taxi after landing may be even more difficult. As the airplane will have a lower gross weight, it will have a tendency to taxi faster with the same thrust. If icing conditions exist during taxi-in, engine anti-ice should be left on until parked at gate and ready for engine shut down. If extended taxi-in delays are encountered, apply the same engine anti-ice run-up procedures as for taxi-out.
Use caution when entering ramp areas. Be alert for obscured taxi and parking lines and surface conditions that may not be conducive to good steering and stopping. Other airplanes may not be parked in proper positions and may not afford sufficient clearance due to contaminated parking areas. If in doubt, request assistance for proper parking and clearance from other airplanes and obstacles.
Parking
The area in which an airplane is to be parked should be cleared of snow and slush. If this is impractical, the area around the main and nose gear wheels should be cleared to reduce the possibility of tires freezing to the ground.
Avoid a parking position during or immediately after completion of a turn. It is best to allow nose wheels to be centered and the airplane to roll forward a few feet to eliminate all side loads on main and nose gear struts.
Both main and nose gear should be properly chocked. Parking brakes should be released to eliminate possibility of brakes freezing. If concerned about chocks holding on an icy ramp, parking brakes may be left on.
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本文链接地址：MD-80 Flight Manual 麦道80飞行手册 2(59)
