曝光台 注意防骗
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engages in
ALT HLD
Above 400 feet
RA
• Select roll
mode
Push TO/GA
switches
• A/T engages
in G/A
Approaching
Missed Approach
altitude •
Pitch mode
engages in
ALT ACQ
• A/T engages
in MCP SPD
MCP SPD ALT HLD LNAV CMD
MCP SPD ALT ACQ LNAV CMD
GA TO/GA LNAV CMD
GA TO/GA LNAV CMD
GA TO/GA CMD
AUTO FLIGHT
Sec. 6.4 Page 28 737
Rev. 11/15/02 #41 Continental Flight Manual
AFS Operation In Windshear
General
The autopilot and flight director provide positive corrective action to counteract
most windshears. The autothrottle system also aids in windshear recovery by
providing quick response to any increase or decrease in speed. The commanded
levels of power may be beyond what the average pilot considers necessary but,
in fact, are required by the situation.
Takeoff Or Go-Around
If windshear is encountered during F/D takeoff or go-around, the F/D pitch
command bar provides commands to maintain V2 + 20 kts until vertical speed
decreases to approximately +600 fpm. At this point, the F/D pitch bar
commands a 15 degree nose-up pitch attitude and disregards airspeed.
V/S 600 fpm Down to 0 fpm – The F/D will slowly adjust from 15° pitch
toward optimum pitch (the angle of attack for stick shaker minus 2 degrees).
V/S Less than 0 fpm – The F/D will maintain the angle of attack for stick shaker
minus 2 degrees.
As the aircraft transits the windshear condition, the F/D programming reverses.
As climb rate increases above approximately +600 fpm, the F/D commands
pitch attitudes which result in acceleration back to V2 + 20 kts. The A/P and
F/D both operate in a similar manner during A/P or F/D go-around.
Approach And Landing
If windshear is encountered during an ILS approach, both the F/D and A/P
attempt to hold the aircraft on altitude, or on glideslope after glideslope capture,
without regard to angle of attack or stick shaker limitations. Airspeed could
decrease below stick shaker and into a stall if the pilot does not intervene by
pushing the TO/GA switch or disconnecting the A/P and flying manually.
WARNING: Although the F/D, A/P and A/T may be performing as
previously described, severe windshear may exceed the
performance capability of the system and/or the aircraft. In
this situation, the flight crew must, if necessary to avoid
ground contact, be prepared to disconnect the autothrottle,
advance thrust levers to the forward stop, disconnect the
autopilot and manually fly the aircraft.
AUTO FLIGHT
737 Sec. 6.4 Page 29
Flight Manual Continental Rev. 11/15/02 #41
Command Speed Limiting And Reversion Modes
AFS command limiting and reversion operation is independent of the stall
warning and mach warning systems.
Command Speed Limiting
The AFS provides speed, pitch and thrust commands to avoid exceeding the
following limit speeds:
· Vmo/Mmo
· Wing flap placards
· Landing gear placard
· Minimum speed.
The commanded speed can be equal to, but does not exceed a limit speed.
Speeds greater than Vmo/Mmo cannot be selected from the MCP. Speeds can
be selected which exceed flap and gear placards or are less than minimum
speed.
Minimum speed is based on angle of attack and is approximately 1.3 Vs for the
current flap configuration. It is sensed by the angle of attack vanes, one on
either side of the forward fuselage.
If a speed greater than a placard speed, or less than minimum speed is selected,
the AFS allows acceleration or deceleration to slightly short of the limit, then
commands the limit speed. The overspeed or underspeed limiting symbol
appears in the MCP IAS/Mach display when the commanded speed cannot be
reached.
Either pitch or thrust, whichever is engaged in a speed mode, attempts to hold
the limit speed. The commanded limit speed and MCP speed condition symbol,
remain until another speed is selected which does not exceed the limit. A speed
15 knots greater than the minimum speed must be selected to remove the
underspeed limiting symbol.
UNDERSPEED LIMITING OVERSPEED LIMITING
- V/Smode performance
reversion (NON EFIS)
-Minimumspeed
FLASHING FLASHING
- VMO orMMO limit
- Flap limit
- Landing gear limit
.
IAS/MACH IAS/MACH
37371201
AUTO FLIGHT
Sec. 6.4 Page 30 737
Rev. 11/15/02 #41 Continental Flight Manual
Reversion Modes
During some flight situations, speed control by the AFDS or A/T alone could be
insufficient to prevent exceeding a limit speed. If this occurs, AFDS or A/T modes
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