(e)
Left and Right Central Maintenance Computers
1) Initiate stall warning BITE test
C.
SWMC Airspeed Outputs
(1)
The SWMC calculates values of maximum operating speed, minimum operating speed, and minimum maneuver speed for the EFIS airspeed tape display (Ref 31-61-00).
(2)
Maximum Operating Speed
(a)
The value of maximum operating speed from the SWMC (Vmax) is displayed on the airspeed tape whenever landing gear is down or whenever flaps are not retracted. 1) Vmax is equal to the landing gear extended placard speed
when flaps are up and any 2 main landing gear are down and locked.
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2) Vmax is equal to the flap placard speed when flaps are not up, regardless of landing gear position.
3) Vmax is set to NCD (no computed data) when flaps are up and any 2 main gear are not down and locked.
(b)
The value of maximum operating speed from the ADC (Vmo) is displayed on the airspeed tape when gear and flaps are up.
(3)
Minimum Operating Speed
(a)
The SWMC outputs a minimum operating speed (Vmin) for the stick shaker speed display on the airspeed tape. 1) When flaps are up, Vmin is equal to whichever of these two
values is greater:
-
the initial buffet speed (Vbflo) calculated by the FMC
-
the stick shaker speed (Vss) calculated by the SWMC.
a) At altitudes of 20,000 feet or higher, Vbflo is the minimum buffet onset speed supplied to the SWMC by the FMC. Under these conditions, Vmin can be greater than Vss.
b) Below 20,000 feet, Vbflo is scaled toward zero. This causes Vmin to be equal to Vss. 2) When flaps are not up, Vmin is equal to Vss.
(4)
Minimum Maneuver Speed
(a)
The SWMC calculates a value of minimum maneuver speed and sends it to the FMC via the EIU's. 1) When flaps are not up, the FMC uses the value from the SWMC
and sends it to be displayed on the airspeed tape for
minimum maneuver speed.
2) When flaps are up, the FMC compares its own value of minimum maneuver speed with the value from the SWMC. The FMC sends whichever of these two values is greater to the airspeed tape display.
D. SWMC Pitch Limit Output
(1)
The SWMC calculates a pitch limit value for the EFIS pitch limit display (Ref 31-61-00). The pitch limit value indicates the maneuver margins available for the airplane to recover from windshear conditions without activation of the control column shakers.
(2)
When flaps are up, the pitch limit value is set to NCD and the pitch limit symbol is removed from the PFD.
(3)
The Ground Proximity Warning Computer (Ref 34-46-00) uses pitch limit data from the SWMC.
E.
SWMC Test
(1)
Each SWMC performs 3 types of self tests. A power up test is automatically performed whenever power is applied. A continuous test is conducted during normal SWMC operation. A CMC confidence test of the system can be initiated from the CMC CDU. The control column shakers will be activated for approximately 10 seconds if the SWMC passes its self test during the CMC confidence test.
(2)
The CMCS receives data from the SWMC via the EIU's.
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(3) If the CMCS is not available, a BITE test of the SWMC can be initiated by connecting the L or R STALL TEST jack on the MAWEA front panel to ground.
3. Control Column Shaker
_____________________
A. The control column shaker vibrates the pilot's control column when activated by the SWMC. A shaker is clamped to the front of each pilot's control column. Each shaker consists of a motor geared to a coaxially mounted weighted ring. Energizing the motor rotates the out of balance ring, and the resulting vibration shakes the control column. Either SWMC activates both the captain's shaker and the first officer's shaker.
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