PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 6th Jun 2019, 02:20
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Smythe
 
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The Max engine center line is near the same as the NG. the moment has changed as the thrust can be higher. Neither design has the engine orthogonally aligned, so the forward position of the Max would alter the arm of the thrustline unless the incidence angle of the engine was adjusted. The original angle is a compromise for performance and handling.
I really doubt they would change the incidence angle of the engine to compensate for the increase moment arm due to the location being further forward and upwards.

Decreasing the incidence angle of the engine would have profound consequences in cruise. The decoupling of the wing angle and engine angle would send the flow computations out of control. Boeing has enough problems with laminar flow over the wings as it is.

Here is the logic. SMYD 1 is used for primary yaw damping and is connected to the both ADIRUs and left AOA Sensor for inputs.




A single AoA sensor is connected. 2 sensors are not connected to look at a disagree.

SMYD 2 is used to match SMYD 1 primary yaw damper commands, and is available as a backup under certain conditions when SMYD 1 is not available. SMYD 2 uses both ADIRUs and the right AOA sensor for inputs.

Only one FCC can control the mach trim actuator at a time. The IFSAU receives the FCC select signal from FCC B. This signal controls a relay in the IFSAU to find which FCC will give the mach trim actuator signals. The IFSAU sends the mach trim select status signal to the FCCs to show which FCC is in control. The IFSAU then sends mach trim power and motor drive signals to the mach trim actuator.

Only one FCC at a time supplies the speed trim signal to the stabilizer trim electric actuator. When the FCCs get electrical power, FCC A supplies the speed trim signals. If power remains on the FCCs, the on ground signal from the proximity switch electronics unit (PSEU) switches the FCC which supplies the speed trim signals. If one FCC fails, the other FCC automatically supplies the speed trim signal.


For Mach trim, Speed trim, (and MCAS?); the single active FCC CPU#1 command is made regardless of CPU#2, and regardless of the non-active FCC.

more at https://www.satcom.guru/2018/11/737-...n-command.html

Last edited by Smythe; 6th Jun 2019 at 02:45.
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