PDA

View Full Version : Autopilot Rudder Authority on 767

QAVION
25th Nov 2001, 09:38
Looked in the Boeing 767 Maintenance Manual, but I can't seem to find any value for autopilot rudder authority when Autoland is engaged (and airplane below 1500').

The autopilots control the rudder during autoland with 3 "Directional Autopilot Servos" (DAS's).... which are connected to the rudder Power Control Actuators.

Although the BMM mentions servo synchronization with rudder position up to +/- 25 degrees, it doesn't appear to specify the DAS's authority after engagement.

The Yaw Damper Authority is only 6 degrees left or right, but I would expect the autopilot to have more than this.

Thanks.
Rgds.
Q.

P.S. Failing that, do you have any values for the 747-400 :-)
Brenoch
27th Nov 2001, 19:33
Appears to be a very good question since Iīve now read through the relevant sections of my manuals and canīt find an actual value.. From what I have done in the sim as far as go arounds on one engine from triple-channel appoaches I would assume the autopilot has full authority over the rudder beause of the abrubt yaw when the G/A roll mode is terminated.. It has atleast authority to counter any yaw when full G/A thrust is applied to the "live" engine.. Hope it might have helped.. :(
trapped off
28th Nov 2001, 00:17
Taken from engineer training notes:
Autoplilot inputs drive the three directional autopliot servo's that, in turn,drive the aft quadrant assembly.Autopilot inputs are provided for autoland mode only and drives the rudder a maximum of 24.8 degrees. Autopliot inputs backdrive the cable system to provide input to rudder pedal steering.
QAVION
28th Nov 2001, 02:42
Thank you gentlemen. Couldn't have asked for (and got) more :-)

No doubt, PPRuNers are the greatest!

Cheers.
Q.
Brenoch
11th Dec 2001, 12:33
So the autopilot could drive it to 24.8 degrees deflection.. How far could I drive it i.e. what is max deflection??
QAVION
14th Dec 2001, 13:36
"So the autopilot could drive it to 24.8 degrees deflection.. How far could I drive it i.e. what is max deflection??"

The 767 has a limit of about +/-26 degrees at low speed and a limit of +/- 4 degrees at 360 kts due to Rudder Ratio.

Rudder trim is also affected, having a limit of +/-17 degrees at low speed and +/- 2.6 degrees at 360kts.

Regards.
Q.
Brenoch
14th Dec 2001, 16:00
Thanks.. You never know when that piece of information might prove useful.. :)