Control column and yoke load feedback on 747-400

[Blake H]

Does anyone know the control column and yoke control load feedback through the flight envelop. What force is required by the pilot in kg/lbs.

[stekeller]

OK:

Looking in D.P. Davies' excellent "Handling the Big Jets" which refers to the B747-100, I found the following...

- Maximum wheel force at full throw for lateral control is only 13 pounds.
- For extreme CG positions, maximum stick forces in pitch are 40 pound pull and 20 pounds push.
- With zero trim in an engine out situation, maximum foot force at full rudder is about 70 pounds.

I know some of these are the outside cases, I will keep looking and see if I can find more normal values.

- Stekeller
KORD

[John H Watson]

Paraphrased 744 Maintenance Manual test values for the elevator:

With trim at 5 units, airspeed at 204~284kts, pull back on stick:
Breakout force =  8.6lbs
Full aft force = 72~106lbs

With trim at full nose up, same airspeed, pull back on stick:
Breakout force = same as above
Full aft force = 40~55lbs.

The airspeed values are achieved by applying artificial pressures to the pitot-static system.

Other test values are given, but involve disconnecting components and measuring trim in stabiliser linear displacement values (not units of trim), so are meaningless to most.

Aileron values (with hydraulics) are given as torque values:
1~2 degrees, torque is between 19 - 33 pound inches
79-81 degrees, torque is between 72 - 128 pound inches

The control wheel has a full radius of 6&3/4" (centreline to extreme edge of handles)

As far as I know, the 747 should be similar to the 744, so I can't explain the variations.

Rgds
JHW

[the mad hatter]

Blake and you might find this intresting, let me know your thoughts

http://bffsimulation.com/BFF-FFB-System.php

[John Golin]

Blake and you might find this intresting, let me know your thoughts

http://bffsimulation.com/BFF-FFB-System.php

Ooh... Matt can we have this please??!

[Matt Sheil]

Blake and you might find this intresting, let me know your thoughts

http://bffsimulation.com/BFF-FFB-System.php

Ooh... Matt can we have this please??!

Looks good John, another side project for you and Rod? ;-)
I wonder if the Autopilot would follow and move the controls also?  I have not had time to read all the documents yet

[Blake H]

The Matt hatter. I definitely think this is a good start.

I am going to buy a system from CKAS.com.au. Might be worth having a look at one of their motion rigs $76k AUD 6dot 2.5tonne payload. Had a drive of their Baron sim yesterday. I am in the middle of a Dash 8 type rating at the moment compared to the Dash the algorithm are much better. Tried a little roll and loop. I was pinned to the seat and lands really nice. Also the deaceleration in a descent in approach configuration is simulated extremely well.

The guy at CKAS need to know the dimensions of the yoke control column and then mathematical work out the force required at the DC motors to simulate through software the force the pilot will have at his hands through the speed range. A larger force will be required at the DC motors as the control column is a large lever and the control wheel is larger then the gear on the DC under the floor attached to a cam.

With the control feedback above this is exponential as airspeed decreases or increases? What is the force on the ground no airspeed? IAS vs control load feedback would be appreciated as the more numbers I have the better I will be able to simulate the control loads.

Cheers.

[Blake H]

I thought this might be a suitable place to announce the sim progression. Electronic panels are complete. The 747-400 cockpit was checked by customs yesterday. This Monday will be delivered to my factory unit. Photos should be available mid next week. If Farrokh is happy to put them up on his web page for me again.  

[farrokh747]

sure, send em over....

fc

[Phil Bunch]

I thought this might be a suitable place to announce the sim progression. Electronic panels are complete. The 747-400 cockpit was checked by customs yesterday. This Monday will be delivered to my factory unit. Photos should be available mid next week. If Farrokh is happy to put them up on his web page for me again.  

Why not create a flickr web page?  It's easy to use and access...

[Zinger]

Just to recall the logic of given flight control mechanical characteristics, which also explain their magnitude. The forces are to match human ability to control with minimum fatigue while providing pilot cues to enable smooth aircraft rates and avoid structural over-stress and unnecessary control movement, for the designed aircraft missions.

Built-in friction must be minimal to not impede these. Breakout is used to mask and overcome friction while providing control self-centering about the trim point. Following the small breakout force there is usually constant slope for 1G, and rising constant stick force per rising G, vital for higher indicated airspeed flight and high mach at altitude with thin air.

After a control had been displaced in one direction, the return motion direction would show for each deflection the same value minus breakout, therefore the forces are not exactly equal. Furthermore, the allowed range shown below is acceptable for the human arm and leg.

The type of aircraft isn't important but rather its flight profile, explaining similarities for B747-200 and -400. Therefore, the main factors used for the design of transport category aircraft control system characteristics include gross weight, pitch, roll and yaw inertial moments, control effectiveness (for a more responsive aircraft, higher stick force per G is required), and natural damping.
HTH

Paraphrased 744 Maintenance Manual test values for the elevator:

With trim at 5 units, airspeed at 204~284kts, pull back on stick:
Breakout force =  8.6lbs
Full aft force = 72~106lbs

With trim at full nose up, same airspeed, pull back on stick:
Breakout force = same as above
Full aft force = 40~55lbs.

The airspeed values are achieved by applying artificial pressures to the pitot-static system.

Other test values are given, but involve disconnecting components and measuring trim in stabiliser linear displacement values (not units of trim), so are meaningless to most.

Aileron values (with hydraulics) are given as torque values:
1~2 degrees, torque is between 19 - 33 pound inches
79-81 degrees, torque is between 72 - 128 pound inches

The control wheel has a full radius of 6&3/4" (centreline to extreme edge of handles)

As far as I know, the 747 should be similar to the 744, so I can't explain the variations.

Rgds
JHW