Will the tiller be seperate to the rudder pedals.

[John H Watson]

Teaser....

If the wing gear is up, how will this affect the body gear steering (electronically)?

Rgs
NSEU

[dutch57]

John,

If one lands a plane with both wing gears up , the FCOM tells them to come to a complete stop on the runway do not attempt taxing as the plane might tip to the left or right in steep turns,

Body gear steering is not affected all the arminf signals are there and the hydraulics as well

KLM made a lh wing gear up landing in SPL, about 25 years ago, we maintenance went onto the runway and after unloading the aircraft we towed it to the hangar for repairs.

Bob

[John H Watson]

Bob, my engineering training notes tell me that the 4th highest wing gear wheelspeed is used as a reference in the BSCU for body gear steering.

Also, during the evening, I had 3 independent people tell me that the Body Gear Steering works with the IRUs off. We do all our maintenance towing with the IRUs off. The steering is significantly degraded if the Body Gear Steering is not working, so it's easy for them to tell.

As I suspected, with NCD from the IRUs, the BSCU generates a valid "below 40kt groundspeed" signal.

Now I need to find out what happens if the wheelspeed sensor cards in the BSCU are NCD

Rgds
JHW

P.S. I've put in a special request to our technical department to clarify BGS ops. Hopefully they'll contact Boeing for a definitive answer.

[dutch57]

Jhon,
My SSM does not give me a real answer, what i can see is that the speed signals iru and wheel speed are compaired on the a/s card (2 cards in total) from there is put on a bus and in the system bite card the bodygear arming is done, speed less 20kn and on grnd.Note as far as i can see it only uses a/s cards 103 and 2-4(lh-wing gear)

As you say SSM`s are not that detailed.

For us normal procedure is towing with only hyd-4 under pressure iru`s off.
And towing is done by our towing department.
I remember in the old days B742 , we switch bodygear steering off.

Looking forward on what your tech department tells you,

Sincerly
Bob

[John H Watson]

Looking forward on what your tech department tells you,

Still no answers from our technical department (doesn't seem to be high on their list of priorities). However, many engineers who routinely tow aircraft do confirm that the body gear steering does operate with the IRU's off.

Anyway, more weirdness in this system continues to surface. During an aircraft tow (steering hydraulics bypass pin inserted), the tiller moves when the nosewheel is moved (the cables are still free to move and they are attached to the nosewheel, so you would expect the tiller to move). However, the rudder pedals do not move, however (they just twitch, like they want to move, but can't). This is strange, as you would expect the same cable feedback to the rudder pedals as you would to the tiller.

Perhaps the 744 pilots can tell us if the rudder pedals move when they turn the aircraft with the tiller? (after tug disconnect).

Perhaps they can also confirm that the rudder pedals move the tiller?

Incidentally, an older Airframe engineer also confirmed my earlier statement that the nosewheel doesn't necessarily move when the tiller is moved with the aircraft stationary (the hydraulics have difficulty overriding the friction between the tyres and the tarmac). Also, he said that he used to use greased plates under the main gear when testing the Body Gear Steering (to overcome the frictional forces)

Rgds
JHW

[farrokh747]

Hi all

In my -200 shell, i knew i had the actuator for rudder/tiller engage/disengage - as discussed, this is controlled by the squat switch in the nosegear. I never went deeper into this until now. On further examination, i found that the rod connecting the tiller mech to the fwd rudder quadrant (capt side) was in fact bolted to the body. So in this config (1978 ) they seemed to have locked out this function - ie, rudder movement will not actuate the tiller system. this could have been because of incidents like this: www.airdisaster.com/reports/ntsb/AAR96-04.pdf

and:

"The chief of flight standards emphasized that the proper nosewheel steering
technique for the takeoff roll should be to use rudder pedal steering, not the tiller.  He explained
that the Tower Air procedure of guarding the tiller during the takeoff until attaining 80 knots was
carried over from an early Pan American procedure.  The older model B-747s operated by Pan
American were not equipped with rudder pedal steering"

I have now re connected the rudder quadrant to the tiller mech, and as seen, rudder pedal movement results in the tiller moving as well. However, tiller movement will not move the rudder system. I have wired the actuator (single one on this acft) and did a check: When extended, rudder movement has no effect on the tiller system. When retracted, rudder moves the tiller, but tiller movement has no effect on the rudder.

This will be on a relay, with squat switch logic.

Now: Here's the problem: FS does not have a separate tiller axis - FSUIPC lets you "split" the rudder axis into two, with a speed limit in the ini file for gradual transfer of authority from tiller pot to rudder pot as speed increases. So it is possible to have 2 separate pots on each axis, both are not active at the same time.

Q: with PSX, with a separate pot on the steering tiller and rudder, will one have issues if one uses rudder steering (pot A) which will now also move the tiller (pot B), sending signals to both axis's...  

Q2: If one uses the pedal steering during TO roll, i guess one is also deflecting the rudder? Is there some hidden transfer logic between the two?

Cheers!

FC

[Hardy Heinlin]

Hi,

the link between the rudder pedals and the tiller is modelled in PSX, it can connect, disconnect or freeze depending on the 744 systems modelled in PSX.

You just need to read/write two PSX variables: One for the tiller and one for the rudder pedals. Each goes from -999 to 999.

Optional inputs:
Tiller: TCP/IP or USB or mouse
Rudder: TCP/IP or USB or keyboard


Cheers,

|-|ardy


P.S.: Users who have limited hardware or limited USB equipment can optionally control both aileron and tiller with a common USB x axis. The tiller is then active on the aileron axis when below 40 knots. Tiller movement is indicated on a small icon. Of course, the regular tiller control via rudder pedals remains intact regardless of the 40 knot limit. The rudders can be on another USB x axis. (As always, on the 744, max tiller deflection is not possible with the rudder pedals alone.)

[farrokh747]

You just need to read/write two PSX variables: One for the tiller and one for the rudder pedals. Each goes from -999 to 999.

Wonderful =  that settles it -


cheers

fc

[Blake H]

In the rudder/tiller interconnection under the captains feet in the floor. I noted there is a linear actuator that connects and disconnects the rudder to the tiller. Airborne it appears the rudder pedals move only, not the tiller handle. On the ground the rudder pedals will move the tiller several degrees of movement. Tiller movement will not move the pedals. There is also a second actuator I have exercised the actuator it appears to have no effect in the flight deck. Can anyone share some light with this one?

[farrokh747]

This is 744 shell, right?

i think you have to have both actuators working for this....

one has to retract and the other extend for engage and vice versa for disengage....

not sure which is primary and which is second....

my kit has just one actuator....

pl verify before firing both together! Im not 100% sure of this....

[John H Watson]

Both actuators should move for completely correct operation. The actuators move in opposite sense (push/pull). If only one actuator moves, disengagement will not occur in the air. Ground ops will be ok.

Rgds
JHW.

[Blake H]

Yes that makes sense.  

It appears the one on the left from the pilots view is the primary. For the sim if I have the secondary retracted all the time (static). This setup will be good enough to just have the primary working.

Primary retracted on ground and extended airborne.

 This has been bugging me for weeks.

Cheers

[John H Watson]

This setup will be good enough to just have the primary working.

Not sure. PSX probably models the individual circuits for each actuator. i.e. individual circuit breakers, different inputs from the Pri/Alt air/ground systems (different CBs and different sensors), but may have a single output for complete lock/unlock.