Question about 747-400 TQ please.

[the mad hatter]

Gentlemen,

I would be grateful if someone would please be so kind as to answer the five questions below:

1) What is used for throttle position, resolver or transducer? Are there 4 separate ones?

2) What is the total movement in an arc from full throttle to full reverse thrust. (example 737 is 9.4")

3) What is the current draw on the auto throttle 28v actuator?

4) Is there anything else one needs to consider when motorising the 400 TQ that I have failed to ask?

Once again my sincere thanks in advance

Bernard

[John H Watson]

1) What is used for throttle position, resolver or transducer? Are there 4 separate ones?

There are separate transducers, but I can't recall if there are 4 dual wind LVDTs (Linear Variable Differential Transformers) or 8 single wind LVDTs. A sensor is required for each EEC channel (A/B)

2) What is the total movement in an arc from full throttle to full reverse thrust. (example 737 is 9.4")

The ranges of angles are listed in the manuals as 85.2deg (Forward Thrust) and 89.25 (reverse thrust), but the lengths of the arms are not given. I have a hand-measured value of 11" from the centre of the forward thrust lever knobs to the pivot point, but you might want to confirm that. It's been many years since I've removed the switchpack covers, so I don't know where the fulcrum points for the reverser levers are. With lever length and angles, you should be able to compute the arc length.

Note, however, on the real aircraft, because the thrust levers are attached to the LVDTs with numerous linkages (linear rods), the angular movement of the levers is not exactly the same as the angular movement of the LVDTs. A conversion has to be made by the EEC (there are conversion tables, but do you intend using a real TQ with all it's linkages?)

3) What is the current draw on the auto throttle 28v actuator?

No data. It probably depends on the load generated by the friction packs. Thrust levers have an allowable range of force required for movement. The motor will probably have a listed "stall current" value, but I don't know how you would use this value.

4) Is there anything else one needs to consider when motorising the 400 TQ that I have failed to ask?

Probably )))

Rgds
JHW

[the mad hatter]

Thanks John G thats' a bloody good start,

Yes I do intend to use real 400 TQ but alas I did not think to consider using the  the linkages, would you please be so kind as to investigate items One and Two on my behalf please. The other thing is finding the 400 TQ linkages would be like finding rocking horse do do would it not? or do you have a design drawing hidden away somewhere that you could share?

I may have some more questions related to this topic once I digest your answers and do some more research. It's one thing to fly'em another to build'em

Once again my thanks
Bernard

[Hardy Heinlin]

For PSX, your bridge software just needs to send to PSX a value from 0 to 5000 for each forward thrust lever angle, and -1 to -8925 for each reverse thrust lever angle.

It's up to your sensor design as to how to convert these values from your hardware sensors to PSX. If you use a real 744 TQ, your TLA design is already correct anyway. Just put a suitable factor in your bridge software.


Cheers,

|-|ardy


P.S.: For those using a good A/T servo, I may add an option switch that inhibits the PSX A/T to directly set its internal 4 throttles. Instead, PSX will send out decrease/increase commands (via a separate single variable) for the hardware A/T and that hardware A/T will, as usual, cause its own levers to inject TLA values into PSX. This has several advantages: No conflict between moving PSX internal levers and moving hardware levers, and no math problems for that single A/T servo that has to move 4 levers at once in any lever constellation.

For those who have no good servo (too slow or too coarse, causing oscillations etc.), PSX should ignore inputs from the hardware as long as the A/T is active. The hardware servo may still move by PSX commands, but in this case it will be a fake movement. Perhaps one should add a adjustable delta threshold value at which the PSX levers are taken over by the hardware levers. (For this fake method only, not for the first method).

[John Golin]

Thanks John G thats' a bloody good start,

No worries... but I'm sure you meant John H...

[John H Watson]

The reverser linkages are part of the clutch pack Assy (resistive device/fwd thrust lever pivot point). I can't imagine the seller trying to separate these. The adjustable rod-like linkages going down to the RVDTs from the clutchpack Assy go through the floorboards. The vendor may separate these to extract the TQ Assy. Unfortunately, there are literally hundreds of parts which make up the RVDT Assy and linkages.

I have no way of sharing this information. I have no details on the geometry of the RVDT Assy. There appears to be only 4 dual winding RVDTs, but there seems to be two different P/Ns. "CU09625119" and "CU09625120", with no visible explanation for their differences.

The Boeing Illustrated Parts Catalogue has these manual references (if anyone asks you):

76-11-01-02 PACK ASSY-ENG CONT THRUST LEVER)
76-11-02-01 RESOLVER INSTL-ENG CONT

Rgds
JHW

[farrokh747]

1) What is used for throttle position, resolver or transducer? Are there 4 separate ones?

as said, four rotary resolvers, one for each lever - each resolver is a dual-channel device, A & B. Each channel has sine, cosine, common, excitation & return pins. Not much use to builders I think, as one would have to get a resolver digitizer, and then get that to talk to the sim - The company Level-D sim here uses  linear Pots for thrust levers.... have posted the link to them elsewhere on the forum....  

Since you have the TQ, you may want to go in for hi quality sensors from someone like http://www.pennyandgiles.com/Rotary-Position-Sensors-pg-29,2,,.php

2) What is the total movement in an arc from full throttle to full reverse thrust. (example 737 is 9.4")

From what I know:

Thrust Lever Angle - TLA
From Idle to full fwd is 0 > 50*
From idle to full reverse is 0 > 89.25*
idle taken as 0*

HOWEVER:

The Reverse Lever Range (TLA) of 0* to 89.25* is mapped to a thrust resolver lever angle (TRA) readout of 35* to 5.2* respectively. IE: at TLA 89.25* the TRA readout is 5.2* (full rev, TRA min)

and

The  Forward lever range of 0* to 50* is mapped to a TRA  of 35* to 85.2*

IE at TLA 50*, TRA is 85.2 (max TLA, max TRA)

The TRA is 35* at idle

3) What is the current draw on the auto throttle 28v actuator?

AFAIK the AT servomotor is a 3 phase 400hz ac device and not DC

and

When the AT motor is driving the levers, it's not fighting the friction brake...  

In my classic TQ, I was using a off the shelf 24vdc DC motor, running off a auto batt

The AT gearbox will take care of any torque fears...  

P.S.: For those using a good A/T servo, I may......

That would be great Hardy! Just like the acft...! But a greater degree of calib will be required..

Note, however, on the real aircraft, because the thrust levers are attached to the LVDTs with numerous linkages (linear rods), the angular movement of the levers is not exactly the same as the angular movement of the LVDTs.

Quite possible, never thought of that, always assumed it was 1:1 - will try and check on my rig....

interesting discussions!

cheers and good night

fc

[John H Watson]

AFAIK the AT servomotor is a 3 phase 400hz ac device and not DC

I don't think it's 3 phase. Single phase 115V AC power is provided to the servo via CB "C10333"'s "C" phase. Servo excitation is provided by the FMC. There seems to be insufficient pins for 3 phase.

When the AT motor is driving the levers, it's not fighting the friction brake...

I don't see how this is possible. If the motor drives the levers, lever movement will be fought by the resistive device. Everything is mechanically connected. There are no electro-mechanical brake circuits mentioned in the manuals.

Rgds
JHW

[farrokh747]

don't think it's 3 phase. Single phase 115V AC power is provided to the servo via CB "C10333"'s "C" phase. Servo excitation is provided by the FMC. There seems to be insufficient pins for 3 phase.

yes, looks like - i see 7 pins @ the servo - 2 for the 115ac, 3 ac gnd and 2 for the tachometer...  but how does it turn cw and ccw...? I knew it was AC, but I assumed it used phases to reverse the rotation...   :shock:  

I don't see how this is possible. If the motor drives the levers, lever movement will be fought by the resistive device. Everything is mechanically connected. There are no electro-mechanical brake circuits mentioned in the manuals.

OK so in my rig (not installed yet) I gave a few hand-turns to the gearbox spline, and it seemed to turn quite easily to move the levers... didn't feel any resistive force -  so i thought that the friction system worked when you move the levers by hand, but not when driven from the gearbox...  let me test this some more and report - it may well be the gear ratio that makes the movement easy....  in any case, a decent 12v/24v dc motor would do the trick nicely....  

cheers!

[Hardy Heinlin]

Perhaps the turn direction is determined by the two 115 AC pins? Connect either the one or the other pin with the ground ...?


|-L

[John H Watson]

i see 7 pins @ the servo

Are you looking at the real servo or at Wiring Schematics?

The Wiring Schematics seem to be missing a few pins for 3 phase operation, but, as I just discovered, extra pins for 3 phase ops are shown in the Wiring Diagrams.

Comparing the AMM with the Wiring Diagrams, it starts to make sense.

The AMM says:
 
"[CB]Power to the autothrottle servomotor generator is 115 volts ac excitation and a variable ac signal derived from 28 volts dc for drive control[from the Left and Right FMC]"

The CB power is one phase (on pin 13). The variable AC (a second phase of AC) seems to be for speed control (This will be cut off completely during Thrust Hold or when the levers reach their target or when the levers have manual intervention). The Left FMC speed/hold control input is on pin 6, the Right FMC speed/hold control input is on pin 24.

However, there are also forward/reverse command AC wires going into the servo from the Left and Right FMCs (Left FMC Forward command uses pins 7&16, Left FMC Reverse command uses pins 15&17,  Right FMC Forward command uses pins 10&21, Right FMC Reverse command uses pins 11&22)

If you're looking at the real A/T servo, then we do have a problem  :mrgreen:

Rgds
JHW

[farrokh747]

morning,

If you're looking at the real A/T servo, then we do have a problem

no, not at the servo... don't have one...

Comparing the AMM with the Wiring Diagrams, it starts to make sense.

yes, i see that now.....  clever guys, these boeing fellows...  

That settles it, no sane way to use this in the sim i think.....


here's how I did it:

http://www.mycockpit.org/forums/showthread.php/14926-HiPowered-Servos-using-Simple-H-from-Robotpower-and-hacked-hitec-servo?highlight=servo

http://www.farrokhchothia.com/simplehservo/


cheers,