Question on thrust reverser inputs

[airforce2]

Hi Pete;

I'm trying to get a joystick controller that uses two throttle axes and a separate reverse axis to work with an FSX add-on that uses FSUIPC4.

When reverser is applied (the output as shown on the reverser calibration page appears OK, ranging from 0 to -4096), the throttle input offsets at 3330 and 3332 do not reflect the reverse input, so the add-on does not respond to the reverser application. If I set up the throttle axes to have a reverse range, then the reverse values are reflected and the reverser works. Is the absence of the reverser input from a separate reverse axis at the post-calibration throttle offsets a bug or a feature?

Cheers

[Pete Dowson]

I'm trying to get a joystick controller that uses two throttle axes and a separate reverse axis to work with an FSX add-on that uses FSUIPC4.

Just one reverser axis for both engines?

When reverser is applied (the output as shown on the reverser calibration page appears OK, ranging from 0 to -4096), the throttle input offsets at 3330 and 3332 do not reflect the reverse input, so the add-on does not respond to the reverser application.

Interesting. I've never heard of an application which interferes with reverse thrust application. All the add-ons which make use of those offsets tend to be either doing fly-by-wire, and are therefore manipulating the modes or settings according to the input, but not applying it directly, or simply autopilots which only control the throttle when A/T is engaged and use those offsets to determine whether to auto-disconnect the A/T on user input. Neither of these normaly has any involvement in reverser operation.

What does this add-on do with the throttle axis offsets that it needs to see the reverser?

If I set up the throttle axes to have a reverse range, then the reverse values are reflected and the reverser works. Is the absence of the reverser input from a separate reverse axis at the post-calibration throttle offsets a bug or a feature?

Neither. Those offsets are described as providing the calibrated axis value from the axis assigned to the stated function. The separate reverser axes are just that, separate axes. I've never known any application for offsets to reflect them specifically, so one was never implemented.

Regards

Pete

[airforce2]

Pete;

I've been using 2/3/4 separate throttles and a single-lever all-throttle reverse lever config with my PFC gear forever. I recently replaced the pots in my PFC yoke/quadrant/rudders with Hall Effect sensors and the quadrant electronics with Bodnar USB joystick interface boards, so I can't use the PFC driver any more to do that.

The commercial add-on in question appears to intercept throttle inputs at 3330/3332 and then uses those as inputs to a FADEC simulation...effectively fly-by-wire control for the engines. If the throttle axis inputs are negative by virtue of a throttle lever calibrated to go into reverse range, the FADEC code sees those negative values on offsets 3330/3332 and puts the engines into reverse. If the reverse range is selected with a separate throttle lever, 3330/3332 remain at zero and it has no effect.

I guess what might be baffling me is that there is no reverser "axis" listed in either the FS control axes menu or the FSUIPC for Programmers document...my belief was that the reverser input was somehow combined with the throttle inputs and applied to the simulation via a negative value on the throttle axis, as throttle is the only "axis" listed in either document for engine RPM control.

Anyway, I ended up solving the problem by programming the reverse lever to send a string of FS throttle-decrease controls...but I remain curious as to where the reverse input from a separate axis is applied to the simulation.

Cheers

Bob

[Pete Dowson]

The commercial add-on in question appears to intercept throttle inputs at 3330/3332 and then uses those as inputs to a FADEC simulation...effectively fly-by-wire control for the engines. If the throttle axis inputs are negative by virtue of a throttle lever calibrated to go into reverse range, the FADEC code sees those negative values on offsets 3330/3332 and puts the engines into reverse. If the reverse range is selected with a separate throttle lever, 3330/3332 remain at zero and it has no effect.

How unusual. I'm left wondering how it manages to override the reverser axis attempts to set reverse thrust. The normal fSUIPC4 facility to intercept the throttles so that the fly-by-wire method can be used doesn't affect the separate reverser axes. There is a separate offset which can be used to stop the reversers operating, but I don't understand why they'd use that. The only other thing i can think they might be doing is seeing the normal throttle axes remaining at zero and continuously resetting FS's throttles to idle in response. That's a bit nasty really.

I guess what might be baffling me is that there is no reverser "axis" listed in either the FS control axes menu or the FSUIPC for Programmers document.

FS does not provide a separate reverser axis. In fact it supplies no reverser axis action at all except by the fortuitous circumstance that Microsoft did not remove the original FS98 throttle controls (ThrottleN_Set) when they implemented the newer ones (Axis_throttleN_set) -- the latter don't have any reverse zone. FSUIPC just takes advantage of the older controls to provide both the reverse-on-throttle-axis facilities and the separate reverser axes.

my belief was that the reverser input was somehow combined with the throttle inputs and applied to the simulation via a negative value on the throttle axis, as throttle is the only "axis" listed in either document for engine RPM control.

Yes, this is true, though maybe not in the way you understand. The term "axis" applies to the input device being assigned. The internal mechanism for controlling the throttle is an FS control which is the result of one or other of those axes. In the case of separate forward thrust axes and reverser axes the resulting controls sent to FS may or may not be the same. For reverse action they have to be "ThrottleN_Set" controls. For forward thrust they can be "ThrottleN_Set" controls or "Axis_ThrottleN_Set" controls, or the generic "Axis_Throttle_Set" control which applies to all selected engines (eg selected by E + 1,2,3 and/or 4). You need to separate the concept of input mechanism and resulting action. The offsets 3330 etc record the inputs, after calibration, not the results sent to FS.

Regards

Pete