JRBarrett

Autopilot roll and pitch modes

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I just installed Beta 3.0, and this aircraft just keeps getting better and better. Thanks for adding the real-time update to the gross weight counter!

In general, the autopilot is working very well when selecting various mode buttons in the current beta.

  • Heading Select works smoothly, and the aircraft rolls out on the selected heading precisely.
  • 1/2 Bank mode works as advertised
  • Vertical Speed likewise operates smoothly and precisely in both climbs and descents.
  • I understand there were some pitch oscillation problems with IAS/Mach hold in the earlier betas, but at the moment it too is working very well.

However

There are two fundamental autopilot functions which are not working correctly...

When an FPS-85 autopilot is initially engaged with no mode buttons selected, it defaults to roll and pitch mode. The aileron and elevator servos engage, and they are then under the direct control of the combined roll and pitch wheel on the center console. (which is now also available as part of the autopilot pop-up in the sim.)

When initially engaged with no mode buttons selected, the autopilot will roll the wings level with the aileron servo, and will hold whatever pitch attitude exists at the time of engagement with the elevator servo, while simultaneously adjusting horizontal stabilizer trim just as it does in other pitch modes.

In this basic mode, turning the roll section of the combined wheel left or right will bank the aircraft left or right. Moving the pitch wheel toward "down" will pitch the nose down, and moving it towards "up" will pitch the nose up. Fundamentally, the roll/pitch acts wheel like an electronic controller for the yoke

It is these basic functions which are not working correctly.

I note from the tool tip associated with the roll portion of the control, that it is mapped to "aileron trim". This does indeed appear to be the case, because I have aileron trim assigned to a switch on my HOTAS Warthog joystick, and when I move that aileron trim switch on the joystick left or right, the "aileron trim" value shown in the tool tip changes.

The roll control wheel should not actuate aileron trim - it should actuate the autopilot roll servo. Unlike the pitch wheel, the roll wheel is spring-loaded to return to neutral when released.

At present, the pitch wheel does not appear do anything at all in basic autopilot mode. Moving it towards "up" or "down" has no effect on pitch, whereas in the real FPS-85 system, it will directly control the elevator servo.

When V/S mode is selected, the function of the pitch wheel changes to select and adjust vertical speed in climb or descent, and that function is working just fine.

When the autopilot is not engaged, neither the roll nor pitch wheels will have any effect at all.

The only other (minor) glitch in the present autopilot implementation is mainly cosmetic. The yaw damper and autopilot engage levers are adjacent to each other. The yaw damper can be (and often is) engaged independently of the autopilot - however, the autopilot cannot be engaged unless the yaw damper is on as well.

The autopilot lever has a one-way mechanical interconnection to the yaw damper lever. If the autopilot lever is raised to the engaged position and the yaw damper is "off", the autopilot will internally latch and raise the yaw damper lever at the same time so that both systems come online together. If the yaw damper lever is already "on", then the autopilot lever moves by itself.

If both levers are "off", raising the yaw damper lever by itself does not raise the autopilot lever.

  • Note to FlySimware: I know you may be reluctant to make changes in aircraft systems based only on my "say so" as a new customer. I do have many years experience as a Falcon mechanic and avionics specialist. If I can answer any questions, or if you would like me to send you my certifications, please feel free to PM me. 

Jim Barrett

 

 

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First thing is i like the information about how the yaw damper is forced mechanically when the autopilot is on. I can do this for sure. Had no idea!

Second. I knew about the servos controlling the bank and pitch as i have coded a navo matic once and we used the aileron trim due to the sim limitations.

However i can do much more these days.

We are also going to look into how to implement current pitch hold and wing lever when AP is on and all modes off.

So we will give this a try as we like realism.

Edited by Flysimware
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Update:

Yaw code is updated.

This is what we can and can't do for the second option. 

When ap is enabled pitch holds current position and wings level. The aileron servo wheel will be disabled due to sim limitations. The Elevator servo wheel will be disabled as well. This will give the pilot time to setup the ap modes.

When the ap modes are being used like VS, IAS, or MACH the vertical speed hold wheel will continue to work.

That's it! Thanks for advising us more info about the falcon 50.

Edited by Flysimware
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7 hours ago, Flysimware said:

Update:

Yaw code is updated.

This is what we can and can't do for the second option. 

When ap is enabled pitch holds current position and wings level. The aileron servo wheel will be disabled due to sim limitations. The Elevator servo wheel will be disabled as well. This will give the pilot time to setup the ap modes.

When the ap modes are being used like VS, IAS, or MACH the vertical speed hold wheel will continue to work.

That's it! Thanks for advising us more info about the falcon 50.

Thanks. The roll wheel in basic autopilot mode is almost never used in real world flight operations in any case, and it’s probably better to have the wheel do nothing in the sim than changing aileron trim - since that could cause unwanted problems with the heading and Nav modes later on if trim remains applied.

I do see that both aileron and rudder trim switches on the center console do work, which is a nice touch. Probably little need to actually use those in the sim in normal operations. unless there is an outboard engine failure, in which case the rudder trim function will come in very handy.

The only other thing that stands out at the moment as a bug in the current aircraft is the activation of the engine 2 FAIL light. I note that when advancing the center power lever to full while doing preflight checks before engine start, that the light comes on instantly, whereas in the real aircraft advancing that lever starts a 15 second timer. The light only comes on when the number 2 engine has not yet reached 85 percent N1 at the end of 15 seconds, or if it later drops below 85 percent at any point after 15 seconds have passed since the power lever was advanced. Once the aircraft is in the air, the weight-on-wheels sensor deactivates the engine 2 Fail system.

All of the other takeoff config warnings based on flap/slat position and stabilizer trim work perfectly. That saved my bacon on a flight last night, as I completely forgot to set the stab trim in the green range before takeoff while testing something else!

All-in-all, you have done an excellent job with systems modeling in this aircraft. 

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