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bpcw001

Lear 35A - changing aircraft attitude under auto pilot

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Hi,

 

I am having a little trouble figuring out how (or if) the Lear's maneuver switch is implemented in the Flysimware Lear.

 

Example:

When climbing in SPD mode with autopilot on, I cannot change the speed with which the aircraft is supposed to climb without first disconnecting the autopilot via ENG button, manually changing attitude to bring the aircraft to the new speed, and then reengage the autopilot.

 

In the real thing, this is supposed to be done using the yoke's four-way trim hat switch while keeping the maneuver switch depressed. While this switch is kept depressed, the autopilot pitch and roll axis are temporarily disconnected, allowing the pilot to make fine attitude adjustments to settle the aircraft on a new speed or V/S rate. Upon releasing the maneuver switch, the pitch and roll axis re-engage and the autopilot continues in the previously selected pitch/roll mode.

 

I tried to use FS controls AP_VS_VAR_INC and AP_VS_VAR_DEC to accomplish this, but during climb, this does nothing, even when climbing in V/S mode.

 

Interestingly, those FS controls work when descending, and I can use them to adjust a V/S sink rate or descent speed.

 

So, my question is:

What is Flysimware's idea on how SPD or V/S changes should be made in the sim when the autopilot is active on SPD or V/S pitch mode, especially when climbing.

 

Thanks for clarification.

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The hat switch you are referring to is not depicted as in the aircraft.It is missing the barrel shaped knob and an arming button which was integrated in the assembly.If in SPD mode and needing to establish a new airspeed or V/S reference, actuating the knob forward or aft ( without pressing the arming button which would disengage the autopilot ) would cancel the active SPD or V/S mode but leave the autopilot engaged in pitch mode and what ever lateral mode was active on the AFCS.Just bumping the the knob fore or aft would accomplish the pitch change.Once the new speed or rate is established then reselect the desired AFCS mode.The maneuver button on the yoke would not need to be used in this example and in my experience in the aircraft only used it if needing to temporarily completely override the autopilot and active modes to avoid traffic, birds etc.

 

As the maneuver button and the complete control wheel switch assembly is not modeled in the sim version the  AFCS / autopilot functions are not completely accurate to the actual aircraft. My method in the sim has been to turn off the SPD or V/S mode then use my controller pitch trim to establish the new rate and then reselect the mode again.You should need to disengage the autopilot to accomplish this.

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CW46,

 

thanks a lot for your insightful post and for clarifying the situation.

Reading the very last sentence of your post: did you omit a "not" or do you really have to turn off ENG, i. e. losing lateral autopilot control while changing (vertical) speed versus temporarily canceling just the vertical AP mode?

 

Thanks

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Sorry I did not adequately proof the post, you should "not" need to disengage the autopilot when changing the airspeed or vertical rate, deselect the active mode make the change then reselect the mode again.

 

Regarding the autopilot I find when using the pitch trim it is extremely sensitive with flaps up and the trim motion is too fast when using that method to change the pitch angle.The Lear 35 has a two speed pitch trim system, high rate with flaps down and slower rate with flaps up for that very reason and as a safety function in the event of a runaway stabilizer trim malfunction.When ever the autopilot is engaged or the flaps are up the low speed trim mode is being used.You will also note the AFCS SPD mode displays Mach / IAS when active, it should display either IAS with one press, a second press would be Mach, it can not display both functions at the same time.

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