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ramprat

Lear 35A Autopilot question.

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Hi all,

 

I don't know how the autopilot works in the real deal.  But I suspect when crusiing at a level altitude and wanting to climb or descend to a new altitude, pushing "Alt Sel" would dis-engage the elevator servo so the pilot can set the desired VS or IAS and then push the respective mode button to maintain it.  With this simulation, I have to select "Alt Sel" twice to free up the elevator.  Is this correct?  I hope I explained this so it's half way lucid.  Does anyone know how the real airplane works?

 

Thanks,

 

Bill

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I was wondering that myself. It's a pretty old system, but still I suspect you're right. So I too would be interested in hearing from someone who has handled that system IRL. In the meantime I'll ask our autopilot guy at work to see if he's ever worked on one of those. If he has, I'll let you know what he says.

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OK, our guy says he's never worked on the Lear autopilots (there are several different manufacturers of autopilots that were available for the various Lears) but he did say (and he has a lot of years on autopilots) that it would be very unusual to have to deselect the Alt Hold/Alt Sel then reselect them plus the V/S. On all the systems he's worked on, you would simply start a descent by dialing in the desired altitude on the pre-selector, select the ALT SEL (which will automatically deselect the ALT HOLD), let the nose drop until you get the rate of descent you want, then hit the V/S button (assuming you aren't going IAS, but typically on descent you are using V/S and adjusting power to keep your speed - thats different to most phases of flight by the by, where you use elevator to hold speed and adjust power to maintain/change altitude). He said that unless you can find something specific written about this particular autopilot, then he thinks it is probably not coded correctly. Without documentation being provided for this by Flysimware, you kind of have to go with what works on the vast majority of systems, which is as I described above.

 

Hope that helps.

 

AMENDED - SEE BELOW - THIS VERSION IS NOT CORRECT FOR AN AIRCRAFT WITHOUT A V/S PRESELECTOR (and this aircraft is not equipped with a V/S preselector)

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AMENDMENT

 

OK, I had a chance to rethink the logic on this one. The above logic is faulty, so here's the corrected version.

 

This aircraft doesn't have a V/S preselector for VS per se. So yeah, you can select your new altitude, then hit ALT SEL, but the autopilot is going to say, "Yeah, ok, but how fast do you want me to go to that new altitude?" Until that question is answered, it's going to remain at the current altitude. There's no bug on the VSI or panel component to preselect the VS so it doesn't know what to do next.

 

So, the way you are doing it now is correct and is one way of doing it. You have to deselect all altitude modes after selecting your new altitude in the preselector, pull the power back a bit and let the nose drop. As you do so, you re-engage the ALT SEL. Then when you have the rate of descent you want, engage the V/S mode and adjust your thrust levers to maintain the speed you want.

 

Now, there is (or should be) another way if you want to maintain full automation. Select your new altitude in the preselector window, then select ALT SEL, then select SPD. Now pull your thrust levers back until you see the aircraft start to descend. Again, once you have the desired rate of descent, then select V/S (which should cancel the SPD mode - if it doesn't, deselect the SPD mode manually), and adjust the thrust levers to suit.

 

So they essentially have it done correctly. The V/S preselector may have been an option back then, which wasn't included on this particular aircraft.

 

Hope THAT helps :smile:

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This bird was designed to be an early S/N, but with a few upgrades over the years. Trust me when I say that not being able to dial in say -1500fpm, and hit a VS hold button has been eye opening for sure. :)

 

Edit: Oh, and this is the more "advanced" FC-530. Not the original FC-200.

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On the control wheel's pitch trim control switch in the real aircraft there has a small "barrel style" knob incorporated as part of the switch that is not modeled here.When the autopilot is engaged you can bump the knob fore or aft to change pitch attitude.When the desired airspeed or vertical speed is attained via the change in pitch you would then select V/S or SPD mode on the AFCS panel.It will maintain that value until capturing the pre selected altitude. For the simulator I have found it is easiest for example on takeoff, set the heading bug to runway heading and after takeoff engage the autopilot and HDG mode, manually adjust your pitch attitude with whatever controller you use to attain the desired climb airspeed then select SPD.

 

One would normally use SPD mode for climbs and V/S for descent.As the aircraft climbs higher if V/S is engaged it would require an ever increasing pitch attitude to maintain the rate and could result in a low airspeed condition.Recommended climb schedule is 250KTS to FL290 then transition to .72 mach for the remainder of the climb.

 

For descent preset the new altitude, turn off ALT Hold and establish your desired vertical speed and engage V/S. I tried using the trim buttons on my joystick to do the same button the rate of movement for trim is too fast as modeled right now and it is very difficult to get the minor trim movement required to do this smoothly.In the real aircraft the pitch trim speed actually operates at a much reduced rate when the flaps are retracted for the very same reason.The 530 version of the autopilot is an improvement over the original FC-200 system and works very well, you have to remember this is pre digital world. I had some of our generation X company engineers onboard one day and one remarked he was surprised to see such an "analog" cockpit and I had to laugh.

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The SPD doesn't seem the hold the speed I select it at very well. Have you noticed that? Or is that normal in the real aircraft?

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It seems to hold it initially but does not adjust pitch attitude to maintain constant speed as climb performance decreases.It is a sim issue, the performance model is not right and needs adjustment for high altitude flight.It struggled to get to 410 and at that altitude should be able to maintain a normal cruise speed of .77 mach or so.I was seeing around .67 and it would not hold altitude very well.That is not representative of actual aircraft performance.

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Hello all, I cannot seem to get the auto pilot to function, I got to select an altitude and the dial does nothing. Also during the start up sequence I cannot get the throttle levers to stay in idle cutoff so I can introduce fuel during a routine start up. With my experience in the Lear series in beginning to thing there was an error in the install or sp2 had some flaws.. Please feel free to chime in!

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Gary, thanks for the input, hopefully their be able to make the necessary changes to the FDE. As a former RW Lear pilot your input is very useful.

 

Cheers

Martin

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Wow due to my lack of fsx knowledge I found that the right button on the mouse did the trick lol!

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Wow due to my lack of fsx knowledge I found that the right button on the mouse did the trick lol!

Glad you got it worked out.  And welcome to our alternate reality.

 

Bill

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Wow due to my lack of fsx knowledge I found that the right button on the mouse did the trick lol!

This is mentioned in our user manual under mouse functions. Also our GNS 530 power button uses the mouse wheel as it has brightness controls. Many customers email me saying it will not turn on.

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Found a bug in V1.7. ALT/HLD will not hold the current altitude. It will auto turn on after reaching a desired altitude using ALT/SEL mode. V1.8 will have the ALT/HLD mode working as it seemed to work before. I found the reason why tonight when looking over the code and works good now.

 

First thing you should always know about complex custom autopilot systems like this one.

 

1. Hardware and keyboard shortcuts will no longer work as our complex coding decides if a default function is on or off. So you must use your mouse on our buttons.

2. Due to conflicks you may have to turn off a mode before you engage another mode.

 

When using ALT/SEL you do not need to turn this off when switching between SPD or VS mode. But if your suing ALT/HLD you need to turn this off before engaging ALT/SEL.

 

If you are not climbing to a specific altitude you should put the ALT SET to zero. This keeps the out of range light off.

If your going to climb or descend to a desired altitude. Turn on the ALT/SEL first then choose between the SPD or VS mode. You need to pitch the aircraft to the angle you would like to climb or descend then press the SPD or VS mode. If you want to increase or decrease pitch turn off the VS pitch then re engage. If using SPD just adjust the thrust lever as this will maintain the same speed but effects the pitch.

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Wow, interesting thoughts....   SPD until F290@GS 250,  then VS.....  Uff  i bet i will practice that.  I have gone into dangerous speed lost during rocket climb sometimes... :P

 

 

About Change in attitude, this is what i do from a leveled steady cruise:

 

1- Change the altitude setpoint and then dissengage hold altitude button

2- Trim the aircraft to desired VSI config

3- Press Alt Selt when VSI starts to move down...

4- Press VS when achieve a stable VSI indication using trim....

 

 

Is that ok that way

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BTW, the GS buton is not controlling the speed at all.... keeps green/yellow lighting....   I can only use VS for climbing... :fool:

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The "GS" button on the AFCS you refer to means "glide slope" as in ILS. If you are doing an ILS approach for landing you arm "NAV" for the localizer, and "GS" to capture the glide slope. It has nothing to do with speed.

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Ohh thanks,   Gee,  i though it was NAV for both.....    Well, i got another one....

 

About the speed button, i though that i could maintain speed somehow.....   Is there any autopilot function to climb as you explained in another thread?

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Ohh thanks,   Gee,  i though it was NAV for both.....    Well, i got another one....

 

About the speed button, i though that i could maintain speed somehow.....   Is there any autopilot function to climb as you explained in another thread?

 

You can using the SPD mode on the AFCS.Have the altitude you are climbing to set and the arm Alt/Sel button.Establish the airspeed you wish to climb at and when it is stable at that speed push the SPD button.If the autopilot is engaged it will now adjust pitch attitude to hold the airspeed in the climb.The SPD mode is similar to V/S in that both modes function by adjusting the aircraft pitch attitude using flight director guidance which tells the autopilot to affect a change in pitch attitude to maintain what ever value is referenced. I use SPD for climbs and then transition to pitch mode at around 500 fpm

for altitude capture.For descent set and select ALT/SEL, initiate the desired descent rate using pitch mode and select V/S when it is established. 

 

Obviously you are controlling the engine thrust in climb, cruise and descent to achieve performance desired.The 800 ITT setting I mentioned is for real world, this is a sim with code and it is not going reflect real world numbers, use what ever thrust setting you need for performance. If you do a little online research there are Learjet pilot training guides on maneuvers, approach procedures etc. as in " how to fly it" The FSW manual does adequate job of explaining what functions are in the sim and what they are for.

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If you do a little online research there are Learjet pilot training guides on maneuvers, approach procedures etc. as in " how to fly it"

 

 

Like this one.

 

Another one is: Flying the Classic LearJet by Peter D. Condon. 

 

cover225x225.jpeg

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You can using the SPD mode on the AFCS.

 

All Right!.... I will test it.  I just downloaded the 1.8.   Will try it, thanks...  :-)

 

 

 

Like this one.

 

Wow!   Just perfect!   Thanks   :wink:

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Just to share... VS Button for VSI control and SPD Button for IAS Control, all during climb is just working excellent  :dance:    Thanks for the advise.

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