In both the Cessna 172 and TBM930, when I engage Autopilot the plane levels out. This makes sense. But how do I get to manually steer the plane without disengaging Autoplilot? For instance, if I want to use Alt Hold or FLC but don’t want Autopilot to keep me level so I can change course.
I have tried engaging HDG and then disengaging it (a method that I used to have to do often in FSX) to no avail.
Use your mouse the increment the heading bug.
When the AP is in Heading mode, it should follow the heading bug on the compass rose on the PFD. Make sure it doesn’t say ROL in the AP mode indicator - it should say HDG.
? Your saying that incrementing the HDG bug will disengage it from AP? How strange- changing the ALT bug does not do the same. Thx! Would never have thought of that.
Actually, it doesn’t work. I tried it just now a couple of times. When I engage AP, the plane levels out and I have to kill the AP to be able to change course, no matter whether I mess with the HDG bug or not. Is this a bug? Shouldn’t ALT and HDG be independant when AP is engaged?
You need a lateral mode engaged also. It defaults to roll.
It doesn’t disengage it, it simply follows the new heading. So rather than turning by using the yoke, you turn the heading knob to change the heading bug to your new course.
It sounds like you want to have the AP maintain altitude while you steer the heading manually. It doesn’t work that way in these aircraft. It’s all or nothing. I think CWS mode in the 737 and maybe other airliners does what you describe.
The best I can suggest if you don’t want to steer using the heading bug is that you can make subtle inputs in ROL mode. If you make too drastic an input it will disengage the AP. But keep it small and you can do it. You can also use the rudder without causing it to disengage.
Thanks but you must not have understood my post. I know how to use HDG mode. I want to be able to have AP on and steer the plane without that, just leaving ALT on the AP. IWhen AP is engaged I cannot turn the plane.It says “Roll” and I can’t defeat it.
OK- that explains it. How strange (in my opinion) that you have to use the HDG bug once AP is engaged. I guess, not being a real pilot, I got used to FSX, where you could turn ALT and HDG on and off independantly.
No…I’m saying that while AP is enabled if you increment the heading the plane will follow.
Once plane is at desired altitude, trimmed and level..
Press AP
Press Altitude Hold
You can adjust altitude to a new level and press Flight Level Change
With correct power plane will move to new altitude. You may have to adjust Vertical Speed. Press Vertical Speed Hold and adjust VS.
Put heading bug in the direction you want to fly
Press Heading Hold
Adjusting heading bug will steer the aircraft.
Forced use of the elevators or ailerons (Yoke) or use of rudder will cancel AP
I think what he is saying is that he wants the A/P to hold the A/C altitude BUTbe able change headings( fly the a/c) manually using the yoke. This can’t be done on modern a/p’s. Engaging the a/p engages 2 channels, Vertical (elevators )AND horizontal (ailerons) Basically if you engage the a/p it will engage and hold the current status of the a/c. If you try to manually turn the yoke to steer the a/c, by design, the a/p will disengage due to be overriden by the pilot. The last a/c that I was familiar with that allowed the channels to be engaged seperately was the 737-200. The a/p had 2 selectors, one for elevators & the other for ailerons. Selecting the various modes does what it says. I am not going to go into Control Wheel Steering (CWS). This is no now available on most a/s of late design. Hope this helps
Kev
You can’t only small move oy routers
The way it worked in FSX wasn’t correct. In FSX the Cessna 172 equipped with a G1000 had a KAP 140 (which was appropriate back then). Later on Garmin swapped this to a GFC 700. With both you can’t engage a vertical mode (in the case altitude) without a lateral mode. When you do the default lateral mode (roll) will be engaged.
Understood. I will of course use the AP correctly and steer either manually (no AP) or with the HDG bug, but I still am surprised that in the 21st century we can’t have independant controls in the real world. Seems like it would be desirable, especially in turbulence, to not have to worry about trim and just navigate manually while ALT is steady.
Thanks for clearing that up, all.
Sounds like a recipe for a stall and even a spin.
I’m not a real world pilot so I’m curious about your reply. Why would having ALT hold while you are steering cause a stall or a spin? The ailerons and elevators are separate. Maybe an extreme bank might be problematic but IRL isn’t the goal to try and keep the same altitude when turning? If so, why not have AP help with that?
Because as you bank the aircraft you need to apply back pressure on the yoke to maintain altitude. Allowing the autopilot to do this without giving it the authority to limit the bank just seems like a bad idea. You can find yourself in an accelerated stall and even enter a spin rather easily if you bank hard enough with the autopilot trying to pitch up to maintain altitude. The aircraft might reach the critical AoA. All it would care about is doing it’s best to maintain the altitude.
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For heavy/severe turbulence most small to medium ops manuals say to disconnect the a/p & fly manually. Why? The a/p will follow every movement & try to correct it. Imagine an a/c rolling & pitching at the same time & the a/p followng all these to correct it. As Makii152 says, you could finish up in a stall. The idea is to allow the a/c to ride the turbulence & you to keep it under control by not following every movement but to manually keep the a/c in a safe and controllable situation. The 747 classic a/p has a turb mode selection that halves the a/p inputs and that is na a/c that is pretty resistant to turbulence.