Big Shout out to the A2A Team & Autopilot Question

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g-kats
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Big Shout out to the A2A Team & Autopilot Question

Post by g-kats »

I just wanted to say a big THANK YOU to the A2A team for producing such first rate aircraft. I started off with the C182 Skylane and then quickly succumbed to the Commanche after I realised just how much detail and immersion goes into these planes.

As soon as I saw the Bonanza was released, I had to have it - and I have to say it's quickly become my favourite plane to fly. The immersion is simply untouched by anything else I've flown in Prepar3d. I even love the fact it's a bitch to start! (I think I've got the knack now though).

I'm mid-way through a tour from the most northerly airport in the United Kingdom, starting in Shetland, and aiming for as far south-west as I can get. I'm throwing all sorts of crazy weather at it, and enjoying the ride immensely.

One question - I can't seem to get my head around the pitch control within the auto-pilot. I'm pre-selecting my target altitude, selecting ARM and then when the a/p is engaged I was expecting it to hold the current climb rate and then allow me to adjust it with the UP/DOWN buttons in the panel. But it looks like when you engage the a/p it simply holds the current altitude, and then you go through a messy period of re-finding the desired pitch using the buttons. Perhaps I'm doing something wrong here?

Anyway, I can't wait for your future releases. I'd love to see a small jet one day, or a faster twin. Or maybe a Caravan?

All the best and thanks again

Tim.

Les Parson
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Les Parson »

One question - I can't seem to get my head around the pitch control within the auto-pilot. I'm pre-selecting my target altitude, selecting ARM and then when the a/p is engaged I was expecting it to hold the current climb rate and then allow me to adjust it with the UP/DOWN buttons in the panel. But it looks like when you engage the a/p it simply holds the current altitude, and then you go through a messy period of re-finding the desired pitch using the buttons. Perhaps I'm doing something wrong here?



Great question and the same one I have. From reading the manual, I thought the current pitch would be maintained when the AP is engaged.

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Orlaam
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Orlaam »

Pretty sure that's normal, using pitch buttons up or down to manipulate the desire climb rate. Power also affects the pitch, so more power will climb faster and less power will descend steeper. You have to press up during climb despite hitting arm. If that's accurate to the real model I don't know.
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Simicro
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Simicro »

Tim,

Thanks for asking. Me too, I did not understand fully.

On a side note, for me the Bo is easier to start than the C172 for example where subtle priming (and timing) is required and a little fault can screw up things.
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Nick - A2A
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Nick - A2A »

Hi Tim,

Thanks for the kind words and welcome to the forums.

One thing to bear in mind with the KFC 200 autopilot which is modelled in the Bonanza is that it's an 'attitude-based' autopilot, not a 'rate-based' autopilot like the ones in the Cessnas and Pipers.

As such, the Flight Director is used to command a pitch angle, and it's this that the autopilot will try to maintain; not the rate of climb or descent shown on the VSI. The other thing to keep in mind is the the vertical trim rocker switch on the autopilot is designed for a press-and-hold type activation rather than momentary presses such as used for the 'up' and 'dn' buttons on the KAP 140.

With these two bits of info, hopefully you find the vertical modes a bit more intuitive to use. Basically, the autopilot just requires a slightly different approach than the rate-based ones you may be used to.

Thanks,
Nick

g-kats
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by g-kats »

Nick - A2A wrote:One thing to bear in mind with the KFC 200 autopilot which is modelled in the Bonanza is that it's an 'attitude-based' autopilot, not a 'rate-based' autopilot like the ones in the Cessnas and Pipers.
Thank you Nick, that makes sense now.

Is there an established procedure for a smooth transition from takeoff and climb into an a/p controlled climb?

I like to have my departure heading bug set before takeoff and hand off to the a/p to take care of that after I've confirmed positive rate of climb and safe speed while I trim out for the climb, set the prop etc, but in this plane as soon as you've engaged a/p you're no longer in direct control of the pitch even if you just want it to control your heading.

My passengers are bitching :)

Thanks!
Tim

tttocs
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by tttocs »

g-kats wrote:
Is there an established procedure for a smooth transition from takeoff and climb into an a/p controlled climb?
What I've found is that I want to be sure that I've established a good, stable climb (pitch trimmed nicely and power set for cruise climb) before engaging the AP. As soon as the AP is turned on, pitch is captured, so if you're not where you want to be in pitch, you're going to be doing a lot of futzing around.

Once you get your mind wrapped around the whole pitch thing, it really becomes quite easy to manage.

Hope that helps,

Scott

SJDobby
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by SJDobby »

Indeed: I would say the overriding advice for smooth autopilot engagement in any aircraft is to already be in smooth steady flight before engaging it, so if engaging soon after takeoff I would say first get into a *gentle* climb, wings level, with climb power already set. Should you need to apply pitch corrections thereafter, the up/down rocker switch only needs to be held for half a second or so for it to "register" your command.
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Paughco
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Paughco »

Say you're flying along in your Bonanza, with the autopilot fully engaged, at 5,500 feet and want to climb to 9,500. Here is one way:

1) Rotate the knobs on the KAS 297 Altitude Selector to get 9,500 feet indicated, and hit the "ARM" button. The ARM light will light up on the KA 285 Annunciator Panel.
2) Deselect the "ALT" button on the KC 290 Mode Controller. The ALT light will go out on the KA 285 Annunciator Panel.
3) Change power settings (pitch, throttle, mixture) from level flight settings to 500 fpm climb settings.
4) Press the vertical trim rocker switch on the KC 290 Mode Controller to get a 500 fpm climb. Easy does it.
5) Keep an eye on things as the airplane begins a 500 fpm climb.
6) She should level off and the ALT light will replace the ARM light on the KA 285 Annunciator Panel.

That's a pretty close description of the process, but I'm not flying in my Bonanza right now, so it may not be perfect.

Seeya
ATB
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Clorix
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Clorix »

Paughco wrote:1) Rotate the knobs on the KAS 297 Altitude Selector to get 9,500 feet indicated, and hit the "ARM" button. The ARM light will light up on the KA 285 Annunciator Panel.
2) Deselect the "ALT" button on the KC 290 Mode Controller. The ALT light will go out on the KA 285 Annunciator Panel.
Just to clarify, when you press the ARM button on the altitude selector after selecting a new altitude, it will automatically disengage ALT on the annunciator panel. At this point, you can just hold the up/down button on the mode control panel to get the pitch attitude you want for your climb or descent. Just change the power settings as needed like Paughco said, and upon reaching the newly-selected altitude, the AP will automatically re-engage its ALT mode to hold that altitude.

It took me a while to get used to it as well, but once I did, I found that it's pretty slick in the way it works IMO :)

g-kats
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by g-kats »

tttocs wrote:As soon as the AP is turned on, pitch is captured, so if you're not where you want to be in pitch, you're going to be doing a lot of futzing around.
That's the issue, I don't think it is capturing the pitch. It wants to capture the current altitude.

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Nick - A2A
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Nick - A2A »

g-kats wrote:That's the issue, I don't think it is capturing the pitch. It wants to capture the current altitude.
Hi Tim,

Are you pressing the 'ALT' button? If so, that's exactly what the autopilot will do. It's an alt hold button, not just a means of activating the vertical mode.

To capture the existing pitch angle, you just need to activate the flight director and then engage the autopilot. Then you can engage whichever lateral mode (HDG, NAV etc.) you wish to use. After you've done this, the aircraft should continue to climb or descend at whatever pitch angle it captured when you engaged the autopilot.

To level off at a predetermined altitude, select it with the altitude selector and press 'ARM', but again, don't touch the 'ALT' button or the autopilot will just level off at the current altitude.

Thanks,
Nick

g-kats
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by g-kats »

Ok I think I've worked out what I'm doing that's causing the problem.

Before takeoff I'm setting my target altitude, then once in flight and established I'm pressing ARM and then engaging autopilot. It then takes away control of the pitch and tries to revert to level flight, whereupon you use the buttons to control up/down, which is a messy transition.

It's the pressing of ARM before engaging a/p that's the issue here. If I do that after I turn on the a/p it retains the pitch I've dialled in nicely.

Although I'm still seeing odd behaviour with the a/p fighting the pitch trim even after ALT is turned off and ARM is not selected in later flight.

g-kats
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by g-kats »

Ok I'm expirmenting right now, and there's definitely a scenario where once you have used the a/p in ALT mode, once you deselect that and have no altitude ARMed yet a/p is still active (maybe on HDG or APPR) where you have no authority over the elevators, and it actively fights manual pitch trim.

Is that a bug?

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Nick - A2A
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Re: Big Shout out to the A2A Team & Autopilot Question

Post by Nick - A2A »

g-kats wrote:(...) there's definitely a scenario where once you have used the a/p in ALT mode, once you deselect that and have no altitude ARMed yet a/p is still active (maybe on HDG or APPR) where you have no authority over the elevators, and it actively fights manual pitch trim.

Is that a bug?
Tim,

No, I don't think so. Just to help clarify a bit, any time the KFC 200 autopilot is engaged it'll be controlling the ailerons, elevators and the elevator trim via servomotors. (That's provided the control wheel steering function isn't active.)

In the sim this means we have no authority over these primary flight controls when the autopilot is engaged, and it will indeed 'fight' any attempt to move the trim wheel. However, manual electric trim inputs (via the rocker switch on the yoke) will cause the autopilot to disconnect.

So, with autopilot engaged, the only flight control we can operate is the rudder. In real life, I believe it would be possible to overpower these servos given the application of enough force, but this kind of functionality would be hard to implement unless everyone had force-feedback hardware.
g-kats wrote:Before takeoff I'm setting my target altitude, then once in flight and established I'm pressing ARM and then engaging autopilot. It then takes away control of the pitch and tries to revert to level flight, whereupon you use the buttons to control up/down, which is a messy transition.

It's the pressing of ARM before engaging a/p that's the issue here. If I do that after I turn on the a/p it retains the pitch I've dialled in nicely.
If you're arming the autopilot before you take off, you must be engaging the flight director beforehand. In this case, the flight director will have captured your pitch angle while you're on the (presumably flat) runway. I think this is why you're levelling off once you engage the autopilot in this scenario; it's not just because you're pressing 'ARM' before 'AP'.

Thanks,
Nick

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