Correct(ish) use of the autopilot for heading and altitude

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Chairman
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Correct(ish) use of the autopilot for heading and altitude

Post by Chairman »

I don't have the sim computer with me but I do have the V35 manual - always a bad combination - and I've been trying to work out how to correctly use the autopilot. I can make it do what I want eventually but I'd like to do it properly so I've been RingTFM :) Assuming I want to take off then pick up the magenta GPS line and climb to 5000', with a GTN750 for GPS, am I thinking along the right lines here -

For takeoff set the heading bug to the runway heading, on the autopilot press FD and HDG, on the altitude selector set 5000 and press ARM, on the GTN set the CDI to GPS - this should if I've read the book properly give me an FD that is flying runway heading and climbing at 500fpm (which I can change with the UP and DN buttons on the autopilot panel) ?

After takeoff at some point on the autopilot press AP to make the autopilot take over following the FD

When ready to follow the gps track turn the plane manually or with the heading bug onto a course where it will intercept the gps plan then on the autopilot press NAV to arm the gps tracking while still in HDG mode

The autopilot will then take care of the rest, i.e. changing from HDG to NAV when it picks up the gps track, and leveling off at 5000' and putting itself into ALT mode.

And at no point do I press the ALT button on the autopilot panel.

Yes ?

If I've got that right then I'll start to think about what I should be doing for the descent :)

Cheers

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AKar
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by AKar »

Sounds about right.
Chairman wrote: 13 Dec 2020, 17:55 For takeoff set the heading bug to the runway heading, on the autopilot press FD and HDG, on the altitude selector set 5000 and press ARM, on the GTN set the CDI to GPS - this should if I've read the book properly give me an FD that is flying runway heading and climbing at 500fpm (which I can change with the UP and DN buttons on the autopilot panel) ?
The FD will command pitch attitude, not vertical speed. A subtle but very important difference. Initial engagement of the FD captures the current pitch angle, not any particular vertical speed.

You'd be engaging the FD in the air after takeoff, not on the ground. I don't remember there was a go-around mode in the A2A Bonanza's autopilot, in some KFC 200s there is. It could be used for rudimentary takeoff guidance, but personally I'd recommend against.
Chairman wrote: 13 Dec 2020, 17:55 And at no point do I press the ALT button on the autopilot panel.
The ALT button manually engages the altitude hold mode. This is automatically engaged at the preset altitude in ARM mode. You can use the ALT for temporary level-outs, for instance, if required.
Chairman wrote: 13 Dec 2020, 17:55 The autopilot will then take care of the rest [...]
Yes, but don't think it that way. Dangerous. :mrgreen:

-Esa

Chairman
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by Chairman »

AKar wrote: 14 Dec 2020, 11:10 The FD will command pitch attitude, not vertical speed. A subtle but very important difference. Initial engagement of the FD captures the current pitch angle, not any particular vertical speed.

You'd be engaging the FD in the air after takeoff, not on the ground. I don't remember there was a go-around mode in the A2A Bonanza's autopilot, in some KFC 200s there is. It could be used for rudimentary takeoff guidance, but personally I'd recommend against.
Now THAT is a gotcha, and explains a lot ! Thank you so much ! I've always hit it on the ground so I have something to aim at for the initial climb. I don't recall ever reading about a go around mode, but this is the first time I've dug this deep into the books :)

Cheers

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AKar
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by AKar »

Chairman wrote: 14 Dec 2020, 22:16 Now THAT is a gotcha, and explains a lot ! Thank you so much ! I've always hit it on the ground so I have something to aim at for the initial climb. I don't recall ever reading about a go around mode, but this is the first time I've dug this deep into the books :)
Yes, on engagement the FD captures the current aircraft heading and pitch attitude. Hence, you'd want to be climbing steadily and nicely trimmed out when selecting the FD on.

-Esa

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MkIV Hvd
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by MkIV Hvd »

AKar wrote: 15 Dec 2020, 00:03
Chairman wrote: 14 Dec 2020, 22:16 Now THAT is a gotcha, and explains a lot ! Thank you so much ! I've always hit it on the ground so I have something to aim at for the initial climb. I don't recall ever reading about a go around mode, but this is the first time I've dug this deep into the books :)
Yes, on engagement the FD captures the current aircraft heading and pitch attitude. Hence, you'd want to be climbing steadily and nicely trimmed out when selecting the FD on.

-Esa
Chairman, the other thing that your thread just brought to memory is that although there is no GA mode in the Flight Director, the Bonanza Input Configurator has the option to assign a button to "AP Yoke CWS" (Spelling??...not at my FS computer...it's second or third in the list I think), which is basically "Pitch Sync". Pressing the button will sync the command bars to your current pitch, so it can actually be used as a poor man's GA switch, by just holding the button while you rotate on takeoff until you've reached your initial climb attitude...with or without HDG mode engaged. I haven't used the Flight Director until I'm ready for the autopilot, but under solid IFR, hand flying it with the Flight Director is a very good option. If not used for takeoff, you can still turn the Flight Director on for departure, continuing to sync the bars until you're in a stable, trimmed climb.

Cheers,
Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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AKar
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by AKar »

MkIV Hvd wrote: 15 Dec 2020, 08:22
AKar wrote: 15 Dec 2020, 00:03
Chairman wrote: 14 Dec 2020, 22:16 Now THAT is a gotcha, and explains a lot ! Thank you so much ! I've always hit it on the ground so I have something to aim at for the initial climb. I don't recall ever reading about a go around mode, but this is the first time I've dug this deep into the books :)
Yes, on engagement the FD captures the current aircraft heading and pitch attitude. Hence, you'd want to be climbing steadily and nicely trimmed out when selecting the FD on.

-Esa
Chairman, the other thing that your thread just brought to memory is that although there is no GA mode in the Flight Director, the Bonanza Input Configurator has the option to assign a button to "AP Yoke CWS" (Spelling??...not at my FS computer...it's second or third in the list I think), which is basically "Pitch Sync". Pressing the button will sync the command bars to your current pitch, so it can actually be used as a poor man's GA switch, by just holding the button while you rotate on takeoff until you've reached your initial climb attitude...with or without HDG mode engaged. I haven't used the Flight Director until I'm ready for the autopilot, but under solid IFR, hand flying it with the Flight Director is a very good option. If not used for takeoff, you can still turn the Flight Director on for departure, continuing to sync the bars until you're in a stable, trimmed climb.

Cheers,
Rob
Oh yeah... I'm a heavy user of the CWS modes in general, I love them in the sim! I've just never thought about using it that way in Bonanza.

-Esa

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MkIV Hvd
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by MkIV Hvd »

AKar wrote: 15 Dec 2020, 10:09 Oh yeah... I'm a heavy user of the CWS modes in general, I love them in the sim! I've just never thought about using it that way in Bonanza.

-Esa
Me neither until now, but it does seem like a pretty good idea for those full blown IMC takeoffs :mrgreen:

Cheers,
Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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AKar
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by AKar »

MkIV Hvd wrote: 15 Dec 2020, 10:48
AKar wrote: 15 Dec 2020, 10:09 Oh yeah... I'm a heavy user of the CWS modes in general, I love them in the sim! I've just never thought about using it that way in Bonanza.

-Esa
Me neither until now, but it does seem like a pretty good idea for those full blown IMC takeoffs :mrgreen:

Cheers,
Rob
Yeah, a creative idea for living perhaps a little longer. :mrgreen:

-Esa

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MkIV Hvd
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Re: Correct(ish) use of the autopilot for heading and altitude

Post by MkIV Hvd »

AKar wrote: 15 Dec 2020, 11:54Yeah, a creative idea for living perhaps a little longer. :mrgreen:

-Esa
Roger that! One crash will tend to spoil your whole day... :mrgreen:

Cheers,
Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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