Simviation Forum - Autothrottle on Turboprop Aircraft

Feb 14^th, 2010 at 8:37am

flipside Offline
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Minneapolis, MN

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I have a number of multi-engine turboprop aircraft and the panels all show a provision for an autothrottle. Whenever I make the changes in the aircraft.cfg (AT Available, AT Arming req) and I try to turn it on in flight the throttle drops down to zero. Is there some other change I need to make for the autothrottle to work? Embarrassed

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Reply #1 - Feb 14^th, 2010 at 12:05pm

Capt.Propwash Offline
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did you set a desired speed in the Speed Hold Window of the Autopilot??

If you did not, it is arming/setting the Autothrottle at ZERO KIAS and that is why your speed is falling to 0.

If your craft is not equipped or set up for an autopilot, one will need to be installed in via the Panel.cfg

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Reply #2 - Feb 17^th, 2010 at 11:08am

flipside Offline
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Minneapolis, MN

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Of course I set a speed in the IAS window on the autopilot. What I want to know is how I can get the autothrottle to work the way it does in jet liners. When I turn the autothrottle on the throttles drop to idle. How can I fix this?

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Reply #3 - Feb 17^th, 2010 at 12:23pm

aussiewannabe Offline
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Did you check the aircraft.cfg file under each turboprop?

Ex.

[autopilot]
autopilot_available=1
flight_director_available=1
default_vertical_speed=1800
autothrottle_available=1
autothrottle_arming_required=1
autothrottle_max_rpm=90
autothrottle_takeoff_ga=1

0=No
1=Yes

When you have an AC panel with the autothrottle shown, it's best to check the above when you first install it.

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Reply #4 - Feb 20^th, 2010 at 8:24am

flipside Offline
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Minneapolis, MN

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I made the recommended adjustments to a British Aerospace ATP with an aftermarket panel and it made no difference. I set the IAS speed to 200 kts, armed the autothrottle, turned on the speed switch, and nothing happened. The aircraft just sat there. Once I took off with the manual throttle, I turned the autothrottle back on, left the IAS speed at 200 kts, hit the speed switch, and the throttles slowly dropped down to idle and the aircraft speed dropped down to 80 kts and started losing altitude.

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Reply #5 - Feb 20^th, 2010 at 1:52pm

JerryH Offline
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Bellevue, WA USA

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Hi flipside,

Needless to say, turboprops don't work the same way as jets in FS. I have some very old notes from FS2002 that suggest using the following under the Autopilot section:

autothrottle_max_rpm=20000 (or any LARGE number)

In other notes, a value of 99999 was suggested.

For some reason, I used 2800 in a Fokker 50. My notes say that the engines surged during cruise and that autothrottle during climb was not working well. At least, the engines were running!

I would suggest experimenting with the max_rpm value and reporting back with your results.

Regards,
JerryH

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Reply #6 - Feb 22^nd, 2010 at 11:06am

exnihilo Offline
Colonel
Tempe, AZ

Posts: 189

I generally have not had problems with autothrottle not working on turboprops, as long as it is set in the aircraft.cfg. However, I have observed another problem where the throttle setting, once the autothrottle is engaged, cyclically ramps up and down to a very noticable degree. Its usually so bad, I've simply given up trying to use autothrottle on turboprops. Anyone else notice this?

300,000 KM/S - Its not just a good idea, its the law.

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Reply #7 - Feb 22^nd, 2010 at 12:26pm

EVVFCX Offline
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Been there done it-well
most of it.
Pontefract, West Yorkshire

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Hi Flip, given chance, maybe on wed evening UK time I'll check for autothrottle settings on the Just Flight C130 package and post back thursday afternoon - no internet access at home at the moment Sad

I've never used the autothrottle on the herc so can't give you any quick feedback.

Busy right now getting radio control setup ready.

May the Mynd be with you.
So far my number of landings either passenger or pilot equal my number of takeoffs, but that is due to change

13/07/11 Passed BMFA Fixed Wing 'A' test.
FSX Gold

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Reply #8 - Feb 25^th, 2010 at 4:56am

EVVFCX Offline
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Been there done it-well
most of it.
Pontefract, West Yorkshire

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Posts: 499

Hi Flipside,

bad news I'm afraid but not as bad as the problem your having, I tried the just flight c130 on autothrottle, you fly at the the speed you want to keep flying at as long as you remain at the same attitude/pitch that is, select AP on, IAS hold on, engage autopilot but it didnt work but then it didnt throttle back either, it just behaved as though I hadn't turned it on.

Otherthing that didnt work was autopilot control of the rudder even with that turned on.

Maybe a config problem.
I did'nt check out any other props with airspeed hold, it worked fine on the learjet/737's.

I'll check again but even read the manual! and it still did'nt work

May the Mynd be with you.
So far my number of landings either passenger or pilot equal my number of takeoffs, but that is due to change

13/07/11 Passed BMFA Fixed Wing 'A' test.
FSX Gold

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Reply #9 - Feb 26^th, 2010 at 7:52am

flipside Offline
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Hello!
Minneapolis, MN

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Posts: 151

Jerry H

What you suggested works! However, I used the number 30000 as a Saab 340's throttle cycled up and down while climbing to cruising altitude. When I raised the number to 30000 the problem was corrected. Many thanks for your advice. I have applied it to a coupls of other aircraft and it works like clockwork. As my mother used to say, "Slicker than snot on a doorknob." Wink

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Reply #10 - Feb 26^th, 2010 at 1:49pm

JerryH Offline
Colonel
Bellevue, WA USA

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Posts: 155

I'm glad you were successful and thanks for reporting back. Your feedback will help others with the same question. You also proved that experimenting with the Saab was worth the time spent.

I hope your mother occasionally took the time to clean the doorknobs.

Regards,
JerryH

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