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06-13-2015, 04:20 PM
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Join Date: Jan 2005
Location: England
Posts: 1,087
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I think you should ask yourself if you are comfortable passing control of your trim and flaps to a multi-purpose piece of uncertified software with no effective cut-out. I know both Dynon and Vertical power have a fine reputation for building reliable products, but just because you can do something does not mean you should. Failure (runaway) of trim or flap control at cruise speeds could make life rather too interesting.
From my perspective these 2 functions are things I will assign to single function systems to ensure reliability. My flaps are currently actuated with a large handle, and will be controlled by a simple switch directly to the motor. I currently have a manual trim, and will have a single purpose box to vary the trim speed with flap position that can be switched off easily. I don't think auto-trim is very useful in RVs - the trim force over the entire speed range is typically low, so the autopilot servos rarely run out of authority. Manually trimming is not a huge overhead to prevent some of the failure scenarios possible with an integrated (simplex with unknown failure monitoring) auto-trim and autopilot.
David - you might like to ask the LAA their view on auto-trim using the autopilot.
Pete
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06-13-2015, 05:10 PM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by penguin
I think you should ask yourself if you are comfortable passing control of your trim and flaps to a multi-purpose piece of uncertified software with no effective cut-out. I know both Dynon and Vertical power have a fine reputation for building reliable products, but just because you can do something does not mean you should. Failure (runaway) of trim or flap control at cruise speeds could make life rather too interesting.
From my perspective these 2 functions are things I will assign to single function systems to ensure reliability. My flaps are currently actuated with a large handle, and will be controlled by a simple switch directly to the motor. I currently have a manual trim, and will have a single purpose box to vary the trim speed with flap position that can be switched off easily. I don't think auto-trim is very useful in RVs - the trim force over the entire speed range is typically low, so the autopilot servos rarely run out of authority. Manually trimming is not a huge overhead to prevent some of the failure scenarios possible with an integrated (simplex with unknown failure monitoring) auto-trim and autopilot.
David - you might like to ask the LAA their view on auto-trim using the autopilot.
Pete
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Hi Pete, I'd like to respectfully disagree with your value assessment of autotrim.
I developed an autotrim controller that works with the SkyView systems as a separate stand alone box. If the EFIS fails, it works as a standard trim controller with speed scheduling determined by flap position. It also has fail safe/recovery mode. This agrees with your premise.
However, I think your assessment of the servo motor authority over the RV speed range is incorrect. Before Autotrim, I was getting constant demands for manual trim intervention from the Dynon Autopilot in my Harmon Rocket. With my autotrim controller, I can change throttle settings and let the autotrim take over. I can even engage the autopilot with large trim offsets so that the servos slip and my autotrim controller will converge to neutral.
This means that I can use smaller, lighter servo motors and I have a lot fewer distractions in the cockpit.
My SOP is take-off, level off at 2000 feet (about 30 seconds later in an HRII), slap on the autopilot and let the trim take care of itself while I tidy up the cockpit.
I would never go back to manually controlled trim with an autopilot. An autopilot without autotrim is so last century.
__________________
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V e r n. ====
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RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
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06-13-2015, 07:17 PM
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Join Date: Mar 2010
Location: KSGJ / TJBQ
Posts: 2,039
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Quote:
Originally Posted by vlittle
I developed an autotrim controller that works with the SkyView systems as a separate stand alone box. If the EFIS fails, it works as a standard trim controller with speed scheduling determined by flap position. It also has fail safe/recovery mode. This agrees with your premise.
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vlittle: Can your autotrim controller be used on a NAVAID servo or a Trio GOLD standard servo?

__________________
Galin
CP-ASEL-AMEL-IR
FCC Radiotelephone (PG) with Radar Endorsement
2020 Donation made
www.PuertoRicoFlyer.com
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06-14-2015, 08:16 AM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by GalinHdz
vlittle: Can your autotrim controller be used on a NAVAID servo or a Trio GOLD standard servo?

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No, it controls trim motors only. It interprets the SkyView serial data stream, integrates auropilot servo force vectors and makes trim commands in two axes.
It works only with Dynon SkyView systems. The fundamental difference with the Dynon control head and my box is that mine is remotely mounted and takes no (or minimal) panel space. I developed it about a year before Dynon rolled out their unit because I was impatient and enjoyed the challenge.
I don't know what algorithms Dynon uses for their controller but the math I used for mine required a high speed processor with critical hand-coded operations. I published the algorithm in the datasheet, if anyone is interested. It's all based on an open source hardware platform, but this particular code is proprietary. Dynon was helpful in pushing me in the right direction, even though they had their own development underway.
__________________
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V e r n. ====
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RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
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06-14-2015, 11:17 AM
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Join Date: Jun 2005
Location: Woodinville, WA
Posts: 1,499
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Quote:
Originally Posted by penguin
I think you should ask yourself if you are comfortable passing control of your trim and flaps to a multi-purpose piece of uncertified software with no effective cut-out.
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You can disconnect the Dynon trim control by pulling your trim breaker, the same one you'd pull if your switch broke and the servo kept moving.
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06-14-2015, 05:56 PM
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Join Date: Mar 2010
Location: KSGJ / TJBQ
Posts: 2,039
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Quote:
Originally Posted by dynonsupport
You can disconnect the Dynon trim control by pulling your trim breaker, the same one you'd pull if your switch broke and the servo kept moving.
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Isn't that the same way you would disconnect a runaway trim in a certified system?
Quote:
Originally Posted by vlittle
No, it controls trim motors only. It interprets the SkyView serial data stream, integrates auropilot servo force vectors and makes trim commands in two axes.
It works only with Dynon SkyView systems. The fundamental difference with the Dynon control head and my box is that mine is remotely mounted and takes no (or minimal) panel space. I developed it about a year before Dynon rolled out their unit because I was impatient and enjoyed the challenge.
I don't know what algorithms Dynon uses for their controller but the math I used for mine required a high speed processor with critical hand-coded operations. I published the algorithm in the datasheet, if anyone is interested. It's all based on an open source hardware platform, but this particular code is proprietary. Dynon was helpful in pushing me in the right direction, even though they had their own development underway.
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INTERESTING. Can I use your box with a SkyView system, an old TRIO Altitude hold and a Ray-Allen electric pitch trim?

__________________
Galin
CP-ASEL-AMEL-IR
FCC Radiotelephone (PG) with Radar Endorsement
2020 Donation made
www.PuertoRicoFlyer.com
Last edited by GalinHdz : 06-14-2015 at 05:59 PM.
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06-14-2015, 06:38 PM
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Join Date: Oct 2005
Location: Estes Park, CO
Posts: 3,947
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Breaker
Quote:
Originally Posted by dynonsupport
You can disconnect the Dynon trim control by pulling your trim breaker, the same one you'd pull if your switch broke and the servo kept moving.
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Trim breaker?
Now I'm confused again. The initial question was whether to connect to the Dynon or the VP-X. The recommendation was to hook up all the wiring to the Dynon. I looked it up and drew the wiring diagram according to the Dynon install manual. All the wires go to Dynon connectors. There is no breaker shown.
Maybe the Dynon EMS has a breaker or in my case, a circuit on the VP-X. If the latter, a switched VP-X circuit would power down the EMS. Please explain. What did I miss?
__________________
Larry Larson
Estes Park, CO
http://wirejockrv7a.blogspot.com
wirejock at yahoo dot com
Donated 12/03/2019, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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06-15-2015, 08:59 AM
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Join Date: Jun 2005
Location: Woodinville, WA
Posts: 1,499
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Larry,
All circuits in a plane have circuit protection. So in your case, we mean turn off the circuit on the VP-X that drives pin 9 on the SV-AP-PANEL.
This circuit protection device is shown on Figure 117, Page 18-7 in the install manual. This does not power down all of SkyView, the EMS, or even the SV-AP-PANEL. This just removes power from the circuit that can move the trim motor.
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06-15-2015, 12:31 PM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by GalinHdz
Isn't that the same way you would disconnect a runaway trim in a certified system?
INTERESTING. Can I use your box with a SkyView system, an old TRIO Altitude hold and a Ray-Allen electric pitch trim?

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Only Dynon servos and any electric trim. FMI http://54.162.78.90/redmine/attachme...stallation.pdf
Vern
__________________
===========
V e r n. ====
=======
RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
Last edited by vlittle : 06-15-2015 at 04:41 PM.
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06-15-2015, 01:28 PM
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Join Date: Oct 2005
Location: Estes Park, CO
Posts: 3,947
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Thanks
Quote:
Originally Posted by dynonsupport
Larry,
All circuits in a plane have circuit protection. So in your case, we mean turn off the circuit on the VP-X that drives pin 9 on the SV-AP-PANEL.
This circuit protection device is shown on Figure 117, Page 18-7 in the install manual. This does not power down all of SkyView, the EMS, or even the SV-AP-PANEL. This just removes power from the circuit that can move the trim motor.
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Ahhh. I haven't gotten to the panel drawings yet. That explains it.
__________________
Larry Larson
Estes Park, CO
http://wirejockrv7a.blogspot.com
wirejock at yahoo dot com
Donated 12/03/2019, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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