VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #31  
Old 03-24-2019, 11:54 PM
pilotyoung pilotyoung is online now
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 124
Default Trim Speed, A question for Scott

Scott,
First of all, Scott I want to thank you for all the help you provide on this forum. I have been reading the read-me file that you posted and have downloaded all the files for my system from the link you provided. Tuesday I am going to go to the hangar and install them.

I have carefully read the section on trim settings, etc. several times. I want to be sure I understand it. It says "If the SV-AP-Panel were to fail, (and I interpret that to be turned off in addition to an outright failure), the switch on the panel would still control the trim motor at full rate trim. The following calibration test will not affect the function of the trim switch on the panel."
So does that mean that when the auto-pilot is off and I am manually flying and trimming, that full speed trim is the only thing that is available to me? In other words, the adjustment pot on the Vans 50,000A will not change the trim speed in manual mode?

After reading that last paragraph I am not sure it is clear. Here is how I fly. I take off and manually adjust the trim within seconds of takeoff. As I continue to fly to altitude, I manually adjust the trim. When I reach my cruising altitude, I manually adjust the trim and then turn on the auto-pilot, using altitude hold and normally either track or gps mode. While at cruising altitude, I let George (the auto-pilot) fly the airplane and the auto-pilot makes all the trim adjustments. When I start to descend, I set my new desired, lower altitude, put the auto-pilot in descent mode, and select a rate of descent. I let the auto-pilot fly down to some altitude when I decide it is time to be hand flying. Then I turn the auto-pilot off and begin manually flying the airplane. All trim adjustments from this point until I land are done manually.

The problem in my airplane is that the trim speed is too fast. Full range trim is about 16 seconds and I have the pot adjuster full range clockwise to yield the slowest trim rate. So If I am understanding the quoted portions of the manual correctly, when the auto-pilot control module is installed, the only trim function in manual mode is full speed.

Please understand that I am asking these questions as a learner. I want to learn my airplane and know what it will do and not do. I am not asking the questions to be argumentative or confrontational.

I am looking forward to your answers so I can understand this system more completely and know what to expect from my trim.

John
__________________
John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
Reply With Quote
  #32  
Old 03-25-2019, 07:30 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,886
Default

You could buy several 1/2 watt resistors ranging in value between 1 ohm and
15 ohms. Set Van's trim pot to the center of its range. Using trial and error,
put one of the resistors in series with one of the trim servo motor leads.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #33  
Old 03-25-2019, 08:46 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,286
Default

Quote:
Originally Posted by pilotyoung View Post
Scott,
First of all, Scott I want to thank you for all the help you provide on this forum. I have been reading the read-me file that you posted and have downloaded all the files for my system from the link you provided. Tuesday I am going to go to the hangar and install them.

I have carefully read the section on trim settings, etc. several times. I want to be sure I understand it. It says "If the SV-AP-Panel were to fail, (and I interpret that to be turned off in addition to an outright failure), the switch on the panel would still control the trim motor at full rate trim. The following calibration test will not affect the function of the trim switch on the panel."
So does that mean that when the auto-pilot is off and I am manually flying and trimming, that full speed trim is the only thing that is available to me? In other words, the adjustment pot on the Vans 50,000A will not change the trim speed in manual mode?

After reading that last paragraph I am not sure it is clear. Here is how I fly. I take off and manually adjust the trim within seconds of takeoff. As I continue to fly to altitude, I manually adjust the trim. When I reach my cruising altitude, I manually adjust the trim and then turn on the auto-pilot, using altitude hold and normally either track or gps mode. While at cruising altitude, I let George (the auto-pilot) fly the airplane and the auto-pilot makes all the trim adjustments. When I start to descend, I set my new desired, lower altitude, put the auto-pilot in descent mode, and select a rate of descent. I let the auto-pilot fly down to some altitude when I decide it is time to be hand flying. Then I turn the auto-pilot off and begin manually flying the airplane. All trim adjustments from this point until I land are done manually.

The problem in my airplane is that the trim speed is too fast. Full range trim is about 16 seconds and I have the pot adjuster full range clockwise to yield the slowest trim rate. So If I am understanding the quoted portions of the manual correctly, when the auto-pilot control module is installed, the only trim function in manual mode is full speed.

Please understand that I am asking these questions as a learner. I want to learn my airplane and know what it will do and not do. I am not asking the questions to be argumentative or confrontational.

I am looking forward to your answers so I can understand this system more completely and know what to expect from my trim.

John
As I wrote in my previous post (# 29), and as mentioned in the read me file, the trim speed reverts to using the normal speed control (the one on the AV-50000) when the AP system is off line.
That is why I said you still need to properly set the speed for that system.

A properly operating AV-50000 speed controller can be adjusted slow enough that the servo will stall and not move, so you either think you are turning it all the way clockwise but your not (the control is a 25 turn pot, so it takes 25 full turns to go from max speed to minimum speed), or something with the speed controller has failed. A failure is rather unlikely because as a rule they either work or don't, but I guess it is possible.
Since the pot can be difficult to access, my recommendation would be that you try again... maybe using a different adjusting tool (note, if you use a small metal screw driver, do not make adjustments with power turned on), and see if you can get it any slower. Because it is a 25 turn pot, it takes a couple of turns to see much of a change.

I would discourage adding resistors to slow the servo speed. It will reduce the torque output of the servo which could cause stalling problems at higher loads on the antiservo tab, and it would be just masking the actual problem (assuming it really wont adjust any slower)
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #34  
Old 03-25-2019, 09:47 AM
pilotyoung pilotyoung is online now
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 124
Default Trim Speed

Scott,

Thanks for that reply, that clarifies things.

I turned it two or three turns and it was then much harder to turn so when I realized that I stopped because I didn't want to damage it.

Tomorrow I am going to install the file and configuration files that I downloaded and I will see about turning it more. As you said it is hard to access. I got a screwdriver small enough to fit and then cut part of the handle off so it would fit in the small space. When I was adjusting it, I had the sheet metal off the top and took out the start module for good access. Some have said you can access it with the skyview out so that is what I will try tomorrow.

Thanks again for your help.

John
__________________
John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
Reply With Quote
  #35  
Old 03-25-2019, 10:40 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,286
Default

Quote:
Originally Posted by pilotyoung View Post
Scott,

Thanks for that reply, that clarifies things.

I turned it two or three turns and it was then much harder to turn so when I realized that I stopped because I didn't want to damage it.

Tomorrow I am going to install the file and configuration files that I downloaded and I will see about turning it more. As you said it is hard to access. I got a screwdriver small enough to fit and then cut part of the handle off so it would fit in the small space. When I was adjusting it, I had the sheet metal off the top and took out the start module for good access. Some have said you can access it with the skyview out so that is what I will try tomorrow.

Thanks again for your help.

John
You can't damage the pot on the AV-50000 buy turning it too far... it will just continue to freewheel when you get to either end (Note... people with the AV-12 switch panel for the D-180 have a pot that is only 4/3 of a turn and it can be damaged if you try and force it too far.)

You can damage it by pushing excessively hard on the pot.

It sounds like you probably didn't turn it enough to make much adjustment.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 07:13 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.