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Skyview NO TRIM

J

JEG

Active Member
After powering up the system I find I have no trim, continuity from trim motor to sub-d at Van's Control Module good on all five wires. I understand there is a pot on the Control Module that controls the trim motor but is not depicted as such on the module. Any ideas?????????John
 
The trim pot is on the aft side of the control module.(The side facing the back of the instrument panel). You can adjust the pot without removing the module by taking the screws out of the Master/ignition sub panel and moving the sub panel out of the way enough to get the adjustment tool on the pot.
 
Bruce Russell said:
The trim pot is on the aft side of the control module.(The side facing the back of the instrument panel). You can adjust the pot without removing the module by taking the screws out of the Master/ignition sub panel and moving the sub panel out of the way enough to get the adjustment tool on the pot.
Click to expand...

Or you can cut the adjusting tool in half. This will shorten it enough to allow access without disassembling anything.

The trim speed is preadjusted to the approx. correct setting during production testing, so it is not likely that adjusting the speed pot will resolve your problem, but I guess it is worth a try.
 
Are you sure that all of the 5 wires are connected correctly at both ends? 3 of the wires go to the servo POT. The other 2 wires supply power to the motor. Have you tried running the motor with a 9 volt battery? Reverse the battery polarity to reverse the motor. Do NOT connect the battery to the POT wires.
Joe Gores
After powering up the system I find I have no trim, continuity from trim motor to sub-d at Van's Control Module good on all five wires. I understand there is a pot on the Control Module that controls the trim motor but is not depicted as such on the module. Any ideas?????????John
Click to expand...
 
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Same thing happened to me and it was the POT! It was all the way off even though the instructions say they leave the factory in mid-range.
 
Great thanks for all the input, I have checked the motor and it runs perfectly with a nine volt batt. Wires are in the correct pin position so will try the pot
adjust. Thanks again all. John
 
rvbuilder2002 said:
The trim speed is preadjusted to the approx. correct setting during production testing, so it is not likely that adjusting the speed pot will resolve your problem, but I guess it is worth a try.
Click to expand...

Both modules I have installed have needed a considerable amount of trim pot adjustment, so I agree it is worth a try!
 
Trim motor run up

My trim went to a up position by itself when flying. I was not sure what happen when I was descending at about 700 ft per mi. The plane just started to clime I pushed the stick hard forward and held it there the plane descended at about 200 ft per min I then cut the rpm down to 3000 and my descent went to 500 ft per min. I landed and and started to check things over. I first checked the servo and no sine of anything wrong. then I turned the skyview on to check the trim and it showed it to the top of the scale I worked the switch and it operated the trim down and seems to work right. I Have no idea what made the trim go to the up position. I also had no trim motor when building and had to adjust the pot in the control module after installing the skyview system.
 
trim

Hi sounds like a short in one of the wires going to the control or to the trim unit have you checked for wires rubbing where they connect into the trim unit
 
I have powered the trim motor from the fuselage sub-d at Vans module and all well. Set the pot and still no joy. John
 
I have used the MAC trim servo in another no built design with a simple double pole double throw switch and it worked great. Vans did us no favors when they got creative and added a trim speed circuit. Sensitivity could have been handled in the mechanical linkage if the higher speed created a problem.
 
RFSchaller said:
I have used the MAC trim servo in another no built design with a simple double pole double throw switch and it worked great. Vans did us no favors when they got creative and added a trim speed circuit. Sensitivity could have been handled in the mechanical linkage if the higher speed created a problem.
Click to expand...

Actually it could not easily have been done with just a linkage change (or that would have been done instead).
Keep in mind... on the RV-12, the servo motor is not adjusting a traditional trim tab on an elevator. It is adjusting the neutral point of an antiservo tab on a full flying stabilator. There is a night and day difference in sensitivity between the two.
 
JEG said:
I have powered the trim motor from the fuselage sub-d at Vans module and all well. Set the pot and still no joy. John
Click to expand...

Hi John,

Have you solved your trim not working problem. Mine is also not working. It looks like we can adjust the pot but also it looks like we may need to calibrate it. Refer to page 7-41 in the Sky View installation guide.

Am I heading in the right direction with this?

Cheers

Julian 120316
 
The trim servo has two completely different circuits:
1. My RV-12 has the original control board. I assume that the new style
control board (AV-50000A) contains the AST trim pot that controls the
motor SPEED. If the motor does not run, this pot should be adjusted for
desired motor speed.
2. A pot inside of the trim servo sends servo POSITION to the SkyView. This
pot is not accessible. The trim tab position display needs to be calibrated
per the SkyView manual.
Joe Gores
 
Thanks Joe, I guess I was stating the obvious. At least there is a couple of things I can try to activate the trim. The OAT problem is a bit depressing. I don't really want to go pulling the probe and cable out until I have some way of knowing that is what the problem is.

Thanks.

Julian 120316
 
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I removed the switch panel and used the tool to adjust the pot and the trim servo now works. I also manage to figure out how to calibrate the trim although I think the take off trim position might be a bit suspect.

Thanks

Julian 120316
 
The trim takeoff position is about 1/3 up from the bottom. On the first test flight, it is better to error on the nose-down side. At least one RV-12 crashed on the first flight because of too much nose up trim. The plane leaped into the air and stalled before the startled pilot could react.
Joe Gores
 
Takeoff Trim Postion

Here is a pic of where to set your trim for takeoff. Adjust your trim to this position then set your Skyview accordingly. ;)
image_zps7a46c741.jpg


Gotta love those Ipads:D
 
Trim speed

My trim runs at noticeable, and measurably different speeds - Up vs Down. Always has. Is that normal?

The Plans state to shoot for 25 secs full travel for starters, then adjust later per pilot preference. I adjusted mine 4 times. I started at 29.28 secs and 37.13 secs. After the fourth iteration I was at 29.5 secs UP to DOWN and 23.6 secs DOWN to UP. I called that Good.

Bob Bogash
N737G
 
Out at the hanger again to see if I could reset the take of trim as per Johns picture. First I pressed the trim switch to the down trim to observe the AST moving up to the full up position then set that. Then I pressed the up trim while observing the AST tab moving to the full down position. I then set that.

Then I set the take of trim as per Johns directions. This placed the green line one third from the top of the trim bar not the bottom of the trim bar.

This makes me think that maybe I have the white wires operating in the AST tab in the wrong direction. I have studied all the plans, maintenance manuals, PAP, flight training manual and a few of the different threads in the RV 12 forums. I must have missed it but how do I confirm that I have the AST wired to move in the correct direction?

Cheers

Julian 120316
 
J, Although I dont have a Skyview it sounds like your wiring is fine and what you are seeing is a calibration issue in the Skyview. Try going back to the calibration menu in the Skyview and when it ask you to move the trim button down move it up instead then when all done see if it indicates properly when moving the switch.:confused:
 
Trim not working

I was ready to do the trim adjustments in an effort to get the proper speed up and down and now it is not working. I started testing back at the plug into the servo and could not get an indication of power out of the plug from the fuslage. Also I could not power the servo with a battery from my cordless drill.
It had been working. Is there a history out there of servo failure or switch failures. I have read of a few issues with switches but those seemed to be discovered early if not first thing. My all seemed to be working out of the box.

Anyother suggestions appreciated. I will have some time on Monday to check further. One other question...can individual switches be replaced or does the whole modual get replaced? Thanks
 
A 9v transistor radio battery should be able to stroke the servo. From your description it sounds like you have a servo and power supply issue.
 
John, Jetguy - I don't understand your picture and accompanying statement. Are you saying you want the stick full aft for take-off???

I don't think so - I tried that with Mike Seager and we both had an "interesting" take-off. Rugged airplane that RV-12!

Bob Bogash
N737G
 
Is this better?

Bob the picture depicts where you want to set the trim for takeoff and how to do it. While in your hanger with the stick full aft
adjust your trim as shown in the Picture. Then as shown on page 7-48 of the Skyview installation manual use the onscreen
wizard to calibrate your trim, then put a small green line on the trim indicator to show you where this takeoff postion is. My picture tells you how to adjust your trim to locate this "Takeoff position" to make the mark on your trim indicator screen.:rolleyes:
As per the POH shown below you need to set your trim to the Takeoff position.
image_zpsd1c1f2f1.jpg

This next picture is for explanation only and is not a true representation of where your Takeoff position might be.
Now note the green line on the indicator, this would indicate where to set your trim for takeoff.;)
image_zpsafa2162b.jpg
 
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Anti-servo tab setting

I've set the tab per your picture - I need to cogitate on the rest.

Thanks for the hand-holding - might need a few more sessions....

Bob Bogash
N737G
 
J.Coles said:
Out at the hanger again to see if I could reset the take of trim as per Johns picture. First I pressed the trim switch to the down trim to observe the AST moving up to the full up position then set that. Then I pressed the up trim while observing the AST tab moving to the full down position. I then set that.
Then I set the take of trim as per Johns directions. This placed the green line one third from the top of the trim bar not the bottom of the trim bar.
This makes me think that maybe I have the white wires operating in the AST tab in the wrong direction. I have studied all the plans, maintenance manuals, PAP, flight training manual and a few of the different threads in the RV 12 forums. I must have missed it but how do I confirm that I have the AST wired to move in the correct direction?
Cheers Julian 120316
Click to expand...

Julian,
The AST servo has 5 wires. 2 are for the motor and 3 are for the indicator. From your description above, I believe that the motor is wired correctly. Confirm this: Pressing the trim down switch will cause the trim tab to move up. In flight, a trim tab moving up will cause the stabilator to move down and cause the airplane to pitch down. If the motor is running in the correct direction, then watch the trim indicator on the EFIS. Does the trim indicator move down when the down switch is pushed? If not, the position indicator is wired incorrectly and 2 of the 3 wires need to be swapped.
Joe Gores
 
Trim not working

I can run my trim by attaching voltage to pins 31 & 32 of WH-00036 while watching the resistance move between 0 & 5000 on the 4 & 22 and the 4 & 25 pins of the same harness. I see the aircraft battery voltage at the molex plug near the servo when I activate the trim switch but when the whole system is connected I have no servo movement. Any ideas what I'm missing?
 
The most likely cause of no Trim control is the trim speed pot adjustment.
A bad electrical connection is another possibility. Have a youngster with good hearing listen to the servo as you press the trim switch. If there is noise, the electrical connections are probably good.
Joe Gores
 
No noise. I have tried turning the pot. There seems to be no resistance on it - like it is just spinning. Is this normal? I have turned it over 100 turns CW and it doesn't seem to do anything.
 
Seaflyer16 said:
No noise. I have tried turning the pot. There seems to be no resistance on it - like it is just spinning. Is this normal? I have turned it over 100 turns CW and it doesn't seem to do anything.
Click to expand...

Clockwise makes the trim servo go slower. Try tuning it about 10 turns CCW and see what happens.
 
Odd-ball 25-turn trimpots

Try turning things more--I had no idea such things existed, but these are appear to be 24-turn trimpots. Seems like about an order of magnitude more tweaking accuracy than needed.
 
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