Autotrim

[sj_rv7]

I have Sorcerer and auto trim installed in Rv7.

The autotrim seems to trim the aircraft a bit but not perfectly. Today I tried a couple of experiments:

Exp#1
Elev Trim set neutral
AP ON
Try to trim nose down
AP OFF
Confirmed trim not operable during AP ON - Passed

Exp#2
Elev trim set to neutral at IAS 145 kts
AP ON
Reduce power slow to 100 KTS
Altitude perfect - passed
AP OFF
Rapid pitch nose down - failed - no trim changes inputted from autotrim

Exp #3
AP OFF
Trim nose down to maintain 5 lbs stick force
AP ON and slowly release pressure
AP shows trim being adjusted with moving bars - passed
AP OFF - rapid nose down pitch - autotimmed adjusted but not nearly enough - failed

Exp #4
Same as Exp#4 with nose up trim
Same result - failed

Can you tell me where the adjustment for this might be to improve to function of the autotrim.

Thanks
Steve
RV7

[TrutrakTech]

Steve,

Does the autotrim move the tab in the correct direction? You can check this on the ground. Engage the AP and make sure it is in an alt hold mode. Then apply some pressure against the elevator, not enough to make the servo slip, but just a constant pressure. Either direction is fine. Down pressure on the elevator should make the trim tab move down. If it's opposite, flip both of the switches on the side of the autotrim module. Hope this helps!

PS Sorry about not seeing this message earlier, I must have just glanced over it. Thanks!

[sj_rv7]

Yes it moves in the correct direction. It removes some pressure on the stick during flight but when I disconnect the AP at the missed approach point I get a rapid pitch change that needs to be trimmed asap.

Steve
RV7

[TrutrakTech]

I'd like you to check the voltage on pin 4 of the autotrim module. Do this with the AP engaged but the controls in neutral. You should see ~2.5v on that pin. If you see something highly deviated from that, then we'll need to have you send the pitch servo back to us for recalibration. Let me know what you find. Thanks!

[sj_rv7]

Will do that eventually. Access to the pins is difficult.

I'm surprised the 'break out force' is so low. While engaged sitting on ground I push forward the trim tab does move down as expected but the motor only makes small 1 second changes. If I push a bit harder but with not very much force at all, it breaks out and I move the elevator a lot.


Steve

[TrutrakTech]

Will do that eventually. Access to the pins is difficult.

I'm surprised the 'break out force' is so low. While engaged sitting on ground I push forward the trim tab does move down as expected but the motor only makes small 1 second changes. If I push a bit harder but with not very much force at all, it breaks out and I move the elevator a lot.


Steve

Is your torque set to 12? If you want to increase the speed at which the autotrim moves the tab, turn the knob on the autotrim module to the right. This increases it's speed.

[sj_rv7]

Here are the settings:

VRT ACTIVITY 3
VRT TORQUE 12
MIN AIRSPD 70
MAX AIRSPD 190
NORM CLIMB 120
STATIC LAG 2
MICROACTIVITY 0
HALF-STEP? Y

A seperate issue. Today I got NO GPS on the Sorcerer. I looked at the wiring diagram (page 3 Install manual) and see P1 GNS480 requires pin 22 (from 480) to pin 25 on Sorcerer. My installation does not have this wire (all others are present). The autopilot has worked before without it so now I'm kind of baffled of why the RS232 wire would be missing. Ideas?

Steve

[TrutrakTech]

Here are the settings:

VRT ACTIVITY 3
VRT TORQUE 12
MIN AIRSPD 70
MAX AIRSPD 190
NORM CLIMB 120
STATIC LAG 2
MICROACTIVITY 0
HALF-STEP? Y

A seperate issue. Today I got NO GPS on the Sorcerer. I looked at the wiring diagram (page 3 Install manual) and see P1 GNS480 requires pin 22 (from 480) to pin 25 on Sorcerer. My installation does not have this wire (all others are present). The autopilot has worked before without it so now I'm kind of baffled of why the RS232 wire would be missing. Ideas?

Steve

Do you have an alternate RS232 source? However, even without the RS232, if the ARINC is connected it will still go into GPSS mode if GPSS commands are present. It simply will not display the track.

[thibiter]

I am building an RV-7A and have a D11 VSGV with harness suplied by Approach Fast Stack. I have recently ordered a Pitch Auto Trim Module and mostly understand the modifications necessary to the pitch servo harnes.

My question relates to the Link Sensor shown in the D11 install manual diagram. I assume that this sensor is not used in my setup and that I need to install a jumper between Pin 1 and Pin 4 of the trim module.

Thanks

Thibiter

[TrutrakTech]

I am building an RV-7A and have a D11 VSGV with harness suplied by Approach Fast Stack. I have recently ordered a Pitch Auto Trim Module and mostly understand the modifications necessary to the pitch servo harnes.

My question relates to the Link Sensor shown in the D11 install manual diagram. I assume that this sensor is not used in my setup and that I need to install a jumper between Pin 1 and Pin 4 of the trim module.

Thanks

Thibiter

If you haven't ordered your Autotrim yet, then you don't have to worry about the jumper. We don't use the Link Sensor anymore, it's just not part of the system. Therefore, the jumper connection is now taken care of internally in the Autotrim module. Thanks!

[thibiter]

Thanks Lucas.

The Auto Trim Module was ordered a couple of days back from Aircraft Spruce and is now on its way accross the Pacific. They had it in stock at West. I don't know how long they might have had it on the shelf.

Is there anyway I can tell, (once it received), if the unit is of the internally modified jumper type? For example by the serial number.

Thanks

Thibiter

[TrutrakTech]

If it looks like the one pictured on the front of this manual, it is the new style.

If it looks different and has two switches on the side instead of one, it's the older version.

[thibiter]

I have just received the Auto Trim Module and it looks like the picture on the forwarded Installation Manual so I guess it is the new type.

Thanks for your help

Thibiter