Elevator trim speed

[bpattonsoa]

I have looked thru the archives and can't find any posts relating to the sensitivity of the elevator trim at cruise. I have not been able to trim the ship level because just a touch of the trim gives me 2 - 3 knots change. Checked on the ground and the system operates correctly.

Same issue as my -6 A, solved easily by a Ray Allen speed controller, but with the -10 slow trim would not be a good thing in the pattern. These things require a lot of trim to land where on the -6A you just pull throttle and land.

I plan to put a micro switch on the flap tube to cut a speed controller into the elevator trim power when the flaps are at full up. Will also act as a reminder if I forget to go full up in cruise.

Any comments?

2.5 hours into phase 1 and watching it rain, bummer!

 

[Bill.Peyton]

I agree with you on the trim speed situation. You want it to trim fast when you are slow and slow when you are fast. TCW makes a trim controller that attaches to an airspeed sensor which will allow you to control the trim speed based upon airspeed. http://www.tcwtech.com/Safety-Trim-Page.htm The Vertical Power systems have this feature built in. I just read a post where a user rolled his own using a Ray Allen speed controller and a micro switch on the flaps. I believe he triggered the high speed trim when flaps were deployed and low speed on all other occasions.

 

[Jackm]

Auto Trim

Bruce,
I am not sure of your system but we are Tru Trak/AFS autopilot with auto trim. We are still learning but I have been using the auto pilot all the way into the pattern till abeam the numbers. Reason is it is so smooth and allows me to focus on landing setup. The auto trim feature pulses the trim during auto pilot engagement and when I disconnect AP abeam numbers the trim is perfect in trim. From there you are slow enough that you want full trim control on the rest of the landing pattern. It is amazing how AFS and trutrak sync with the controls. On top of that we have the VPX that controls trim speed when hand flying. Again careful with our advice cause we are only 22 hrs into our phase 1 and there are guys here that know far more with far more experience. Hope this helps.

 

[BobTurner]

Or the Trio

The Trio autopilot with auto trim will do exactly the same thing as described in the last post when the autopilot is engaged...but, it can also be used to adjust the trim manually, when the autopilot is disengaged. The trim speed is programable by airspeed (full speed trim at low airspeeds, slow trim speed at high airspeeds).

I use my stick top hat switch (full speed trim) for landing and takeoff or anytime I'm going slow or need a large trim change. In cruise I use the knob on the autopilot to make very fine trim adjustments. I have a rocker switch on the panel for right seat pilots - I didn't want a top hat switch on the right stick, to prevent passengers from accidentally bumping the trim. (Others use the Safety-Trim described above to cut off trim after 3 seconds).

One note: these adjustable trim speed systems usually use a pulse width modulated set up to change the speed. Any relay system you use (to prevent short circuits if more than one switch is pushed simultaneously) has to be compatible with the pulse width modulation (a fast on-off) if it goes thru that relay system, as mine does.

 

[N15JB]

The TRW and other 2-speed controllers were not yet on the market when I was setting up my trim system. I used the Matronics Mk II, which is a single speed, but adjustable, controller. After some trial & error, I settled on a speed that gave me full up to full down elevator trim in 30 seconds. This turned out to be Goldilocks for me; not too fast, not too slow. Works well in all configurations. I was prepared to upgrade to the TRW when it became available, but have never felt the need. The only exception is runaway trim. If that ever happens, I will need to pull the CB.

Jim Berry
RV-10

 

[BobTurner]

The only exception is runaway trim. If that ever happens, I will need to pull the CB.

RV-10

Good point. Because I use both the autopilot and the usual trim switches to control trim, I have the autopilot and trim CB's well marked, side by side, in front of me. In case of a runaway trim I need to pull both of them, then sort out which is the problem.

 

[rleffler]

The VP/X Pro functions similarly as the TWC Safety Trim. It changes the speed of the trim based upon a definable air speed. It will also disconnect the trim should a runaway situation is sensed.

bob

 

[bpattonsoa]

My EFIS is dual Skyviews and their autopilot does not do trim (yet). I studied the archives about trim. Looked over the TCW two speed system.

I am going to put in a two speed TCW. After 2.5 hrs in my -10 and 2.7 with Mike Seager in the factory -10, I am still shocked at the trim forces in this design. A runaway trim might not end up with a good result. In my -6A, trim runaway trim would not be such a disaster, so in the -10 I located a trim power switch in my bank of seven always on for flight right in front of the pilot. After my brief experience with the -10 I realize that is not enough! Thus the TCW.

Added later: version 10 for Skyview has incorporated all the TCW features into their autopilot box. Plus you do not need a separate flap position or speed sensor.

 

[Wayne Gillispie]

I have the factory rocker switches on the panel. Pitch rocker with an added "pitch trim enable" push button right beside the throttle and flap switch. Without the PTE button pushed in, no power can go to servo, preventing runaway. No speed controller or auto trim installed. My TT AP tells me if I am out of trim. While hand flying, it just takes a quick tap of the switch. Third year flying and I do tons of TnG's. I also don't remove all stick force if doing planned TnG's, much less forward pressure needed when applying full power.