Quote from Hangar45 Admin on December 14, 2017, 12:03 pm

(Original thread started on 09-08-14 by Ron Rollo)

Now that the Pitch Trim Panel is complete I have been doing some additional test flying and have come to the conclusion that the Pitch Trim Bias switch on the SYS Test Panel can be a functional addition to our simulators!

 

What I have found is that when the aircraft is flying in Autopilot mode, the trim wants to go all the way to -10 (MAX) in an effort to try to keep the plane flying either at it's selected altitude or rate of climb. I find that when I push the control columns forward it gives the pitch trim system "trim head room" for lack of a better term. When I do this, the aircraft is able to fly at the select altitude or rate of climb with pitch trim numbers between -4 and -6. Of course the further I push forward on the control columns the lower the pitch trim numbers are. Basically what is happening here is I am re leaving some of the negative pitch trim for the pitch trim system. So what I was thinking is to use something like this:

 

This is a 12 volt power automobile seat motor with a gear that would enable us to add or remove pitch trim pressure to the control columns. The idea is to be able to add or remove pitch trim tension while still being able to physically control the control columns to their full range of motion.

 

The hard part, if there is one is mounting the motor aft of the cross over column and to the two rear springs:

 

My idea is to attach the motor to the floor base under the Center Pedestal and the two rear springs to the little plastic trolley that rides up and down the worm gear attached to the motor. Simply releasing the rear spring pressure will allow the control columns to fall forward while still having full range of motion and control. In addition, adding tension will pull the control columns back towards the pilots adding pitch up if needed.

 

One thing that may be an issue is possible Electromagnetic interference (EMI), also called radio-frequency interference or RFI due to the magnetic motor. I have found that any electromagnetic motor, (stick shakers, relays etc...) can cause havoc on the FDS interface cards. There are ways around this by adding capacitors and shielded wiring. I always like to throw this info out there when we are talking about adding electric motors to the simulator.

 

This is an idea that I have had for a few weeks now and wanted to at least get it down in writing. If you guys have any thoughts on this subject please pipe in. This should be fun!

 

(Posted by Alan Norris on 09-10-14)

Does the pitch trim bias switch activate the motor? Also if the motor is attached to the column how can you move it manually?

 

(Posted by Ron Rollo on 09-10-14)

Yes, the Pitch Trim Bias switch activates the motor. It will run the motor one way and the other depending on which direction you move the toggle.

 

Do you see the little plastic thing on the gear in the photo? That is what the rear springs are going to attach to. Basically all I am doing is moving the place where the springs are currently attached to the base floor and moving them with the little white plastic thing on the gear.

 

Another way to look at it is imagine unscrewing the rear springs from the floor base in the photo. If your holding them in your hand and then move your hand closer to the front of the nose, the columns will fall forward. Same thing if you move your hand back towards the tail, the columns will fall backwards. As you do this you will notice that the columns will still have full range of motion, the only difference is where the columns want to settle down and be comfortable. And that all depends on where your hand is holding the springs. Now all you have to do is replace your hand with this motor and gear. And this is what we call Pitch Trim Bias.

 

Now in the real airplane it works just a little bet differently. It is still the same concept but in the real airplane, it is the force of the air over the wings, or in this case the elevator that would have you wanting to adjust the pitch trim bias. In the more complicated and advanced sims, there are guys that have things like simulated environmental forces pushing and acting on the flight controls. One day if I get bored I will look into this more, one day!