R22 Trim

[cryesis]

Can someone explain when you should use the trim in the r22, when to apply it, when to remove it and how it works? Thanks

[Pohi]

If used at all, use it in cruise flight.

 

Apply after takeoff in cruise flight, and take it off before landing. Probably either before entering the pattern, or during downwind checks.

 

It's nothing more than a bungie cord that when trim is applied adds tension to the cord which applies forward pressure to the cyclic. It pulls on the bottom, which pulls the top forward, which then reduces the amount of forward pressure needed to maintain the cyclic forward.

 

Although it is possible to leave it on all the time, it really makes hovering hard. This is usually discovered when a person forgets to turn it off before landing and then can't figure out why their approach and hovering is so horrible.

[cryesis]

Is it variable to when you apply it? Say you apply at 70kias does it make it easier to hold 70 but harder to maintain 60 or 80kias?

[Pohi]

It's just a bungie cord. It applies x amount of pressure, no matter when you apply it. Either on or off. There is a little knob, I believe, that you can turn to change the amount of tension a bit.

 

[Azhigher]

If memory serves (It's been a while since I was in a 22) pulling the right trim engages a little "bungie cord" that applies right pressure to the cyclic to help counter the feedback from the MR at high speeds that want to push it to the left. (May have the left/right backwards)

 

So basically at high speeds it helps keep the cyclic feeling neutral and takes away the need for the pilot to input the lateral force to keep the aircraft level. If you keep it engaged during a hover it will try to push the cyclic one way when it's not needed and once again it'll be the pilots arm that will need to compensate.

 

So pull it up when you're in cruise flight and put it back down before final approach.

 

R22 guru's feel free chime in and correct anything in here.

[mrkik]

The only time I've ever used it is on longer flights not involving lots of maneuvering. And as others have said, don't forget to remove it when landing. It just makes it so you have to put less pressure on the cyclic, and it does help.

[nightsta1ker]

AZhigher is correct I believe. It might add some forward tension too, but I think it's mostly lateral. I don't even like using it on longer flights. I just readjust my elbow and that seems to be all the trim I need.

[lelebebbel]

The trim knob does not control the bungie cord. The longitudinal bungie cord is permanently engaged and pulls the cyclic forward.

 

The trim knob straightens a spring which pushes the base of the cyclic assembly to the right. It is a lateral trim. The round knob on the left side of the center console is a preload adjuster that sits at the end of this spring, and you can see it move as you pull the trim up.

 

Having the trim on while hovering or during any other part of the flight will not harm anything, but it creates a uncomfortable right push in the cyclic. Normally, you'd use it only in cruise (or not at all) to make it a bit easier to hold the cyclic.

 

 

 

Here is a schematic (slightly simplified) drawing of what happens when you pull that knob:

Edited April 19, 2012 by lelebebbel

[Brentd2183]

Lelebebbel has got it right, you can also order different tensioned bungee cords for the longitudinal trim. What is nice is if you know how the aircraft is loaded typically, 3/4 tank and just the pilot at 180 pounds, your mechanic can set it up so at your preferred cruise airspeed the aircraft will practically be hands off. Of course in the CFI world with the config changing so much between various flights of different weights of students, CFI, fuel and solo flights all you can do is just put it somewhere in the middle of the road.