I purchased FSX about 2 weeks ago.  After huge problems with the product key, I FINALLY got the darn thing installed about 3 days ago.  I started going through the lessons and missions and pretty much figured out that while I can finish the first 5 tutorial missions rather easily, I really don't know what I'm doing.

So I decided to go into the lessons where you have the instructor (Rod?) telling you what to do.  Well, I'm on lesson 3 and I'm completely stuck.  Basically, I have absolutely no grasp of what "trim" is.  The lesson is telling me to climb from 4,000 feet to 5,000 feet by using:

First:  Attitude
Second:  Throttle
Third:  Trim

Ok, well I get the attitude and the reason for going full throttle, but then I have absolutely no clue what to do with the trim.  I thought that the trim kind of evened out the plane so that when I'm climbing with the stick pulled back, adjusting the trim upwould allow me to keep climbing while putting my stick back to the neutral position. 

If, in fact, that is the right definition then it's certainly not working.  Or I just do not know how to realize when the trim is enough.

Am i completely wrong?  I get confused because the instructor seems to allude that the trim has something to do with airspeed as well, as he says to adjust the trim when it gets to 75 knots, and that adjusting trim will make the plane stay at 75 knots like an auto-pilot.

ANY help would be appreciated.  I'm on AIM at JetsMets77 if anyone wants to chat.  I hope that I can lean to fly these darn planes and be a part of this community which I've been lurking at for 2 weeks now!

Thanks in advance.

There's an old joke... "How long does it take to trim a Cessna172 ?  ...  about 20 hours"  

Meaning obviously, it takes some training and practice....

Quote:


This is the old rule of thumb, and is more commonly worded:  "Pitch, Power, Trim" .. in that order.

Due to the limitations  of hardware (especially joysticks) , it's difficult to represent realistic trimming in the sim... BUT.. the functionality is there. Basically, the trim is used so that the pilot does not need to maintain a constant input pressure. In other words, when you apply back-pressure (pull back on the yoke) to pitch the nose up and start a climb.. you'd then use trim so that that climb continues, without the pilot having to continue the back-pressure. Perfectly trimmed for that climb, the pilot would be able to let go of the yoke. The trim is like a fine tuning.  

The trimming for airspeed is important, because at a given power setting (normally full power for a C172 climb), your rate of climb is pretty much a function of your airspeed. Sure, you can change pitch and power all over the place, and still keep climbing... BUT for a steady, constant, controlled climb, you need to be at a certain airspeed. And how do we primarliy control airspeed ?  ... PITCH  

Ideally, you'd pitch for the airspeed and then just trim to maintain it... but in reality, you'll have to trim for airspeed, too.

Here's the step by step for a transition from level flight, into a climb, and then back to level flight at the new altitude:

-Pitch for the target airspeed (normally 75kias in a 172.. it gives you the best rate of climb (a fundemental number that you should know before even taking off alone)..

-Immediately after pitching for 75kias, apply climb power and continue using PITCH to keep the airspeed at 75kias.

-As soon as the airspeed is stable at 75, then use trim until that pitch and airspeed will sustain themselves, even if you let go of the yoke.


-When you reach your new altitude, its "Pitch, Power, Trim" again.. in that order...

-PITCH to stop the climb

- Reduce POWER When the airspeed comes back up to the cruise value (~105kias)..

-TRIM so that the airpseed and attitude stay constant, even if you take your hands off the yoke.

You mention that trimming isn't working like it should for you... but it will (in about 20 hours   ).  You just gotta get a feel for it. And you will. Just  remember to be patient while stabilizing the airspeed with the yoke.. and then 'finesse' it with the trim.

Just like in a real C172.. eventually it will be like one motion. When it's time to climb; you'll just push the throttle in; pull the yoke back... and then throw a little trim in, and the plane will settle into a nice climb.

Same for leveling off. Eventually it will be a  one-two-three snap...  push the nose down, pull the power back, spin the trim wheel... bang, bang, bang.. and the plane will level off nicely...  


EDIT:  Almost forgot...  feel free to visit the 'Flight School' section in this forum. We're going through a Sim Private Pilot program...

PLUS......you gotta know where your trim buttons are on the joystick ( i hope you're using a joystick!)  Even so, it is not nearly the same as having the seat of the pants actual yoke pressure from the aerodymanics of real flying.  So, program you some trim buttons and watch your pressure on the joystick as you trim and climb,etc.  It will come.....but it's a bit erratic in the sim.  IMO.  And I know squat!, barely!

The idea of trim is to reduce stick or yoke loads to reduce pilot fatigue.

You should be able to just let go of the Stick/Yoke once you are trimmed properly and the attitude should remain constant (or nearly so).

Set the buttons/controls up where they are handy, ( I use the top right buttons on my joystick), because you'll find that trim is used extensively once you learn to fly.

Rudder trim can be used the same way to offset yaw creeping under different power settings.

Trim as required, up or down, nose up attitudes will require positive trim etc. Both power and attitude adjustments will throw the trim off, that's why you trim last when adjustments are made. Also, if the plane is accelerating or decelerating, the trim will alter.

Here is a noob trick...... Trim the same way you fly, in other words, back trim corresponds to back stick, up is up , down is down, don't reverse the trim from the primary flight controls.

After a while, you'll find that you are flying with trim as much or more than your primary controls, it's much easier to make small adjustments in trim than to fly with the primary controls and then trim for balance. This depends a lot on aircraft type. Larger aircraft (in general) are more easily handled with trim. In fact, elevator trim becomes the larger force on the big jets, load up one into the sim, go to  outside view and watch the horizontal stabliser when you use trim

The way that trim sensitivity is adjusted is by slider in the controls  section of FSX. I prefer full sensitivity so I just need to tap the trim button for effect. The longer you hold the trim, the more it reacts, unless you set it up on a separate control axis.

The trim is correct when you can release the controls and the plane remains stable. Therein lies the essence of trim.

Edit:
About 20 hours to trim a cessna is not a far fetched estimate, it requires practice as stated before.

steve s wrote on Feb 7^th, 2008 at 8:04pm:


While this is true, in a sense; you don't trim for a vertical speed. You really don't trim for anything except to make it so that you can let go of the yoke (or joystick) and everything stays the same. If you try to trim yourself to a specific vertical speed, you'll spend too much time chasing the vertical speed needle. This isn't as much of a problem in the sim, as it is in a real plane.. but it's still poor practice. You want to pitch for all these things.. and use trim so that you can let go of the control... and then the vertical speed takes care of itself.

And even pitching for a vertical speed isn't a good idea (though you kinda have to for level flight). You'll know the power setting and target airspeed for whatever it is that you want to do. For example... Best rate of climb in a C172 is full power and 75kias. So... pitch for 75kias; apply full power, and keep pitching for 75knots. When it all stabilizes, then you trim so that you can let go of the control... and again, let the vertical speed take care of itself.

All this focus on fundementals will serve you well when you get into more advanced flying. If you're flying by instrument, and trying to fly with the trim instead of the yoke, you're just adding to the cockpit workload. Again.. MSFS is more forgiving than a real C172, but don't let that slip you into a trimming habit  

here's what typically happens.  I pitch to the proper angle, go full throttle and I can get it stable fairly easily at 75 k.  So I start to apply trim.  Then I release the yoke a bit to see if the trim will keep it at the rate of climb that I want.  But it doesnt stay steady. The plane drops because I didn't add enough trim.  Because the plane drops, the airspeed increases and now I'm back where I started.  Basically, I have no idea when to stop trimming up.

Am I supposed to be releasing the yoke at the same time that I apply trim?  Or do you apply the trim and then release the yoke?  Do you release it steadily or just let it go back to default all at once?

Brett,

The CH flight yoke is the one I have. For the longest time, I used the wheel on the left thinking that was trim. I realize now that that's not connected to the computer at all, but its a tuning for the flight yoke itself!

Now I do have it mapped to the rocker under the left thumb.

On a similar note, I was flying the Airbus A321 last night, and noticed that the trim didn't seem to work at ALL. I could hold trim down one way or the other indefinitely, and nothing happened. Is there something I'm missing there?