Rudder trim... What for?

Okay so if I have the rudder trim neutral, I'm going straight and level or if I'm crabbed and the ball isn't centered then it's something else like the rigging or trim tab?
 
Okay so if I have the rudder trim neutral, I'm going straight and level or if I'm crabbed and the ball isn't centered then it's something else like the rigging or trim tab?

Quit being obsessed with crabbing. Like I said, once in the air, the airplane is ALWAYS going straight. If, in this condition, the ball is not centered, you should make small adjustments to center it.

If you can't trim the airplane to fly itself in cruise flight, you potentially have a rigging or some sort of other issue.
 
Okie, to answer your question, if the out of center condition is consistent? You may have a rigging issue. Beware of making adjustments until you've identified the cause. That advice comes from personal experience. :)
 
Okie, to answer your question, if the out of center condition is consistent? You may have a rigging issue. Beware of making adjustments until you've identified the cause. That advice comes from personal experience. :)

Oh I'll direct the issue to someone who knows what they're doing. With my vast 60 hours of flying I can't identify between equipment and technique. So next flight I'll pay more attention.
 
Makes sense. Haven't encountered a climb long than about 5 mins yet. I'll mess with it next flight. Straight and level flight you neutral it back out or just put it to whatever you need to hold your bearing?

Give yourself time. You will. KOLM is at 206 MSL and I climb to 11,000 MSL to cross the Cascades. Takes a while in a 172 or even a 182. :D

What are you flying that has aileron trim?

P-51? :D
 
I've flown a lot of airplanes with improperly-mounted inclinometers...you center up the ball, and the airplane flies in a slight bank.

The amazing part to me is how many pilots are willing to let one inclinometer override 3 attitude indicators and the second inclinometer.:yikes:

Yep. A good but not necessarily perfect indication is how it's reading on the ground. And in the air, you should be able to level the wings relative to the horizon. I need to get mine adjusted. Annual is coming up.
 
What are you flying that has aileron trim?

A185F.

Had electric aileron trim on it when I bought it. I don't use it often, on a long cross country I'll tweak all the trim axis to get her flying cleaner.

All the planes I fly for work have 3 axis trim as well.
 
Makes sense. Haven't encountered a climb long than about 5 mins yet. I'll mess with it next flight. Straight and level flight you neutral it back out or just put it to whatever you need to hold your bearing?

It's really simple, whenever you are going to hold a prolonged attitude, use the rudder trim to keep the ball centered without having to stand on a rudder.
 
Oh I'll direct the issue to someone who knows what they're doing. With my vast 60 hours of flying I can't identify between equipment and technique. So next flight I'll pay more attention.

Next annual you could ask for a rigging measurement, or you can do one yourself.
 
Well lets start with what I was trying to convey. In an example I'm tracking a course of 360, but because of wind my airplane heading is pointed to 355. To maintain the bearing of 360 (Am I using this term wrong?) I would have to apply rudder to keep the ball centered and the plane crabbed. My question was do I use rudder trim in this case to relieve the pressure. I believe the answer was that I could.

Okie,

Like Charlie Tango said, I call these "Stick and Rudder" moments.

Nothing to be ashamed of - we all have gaps in our knowledge and understanding.

As an intro to ground reference maneuvers, you should have been shown how a plane in flight feels no "wind". It is just flying in an air mass which is itself moving.

I would explain this to a student, and then demonstrate by flying crabbed, straight and level, over a road or section line, with enough of a correction angle to track it properly. Then have the student note that other than the heading being angled into the "wind", the plane was, in fact, straight and level.

Anyway, I recommend finding a copy of Stick and Rudder - it explains all this a lot better than I can.

Also, maybe work on your terminology a bit. Heading, track, bearing all have different meanings, and to be understood you should try to use them appropriately.

And to make you feel better, let me see if I can track down an perception very similar to yours exhibited by a Cirrus demo pilot.
 
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Found that anecdote:

"Flying a demo Cirrus northbound it FL, I noticed on autopilot it was flying slightly right wing down. I mentioned it to the demo pilot, who opined that it was probably just the autopilot correcting for the right crosswind."


It's from this longer post on the topic, on another forum:

http://ctflier.com/index.php?/topic/2645-stick-and-rudder-moments/
 
Found that anecdote:

"Flying a demo Cirrus northbound it FL, I noticed on autopilot it was flying slightly right wing down. I mentioned it to the demo pilot, who opined that it was probably just the autopilot correcting for the right crosswind."


It's from this longer post on the topic, on another forum:

http://ctflier.com/index.php?/topic/2645-stick-and-rudder-moments/

No. No. That was not said. If it was it was a joke. I have to believe that was a joke. Ha ha, get it? Aileron down for wind correction....see? Funny, right? Right?

I, on an interview Sim, once joked on the approach that the plate said, "Radar Required" and asked the Chief Pilot sitting right seat to turn it on. See? A joke, right?

Please god let that be a joke...from a demo pilot...please?
 
He really seemed quite serious.

I've seen and heard these "moments" regularly enough over the years that they don't really surprise me. Often from experienced pilots.
 

Well, the thing is that they are experienced...just maybe not so well trained or self-educated.

I learned about rudder trim from reading the autopilot operating instructions. When I asked a CFI about rudder trim he just told me to never change the setting and if I did I would just screw things up. Okay, yup, it took a little figuring out but really not much to it.
 
What is it good for?...Absolutely nothing...Say it again
 
War-unh-good god- absolutely nothing
 
I don't mean to beat down the OP, but man...the dumbest threads on here end up with the most responses. I don't even care to read them all. But then again, I know what rudder trim is. :) Certainly the OP has heard/used elevator trim? Wouldn't the same logic apply to rudders? I dunno.

:dunno:
 
What is it good for?...Absolutely nothing...Say it again
You must not be flying HP piston singles. In such airplanes, the lack of rudder trim is going to drive you crazy (and leave your legs weary). It's there so you can balance the rudder forces in all phases of flight (climb and approach which need more right rudder, cruise which needs near neutral rudder, and reduced power descent which needs more left rudder). Otherwise, you're going to have to hold some rudder pressure nearly all the time, and that's a real pain. Yes, you can set the external rudder trim tab to take care of cruise as long as you cruise at the same power setting and IAS all the time, but that won't help you with anything else.
 
War-unh-good god- absolutely nothing

You must not be flying HP piston singles. In such airplanes, the lack of rudder trim is going to drive you crazy (and leave your legs weary). It's there so you can balance the rudder forces in all phases of flight (climb and approach which need more right rudder, cruise which needs near neutral rudder, and reduced power descent which needs more left rudder). Otherwise, you're going to have to hold some rudder pressure nearly all the time, and that's a real pain. Yes, you can set the external rudder trim tab to take care of cruise as long as you cruise at the same power setting and IAS all the time, but that won't help you with anything else.


Seriously Ron?

 
I don't mean to beat down the OP, but man...the dumbest threads on here end up with the most responses. I don't even care to read them all. But then again, I know what rudder trim is. :) Certainly the OP has heard/used elevator trim? Wouldn't the same logic apply to rudders? I dunno.

:dunno:

This was never a 'what is trim' thread... more of 'when to use it' with some Karaoke mixed in. These typically have a higher post count because someone assumes the thread is about one subject and knee jerk responses without reading through. May have been dumb to you but very insightful to me.

I'm going to pick up that Stick and Rudder book, I've seen it mentioned a number of times.
 
As has been posted before, the sole reason for trim is to relieve control pressure.

Seems like it should be obvious, but instructors have to be alert to what is called "flying the trim", which is generally seen to be a bad habit.

For instance, if an instrument student sees he's 40' high, the first action should be to lower the nose to get the desired performance, and then and only then to trim out any control pressure that ends up being held.

But what often happens is the student instead just trims nose down. This does of course work, but everything is less precise as the correction is delayed a bit - and the student does not "feel" the correction necessary before trimming it out. And it often leads to overshooting the desired altitude and trimming back in the other direction - "chasing the altimeter" is what its generally called.

Same concept with rudder trim. Ball not in the center? "Step on the ball" to center it. Then, and only then, trim out whatever pressure is being held. Don't just trim it to the center.

I know some like to "fly the trim" in the landing process, and if it works for them - fine. But I still feel it gets in the way of aircraft "feel" and should generally be avoided.
 
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