How much do you trim?

"Cubdriver" usenet AT danford.net wrote in message
...
On Mon, 09 Oct 2006 17:04:35 +0200, Mxsmanic
wrote:

But if you set by feel, how do you keep track of how much control
surface movement you have remaining? If the trim has a control
service held very near the limit of its travel, you might run out of
space when you need it.

That's what 'weight & balance' calculations are all about!

And that's why you don't fly a J-3 Cub solo from the front seat. It's
just barely possible (if it's not placarded!) but you run the risk of
running out of control with the stick.

In the Cub, I always run out of TRIM control in level flight. It's
right up against the stop.

I remember in my "engine-out" practice for my license, trimming for best
glide speed of 65 kts in a C-172, basically when you run out of nose up
trim, you will be at best glide speed. Evertime I have trimed it (C-172)
for 65 kts, I ran out of nose up trim, but still had enough movement in the
elevator to fly the airplane. You have to be prepared though when you go to
apply full power with all that nose up trim, as you are going to have to
push hard on the yoke to keep it from pitching up too much, and retrim after
adding the power. :-)

Wade Hasbrouck
PP-ASEL
http://spaces.live.com/wadehas

Thomas Borchert wrote:
Dylan,

Is pay really that low in France?


You really need to read the other threads involving the guy. Pay is not
that low in France. One only needs to work.

Seriously. He owns a computer, after all. Along with MSFS and internet
access. Chop the internet access for a few months and you've got an
intro flight.

How much does an hour of flight time run you in Germany?

"Mxsmanic" wrote in message
news
Robert Chambers writes:

The discussion of trim in a flight sim on a PC is academic.

Hardly. Trim does the same thing on a simulator that it does in real
life.

In an aircraft, trim is not so much a "convenience" as you seem
to think.

A lot of aircraft and pilots seem to do without it, so obviously it is
not necessary.

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They must be some really strong pilots... as not trimming a C-172 will give
your arms quite a workout and results in a lot of unnecessary work on behalf
of the pilot, and makes it harder to fly "smoothly and precisely" as you are
constantly "fighting" the force on the elevator control. I can tell which
the difference between approaches where I have the plane nicely trimmed on
on final and the ones where the plane is slightly out of trim, as on the out
of trim approaches I am having to "work more" than I need to and it takes
away from other things I need to be concentrating on to ensure a nice smooth
landing.

Wade Hasbrouck
PP-ASEL
http://spaces.live.com/wadehas

Just about every time I touch the throttle or tweak my altitude.
--
Gene Seibel
Gene & Sue's Aeroplanes - http://pad39a.com/gene/planes.html
Because we fly, we envy no one.


Mxsmanic wrote:
What I see in the literature seems to vary between warnings against
spending too much trim or flying with trim tabs, and not ever trimming
the aircraft at all. So how much and when should I trim?

I understand trim to be a convenience, so that a pilot doesn't have to
constantly maintain force against the controls for long periods. Thus
it should never be dangerous not to trim, except insofar as it can be
tiring to hold an untrimmed aircraft in a given attitude for long
periods.

The thing I wonder about is the possible distraction of trimming the
aircraft. It looks like trim controls are often in spots like the
pedestal or throttle quadrant, where presumably one must direct one's
attention in order to adjust trim. It's hard to imagine doing this
during critical phases of flight such as take-off or landing, and yet
I read recommendations for trim in both cases. Where do you draw the
line between trimming unnecessarily and not trimming enough? How
often do you actually reach for the trim controls?

Also, it seems that most trim is pitch trim. I don't see much mention
of aileron or rudder trim. Do you use it? Do you ever trim out
P-factor or torque effects? I turned both back on in my sim and
adjusted them to where the vendor says they should be to match the
real aircraft, and I find them irritating, but not overwhelming (the
vendor has apparently set the most realistic factors at 50% instead of
100%, so that masochists can increase their effects beyond real life
if desired).

Another problem I have: How do you remember where you set the trim?
I know you can look, and I know that you can guess if the aircraft is
behaving strangely, but how do you keep track of where you last set
the trim? Each time I set it I tend to forget about it until some
important moment when I'm already busy with other things.

Also, I presume that most autopilots use trim for pitch control. If
you shut off the autopilot, does the trim remain whereever the A/P set
it? If so, do you change it? Is it hard to remember that the A/P has
probably changed it?

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Emily writes:

He owns a computer, after all.

The computer doesn't belong to me.

Chop the internet access for a few months and you've got an
intro flight.

I can't work or communicate without the Internet. I need it for work,
school, and (to a lesser extent) for leisure.

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mike regish writes:

The springs don't really serve the "same" purpose. The springs just return
the stick to the center position. When trimming a real plane, you hold yoke
pressure until your speed and altitude stabilize, then trim out that
pressure until you can let go of the yoke and the plane remains stable.

OK, but aircraft like those of Airbus have no mechanical connections
to the control surfaces. How do they do it? It must be some sort of
elaborate force-feedback joystick, too (if they provide any feedback
at all).

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Gig 601XL Builder writes:

MSFS has a reasonable simulation of trim you should be able to trim the
aircraft to the point it will fly straight and level with the joystick
centered.

It works pretty well, although it's time-consuming to get it right.
Also, the keyboard adjusts trim in fairly significant steps, whereas
something like the autopilot can adjust it to a thousandth of a
degree.

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Dylan Smith writes:

This means that the controls on a
simulator are _insanely_ sensitive if you want them to be able to make
full control deflections.

And the cheaper the controls, the worse they are. I tried a cheapo
joystick today and almost dived into the ground. I don't think it
moves more than a quarter of an inch from stop to stop for control
surfaces.

Name ten!

Anyone who flies an aircraft that doesn't provide trim.

Trim is absolutely essential in pitch.

I just worry about not knowing how far away I am from neutral. I
could be applying enormous control surface deflection with trim
without necessarily being aware of it. So I might try to move a bit
further with the yoke and find that I'm already against the stop.

The other thing that worries me is distraction. Takeoffs, landings,
climbs, and approaches seem like bad times to be fiddling with trim,
although I suppose that depends on where the trim controls are (I get
the impression that they are often in odd places).

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Robert M. Gary writes:

It totally depends on the plane. I used to fly a Globe Swift and I
never found any reason to need to touch the trim. The plane flew hands
off at whatever you pointed it to. I currently own a Mooney and I spend
more time in the pattern moving the trim than holding the throttle. The
entire downwind of a Mooney is rolling the trim back, slowing the plane
down.

Interesting. So what is it that's different between the two planes?
If the aircraft requires no trim, does that mean that control surfaces
stay where they are put, or what?

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Dylan Smith writes:

When we were taxiing in, I grumbled about how terrible the ILS was - and
how I couldn't figure out how I'd flown it so badly. Paul did not say a
word. He just slid his seat back then forwards! The seat rails in a C172
are very long, so he could move an awful long way fore and aft - and
he's quite a big guy...

So what was his purpose in messing up the approach?

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