How much do you trim?

If you can't let go of the stick without starting to climb or descend, you
need it. This is the thing I always had trouble with in sims, especially
with a cheap stick that didn't have trim on it.

mike

"Mxsmanic" wrote in message
...
Doug writes:

Trim every time you change pitch. Trim when needed even in level
flight. Basically, you trim whenever you need it, and that is fairly
often.

So how do you know when you need it?

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"Mxsmanic" wrote in message
news
mike regish writes:

While flying, it is set by feel.

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.

You don't need to keep track of anything. The only way you'll ever run out
of trim or control movement range is if you've loaded the plane grossly
outside the weight and balance envelope. Generally, the trim setting has
nothing to do with the range of control movement. It can be a small
adjustable tab on the elevator trailing edge or it can be the entire
horizontal stabilizer.

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.

Bottom line is that it depends on the design of the plane how sensitive
it is to trim and how much trim change it requires for any
displacement.

-Robert, CFII

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.

mike

"Mxsmanic" wrote in message
...
B A R R Y writes:

Oh that's right... Your simulator doesn't have control pressure.

It has springs, which serve much the same purpose. It's tiring to
hold the controls against a spring, too.

What does an A320 have?

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On 2006-10-09, Mxsmanic wrote:
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.

Not really. In a real aircraft, you trim out the forces you're feeling
without actually moving the control itself.

However, controls for a PC don't work like this - so you have to feed in
trim to the simulator, while gradually moving the joystick to the centre
position - because all that's providing resistance is a set of static
springs.

It would be possible to design flight controls for a PC simulator (which
are inadequate on so many levels - even the expensive ones) which work
just like trim works on a real aircraft, but it would be extremely
expensive. The other problem with PC controls is that they don't move
nearly far enough. The CH yoke for example, goes in and out (for pitch)
about 3 or 4 inches, and turns about 45 degrees in each diretion. The
yoke on a Cessna 172 has probably 18 inches of fore/aft travel and turns
through about 120 degrees in each direction. CH rudder pedals maybe
displace an inch or so, but the rudder pedals on a C172 probably
displace a good 5 or 6 inches. This means that the controls on a
simulator are _insanely_ sensitive if you want them to be able to make
full control deflections.

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.

Name ten!

If you're doing without trim in a real aircraft, you _are_ doing it
wrong, at least for any conventional light plane right up to airliners.
Trim is absolutely essential in pitch.

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Mxsmanic wrote:

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?


It seems that nobody has responded to this yet ...

The autopilot controls pitch with the elevator servo,
much in the same way the roll is controlled with the
aileron servo. The elevator servo can measure the force
needed to keep the proper attitude, and after a small
delay, it trims the force off with the trim servo.

When the autopilot is released, it leaves the airplane
in trim to the pilot - there's no need to remember the
trim position.

HTH

--

Tauno Voipio
tauno voipio (at) iki fi

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?

A one-hour introductory flight (in a real airplane) would answer
so many of your questions. Why not do it?

Dan

writes:

A one-hour introductory flight (in a real airplane) would answer
so many of your questions. Why not do it?

If you don't want to answer my question, why waste my time and yours?

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Mxsmanic wrote in
:

writes:

A one-hour introductory flight (in a real airplane) would answer
so many of your questions. Why not do it?

If you don't want to answer my question, why waste my time and yours?

The above answer is as good as it gets.

Why wast our time asking questions when all your answers can be answered as
suggested above.

Or better yet, just go to a sim group and ask your questions since you
don't want to experience flying a REAL PLANE.

Allen

On Mon, 09 Oct 2006 19:11:06 +0200, Mxsmanic wrote:

writes:

A one-hour introductory flight (in a real airplane) would answer
so many of your questions. Why not do it?

If you don't want to answer my question, why waste my time and yours?

Because no matter who responds, you're getting the answer filtered through their
senses and experience. It's like asking someone what an apple tastes like,
rather than biting into one yourself. Everyone's experience differs; you will
not gain a consensus on which to base an opinion. Five minutes in an aircraft
would allow you to understand the issues of trim, from both a conscious and
muscle-memory perspective.

Ron Wanttaja