Procedure for calculating weight and balance

Recently, Mxsmanic posted:

Anno v. Heimburg writes:

NB that I'm not saying that this position is necessarily marked
anywhere, nor that it is relevant to actually flying the plane.

It is slightly relevant. If you have a substantial amount of trim set
for a control surface, the distance remaining to the limits of its
travel are substantially modified, and you may forget about the trim
and mistakenly believe that you have more remaining control authority
than actually exists.

You are presenting yet another absurd scenario that has no relation to the
reality of flying. Nobody flying a real plane will "forget" about trim set
near the limits of it's travel, because the control forces are a constant
reminder.

Neil

Neil Gould writes:

You are presenting yet another absurd scenario that has no relation to the
reality of flying. Nobody flying a real plane will "forget" about trim set
near the limits of it's travel, because the control forces are a constant
reminder.

When the aircraft is correctly trimmed, there are no control forces to
serve as a reminder. And some aircraft don't have control forces.

--
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Neil Gould wrote:
You are presenting yet another absurd scenario that has no relation to the
reality of flying. Nobody flying a real plane will "forget" about trim set
near the limits of it's travel, because the control forces are a constant
reminder.

Umm. Nobody *hand* flying should in theory forget about trim setting.
(We all know the problems that can be caused by autopilots or FBW
systems mucking with the trim behind a pilot's back ;-)

Of course, sometimes pilots *do* forget... thus the number of take-off
accidents caused by the trim being in the wrong place. Yes, at the
last second they feel the extra control force coming in, but it's too
late.

Kev

Mxsmanic,

It is slightly relevant.

Both of these potential problems can be avoided by keeping a strong
awareness of the trim state of the aircraft. As long as you keep in
mind that you've applied x trim while flying, you should be fine.


How would you know? You're ridiculous!

--
Thomas Borchert (EDDH)

"Anno v. Heimburg" wrote in message
...
Thomas Borchert wrote:

Ok, you got me curious. No default position in all Cessnas I have flown.
Not in the Bo. Nor in the Tobago. Not in the Cirrus nor the DA-40 or the
-20. Nor any other plane I can remember INCLUDING the big airliners in
MSFS.

The position where the control surfaces align with the stabilizer, that
is,
no deflection upwards or downwards. At least that's what I interpreted the
expression to mean. I freely admit I'm clueless, though.

Which, depending on how the airplane is designed, may or may not result in
the desired force from the elevator to keep the aircraft in level flight
with the Cg somewhere within range.

I would suspect that on a lot of aircraft with flying tails (e.g. T-18 which
is one example that I have flown) , some deflection between the elevator and
the trim would be necessary to trim properly during all normal cruise when
the Cg is within the limits. And I would further suspect that whoever
designed the aircraft was aware of that fact, and would have set the limits
of the elevator travel with that in mind.


NB that I'm not saying that this position is necessarily marked anywhere,
nor that it is relevant to actually flying the plane.


I'll agree with that.

On the other hand, Captian Kirk frequently took the Enterprise into the
Neutral Zone when he suspected that the Romulans were threating the
Federation.

--
Geoff
The Sea Hawk at Wow Way d0t Com
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When immigration is outlawed, only outlaws will immigrate.

Anno,

NB that I'm not saying that this position is necessarily marked anywhere,
nor that it is relevant to actually flying the plane.


Ok, we're on the same page then.

--
Thomas Borchert (EDDH)

Thomas Borchert writes:

Ok, you got me curious. No default position in all Cessnas I have flown.

Both neutral and default positions were mentioned. While there is no
default position, there is most definitely a neutral position, wherein
the trim tab is aligned with the control surface, so that it creates
no deflecting force.

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Transpose mxsmanic and gmail to reach me by e-mail.

Anno v. Heimburg wrote:

Okay, now that I've made the mistake of reading this discussion, you've got
me curious: How does your plane's trim work? It's obviously not a trim tab.
And how can there be no neutral/default position of the elevator or the
trim device?

It's the common anti-servo tab across entire trailing edge
of the elevator. The trim tab position indicator is marked
only as to a "takeoff" setting, which is roughly in the
center. There is a sweet spot for aerodynamicists where all
three horiz flying surfaces are in trail, not marked on the
indicator, and it is forward of "takeoff," well toward nose
down. A logical way to set tail incidence is so everything
is in trail at 75% cruise velocity in std atmosphere at the
alt where you can have the best cruise book number
(marketing, really). As long as you still comply with Part
23 re trim effects.

In MSFS, the indicator has a center mark, an apparent
"default". In a typical real airplane, this ain't cruise.
Where MX is getting all screwed up besides not understanding
the the lift/drag effects of trim (it's almost a whole
chapter in Dr. S. Hoerner's classic text, Fluid Dynamic
Lift), is assuming MSFS knows when all surfaces are in
trail. Such a tiny flight model tweak would be bizarre for a
game sim which doesn't even fully understand air density.

All trim essentially does in MSFS is tweak the same variable
as elevator to allow for centering springs in joysticks.
I've removed the springs from some of my joysticks, because
then one fiddles less if at all with trim, and it can make
hand flying even the jets easier. Much less unrealistic
phugoid chasing.

F--