Procedure for calculating weight and balance

TxSrv writes:

Then you definitive statement about "how far you are from
each stop" was flat wrong.

No, there are simply some aircraft designs to which it does not apply.
There are a lot of ways to design control surfaces.

--
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"Mxsmanic" wrote in message
...
BT writes:

Changing the trim setting does not change the set screws (Stop bolts)
that
limit the amount of Rudder, Aileron or Elevator travel.

But it does control how far you are from each stop.

only in your own mind

how far from each stop when?

BT writes:

how far from each stop when?

Trim tabs deflect control surfaces towards one of the limits of their
travel. The greater the trim applied, the greater the deviation, and
the less the amount of travel remaining.

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Mxsmanic wrote:
BT writes:

how far from each stop when?

Trim tabs deflect control surfaces towards one of the limits of their
travel. The greater the trim applied, the greater the deviation, and
the less the amount of travel remaining.

False. Except possibly in MSFS.

F--

The following comments are really intended for new pilots -- Mx is
beyond help.

Real pilots in real airplanes set trim so they do not need to maintain
pressure on the yoke during norrmal cruise operations. That may not be
a consideration for sim games.

The aft cg position is most ofter determined so that the airplane still
pitches nosedown when the wings stall. If the weight is too far forward
elevator authority is a serious limit -- the pilot may not be able to
get the nose up during low speed operations, like take-offs.

The physics of flight (Mx had already demonstrated he does not accept
Newton's approximations of motion in other threads the careful reader
will smile at my use of the word 'approximations' since he or she will
understand their limitations) would suggest airplanes are more
efficient with cg close to center of lift since when loaded that way
the airplane is not made artificially heavy because the elevator is not
exerting negative (downward) lift. One could argue that 'neutral'
aircraft loading would be such that the elevator would not have to add
either upward or downward force.

If you're close to either limit, airspeed is your friend.




On Jan 7, 7:45 am, Mxsmanic wrote:
BT writes:
how far from each stop when?Trim tabs deflect control surfaces towards one of the limits of their
travel. The greater the trim applied, the greater the deviation, and
the less the amount of travel remaining.

--
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Tony, great explanation!

To add a little to this fun little conversation, what strikes me is
what it reveals about the result of someone teaching himself to "fly"
via a PC "simulation". I work in the aviation simulation industry, and
MSFS could conceivably be describes as a "training device", OK for
procedures and avionics training, but not for primary flight training.
As a result of his self training, MXS has been completely misled by the
way his "game" flies, and is drawing some wrong (if somewhat
interesting) conclusions!

The whole concept of the trim limiting the control authority is a
classic example of this. In a real aircraft, as previously stated, the
trim is used to relieve control pressures. It does not limit control
authority (except for the very limited effect of a trim tab fully
deflected, which is allowed for in the design of the control surface),
since the control authority is required to be sufficient to cope with
any conceivable need. I think the worse case is usually full gross (or
max landing) weight landing at full forward CG - that will drive the
size and power of the elevator. Any bigger, and pitch becomes too
sensitive at higher speed and adds useless drag.

Also, MXS does not seem to appreciate that the control position (of the
elevator) is a function of the speed (or AOA) of the aircraft, not the
trim position. I can slow down and crank in full nose down trim and
fly just fine with the stick almost fully aft - and get a good workout
in the process! And as the pilot, I know I'm slow since the stick will
be in my lap. As I then crank the trim in, the control surface will
not change position (especially on aircraft with no trim tabs), but the
stick forces will go away (without the stick moving). But I will not
add or remove any control authority - the stick is still way aft! As
a pilot, you are taught this from the beginning - the relationship
between stick position, speed, angle of attack, CG, etc. Their
interrelation is what makes flying so interesting - and where low level
PC "simulations" fail the most.

Oh, by the way, many aircraft do not have any trim tabs at all - most
gliders use springs in the control circuit, J-3 Cubs move the
horizontal stabilizer, the F-4 I used to fly changed the neutral
position of the whole flying tail, etc...

Oddly enough, the F-15 is an exception that actually acts the way MXS
thinks - the flight control system is always resetting itself to 1g
(always in trim), so when you slow down, the stick doesn't move. On
takeoff, if you add a forward trim input, you will extend your takeoff
distance since you will get less angular deflection when you pull full
aft stick to rotate. So maybe MXS should get an F-15 addon to MSFS!

MXS, if you really want to learn about changing CG to affect flying
performance, try a gliding sim like Condor (it is supposedly much
better than MSFS anyway). In high performance gliding, we carefully
adjust our CG for minimum trim drag (usually set to 30 - 40 % forward
of the aft CG limit), carry water ballast to go faster, don't have any
trim tabs (springs instead) and in flapped gliders, control speed with
the flaps. That concept should keep you busy for a while!

Finally - MXS, if you want to have enough control authority "just in
case", then set your speed to just under Va (maneuvering speed). That
way, by design, you can pull back on the stick all you want and not
break the plane - faster and you can over-G and bend things; slower and
you will just enter an accelerated stall a bit earlier. And you can
set your trim wherever you want....

Cheers!

Kirk
Ls6-b "66"

Mxsmanic wrote:

Trim tabs deflect control surfaces towards one of the limits of their
travel. The greater the trim applied, the greater the deviation, and
the less the amount of travel remaining.


For Mxsmanic only:

Please define "servo tab" and "anti-servo tab" and how they relate to
the horizontal stabilizer.

Mxsmanic,

This is why I prefer to stay near neutral trim.


So you go ahead and do that in your little game. Jeeze, you elaborately
construct a problem that simply doesn't exist in real life. Get over
it.

--
Thomas Borchert (EDDH)

Mxsmanic wrote:

BT writes:


Changing the trim setting does not change the set screws (Stop bolts) that
limit the amount of Rudder, Aileron or Elevator travel.


But it does control how far you are from each stop.

It does no such thing.

Mxsmanic wrote:

Thomas Borchert writes:


Why would "neutral trim" be important?


It allows for maximum control movement in both directions.



The trim doesn't affect the total control movements one iota.


Any trim adjustment has an effect on the remaining elevator authority
beyond the trimmed position.

It does no such thing.