Re: Mechanics of Elevator Trim. In Detail.

On Jun 8, 3:39 pm, More_Flaps <Morefl...@[EMAIL PROTECTED]
> wrote:
> On Jun 9, 9:24 am, Bertie the Bunyip <A...@[EMAIL PROTECTED]
> wrote:
>
>
>
> > More_Flaps <Morefl...@[EMAIL PROTECTED]
> wrote
innews:d998f060-3e6a-4b62-8179-88afe9032aa2@[EMAIL PROTECTED]
>
> > > On Jun 9, 9:06 am, Bertie the Bunyip <A...@[EMAIL PROTECTED]
> wrote:
> > >> More_Flaps <Morefl...@[EMAIL PROTECTED]
> wrote
> > >> innews:64b157a9-99f5-4429-9125-d1e2
> > > a5aea...@[EMAIL PROTECTED]
>
> > >> > On Jun 9, 7:29 am, "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow
Way
> > >> > D0t C0m> wrote:
> > >> >> "Le Chaud Lapin" <jaibudu...@[EMAIL PROTECTED]
> wrote in
> > >> >> messagenews:5c4deac0-2b92
> > >> > -46e8-865e-de41aca34...@[EMAIL PROTECTED]
> > >> >> On Jun 8, 11:07 am, "Robert M. Gary" <N70...@[EMAIL PROTECTED]
> wrote:
>
> > >> >> > On Jun 7, 10:08 pm, Le Chaud Lapin <jaibudu...@[EMAIL PROTECTED]
>
wrote:
>
> > >> >> > > What exactly happens when the trim is adjusted to point the
> > >> >> > > nose upward?
>
> > >> >> > What type of plane is this for? I have a Mooney and also fly a
> > >> >> > 182. Both trim system are very, very different.
>
> > >> >> For sake of those of us who only own MSFS, let's say a C172.
>
> > >> >> Does MSFS emulate the servo tab on the elevator? What does it do
> > >> >> when you change the trim in the air?
>
> > >> >> Trying to emulate real life trim on a simulation system that
uses
> > >> >> spring centered control sticks isn't going to work like real
life
> > >> >> as you may already know.
>
> > >> >> Should I post the spoiler on how a couple other mechanisims work
> > >> >> (besides servo tabs)?
>
> > >> > I'll raise you one to make three additional trim systems. Any
more?
>
> > >> I can think of four for a total of five, depending on whether you'd
> > >> consider hydraulic centering to be the same as a bungee trim
system.
> > >> theothersa re of course, a tab system which is th emost common
light
> > >> aircraft system. the trimmable stab, a'la Cub and most airliners
and
> > >> the vane, like some early T-carts had.. There're probably some
> > >> others, but i can't think of any.
>
> > > I'd count that as the same -the acutuating system doesn't count,
just
> > > the aerodynamic priciples. So, if you have four I'll raise you again
> > > one to make five... Any raise on five basic methods?
>
> > Yeah, they;re essentially the same.
>
> > Go on. I'll call.
>
> Should'nt we wait to see if there's any other raise?
>
> Cheers

       Some sailplanes, some ultralights and a few other light
aircraft use bungees or springs in the elevator control system.
Adjusting the tension of the bungee or spring will apply appropriate
force to the elevator system to achieve trim.

       Tabs are most common. Some ultralights have a ground-adjustable
tab. Others use a chain-and-cable arrangement that work a small
jackscrew inside the stab that pushes and pulls a rod attached to the
tab. Cessna likes that one. Taylorcraft used a crank that drove a
cable loop that worked a pulley that had a thread through it, and ran
a screw back and forth to work a shorter push-pull cable to the tab,
IIRC. Some just use a long push-pull Bowden cable directly from a
lever to the tab. Champs/Citabrias use a lever that works two 1/16"
cables directly to the tab, via pulleys. Some homebuilts use an
electric jackscrew to work the tab. Electrical failure means no trim.

       Adjustable stabilizers are not uncommon. The Supercub and Tri-
Pacer use them but also have a bungee affair that applies tension to
the elevator cables. Two systems in one airplane. The Cessna 180/185
adjusts the stab via two jackscrews at the leading edge, operated in
unison by sprockets and a chain diven by a cable loop.

       I once saw somewhere a light aircraft (homebuilt ultralight, I
think) that had its battery on a sliding device that moved fore-and-
aft to change the CG and therefore trim. This sort of thing adds
unacceptable weight.

       Stabilators use adjustable antiservo tabs. That tab has a lever
on it whose forward end is hinged at a point behind the stab hinge to
get the desired antiservo action, and that hinge point is on a nut
moved fore and aft by a jackscrew to get the trim action.

       Mooneys used to move the WHOLE TAIL, fin and stab and all, to
change the angle of the stab. Do they still make them that way?

       The Spratt Controlwing moved the wings for all control
including trim. The tail did nothing but keep the nose pointed into
the wind. See  http://www.flyingflea.org/docs/SprattControlwing.htm

       Didn't the Wren 260 use a small canard for low-speed trim?
http://en.wikipedia.org/wiki/Peterson_260SE

        Dan