Aircraft TRIM

[alexshaggy 0]

Hello Simers!my doubt is about the Trim,first,what is Trim and what is its use?i always see on videos or forums,people saying to ''Trim'' the aircraft brefore takeoff! is it really necessary?i play with Sms aircrafts,free,i know,but i cant ''understand'' how to set a route,sids,stars and things like that on the FMC!

if someone can explain me about Trim i apreciate very much!

 

bye!

[Egbert Drenth 250]

people saying to ''Trim'' the aircraft brefore takeoff! is it really necessary?

 

I guess it is.

http://en.wikipedia.org/wiki/Trim_%28aircraft%29#Secondary_controls

[HaraldG 559]

Trimming your elevator is essential for a pleasant flight, if you don't want to push or pull your yoke permanently. You will realize it if you take a lesson in a semi-real flight simulator or a real GA aircraft.

[Glynn 405]

http://x-plane.deinon.com/aircraft_trim.pdf

[alexshaggy 0]

thanks guys!

just one more question,what is the best Trim value?or it depends on the aircraft and its weight?

[Glynn 405]

thanks guys!

just one more question,what is the best Trim value?or it depends on the aircraft and its weight?

 

Hello

Did you read the PDF in the link I posted ?

 

Q: Why to airplanes need to trim?

A: Because the lift forces on the wings, horizontal stabilizer/elevator, and the vertical stabilizer/rudder

vary with the plane’s airspeed and the angle of attack (the angle at which that air strikes the leading

edge of the affected airfoil) and its weight and balance (W&B).

If the airplane flew in a straight line at a constant altitude at a constant speed and constant weight all of

the time we could attach all of the airfoils at the proper angles so that balanced forces are created and

no trim devices would be needed. But since we want the airplane to climb, descend, speed up, slow

down and carry different loads, the lift forces acting on the airfoils vary with each change in condition

and any such change means we have to hold pressure on the flight controls to compensate. This can

be very fatiguing unless we have a means of adjusting those controls so that they maintain their new

positions .

 

From that you can deduce that you will need to re trim and there is no "best value"

[alexshaggy 0]

sorry maddog,i didn´t see your link! :Loser:

 

tks!!

[FLEX1978 373]

Hey Alex,

 

Since you specifically asked about take off trim I will focus on that. Take off trim values are provided in the FCOM (Flight crew operating manual) along with all the other performance data required to correctly operate the aircraft safely.

 

Many companies also provide onboard laptops that provide take off and landing performance data including take off thrust settings, optimum flaps and correct trim. Your trim value is based on the aircrafts CG which is a result of fuel,cargo and pax.

 

So, using the correct trim value based on correct CG is extremely important. Using the wrong trim value can result in anything from the controls feeling too heavy/light on rotation, a tail strike, or an extreme case resulting in loss of control during a critical phase.

 

Here’s a link to what is considered the best performance calculator available for simmers.

 

http://www.topcatsim.com/

 

 

 

Regards

[vc10man 732]

Fully concur with Rob. Cannot beat Topcat for a tool to aid take-offs, landings, Flex temps, etc.

[Chock 17,769]

Trimming in flight is one of the things which is a lot easier to do on a real aircraft than it is on a sim, since on most aeroplanes, you can easily feel your way to the correct trim setting in flight, by letting go of the controls lightly and feeling if the yoke moves, whereas in FS, you tend to have to watch to see if you start to veer away from level flight to know if your trim is good. On the ground, you can often see the most common trim setting from the wear and tear on the trim wheel or lever too!

 

In the absence of any other requirements, I usually trim GA aircraft ever so slightly nose down for the take off, just so that the thing would not lift off early if my hand happened to slip off the stick, but one has to be aware of the potential for prop strikes or too much load on the nose wheel if doing that. It's certainly a good idea to give it a slightly nose down trim on a glider aerotow, since if you don't, the glider can lift off and climb well before the tow aeroplane has flying speed and that would pull the tow plane's tail up and cause a prop strike on it, and you would not be popular.

 

In airliner operations, the take off trim setting is calculated either by the data on the loadsheet (often called a zig zag in airline parlance, since it ends up with a load of check marks forming a zig zag on the bits filled in on the paper sheet), or in more modern operations, it is inserted directly into the FMC from a laptop which has the load data and flight plan on it which gets 'plugged in' to the aircraft. Then the trim wheel is adjusted to match as part of the pre-flight checks. Mostly, take off trim is used to ensure that the aircraft will be well set up to fly without too much adverse yoke pressure upon rotation and with any necessary rudder or aileron trim for wind conditions, so the trim will have to be adjusted as the flight progresses.

 

As others have noted, the payware program TOPCAT is good for finding the elevator settings for trim on many airliners, since it effectively gives you a loadsheet, although TOPCAT doesn't support every airliner you can get. It is possible to kind of work elevator trim settings out from the sim too with a bit of effort, although it is a bit of a black art: if you go to the fuel and payload screen in FS and count back how many marks the CoG target is, and if you have the performance data chart for the real aeroplane, you can set it based on the percentage, for example, the take of trim might have to be 4 notches up on the elevator for a CoG of 18 percent or whatever, although that stuff does depend on payload distribution and aircraft type.

 

For flight simming, getting familiar with the trim will mean you can go afk without the autopilot engaged and still stay reasonably well on course, unless you have a particularly skillful cat or dog to take over as your co-pilot. I have trained Dave - my German Shepherd Dog - to fly most of my FS aeroplanes with reasonable precision for those eventualities, although he is often reluctant to hand control back to me when I return unless I have brought him a biscuit.

 

Al

[vc10man 732]

dog to take over as your co-pilot. I have trained Dave - my German Shepherd Dog - to fly most of my FS aeroplanes with reasonable precision for those eventualities, although he is often reluctant to hand control back to me when I return unless I have brought him a biscuit

Al, just absolutely priceless :LMAO: :LMAO: :LMAO: :LMAO:

 

Can I borrow him for my FS2Crew FO who seems a bit peeved that I won't let him be the PF?