J41 Trim

[Cuddly1956 1]

Can someone explain the Start Index - Final Index/Trim on the J41 loadsheet please? It was stated that it would be further explained in the tutorial but I can't find it. All I can find is set trim to the centre of the green band.John Ellison

[Nyxx 6,994]

I use the start index as the # to set the trim to for take of.

[CaptAAE 0]

Hi John I think you are talking about the number which appears in the Final Index/Trim, right? If you look at the green band in the centre console you can see three diferent numbers which are 10, 20 and 30, if Im not incorrect, you have to adjust Final index/Trim number in the green band between 10, 20 or 30 depending on the CG calculations.Asier

[Brent 2]

Hi John I think you are talking about the number which appears in the Final Index/Trim, right? If you look at the green band in the centre console you can see three diferent numbers which are 10, 20 and 30, if Im not incorrect, you have to adjust Final index/Trim number in the green band between 10, 20 or 30 depending on the CG calculations.Asier

I would be grateful if someone could explain the procedure because the tutorial is silent on the issue. If the load sheet has 22.3 for the "Start Index" under the CG Calculation section, is this what is used to set the elevator trim for takeoff? Seems like a pretty precise number to use on such a rudimentary scale (i.e. 10, 20, 30....).What about the Final Index/Trim which has two numbers 24.0/4.0. When is that used and which number is used? The manual and the tutorial merely advises to center the elevator trim in the green arc which works fine for TO but is there a more precise adjustment that can be made according to the CG Calculation and proper procedure?Cheers

[downscc 1,327]

Turn on tool tips, position the cursor over the trim wheel, it will display the trim setting. A setting of 4.0 is typical for a full airplane.

[Guest BlueRidgeDx]

I would be grateful if someone could explain the procedure because the tutorial is silent on the issue. If the load sheet has 22.3 for the "Start Index" under the CG Calculation section, is this what is used to set the elevator trim for takeoff? Seems like a pretty precise number to use on such a rudimentary scale (i.e. 10, 20, 30....).What about the Final Index/Trim which has two numbers 24.0/4.0. When is that used and which number is used? The manual and the tutorial merely advises to center the elevator trim in the green arc which works fine for TO but is there a more precise adjustment that can be made according to the CG Calculation and proper procedure?Cheers

The Start Index is aircraft specific, and is directly related to Basic Operating Weight, and the specific Weight & Balance configuration of that airplane. The BOW and Start Index are found on the Dispatch Release, and sometimes it's placarded somewhere in the cockpit.To determine the Final Index value used to determine Takeoff trim, a special calculator called a See Gee "wheel" is used. It's difficult to explain unless you've seen one, but the Calculator uses a set of fixed scales, a rotating disc, and a rotating index. Imagine a simplified E6B type of device.Here's a picture:The Index mark is rotated around the calculator as passengers, bags, fuel, jumpseaters, etc are added or removed. Once all of the weights have been "spun", you can read the Final Index and Takeoff Trim from around the outside edge of the calculator. You can also determine where you are within the Weight & Balance envelope, and whether you'll still be within limits after you've burned off your Trip Fuel.The company that makes the See Gee calculator charges several thousand dollars to provide these calculators to airlines, and reproducing one is well outside the scope of a desktop simulation. Trust me, I lobbied for one on several occasions.

[Cuddly1956 1]

Cheers Nick, that explains it very well to me. I fully understand now, thanks very much.John Ellison

[Peacedivision 4]

Still a bit confused on takeoff trim settings. Prior to SP1 the load sheet always displayed 4.0 regardless of weight. After the update my load sheet doesn't give any trim figure, only the final index. So how do we determine the trim for takeoff without one of these thousand dollar calculators or some performance charts in the manual?Any help would be appreciated :)-Sam Zilboorg

[Nyxx 6,994]

The picture above gives 11.3 So use the window and set trim to that setting ok .3 = no way, but just round up or down. Then best as you can set 11. I find these start index are always in the green but unlike setting to tool tips to 4 the Js41 seems much better balanced when set to the start index on TO.

[Lmaire 38]

Hi,Even though tool tips is turned on, it does not indicate the CG value (22,23,24 and so) but the value that we had before SP1 example 24 (4.0) (value in brakets). Hope you understand. Why we don't have this value anymore after SP 1. Thanks and regardsL'maire

[Nyxx 6,994]

you dont need the tool tip just your eyes :)

[Brent 2]

The Start Index is aircraft specific, and is directly related to Basic Operating Weight, and the specific Weight & Balance configuration of that airplane. The BOW and Start Index are found on the Dispatch Release, and sometimes it's placarded somewhere in the cockpit.To determine the Final Index value used to determine Takeoff trim, a special calculator called a See Gee "wheel" is used. It's difficult to explain unless you've seen one, but the Calculator uses a set of fixed scales, a rotating disc, and a rotating index. Imagine a simplified E6B type of device.

NickThanks very much for the detailed and interesting explanation - I'll give it a try. Kudos to PMDG and the testers, I've not had any issues with SP1! :(

[Peacedivision 4]

The picture above gives 11.3 So use the window and set trim to that setting ok .3 = no way, but just round up or down. Then best as you can set 11. I find these start index are always in the green but unlike setting to tool tips to 4 the Js41 seems much better balanced when set to the start index on TO.

Not trying to come down hard, but that sounds very much like an uneducated guess. The start index has nothing to do with setting final trim for takeoff.Final index is supposed to have a trim value after it, for example 24/4.0 as was the case before SP1, however there was a stated bug where the trim never changed with loadout, and always displayed 4.0We were told that this was fixed with SP1, however now there is no trim value, only final index which does not help since we have no performance charts or expensive calculators.The flight tutorial states "We

[downscc 1,327]

These birds are flown by the numbers, not by making your best guess at how something is set

I believe the trim is not near as critical in the JS41 as in something like an MD11. I honestly believe as long as the trim is in the TO range you can easily trim the difference after rotation. I have always used 4.0 light or heavy and she flys okay.

[Lmaire 38]

I agree, even it's not trimmed with precision it works perfectly. I can live with that.Best regardsL'maire