Variation of Take Off Stabiliser with weight and flap setting

[renard]

Hi,

On the a/c types I fly - E170/E190 - we get a MACTOW on the loadsheet.

We then have to consult a table to convert this to a trim setting.

On the E170 we have to consider the flap settting.

On the E190 we have to consider flap setting and take off weight.

My question is - Why does the trim setting for a particular MACTOW vary with flap and take off settings?

On other aircraft I have flown, including the E145 with a stabilize, there has not been that variation.

[rudderrudderrat]

Hi renard,
Why does the trim setting for a particular MACTOW vary with flap and take off settings?
Your V2 speeds will change with flap setting and TOW. Therefore the TO trim setting will change in the same way you would need to trim if you were flying at different speeds and with different flap settings.

Does your E145 have the same variation in V2s?

[BOAC]

Not forgetting flap downwash.

[renard]

It's quite a while since I flew the E145 so can't remember.

I can see that different weights / flaps would give a different V2 so trim could be affected but on the RJ100 there were four different flap settings for take off.

The flap setting on the RJ was not considered when calculating take off trim.