The impact of seating configuration on aircraft stability

[Wrist Watch]

I've been wondering about this.

What are the effects of 2-3 (or 1-2) seating configurations (on A/C such as MD80, EMB135, CS100, etc.) on lateral stability and centre of gravity?

I would assume not much because the additional seats lie almost directly above the longitudinal axis so not a lot of moment would be produced.

But still, is that 'imbalance' still actively offset somehow, for example with cargo location or fuel (re)distribution?

Thanks.

[DaveReidUK]

I think they compensate by arranging for the heavier passengers to sit on the side with fewer seats.

[B2N2]

I think they compensate by arranging for the heavier passengers to sit on the side with fewer seats.

I seriously hope that was attempt at humor and not actually a thought out answer...

[Check Airman]

Having flown an airplane with asymmetric seating, the aisle is so narrow, that it really doesn't matter. Of all the times I've used aileron trim, I never thought about the pax distribution. Perhaps that was why I needed the aileron trim...

That being said, if we needed aileron trim on one leg, we probably needed it on the subsequent legs, which tends to suggest the pax distribution wasn't the issue.

[wanabee777]

Some military transport planes (eg KC-135's) have "troop seats" running along each side of the fuselage.

I've never heard of any restrictions on pax distribution on one side or the other, laterally, but maybe I missed it.

[DaveReidUK]

Originally Posted by B2N2

I seriously hope that was attempt at humor and not actually a thought out answer...

I did consider adding a smiley, but I didn't think it would be needed.

[compressor stall]

It's not in Airbus w&b manual. I assume the arms are too short.

This flight has seats removed on one side.

[stilton]

When I flew the MD80 with it's 2-3 seating I used to ponder this.


I came to the realization that the seating is not asymmetric at all when
you think about it.


Its the Aisle that's offset from the centreline, the closest seat to the aisle on the right is actually right in the middle of the cabin with two seats on either side
'balancing' the lateral load.


So the only off centre load is in the aisle itself, not much of an issue.

[Old Fella]

asymmetric seating

I find it interesting that this question would even be raised. With it not uncommon for standard pax weights to be used, and the large variation in actual individual pax weights encountered, if it were to be a factor there would be a system in place which dictated seat allocation based on individual weights of pax.

Stilton's explanation tells the story, if there ever was an explanation need.

[DaveReidUK]

Originally Posted by stilton

Its the Aisle that's offset from the centreline, the closest seat to the aisle on the right is actually right in the middle of the cabin with two seats on either side 'balancing' the lateral load.

That's just another way of saying the same thing. Whichever way you look at it, it's an asymmetric layout.

not much of an issue

Agreed. In fact I don't recall the topic ever coming up in all the years I was involved with the Shorts commuters (1+2).

[megan]

Helicopters usually have a lateral C of G limit listed. Bell 412 for example is 4.5 inches either side of centre. Can't say I ever worked one out in anger though.

[john_tullamarine]

Helo lat cg is there because it's necessary.

If lat cg in a fixed wing is critical, there will be an AFM/POH limitation.

If an operator is in doubt re an oddball configuration, an NTO request to the OEM should resolve the matter.

[Microburst2002]

In cargo wide bodies the loadmasters also find the lateral CG, aside from the longitudinal, but I guess that when it comes to cargo, a significant CG shift can occur that must be taken into account.