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Cabin Weight Distribution - Unbalanced?  
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 8
Posted (12 years 3 months 1 week 4 days 20 hours ago) and read 3518 times:

Hi guys.

I have a question about the weight distribution of passengers and their carry-on luggage in the cabins of the Saab 2000 and the Embraer ERJ-145.

Both of these regional aircraft have a standard passenger accommodation for 50 people, with a seating configuration of 3 abreast. They both have a Max Takeoff Weight close to 50,000 pounds (48,500 Lbs for the ERJ-145 & 50,265 Lbs for the Saab 2000), so they are similar enough in design for this question.

If you look at the photos of the cabins of both the Saab 2000 & ERJ-145 below, you can see that their overhead luggage bins are only located on the right side of the cabin.

Also, both cabins have 2 rows of seats on the right side, with only 1 row on the left.

Even though the middle row of seats is almost alligned with the aircraft's centerline, causing the aisle to be offset to the left, doesn't it appear that these cabins are still un-balanced regarding weight distribution?

My question are ......... Are the cabins on these 2 aircraft un-balanced when fully loaded?

If they are, how is the unbalanced condition compensated for?

Are internal aircraft systems intentionally routed along the left side of the aircraft? Is the cargo compartment in the belly loaded differently, etc, etc?

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Photo © Dion Fuchs
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Photo © Dion Fuchs


Chris  Smile

"Just a minute while I re-invent myself"
2 replies: All unread, jump to last
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 66
Reply 1, posted (12 years 3 months 1 week 4 days 19 hours ago) and read 3388 times:

Not specifically familiar with these aircraft but you can be sure that there is no crew action required by this situation.

Using these assumptions:

50,000 lb gross weight
2720 pounds of pax in the center seats (170lbs each X 16 rows)
1500 pounds (50 ea. 20lb carryons plus 500 lbs for the bins themselves.

and guessing the centroids at
24" right of centerline for the center seats
30" right of centerline for the overhead

My calculations indicate that would shift the aircraft CG 2.2 inches right of its original location as compared with that weight having been previously located exactly along the centerline. This is a negligible amount and aileron trim alone could easily overcome it.

It is possible that things like aircraft batteries etc. could have been placed to the left of centerline to offset. Perhaps the basic aileron rigging factors this in. I just don't know anything about these planes, but the problem is not a difficult one at all.

This was previously discussed in a thread regarding the 2-3 seating on the DC-9/MD-80.

Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 8
Reply 2, posted (12 years 3 months 1 week 3 days 18 hours ago) and read 3283 times:

Hello SlamClick.

Thank You, for your reply and effort in figuring out roughly where the CG would be in comparison to these aircraft's centerlines.

I was also thinking about the possibility of any aerodynamic features such as fixed trim tabs that might help hold the right wing level ........ if the aircraft needed it.

I just kept on thinking about what would happen if these cabins were in a small boat instead of an aircraft. The boat would surely be leaning to the right while floating in the water. Therefore I was visualizing these aircraft wanting to lean to the right (roll into a right bank around the longitudinal axis)

I guess that even though the CG may be a few inches off the aircraft's centerline/thrustline, it's not far enough off to dictate any noticeable changes in how these aircraft are operated.

Chris  Smile

"Just a minute while I re-invent myself"
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