Horus
Topic Author
Posts: 5131
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### Weight Distribution And Balance On The ERJ-145

I just have a quick (probably stupid) question regarding how the weight distribution and balance are maintained on the ERJ-145/135.

The cabin configuration is 1-2 as shown in these photos:

 View Large View MediumPhoto © Europix View Large View MediumPhoto © Helmut Bierbaum

How is the balance maintained when you can have upto double the weight on the right side of the jet compared to the left?

Do they load cargo and luggage on the left? What if the flight is full in both the passenger cabin and cargo hold?

Now I realise this question is probably quite trivial and stupid so no sarcastic remarks please, just a simple explanation will suffice. Thanks in advance

Horus
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speedracer1407
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Joined: Fri Dec 24, 2004 4:19 pm

### RE: Weight Distribution And Balance On The ERJ-145

I've wondered the same thing about the MD-80 and it's variants with 2+3 seating configuration, but just figured that the explaination must be so simple or fundamental that it would eventually come to me. It hasn't, and I give up.

O
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PPVRA
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Joined: Fri Nov 12, 2004 7:48 am

### RE: Weight Distribution And Balance On The ERJ-145

Good question. My guess is that they can balance it with fuel... otherwise I don't know.

PPVRA
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CRJ200Mechanic
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### RE: Weight Distribution And Balance On The ERJ-145

My guess is the fuel too. I'm pretty sure the cargo hold is on the left side, so I'm sure that helps too
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troubleshooter
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Joined: Mon Feb 07, 2005 5:22 am

### RE: Weight Distribution And Balance On The ERJ-145

There is no balancing with fuel or cargo load. The aisle seats on the r/h side are very close to the centerline which will not produce any noticeable lateral imbalance.
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Horus
Topic Author
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### RE: Weight Distribution And Balance On The ERJ-145

Troubleshooter, yes its 'close' to the cetreline but its not actually on it (most of the seat is positioned to its right) so wouldn't there still be siginificantly more weight on the right?

Horus
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USAFMXOfficer
Posts: 168
Joined: Fri Nov 12, 2004 4:20 am

### RE: Weight Distribution And Balance On The ERJ-145

OK....if you put a 200 lb person in each seat and figure out weights and moments, you determine that the lateral CG shifts 3 inches off the centerline (to the side with 2 seats) because of the seat configuration.

This is negligible, and is not countered by "shifted baggage" or fuel.

I would wager that a lateral cg shifts several inches to either side of centerline throughout a flight, due to fuel shifting, pax movement, etc.

Not an issue.
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bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

### RE: Weight Distribution And Balance On The ERJ-145

Like any aircraft, it must be loaded within limits. You can't fill the B and C seats with the A seats empty. After that, though, it's likely easy to keep level with aileron trim.

The only stupid question is the one that isn't asked. I've wondered the same thing often, especially when flying American, as I always get an MD-80 to DFW, then an ERJ to the smaller destination city.
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EMBQA
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### RE: Weight Distribution And Balance On The ERJ-145

Left to right balance is just not that big of an issue when the moments are that close to a center line.... unless the difference is that drastic. Fwd and aft are the key and critical weight and balance figures with any aircraft. Besides, you can always kick in a little aileron trim to make up the differance.
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troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

### RE: Weight Distribution And Balance On The ERJ-145

I know some Avro RJ operators with a 2+3 seat config. It´s the same issue. No noticeable lateral imbalance which requires trimming with fuel or cargo. I don´t even think that it requires extra aileron trim.

Just keep in mind that in case of a fuel imbalance the applicable warning is given at an imbalance of a few (I don´t have actual values at the moment) hundred kilos. Before that it might not affect the aircraft handling in a dangerous matter.
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loggat
Posts: 431
Joined: Sat Feb 12, 2000 11:34 am

### RE: Weight Distribution And Balance On The ERJ-145

 Quoting Troubleshooter (Reply 9):Just keep in mind that in case of a fuel imbalance the applicable warning is given at an imbalance of a few (I don´t have actual values at the moment) hundred kilos. Before that it might not affect the aircraft handling in a dangerous matter.

800 lbs in the ERJ-145
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Starlionblue
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### RE: Weight Distribution And Balance On The ERJ-145

Same with the DC-9 and the MD-80/90. The shift in CG is so small as to make no difference.
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KAUSpilot
Posts: 1662
Joined: Mon Jan 28, 2002 2:15 pm

### RE: Weight Distribution And Balance On The ERJ-145

I've never had to use aileron trim in this airplane. In addition, the galley equipment is all on the right side of the aircraft, and most of the bags are loaded toward the right side since the door for the rampers to get in and out of is to the left. On the other hand, the APU does burn fuel out of the right side fuel tank, so it's not uncommon to take off with 100 lbs or so more fuel in the left than the right.

Still, when you're talking about a 50,000 lb airplane, having the CG a couple of inches off centerline doesn't make a noticeable difference.

jetskipper
Posts: 363
Joined: Tue Jun 12, 2001 1:50 am

### RE: Weight Distribution And Balance On The ERJ-145

As an Embraer captain in the US with over 3300 hours of Embraer flight experience. I can attest that balance along the lateral axis is never of concern. The slight misbalance from left to right can be easily overcome by a slight airleron trim input. As was stated earlier the max fuel imbalance is, I have flown aircraft with imbalances of upto 700 pounds with no adverse flight characteristics.

loggat
Posts: 431
Joined: Sat Feb 12, 2000 11:34 am

### RE: Weight Distribution And Balance On The ERJ-145

 Quoting Jetskipper (Reply 13):I can attest that balance along the lateral axis is never of concern

I assume you meant to say the longitudinal axis? That being the axis that goes from nose to tail, of which lateral balance is pivoting/rotating on.
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mrocktor
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Joined: Mon Jan 24, 2005 12:57 am

### RE: Weight Distribution And Balance On The ERJ-145

 Quoting Loggat (Reply 14): assume you meant to say the longitudinal axis? That being the axis that goes from nose to tail, of which lateral balance is pivoting/rotating on.

Although literally speaking you are correct (as the axis the aircraft rolls around is longitudinal as you described), traditional aeronautical terminology is:

longitudinal axis = pitch
lateral axis = roll

troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

### RE: Weight Distribution And Balance On The ERJ-145

 Quoting Mrocktor (Reply 15):Although literally speaking you are correct (as the axis the aircraft rolls around is longitudinal as you described), traditional aeronautical terminology is: longitudinal axis = pitch lateral axis = roll

That´s not correct! The movements along the three axes are as follows:
longitudinal axis = roll (controlled by the ailerons)
lateral axis = pitch (controlled by the elevator)
vertical axis = yaw (controlled by the rudder)

So Loggat was correct in reply 14.
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