KLM-MD11
Posts: 429
Joined: Thu Mar 28, 2002 8:09 am

Moving Pax For Balance (A320)

Sat May 08, 2004 10:20 pm

hi all,

flew on V-BIRD yesterday from VIE to NRN on an Airbus A320.

Pax load was light (67 pax)

the crew requested pax (12) seated in rows 7 through 12 to move towards the back of the cabin to balance the a/c

could someone explain how this little weight makes such an impact on the balance or could there have been another reason?

thnks for your replies,

regards,

KLM-MD11
GELUK IS GELUL MET EEN K
 
citationjet
Posts: 2259
Joined: Sun Mar 09, 2003 2:26 am

RE: Moving Pax For Balance (A320)

Sat May 08, 2004 11:02 pm

Personally, I don't think it makes much difference. The airlines use estimates for the weight of passengers and baggage. The only items that the airlines know the weight of are the empty plane, fuel load, freight and mail. These items make up the majority of the aircraft's weight.
You were asked to move because of the center of gravity (CG). The airline doesn't know the exact CG locations of the baggage, freight, or passengers. "Towards the back of the plane" is such a general criteria that leaves a large uncertainty about the center of gravity of these moved passengers.
My wife and I were asked to move from first class to coach (we were non-revs) on an AA 767-200 flight departing ORD for BRU. The passenger load was much lower than planned for weight and balance (due to misconnecting passengers). As we were taxing to the active runway, the F/A asked us to move back to "anywhere in coach". The length of the coach section meant that moving within coach would have more impact on the CG than moving from the last row of First to the front of coach.
Anyway we moved back to coach as we taxiied. Then two minutes after takeoff, still in a steep climb, the flight attendant had us move back up to first, even though the seat belt sign was on and we were in a steep climb.


[Edited 2004-05-08 16:05:14]
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SlamClick
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RE: Moving Pax For Balance (A320)

Sat May 08, 2004 11:43 pm

Keep this in mind: When exercising oversight over airlines, the government agencies cannot often inspect actual operations. Mostly they inspect records of operations.

The weight and balance record is a snapshot of the configuration of the plane at the start of takeoff roll. They asked you to move to correct a forward CG issue. Reality is that you would not have presented any problem to the flight crew staying where you were, but they had to show on the W&B closeout that they had corrected the CG in the required direction.

Once in flight, the autopilot will trim the airplane in pitch and the crew will not even know where you are sitting.

All airlines have loading plans for each type plane. It is possible that with the planned passenger load, the bags all went into the forward pit. It is easier to have you get up and walk aft than for a team of rampers to open up the front pit, drive up a beltloader, offload the appropriate number of bags, close the pit, drive the beltloader to the back, open the rear pit and reload the bags.

Instead, you walk a few rows back and sit down, rampers move on the next airplane and you depart on time.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
RyDawg82
Posts: 833
Joined: Fri Sep 14, 2001 8:30 am

RE: Moving Pax For Balance (A320)

Sun May 09, 2004 6:50 am

While I am not familiar with the weight and balance issues of a A320, I can share some information on other types. Here is a very basic statement for you regarding a 737-400. "It takes 12 coach passengers to offset the CG movement of each first class passenger."

Most carriers choose to fill their first class on all flights. If you have a lightly booked flight in coach and little cargo to help you out aft then zone seating becomes important. On the longer 737-400 and 737-900 models you will have three zones of seating: A, B, and C. Zone A being first class (Rows 1,2,3), Zone B being the first 60 seats of coach (rows 6-15), and Zone C being the rest of coach (Rows 16-26 on a -400 or 16-31 on a -900). If you choose to fill first then you calculate how many passengers you can carry in Zone B, the rest sit aft in Zone C and pull your CG aft. Again these procedures can be critical for lightly booked flights just in the takeoff phase of flight. You can move about in flight without issue.

The MD-80 when empty or very light can actually require passengers being upgraded or loading cargo forward to pull the CG forward, as she sits out of aft limits empty. When an MD has more than 85 passengers aboard or more, random seating relief units can be used to help your CG out. Essentially this takes into a account that passengers won't fill only the first 85 seats but will stretch out further aft in the remaining seats. You take your original CG (only if it were out of forward limits) and calculate an adjusted CG to account for random seating.

Hope this helps,
-R
You can take the pup out of Alaska, but you can't take the Alaska out of the pup.
 
KLM-MD11
Posts: 429
Joined: Thu Mar 28, 2002 8:09 am

RE: Moving Pax For Balance (A320)

Sun May 09, 2004 6:03 pm

thanks guys,

that answered my question!

regards,

klm-md11
GELUK IS GELUL MET EEN K
 
Demoose
Posts: 1891
Joined: Thu Mar 08, 2001 8:06 am

RE: Moving Pax For Balance (A320)

Tue May 11, 2004 1:07 am

I read the following air incident report a few months ago, where, due to incorrect seating of passengers on an A320, as the aircraft started take off the nose pitched up quickly. The pilot aborted and the problem was realised back on stand. The report goes into alot of detail about the issue of where to seat passengers when the plane is not fully loaded and is quite interesting to read.

http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_026644.hcsp

Mark
Take a ride...fly across the sky
 
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RE: Moving Pax For Balance (A320)

Tue May 11, 2004 1:24 am

Using for example a standard winter male weight, 12 pax could equal as much as 2256 lbs... which on an aircraft the size of an A320 can be significant amount. I'm only familiar with working with the 737-700. On that aircraft a weight difference of 1000 lbs could be a big difference. So when you look at it in those terms.

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