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UA - 'load balancing' to deny upgrades, What is Weight & Balance all about? Why?

UA - 'load balancing' to deny upgrades, What is Weight & Balance all about? Why?

Old Nov 22, 2023, 7:18 am
  #1  
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Angry UA - 'load balancing' to deny upgrades, What is Weight & Balance all about? Why?

I was on UA 187 from JNB-EWR on 18 Nov. The flight was not full and on boarding, flight attendants announced that people would be able to change their seats. I was on the upgrade list and based on space was definitely getting upgraded to Premium Plus (with an outside chance at Polaris). They then changed their announcement to say no seat changes and no upgrades due to load balancing on the plane with expected strong headwinds. I think it's outlandish to suggest moving 3-4 people from economy to the front of the plane could cause a load balance issue on a 787, but I'm not an engineer. I also think it's outlandish that UA would leave premium seats empty on a nearly 16 hour flight when people had paid/used miles for the chance to upgrade. It felt more like UA pulling the carpet out from under loyal customers. Flight attendants were very vague about it when asked directly. Has anyone else experienced this before? I'd love any insight.
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Old Nov 22, 2023, 8:56 am
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Not only possible, but very likely.

That flight is operated by a Boeing 787-9 aircraft. Maximum range on a 787-9 is 7,565 nautical miles.
JNB-EWR is 6,943 nautical miles.

Pretty close to the maximum distance the plane can fly. So weight-and-balance calculations are pretty dang important - especially when that flight is going to be loaded with cargo.

There simply isn't much "fluff" in the numbers.

I'm sure not getting the upgrade hurts, but - especially for takeoff and landing - the pilots have to do a bunch of math to calculate the proper center of gravity, thrust required, takeoff rollout distance, landing runway length needed in case of emergency, so on and so forth. Moving passengers around affects all of those calculations, and especially when fuel margins are right at the limit -- I can see why they didn't want anyone moving around.

My point being ... there's a lot that goes on behind the scenes to prepare for a flight that you and I don't see.

Simply, if the pilots say "stay where you are" --- it's best to do so. W&B miscalculations can be ... catastrophic.
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Old Nov 22, 2023, 9:04 am
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I suspect the captain did the W&B calculation with the seat map as it was just before boarding and found it was just inside the acceptable envelope. Because of the margin, the calculation would have to be re-run with a new seat map after upgrades were run, with a risk it wouldnt be acceptable, forcing other seat adjustments (or forced downgrades) to compensate. That may have delayed departure, which could have risked a crew time out, canceling the flight altogether.

The crew made the call to make 4 people unhappy to keep 250 others happy.
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Old Nov 22, 2023, 9:07 am
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Originally Posted by gmbeid
I was on UA 187 from JNB-EWR on 18 Nov. The flight was not full and on boarding, flight attendants announced that people would be able to change their seats. I was on the upgrade list and based on space was definitely getting upgraded to Premium Plus (with an outside chance at Polaris). They then changed their announcement to say no seat changes and no upgrades due to load balancing on the plane with expected strong headwinds. I think it's outlandish to suggest moving 3-4 people from economy to the front of the plane could cause a load balance issue on a 787, but I'm not an engineer. I also think it's outlandish that UA would leave premium seats empty on a nearly 16 hour flight when people had paid/used miles for the chance to upgrade. It felt more like UA pulling the carpet out from under loyal customers. Flight attendants were very vague about it when asked directly. Has anyone else experienced this before? I'd love any insight.
I am not an engineer, but this has happened to me twice before.
Once on the 757, I was asked to move half way during the flight (alone with other F passengers) to move to economy to balance the weight due to unexpected weather condition.

Second time, I had paid C and did not move. It was on 787-10 from IAD to PEK. I believe IAD-PEK was just under the range of the 787-10. No one got upgraded and Polaris cabin was fairly empty.

Again, I am not an engineer and just share my experience.
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Last edited by UA_Flyer; Nov 22, 2023 at 9:30 am
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Old Nov 22, 2023, 9:15 am
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Originally Posted by gmbeid
I was on UA 187 from JNB-EWR on 18 Nov. The flight was not full and on boarding, flight attendants announced that people would be able to change their seats. I was on the upgrade list and based on space was definitely getting upgraded to Premium Plus (with an outside chance at Polaris). They then changed their announcement to say no seat changes and no upgrades due to load balancing on the plane with expected strong headwinds. I think it's outlandish to suggest moving 3-4 people from economy to the front of the plane could cause a load balance issue on a 787, but I'm not an engineer. I also think it's outlandish that UA would leave premium seats empty on a nearly 16 hour flight when people had paid/used miles for the chance to upgrade. It felt more like UA pulling the carpet out from under loyal customers. Flight attendants were very vague about it when asked directly. Has anyone else experienced this before? I'd love any insight.
Do you think they did it just to make people angry?
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Old Nov 22, 2023, 9:17 am
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Originally Posted by prometa
I suspect the captain did the W&B calculation with the seat map as it was just before boarding and found it was just inside the acceptable envelope. Because of the margin, the calculation would have to be re-run with a new seat map after upgrades were run, with a risk it wouldnt be acceptable, forcing other seat adjustments (or forced downgrades) to compensate. That may have delayed departure, which could have risked a crew time out, canceling the flight altogether.

The crew made the call to make 4 people unhappy to keep 250 others happy.
Not to mention keeping 250+ people alive ...
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Old Nov 22, 2023, 9:22 am
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Originally Posted by gmbeid
I was on UA 187 from JNB-EWR on 18 Nov. The flight was not full and on boarding, flight attendants announced that people would be able to change their seats. I was on the upgrade list and based on space was definitely getting upgraded to Premium Plus (with an outside chance at Polaris). They then changed their announcement to say no seat changes and no upgrades due to load balancing on the plane with expected strong headwinds. I think it's outlandish to suggest moving 3-4 people from economy to the front of the plane could cause a load balance issue on a 787, but I'm not an engineer. I also think it's outlandish that UA would leave premium seats empty on a nearly 16 hour flight when people had paid/used miles for the chance to upgrade. It felt more like UA pulling the carpet out from under loyal customers. Flight attendants were very vague about it when asked directly. Has anyone else experienced this before? I'd love any insight.
What do you think UA's reason was for doing this?
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Old Nov 22, 2023, 9:23 am
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Originally Posted by malgudi
Not to mention keeping 250+ people alive ...
Overrated!

If the choices are:
  • That sweet, sweet Polaris chow
  • Risk of catastrophic hull loss
I'm picking the former option every time.
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Old Nov 22, 2023, 9:27 am
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Ok, but what happens if Polaris and PP had checked in full ?
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Old Nov 22, 2023, 9:29 am
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Originally Posted by prometa
I suspect the captain did the W&B calculation with the seat map as it was just before boarding and found it was just inside the acceptable envelope.
We don't see those kind of details on the weight and balance calculations. We see the limiting weights and which limit is the most restrictive. Everything else is handled by a Load Planner in Chicago.

They start out with the planned information for bookings, cargo, assumed checked bags, and weather. As departure time approaches, the estimates are replaced with actual data from actual bags checked and passengers and cargo boarded. The initial load plan, for the rampers, is based on the estimated data and is also refined as estimations are replaced by actual data. Sometimes they will have the rampers move bags from one pit to another when the actual data differs significantly from plan. Other times a pit can bulk out before the planned weight for that pit can be loaded and they can't load anymore into it.

The Load Planner in Chicago has no reason to restrict upgrades unless he needs to do so to prevent the C.G. from being too far forward.

As far as how much difference moving three passengers would make, there is a hard line at each limitation. If the calculation returns a C.G. that is exactly on the forward limit then you are good. If the calculation comes up 0.01* over the limit then you are not and something has to be moved. There is no grey area were it is okay to go "just slightly" out of the limit.

(*C.G. is presented in percentage of Mean Aerodynamic Chord (%MAC) and is calculated to two decimal places (at least on the Boeings I've flown)
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Old Nov 22, 2023, 9:30 am
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Originally Posted by UA_Flyer
I am not an engineer, but this has happened to me twice before.
Once on the 757, during landing, I was asked to move half way during the flight (alone with other F passengers) to move to economy to balance the weight due to unexpected weather condition.

Second time, I had paid C and did not move. It was on 787-10 from IAD to PEK. I believe IAD-PEK was just under the range of the 787-10. No one got upgraded and Polaris cabin was fairly empty.

Again, I am not an engineer and just share my experience.
Interesting data points. Would love for a United pilot to chime in on this one. Would guess that something in the plane's handling characteristics indicated they should look at W&B. I don't think they would re-run calculations in-flight, but maybe?

All my experience with W&B has been with take off, which I assumed is the most critical phase of flight for it. I recall passengers being asked to move seats for take off, but then being allowed to return to their original seats towards the front once in cruise flight.

There has to be some allowances in all this as passengers and crew aren't static in flight.
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Old Nov 22, 2023, 9:33 am
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Originally Posted by benewr
Ok, but what happens if Polaris and PP had checked in full ?
Operational Fuel stop? That has happened to 752 across the pond and JFK-HKG (PMUA 747/777) and EWR-HKG (PMCO and post merger) during winter months.
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Old Nov 22, 2023, 9:38 am
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Originally Posted by benewr
Ok, but what happens if Polaris and PP had checked in full ?
The weight and balance calculations would have been run that way and wouldn't have been needed to be re-run. Potentially they also allocated cargo differently to compensate.

Or they downgrade people.
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Old Nov 22, 2023, 9:41 am
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Originally Posted by Bear96
Do you think they did it just to make people angry?
Ha ha fair. I've just soured so much on UA I'm skeptical of everything now. Thanks for putting it in perspective. :-)

Originally Posted by goodeats21
Interesting data points. Would love for a United pilot to chime in on this one. Would guess that something in the plane's handling characteristics indicated they should look at W&B. I don't think they would re-run calculations in-flight, but maybe?

All my experience with W&B has been with take off, which I assumed is the most critical phase of flight for it. I recall passengers being asked to move seats for take off, but then being allowed to return to their original seats towards the front once in cruise flight.

There has to be some allowances in all this as passengers and crew aren't static in flight.
The latter was also my thought. There were dozens of rows in back with only one person in them. It all just seemed weird. Also, concerning given that we were pushing the plane's range?

Originally Posted by LarryJ
We don't see those kind of details on the weight and balance calculations. We see the limiting weights and which limit is the most restrictive. Everything else is handled by a Load Planner in Chicago.

They start out with the planned information for bookings, cargo, assumed checked bags, and weather. As departure time approaches, the estimates are replaced with actual data from actual bags checked and passengers and cargo boarded. The initial load plan, for the rampers, is based on the estimated data and is also refined as estimations are replaced by actual data. Sometimes they will have the rampers move bags from one pit to another when the actual data differs significantly from plan. Other times a pit can bulk out before the planned weight for that pit can be loaded and they can't load anymore into it.

The Load Planner in Chicago has no reason to restrict upgrades unless he needs to do so to prevent the C.G. from being too far forward.

As far as how much difference moving three passengers would make, there is a hard line at each limitation. If the calculation returns a C.G. that is exactly on the forward limit then you are good. If the calculation comes up 0.01* over the limit then you are not and something has to be moved. There is no grey area were it is okay to go "just slightly" out of the limit.

(*C.G. is presented in percentage of Mean Aerodynamic Chord (%MAC) and is calculated to two decimal places (at least on the Boeings I've flown)
So interesting! Thank you for sharing.

Originally Posted by dmurphynj
Not only possible, but very likely.

That flight is operated by a Boeing 787-9 aircraft. Maximum range on a 787-9 is 7,565 nautical miles.
JNB-EWR is 6,943 nautical miles.

Pretty close to the maximum distance the plane can fly. So weight-and-balance calculations are pretty dang important - especially when that flight is going to be loaded with cargo.

There simply isn't much "fluff" in the numbers.

I'm sure not getting the upgrade hurts, but - especially for takeoff and landing - the pilots have to do a bunch of math to calculate the proper center of gravity, thrust required, takeoff rollout distance, landing runway length needed in case of emergency, so on and so forth. Moving passengers around affects all of those calculations, and especially when fuel margins are right at the limit -- I can see why they didn't want anyone moving around.

My point being ... there's a lot that goes on behind the scenes to prepare for a flight that you and I don't see.

Simply, if the pilots say "stay where you are" --- it's best to do so. W&B miscalculations can be ... catastrophic.
Heard! It just felt very weird given how empty the back of the plane was. Rarely am I on that flight when I see dozens of rows with only one person in them - it's usually quite full if not entirely so.

I appreciate your answer and all of the expertise in this group. Thank you!

Last edited by WineCountryUA; Nov 22, 2023 at 11:27 am Reason: merged consecutive posts by same member
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Old Nov 22, 2023, 9:53 am
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Originally Posted by goodeats21
Would guess that something in the plane's handling characteristics indicated they should look at W&B. I don't think they would re-run calculations in-flight, but maybe?
The C.G. is calculated before takeoff. It is calculated both at takeoff weight and at Zero Fuel Weight (ZFW). This ensures that you are within limits both at takeoff and at landing, no matter how much of your fuel you burn. The actual C.G. moves during flight as fuel is burned and the forward and aft limits change based on aircraft weight.

I can't think of any reason why a change would be needed after takeoff other than a mistake in loading the aircraft that wasn't discovered until after takeoff.

There has to be some allowances in all this as passengers and crew aren't static in flight.
There are no sharp lines between "safe" and "unsafe". A hard line is drawn but it is based on certification requirements with built in buffers.

With regard to balance, as the C.G. moves aft, the airplane because more efficient*, less stable, and the elevator control has greater authority. As C.G. moves forward, the airplane becomes less efficient, more stable, and the elevator control has less authority. The forward and aft limit lines are drawn where the negative affects of movement in that direction have reached the certification limits.

(* The MD11 had a system called 'relaxed stability'. It pumped fuel into trim tanks in the tail at cruise to move the C.G. farther aft at cruise to improve efficiency. That fuel was later pumped back into the main tanks for descent and landed when the greater stability was needed. Concord also had tail trim tanks though I'm not sure how it was used operationally. There are likely more examples.)

Originally Posted by gmbeid
Heard! It just felt very weird given how empty the back of the plane was. Rarely am I on that flight when I see dozens of rows with only one person in them - it's usually quite full if not entirely so.
Balance is like a see-saw with the fulcrum somewhere between the leading and training edges of the wing (the Mean Aerodynamic Chord). Moving someone in rows close to the wing don't make very much difference. Moving one passenger from the very front or back make a much bigger difference.

Last edited by WineCountryUA; Nov 22, 2023 at 11:28 am Reason: merged consecutive posts by same member
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