Musical Chairs on board a Plane

[Oliver Hardy]

I recently flew Ryanair from Manchester, the plane was about 70% full.

Once everyone was seated the cabin staff came along and moved nine people from the right hand side of the plane from the first six rows. They then moved 6 people back into the seats at the front of the plane. The pilot came on to the speakers and told the staff to move another 8 passengers from the middle of the plane to the front.

This all took about 30 minutes. The pilot then came on, apologised for the delays but said it was necessary because of a run way change?

Anyone care to explain

edited the wtong thread

Edited by Oliver Hardy on Thursday 26th January 23:58

[Neddy Sea Goon]

Weight distribution

[Caddyshack]

Obviously weight distribution, I suspect the runway change made it far more critical for some reason such as camber, incline, length etc.

[Jim H]

I’d be keen to learn more about this. I fully understand how critical an aircraft CofG is in relation to operation and performance. However, what is the base that the crew start from? Is the aircraft neutral CofG unladen or perhaps a little nose heavy?

How do they calculate which cases go where etc, as for moving around a small number of people? I’m surprised it would be that critical, and how do they calculate how many to where?

Is there a system (or similar) that provides weight distribution onboard the aircraft as it is loaded with passengers and luggage?

I mean, maybe a daft question, but individual persons weight? How could that be known, or is it an combined estimate?

Edited by Jim H on Thursday 26th January 12:02

[LimaDelta]

Jim H said:

I’d be keen to learn more about this. I fully understand how critical an aircraft CofG is in relation to operation and performance.

It is hugely important, and there have been very notable accidents where incorrectly loaded or secured cargo has resulted in total loss. It is a complicated subject, but John Denker's page does a far better job of explaining it than I could.

[essayer]

Must have switched from the 3050m long runway to the shorter one

the 3048m one

[Simpo Two]

Oliver Hardy said:

Once everyone was seated the cabin staff came along and moved nine people from the right hand side of the plane from the first six rows. They then moved 6 people back into the seats at the front of the plane. The pilot came on to the speakers and told the staff to move another 8 passengers from the middle of the plane to the front.

Overall that sounds like more people at the front, so CG further forward - how does that fit with a shorter runway?

[Mr Pointy]

Do they have load sensors in the landing gear so they have active indication of the current CoG position?

[STe_rsv4]

Interesting..

I wonder if they also calculated the weight of each individual...
"could the 3 morbidly obese people from row H please move to row P on the left of the plane and the orange skinny girls at the front move to the back please"

[Claret m]

essayer said:

Must have switched from the 3050m long runway to the shorter one

the 3048m one

It's an interesting one this!
C of G on the aircraft does affect aircraft performance, assumed passenger weights are used for male, female, children and infants plus actual weight for hold bags.

I think it is likely that just runway 23R/05L was in use (same length ), however 23R slopes down and 05L slopes up. So a change from 23R to 05L would require more performance, also because of the hills east of Manchester.
The thing that surprises me is the first thing to do would be to "reduce" the reduced power setting (full power is hardly ever used)ie use 90% power instead of 85% power. This is called derated power if you are interested.

It sounds more like the hold bags had been loaded in the wrong hold/s.

I hope this helps a bit.

Edited by Claret m on Thursday 26th January 16:48

[Claret m]

Mr Pointy said:

Do they have load sensors in the landing gear so they have active indication of the current CoG position?

The Boeing 787 does, it checks for gross error.

[smallpaul]

Jim H said:

How do they calculate which cases go where etc, as for moving around a small number of people? I’m surprised it would be that critical, and how do they calculate how many to where?

Is there a system (or similar) that provides weight distribution onboard the aircraft as it is loaded with passengers and luggage?

I mean, maybe a daft question, but individual persons weight? How could that be known, or is it an combined estimate?

Edited by Jim H on Thursday 26th January 12:02

Individual weight is 85kg (including hand baggage, excluding checked baggage). We don't weigh people.

There is a computer that calculates weight distribution and outputs something called a "loadsheet". You can also complete this on paper.

Weight distribution doesn't have to be exact. You can resolve some imbalance by changing the settings of the horizontal stabilizer (using the settings you received from the loadsheet). When you are out of the range that this is effective, you are "out of trim" and have to move passengers or luggage or cargo about.

Yes weight and balance is critical. I denied the travel of boxes of biscuits because they did not have the weight printed on the box.

[Oliver Hardy]

Interesting. I have been on planes where the last rows on both sides have been closed both on the back and front, I understand closing the back rows, no so much the front ones and not at all 6 rows on one side. Moving nine passangers must be less than 1% of the planes take off weight capability?

[smallpaul]

Not so much the take off capacity, but the total moment (weight x distance) from the wing.

9 passengers is 765kg. If I asked you to load a classic mini onto an aeroplane, you would think very carefully about where it went. 9 passengers is the same weight as a small car.

[GT03ROB]

smallpaul said:

Not so much the take off capacity, but the total moment (weight x distance) from the wing.

9 passengers is 765kg. If I asked you to load a classic mini onto an aeroplane, you would think very carefully about where it went. 9 passengers is the same weight as a small car.

I fly home on a A321neo. The flights are usually quiet, maybe 50-60 passengers. About half of these are in business so occupy the front of the aircraft. Everytime on check in I get my seat reallocated & the balance of plebs back in economy get crammed in the last rows of the plane, despite the rest of the plane being empty, Nobody is allowed to move. Seat belt light goes off after take off & everybody moves seat forward.

[Viperzs]

This is an interesting topic.

Once we had arrived at a gate the crew announced that due to weight balance and to reduce the risk of the aircraft tipping, they would call out rows to disembark.

At first I thought that seemed perfectly reasonable, however what didn't make sense was that they were disembarking from the forward exit only and called out rows starting at the front of the aircraft. Surely the only risk of tipping an aircraft is if it's bottom heavy (lol), so you'd disembark the rear rows first?

I haven't been able to work out the logic.

[fiatpower]

I remember flying from Edinburgh to Cardiff on a small turbo prop plane and they had to do that. There was an obese couple sat together who got told they had to sit on opposite sides to balance the plane.

[Jim H]

fiatpower said:

I remember flying from Edinburgh to Cardiff on a small turbo prop plane and they had to do that. There was an obese couple sat together who got told they had to sit on opposite sides to balance the plane.

I’d be mortified if that ever happened to me.

‘Excuse me sir, it appears you may have eaten too many pies’….

Thanks to all so far for replies so far.

What I’m trying to understand is are all aircraft pretty much within a range of CofG from manufactures spec - unladen (without fuel and passengers)?. Depending on any modifications etc?

Be it a 737, Airbus etc and that’s taken as a given and is always the base?

I know when I’m checking CofG on my RC planes it’s fairly easy.

Two fingers either side of the fuselage about a 1/3rd of the way back from the leading edge of the wing.

Not so easy on 777?

[Mr Pointy]

smallpaul said:

Jim H said:

How do they calculate which cases go where etc, as for moving around a small number of people? I’m surprised it would be that critical, and how do they calculate how many to where?

Is there a system (or similar) that provides weight distribution onboard the aircraft as it is loaded with passengers and luggage?

I mean, maybe a daft question, but individual persons weight? How could that be known, or is it an combined estimate?

Edited by Jim H on Thursday 26th January 12:02

Individual weight is 85kg (including hand baggage, excluding checked baggage). We don't weigh people.

There is a computer that calculates weight distribution and outputs something called a "loadsheet". You can also complete this on paper.

Weight distribution doesn't have to be exact. You can resolve some imbalance by changing the settings of the horizontal stabilizer (using the settings you received from the loadsheet). When you are out of the range that this is effective, you are "out of trim" and have to move passengers or luggage or cargo about.

Yes weight and balance is critical. I denied the travel of boxes of biscuits because they did not have the weight printed on the box.

Do you get notification of special circumstances like the Tongan rugby team are on board? 32 huge blokes who are way over the standard weight would probably need special consideration?

[Simpo Two]

Mr Pointy said:

Do you get notification of special circumstances like the Tongan rugby team are on board? 32 huge blokes who are way over the standard weight would probably need special consideration?

I'll let someone else tell them to get off