Speaking of daft questions ..

[Riccal]

When flying the loco airlines (Ryan/Easy) I have always found that excess seats on not particularly busy flights are blocked from use and the reason given is that the balance of the aircraft would suffer. Personally I think it is to facilitate turnround by making the plane easier to clean.

I can understand if it is to facilitate turnround as this all works to the advantage of cheap flying. But I dislike being patronised as I believe this explanation does.

I have flown scheduled many times where capacity has been about 50% and it has never been an issue. Or am I missing something - do the check in staff sort out the seating with the aircraft balance in mind.

Rick

[Final 3 Greens]

Personally I think it is to facilitate turnround by making the plane easier to clean.

You are wrong.

It is to operate the aircraft within weight and balance limits.

[Riccal]

Hi F3G - if that is the case why doesnt it seem to be an issue with the scheduled carriers or, as I asked in my OP, has this situation already been dealt with by the check in staff?

[Dit]

Because most airlines assign you a seat, they can calculate the actual balance of the aircraft, RYR use a free seating policy, so by blocking off these seat it guarantees that where ever everyone sits the aircraft will be within its balance limits.

It has nothing to do with cleaning.

[Avitor]

On a large charter Monarch from Corfu, there were 37 pax. The Captain asked us to occupy the first 15 rows on take off, after that we were free to move around.

So my uninformed view is that aircraft balance is the correct answer, a pilot does not want his harse end ploughing up the runway....I think that is the correct terminology! :oh:

[cherrycoke]

It depends on the size of the plane. Ezy's 319/20s don't have a problem with it, but 321s do. We have to security check each and every seat before the first flight of the day and during every turnaround, even if it has not been occupied. After take off the restriction is lifted, and you could move to these seats if you wish. I believe that airlines with allocated seating deal with this issue at check in. I think Ryanair do it because they have 737-800s which are quite long too.

[lexxity]

I work for a scheduled carrier and we routinely block seats on quiet flights. For weight and balance purposes. It's nothing to do with cleaning or a quicker turnaround.

[Riccal]

Thanks for that everyone. Whilst I would never argue with CC telling me I couldnt sit in a particular seat I had always felt a bit miffed on being forced into sharing rows when there were enough empty seats to have a bit more room. I will view this differently from now on.

Cheers

[TightSlot]

I believe that the 737-800 (as used by FR) is especially critical on trim in a hi-density config.

That said, my understanding is that once airborne, the aircraft effectively trims itself, and therefore seat changes should be available - there may be a requirement to return to allocated seats for landing however.

[OFSO]

That said, my understanding is that once airborne, the aircraft effectively trims itself, and therefore seat changes should be available - there may be a requirement to return to allocated seats for landing however.

Please note that from 1st January 2009 an extra charge of 5 pounds/euros will be levied per passenger on all Ryanair flights on each movement of seat forward (towards the sharp end) and a deduction of 2 pounds/eurs per passenger on each movement rearwards (towards the blunt end).

RaF

[Contacttower]

Do airliners have different weight and balance limits for take-off and cruise?

[richardnei]

The blocking off, of seats is to ensure the aircraft remains in trim. For flights that have allocated seating, check-in staff would be restricted to the number passengers that can sit in different areas of the aircraft to enure it remains in trim.

Once airbourne you would be free to move seats but may have to return to your allocated seat for landing.

It's always going to be on flights that have a free seating policy that your goin to see the blocking off, of seats if the flights isn't full.

[TightSlot]

Do airliners have different weight and balance limits for take-off and cruise?
The aircraft has to be balanced (trimmed) throughout flight. Once in the cruise, if you think about it there is a constant shifting of weight around the centre of gravity - people walk up and down to the loo's, FA's push heavy carts, toilet tanks become full and potable water tanks empty etc. etc. This all compensated for by the aircraft automatically adjusting the trim.

At the point of take-off, where the aircraft transitions from being supported by the gear to being supported by lift, the crew have to know in advance that the aircraft is within a calculated balance range for safe flight.

I've probably used some incorrect technical terms here, but the broad concept is about correct, I believe - if not, then I'll stand to be corrected

[Contacttower]

I've probably used some incorrect technical terms here, but the broad concept is about correct, I believe - if not, then I'll stand to be corrected

Essentially what I was wondering was is it just a trim issue or is it actually to do with staying within the weight and balance envelope - the light aircraft I fly have a fixed envelope that is the same for all phases of flight....but it is possible that airliners have an envelope that expands after take off to allow a greater range of weight distribution?

[Final 3 Greens]

Contacttower

I am a PPL like you, so don't know the answer.

However, I'd speculate about the effect of the differential speed on the control surfaces when operating at cruise speeds (say 350kias) versus 150ish for take off/approach.

Logic would say this would give you more control (and trim) authority, but I'm just speculating.

[ambasador]

The envelope remains the same throughout.. that's why you work out the ZFW and TOW within the envelope.

I've done weight and balance on B737/747/767/777 and some smaller AC... the concept of W and B remains the same regardless of what aircraft it is ... each aircraft has it's envelope and the balance needs to be within that on both zero-fuel-weight and take-off-weight. There are indexes given as max and min limits - this counts for take off or landing - in other words the balance will remain within the envelope if the ZFW and TOW is within - ie: during flight.

So during flight, as the fuel is used and the CG (centre of gravity) shifts - the A/C will trim itself automatically.

so yes - for take off the seating play a very important role in the calculations for balance and finding the CG. (As or frind earlier pointed out - it depends on the size of the aircraft)

A smaller aircraft like the 30 seater communters/props have an issue if only one seat is changed before takeoff as it could affect the trim radically - but a larger 80+ seater for example will not have as big effect. So to make sure not too many people move around - they keep you in your seat to guarantee the trim calculations etc.

[Contacttower]

Just out of interest ambasador do airliners have left and right weight limits as well as fore and aft?

[AMEandPPL]

do airliners have left and right weight limits as well as fore and aft?

As far as I know the answer is an emphatic "no" ! The distances involved, and the proportions between them just would not allow a significant shift to occur.

Take worst case, ALL passengers on a commercial plane move to one side of the aisle. . . . distance might be ten feet. But lift is still being generated by one hundred feet of wing on each side.

If any professionals know better, I do, of course, stand to be corrected !

[Harry Lime]

With pax moving left or right within the cabin, there is very little change of 'Moment'. Now consider a four engined aeroplane with one engine shut down, - any one, and think how you would manage the fuel panel. Tonnes of fuel are in the wing tanks and the 'moments' most certainly have to be taken into consideration.

As I recall, I have been retired for nearly eight years now, but on a 747 there was no guidance for lateral weight balance in the Checklist or Flight Manual as I can remember, actual limits. My previous experience on C-130s in the military which did give guidance on inter-wing balance gave me suitable knowledge of how to handle the situation when it happened to me on a flight from LHR to HRE "one dark and dirty night in 1996!

It doesn't take 'rocket science', but as an exercise how would you 'Fuel balance' for the remainder of a ten hour sector, assuming the problem occured three hours into the flight.

[flyin_phil]

coming back from Istanbul on BA677 on 14th dec, was a 767 aircraft butonly 44 pax on the flight. what i thought was strange as they opened all the seats in the rear and had to leave the forward section empty for the weight balance on take-off, even for an ex baggage handler this confused me thinking they put all the weight at the back, wouldnt that unbalance it? then i guessed they did it because they put all the cargo in the forward hold? would that make sense? the crew were fantastic, didnt use the tannoy to tell about our seating cause we were all at the back, very nice and entertaining crew. The sccm told us we were free to move after take off, but i stayed where i was, had the nice exit seat behind wing. it was nice relaxing flight and basically had 1 person per row almost.
so am i right in thinking having the pax at rear on take off because the cargo is in the front hold?

[PAXboy]

Non pilot speaking. A possible reason for flyin_phil's flight to have the few pax at the back is because the fuel is basically across the centre of the machine in the wings and a centre tack. So they would want to counterbalance with pax down the back? I sit to be corrected.

[dwshimoda]

Paxboy - sit down! (sorry - but you asked!)

I don't know for this aircraft, but for the B757 I fly, the centre and wing tanks are based pretty much around the C of G, so as the fuel is used, the C of G change is minimal.

Flyin_phil is most likely right - there may be all sorts of cargo in the holds that you aren't aware of, and may weigh much, much more than the pax load.

It also may make it easier for the CC to look after everyone if all 44 pax are in one place as opposed to all over the aircraft - as long as M & B isn't compromised.

Hope this helps.

DW.

[Friendly Dispatcher]

You'll find most scheduled flights with assigned seating will have particular seating restrictions when the flights are not full.

I can't comment on the particular 767 query, as I have little experience with them, though 40 people sitting upfront in an empty 767 may have put it out of trim, maybe not. In my experience we'll generally start loading cargo in the rear unless the aircraft is particularly tail heavy, rather than the front so not sure about that possibility, unless it's BA specific.

Who knows, but yes blocking off rows for weight and balance is a valid reason. Might seem hard to believe, but take the first three rows on Ryanair or easyJet, 18 seats, average of 76kg per person = 1368kg. It all starts to add up, especially when there is very little towards the rear to counteract it.

[The Real Slim Shady]

And on the 737 you have 4+ tonnes of engine ahead of the C of G.

[ambasador]

Remember alot of the weight on the aircraft is fuel.. so on a B767, my guess would be, yes, that there was alot of cargo in the forward hold, and/or that the amount of fuel onbaord required more weight in the back to move the center of gravity and get the a/c balanced.

I stand corrected, but I as far I can remember, there is not left/right balance. The fuel loading is the main factor here with the amount of fuel in each wing - but pax are right in the middle of the vessel, having so little movement to play with between left and right weight. I'm not a pilot, but if I am right, the x-feed would be used to correct an imbalance between left and right tanks...

[LH2]

As dwshimoda has said, the wing fuel has a short moment arm around the CG limits on most aircraft, precisely to minimise the amount of trimming needed as fuel burns.

All other things being equal, an aft CoG is preferrable for fuel consumption and stability/handling reasons, so it could be that the Istanbul 767 mentioned earlier had few passenegers and little cargo.

[aviatordom]

This happened to me once whilst on a FR flight back in '06.

Whilst boarding, we noticed that a good few rows were blocked off with tray tables down.

So, yes, the 738 does suffer from it as it's obviously a narrow-body and quite long. :ok:

[Seat62K]

With Ryanair isn't it also something to do with where passengers' luggage is loaded? (I seem to recall reading this somewhere - on PPRuNe?).
I'm surprised that Ryanair sometimes also blocks off rows when the aircraft is really quite full. Once or twice I've seen Ryanair flight deck crew permit passengers who've complained to use blocked off seats.

[Abusing_the_sky]

Once or twice I've seen Ryanair flight deck crew permit passengers who've complained to use blocked off seats.

Since when do F/D crew do the boarding? :}

I'm surprised that Ryanair sometimes also blocks off rows when the aircraft is really quite full

This is what we call Rule 1. When the load is 177 pax or less (capacity as i'm sure you know is 189, so it would be a quite full flight), we block off rows 3 and 4 for take off and landing. During cruise pax are free to sit there should they chose to. Hope this helps.

Rgds,
ATS

[Seat62K]

Thanks, ATS.

I sit at the back - except when travelling to Madrid - usually in row 32 (or 33 now that my hand luggage can be stored under the seat), and have noticed rear rows blocked off when aircraft seem to be as full as you describe.

As far as flight deck crew allowing passengers to occupy blocked off rows is concerned, I've seen this twice. On one occasion, a flight attendant went forward to the flight deck and returned with permission; on the second, a member of the flight deck crew actually came aft.

[LH2]

Keep in mind that some of the destinations RYR flies to are performance limited, meaning that you will never seen a full plane going to those places, regardless of demand.