View Full Version : 737 weight and balance

Dick Fisher
3rd Dec 2006, 16:35
My wife and I have flown several times this year with Ryanair on one of their 737-800's from East Midlands to Carcassonne.

We've noticed that on a couple of occasions, rows of seats have been left empty at the front and rear of the aircraft, and have been curious as to the reason.

On Friday, someone other than my wife who was travelling on the flight, asked the question of a cabin crew member who responded that it was to "help balance the aircraft".

Now I have been very interested in flying for most of my life and while I can understand that this might be critical in a small 8 to 10 passenger aircraft, I can't believe it makes any difference in a 737 of this size. Otherwise, they would surely be weighing every passenger and every piece of hand luggage stuffed into the overhead bins wouldn't they?

I'd be very interested to know what other reasons there might be or whether in fact, I've been wrong for all these years!

3rd Dec 2006, 18:31
Yes it is as she/he said, it helps balancing the aircraft. It is called Rule 1 or Rule 2, depends on how many pax there are and what result u want. blocking certain rows make u widen the CoG limits (front e back limits) just a little, to allow you to accept a ZFW calculated limit and not unload or move baggages or load ballast.Remember that even if a pax is considered 80 kgs without a luggage (93 before checking) depends how far he sits from the CoG to determine what influence he has on the overall aircraft balance.
i hope i have been helpfull,
best regards,
Damiano 738 FO

3rd Dec 2006, 22:02
Interesting to note that the CAA now make a point in CAP's realting to Mass and Balance that 'free seating' can lead to excessive or significant variations in CoG. Especially for pax loads of 50-100 allowed to all sit at the front or rear of the aircraft. This also applies to re-distribution of pax during flight. In such cases where pax are re-distributed or move themselves, cabin crew should advise the crew so that they are aware or a CoG shift. Also worthy of note that it tends to be advantagous to plax pax as far aft as is allowed to get the CoG towards the aft limits. This reduces the amouts of stab trim required and hence drag and fuel burn.