P and L Question

[Paul Alfred]

Hey guys

First of all Happy New Year....I've got performance again on the eleventh
After missing out by a few percent the first time.....felt confident pressing
The submit button but obviously didn't know my content well enough.

Can you have pax and a bolted item under the seat if 87kgs is not exceeded?

Another one was full tanks and what would be the most forward cg position during the first 6000kgs of burn twenty degree flap

Cheers
PA

[Arnold E]

Another one was full tanks and what would be the most forward cg position during the first 6000kgs of burn twenty degree flap

On a 747 SP!

[john_tullamarine]

Can't speak to what the examiners might want these days as I am too far removed from theory training. However, a couple of observations for the real world.

Can you have pax and a bolted item under the seat if 87kgs is not exceeded?

Seat design addresses a standard weight plus seat weight and, often, includes provision for underseat baggage which is restrained by seat structure.

If you are looking at loading both the seat and the floor underneath the seat, that would require knowledge of the seat and aircraft design.

If guidance is not provided you would start with the standard occupant weight for the seat design plus the weight of the seat (plus the weight of permitted underseat baggage, if relevant).

Another one was full tanks and what would be the most forward cg position during the first 6000kgs of burn twenty degree flap

Be aware that most larger (and many smaller) aircraft have convoluted fuel trim lines which are often approximated for pilot loading calculations. As a consequence one needs to be a bit careful when pontificating on what happens to the loaded CG with fuel use.

[Steve888]

I'm assuming you mean ATPL performance and therefore are talking about the B727 for which I happen to have the weight and balance booklet right next to me.

On page 6, under 'Configuration Notes' paragraph E it states:
Unless special authorisation is issued, a load of 87 kg per seat must not be exceeded. This means if the item is bolted under a seat that seat cannot carry a passenger.

I would interpret this to mean any weight item under the seat, even if it's say 10kgs and the seat is carrying a child. But someone with more knowledge of the exam itself may have a different opinion (note I haven't done the exam yet but I'm nearing the end of my study for it).

I'm not 100% sure what you mean by your second question, so I'm going to guess you mean how the CG moves when burning off the first 6000 kgs of fuel with full tanks.

Again, in the 727 WB booklet, page 10 gives the fuel usage details. With full tanks you would have fuel in both the forward and aft aux tanks.

The booklet states to first burn fuel from tank 2 until not less than 3629 kgs has been used.

Then, the forward aux tank is burnt dry, then the aft aux tank, then return to tank 2 until fuel in tanks 1, 2 and 3 are equal, then operate tank to engine.

The work out the CG movement during this, the tip I got from the AFT notes was to turn the trim sheet on its side so the left side is now the top. Then, use the lines on the fuel loading curve to work out the CG movement, imagining the left side of the box is a forward movement, and the right side is an aft movement.

So, the movement's when burning the first 6000 kgs of fuel is:

Aft (as 3629 kgs is burnt from tank 2)
Aft (as the forward aux tank is burnt)After this, the movement is:

Forward (as the aft aux tank is burnt)
Aft (as more of tank 2 is burnt to equalise tanks)
Forward (as the tip tanks of the mains are burnt)
Aft (as the mains burn)Hope this helps with your study as it's helping concrete it my mind as well.

[Paul Alfred]

Thanks for the responses....really appreciate your time and help.

Regards

PA