Seeking information about structure weights of aircraft, especially airliners

A further thought towards making an approximation to structure weight:
Structure weight = empty weight – (weight x number of engines) – (weight x number of seats)

Presumably engine weights are published, and a standard weight could be used for all seats?

Is there anything else substantial that should be deducted from the empty weight to get structure weight only? Older aircraft tend to have removable fuel tanks, whereas more modern aircraft have the tanks as part of the structure, so not sure how to handle that.

Thanks for any comments on these.

Iain.

Iain, perhaps an email to Boeing and/or Airbus might be fruitful. I have no compunction asking questions like that, they can only say yay or nay. I will ask them for you.

That would be kind, thanks. The only online contacts for both are the press office/media centre and I have e-mailed at least one of these in the past and got no response, not even a yay or nay.

I thought Boeing would have been keen to push the 787 being the lightest strongest airframe (if such it is) as they made so much of the composite construction.

The comparative sizes between the aircraft is not important, I just want to compare the percentage of weight as structure within each aircraft – is the structural weight percentage getting larger (with size) as theory suggests, or getting less, as the use of more composite would suggest?

Thanks again,

Iain.

The 757 was well known for being overpowered with the Rolls Royce engines on it.

These are closer though, but look at the huge difference in MTOW :

Iain, I will still look for your answer but you’re comparing apples with pears as far as the 757 and 787 are concerned:

Iain, perhaps an email to Boeing and/or Airbus might be fruitful. I have no compunction asking questions like that, they can only say yay or nay. I will ask them for you.

I thought these might have it, but it appears not, it does cover several weight permutations though.

http://www.airbus.com/support/maintenance-engineering/technical-data/aircraft-characteristics/

Thanks for your reply.

Approximation is really what I’m wanting to avoid – unless you can give a reasonable formula for making the approximation!

One aspect I want to get to is the effect that the increasing use of composites has had on structural weights. Presumably they are used to save weight, but how much is that saving? As other weights are published, why not structural weight – it wouldn’t be commercially confidential, would it?

Consider a 757-300 and 787, which are roughly the same size:
757-300 MTO = 272,000, empty = 142,000, so can carry 92% of its empty weight
787 MTO = 502,000, empty = 242,000, so can carry 107% of its empty weight
Presumably that is due to a combination of more powerful engines and lighter structure … but in what proportion? Very tricky to guess!

Thanks,

Iain.

I think you gonna have to calculate those weights using approximation. I have never seen numbers like that published.