embrider
Topic Author
Posts: 21
Joined: Fri Mar 26, 2010 10:17 pm

Weight Difference Between Early And Late Frames

Tue Sep 27, 2011 12:35 pm

I read all the time that for a certain new aircraft- 787 for exemple- the first frames are ^heavy^and some weight loss and consequent performance improvement is expected for future frames. How does this "weight loss" happen? What parts/component loose weight and why this can not happen in the first frames? What is the magnitude of weight loss, 0.5%, 2% 5%?
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Weight Difference Between Early And Late Frames

Tue Sep 27, 2011 2:01 pm

Quoting embrider (Thread starter):
How does this "weight loss" happen? What parts/component loose weight and why this can not happen in the first frames?

Mostly redesign of structural components and cleaning up systems. That takes time and data, both of which you don't have when you build the first frames. You may discover that this rib is 2% stronger than it needs to be and you can take this material away, or that you put three fans in this cooling system but it's performance is better than you thought and you only really need two.

In some cases, there may also be provisions for system modifications that you think you might need (e.g. Rolls Royce originally had a clutch between two of the spools on the Trent 1000 but it turned out it wasn't required). Once you have the data to know if you need that system or not, you can get rid of the system and the provisions that were supporting the option.

There's no inherent technical reason you can't refit earlier frames with weight-saving modifications after they're built but, in the case of big structural changes, it's economically prohibitive.

Quoting embrider (Thread starter):
What is the magnitude of weight loss, 0.5%, 2% 5%?

As much as you can get away with...weight is everything.

Tom.
 
User avatar
lightsaber
Crew
Posts: 12041
Joined: Wed Jan 19, 2005 10:55 pm

RE: Weight Difference Between Early And Late Frames

Tue Sep 27, 2011 2:25 pm

Quoting tdscanuck (Reply 1):
As much as you can get away with...weight is everything.

Yep. About $500 per kg. For every kilogram removed, the sales value of the airframe increases.

Weight removed is added payload (assuming same MTOW, MZFW, and MLW) or free range.

Quoting tdscanuck (Reply 1):
There's no inherent technical reason you can't refit earlier frames with weight-saving modifications after they're built but, in the case of big structural changes, it's economically prohibitive.

   I've seen it done for easy changes and special cases, but the trade is always cost per pound removed. The older the airframe, the less likely money will be spent due to the shorter expected flying life.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
lhcvg
Posts: 1255
Joined: Mon May 25, 2009 2:53 pm

RE: Weight Difference Between Early And Late Frames

Tue Sep 27, 2011 2:36 pm

This even happens in cars all the time. In addition to incremental, year over year changes, don't forget the mid-lifecycle "refresh" where they institute a number of changes of varying degrees at once, creating in effect a "model 1.5".
 
embrider
Topic Author
Posts: 21
Joined: Fri Mar 26, 2010 10:17 pm

RE: Weight Difference Between Early And Late Frames

Wed Sep 28, 2011 2:47 am

This is all very informative; Thank you
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Weight Difference Between Early And Late Frames

Wed Sep 28, 2011 3:02 am

Quoting lightsaber (Reply 2):
Yep. About $500 per kg.

It's come down then...I thought it used to be about $500/lb.

Tom.

[Edited 2011-09-27 20:03:06]

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos