JAM747 From United States of America, joined Feb 2005, 550 posts, RR: 1 Posted (7 years 4 months 1 week 2 days 19 hours ago) and read 2207 times:
Boeing has been trying to meet EK in particular need for longer range. Will the 748 use al-li alloys, and if not could more of this or composite materials boost the 748? I think if Boeing could use as much of these materials as economically possible or feasible, it would help the 748 to have longer range and be even more efficient. I believe the 748 sales will pick up especially in the next 2 years and it will perform very well, but wonder if these new materials could be used as a boost to the program. Has anyone heard anything in regards to new materials on the 748?
EI321 From Iraq, joined Jul 2009, 0 posts, RR: 0
Reply 4, posted (7 years 4 months 1 week 2 days 7 hours ago) and read 1836 times:
Quoting JAM747 (Thread starter): Boeing has been trying to meet EK in particular need for longer range. Will the 748 use al-li alloys, and if not could more of this or composite materials boost the 748? I think if Boeing could use as much of these materials as economically possible or feasible, it would help the 748 to have longer range and be even more efficient.
Almost anything that can decrease weight will increase range but not as much as it would increase the development cost.
Its possible that we could see Li-Al on the proposed '777X' that has been mooted lately, if it goes ahead.
Tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 80
Reply 5, posted (7 years 4 months 1 week 1 day 17 hours ago) and read 1634 times:
Quoting LTU932 (Reply 3): Quoting Tdscanuck (Reply 2):
No. Material selection would be considered part of detail design, which is just getting started.
So they can still decide on using lighter alloys and/or more composites for the aircraft? I always thought design freeze means that the materials to use have already been decided.
Design freeze means, basically, the mold lines (external shape) of the aircraft are frozen and the system architectures are known. Detailed design of parts, which would include material selection, comes down the road. Gross material selection options like "is the wing composite or metal?" are typically done by now but things like which composite (and what layup), which alloy, etc. are not. Also, it's normal for development programs to have weight-reduction programs right up to the end. Airplane design doesn't freeze at certification and changes are constantly being made before certification and right on through production.
Design freeze basically says they know what airplane they're going to build in terms of specifications. Detailed design figures out what all the parts actually are, how they're going to be made, and how they'll fit together to realize the design.
A good example of this would be wing ribs on the 787, which were metal through most of the development (and possibly through the first few shipsets) but got switched to CFRP very late in the game.