horstroad From Germany, joined Apr 2010, 188 posts, RR: 0 Posted (6 months 5 days 3 hours ago) and read 2954 times:
besides the obvious things like the wings or the engines, what is actually new?
to me the -8 is just a 50 year old (stretched) airframe with new engines and wings.
well, I know of the RAT, some improvements in the cockpit and the new flaps, but what else is essentially new?
have there been changes to the hydraulics, fuel, electrics, landing gear, flight controls, air conditioning, ... ?
are the wings completely new from the scratch or just improved? is it just me or does the horizontal stabilizer look different, too?
is there any website or PDF that lists all changes from the -400 to the -8?
ak907 From United States of America, joined Mar 2012, 35 posts, RR: 0 Reply 3, posted (6 months 5 days ago) and read 2958 times:
That PDF is good, but I believe it also has a new APU, new ACM's that are much quiter, landing gear doors are a little different, ACM cooling overboard vents are different. Freighter has updated cargo handling system, which includes more rollers and locks, more PDU's, and new PDU control system from Telair. But even then the whole cargo system is lighter than the 747F's. There are also dampeners for the cargo side rails on the maindeck near the wing area because of the fuselage flexing during flight. That's all I can think of right now.
Regarding the 747-8 bleed system and ACMs, I'm pretty sure Boeing stole a page from Airbus' playbook and had the new system provided by Liebherr - a traditionally Airbus supplier. I believe this was the first time Boeing has ever done business with Liebherr.
As to the main question being asked, Boeing claims 70% of the systems content and nearly 70% of the structure on the 748 is new compaerd to the 747-400.
AA737-823 From United States of America, joined Mar 2000, 5334 posts, RR: 11 Reply 5, posted (6 months 1 day 21 hours ago) and read 2957 times:
Many of the systems on the 747 are reliable, time-proven, safe systems that don't require much in the way of updates.
What's the point of updating the hydraulic system? You've got pumps, fluid, tubes, and actuators... what is there to really improve? You can replace components with lighter-weight options, but there's no need to wait for the debut of a new variant (in this case, the -8) to do that.
Yes, the design of the airframe itself is several decades old, but that doesn't really matter, either. A metal tube is a metal tube- the advances we've made in that area have been incremental improvements, rather than order-of-magnitude changes.
Similarly, the A330/A340 fuselage bears quite some design similarity to the 50-year-old A300 (I know the A300 isn't fifty, but neither is the 747, so hey...). Why change it? It works.
bikerthai From United States of America, joined Apr 2010, 1588 posts, RR: 4 Reply 6, posted (6 months 7 hours ago) and read 2954 times:
Quoting AA737-823 (Reply 5): You've got pumps, fluid, tubes, and actuators... what is there to really improve? You can replace components with lighter-weight options, but there's no need to wait for the debut of a new variant (in this case, the -8) to do that.
When you are talking about systems that are 40 or even 20 years old, you have to contend with diminishing supplier. Say you got a pump that was designed 20 years ago. You can ask the supplier to build the same pump for you even though the supplier have moved on to other pumps that may be of better design (new materials and manufacturing processes). The supplier will charge you a hefty penny because they are not making many of the old pump any more.
As for waiting for a new variant . . . even though newer/lighter components becomes available over the life of an airframe, unless the savings is really significant, you usually want to wait for a block point, minor model or variant change in the airframe to incorporate these new components. The cost of drawing changes up to the installation drawings, along with certification cost, makes it more cost effective to wait for these major re-design where you can get all the changes rolled in at one time.
747classic From Netherlands, joined Aug 2009, 1779 posts, RR: 11 Reply 7, posted (6 months 5 hours ago) and read 2954 times:
Quoting AA737-823 (Reply 5): What's the point of updating the hydraulic system? You've got pumps, fluid, tubes, and actuators... what is there to really improve?
Quoting bikerthai (Reply 6): When you are talking about systems that are 40 or even 20 years old, you have to contend with diminishing supplier. Say you got a pump that was designed 20 years ago
In this particular example IMHO you both are not correct.
The 747-8 hydraulic system had to be changed, because of the higher demand of the new actuators, caused by Increased operating weights with the same maneuverability.(higher wing loads).
As a consequence all 8 hydraulic pumps (4xEDP and 4xADP) had to be changed to a higher capacity variant. For (maintenance) cost saving reasons the 777 pumps were selected.
However these changes caused a lot of problems during the test-flight program, because an "iron bird "was not used to test the adapted hydraulic system to keep the costs down.
During flight testing a low speed aileron vibration popped up when applying full aileron. This was caused by the dimensions of the piping and the new aileron actuator, together with the higher flow rates. The actuator and piping was finally modified to cure the problem, but at considerable extra test-flight time and a lot of extra money
bikerthai From United States of America, joined Apr 2010, 1588 posts, RR: 4 Reply 8, posted (6 months 2 hours ago) and read 2954 times:
Quoting 747classic (Reply 7): As a consequence all 8 hydraulic pumps (4xEDP and 4xADP) had to be changed to a higher capacity variant. For (maintenance) cost saving reasons the 777 pumps were selected.
However these changes caused a lot of problems during the test-flight program, because an "iron bird "was not used to test the adapted hydraulic system to keep the costs down.
Been there . . . done that. We made a design change hoping to get some weight saving. The new design didn't work out so well and we had to go back. The principle is the same. You target a block point to make a change. Unfortunately sometimes we don't execute as we should and thus take a step backward.
B777LRF From Luxembourg, joined Nov 2008, 998 posts, RR: 3 Reply 9, posted (5 months 4 weeks 1 day 6 hours ago) and read 2840 times:
If you ask what Boeing told the FAA it was probably along the lines of "not a lot of changes, basically the same aircraft, can we have grandfather rights please?", but when talking to their customers it was more along the lines of "brand new everything". The truth is, I suspect, somewhere in the middle.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
CM From , joined Dec 1969, posts, RR: Reply 10, posted (5 months 4 weeks 1 day 5 hours ago) and read 2817 times:
Quoting B777LRF (Reply 9): If you ask what Boeing told the FAA it was probably along the lines of "not a lot of changes, basically the same aircraft, can we have grandfather rights please?", but when talking to their customers it was more along the lines of "brand new everything". The truth is, I suspect, somewhere in the middle.
Absolutely. Boeing not only completely deceived the FAA in the cert process, they are now out lying to potential operators in an effort to sell the airplane. Somehow, nobody at the ACO office of the FAA has been sharp enough to pick up on this, despite the fact it's their job to understand and verify compliance for every detail of the changes. As for deceiving the airlines, that part was easy; the evaluation teams at LH, CX and a host of other top-tier operators were easy to fool, as they basically know nothing about airplanes.
Sheesh! Do people even listen to what they are saying? Seriously, try to write something sensible next time. At a minimum, leave out the unfounded accusations of criminal behavior.
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