Originally Posted by 18-Wheeler
Apart from the tail section not fitting to the rear fuselage when first mated.
The 747-8 has had problems with all the new to old section joins, that is what you get when you design something on paper 40+ years ago and then design updates with higher tolerances on CATIA. A lot of shims were needed to join the 747-8 together.
Originally Posted by 18-Wheeler
Oh and the 380 centre wing section failing the 150% load test on the first try, requiring design changes and patches on aeroplanes already built.
The wing that failed on MSN5000 a few percent below 150% was not the same standard as what was installed on MSN001. I am not aware of any problem with the "centre wing section". The failure on MSN5000 occurred between the inboard and outboard engine at 147% of the limit load. The design requirement is to hold 150% for 3 seconds.
In comparison the wing on the C-17 failed at 124%, and the wing on the 787 also failed in the 120-130% range. The 747-8 wing will not be tested, we know of a number of examples of 747 having inadequate design margins, I can think of two incidents where 747s lost engines in flight due to turbulence as side that were not accounted for. The “new”: 747-8 wing is “grandfathered” off this same 40+ year old design.
Originally Posted by Going Boeing
A380-800 driver, you conveniently left out the comparison of the Basic Operating weight of each aircraft type as that would give a true indication of the potential payload.
That is a useless metric, comparing the OEW numbers for the 747-8i to the A380-800 is a stacked deck, it does not take a genius to realise that an interior for 100+ less seats is going to be lighter.
The "green" A380 has a weight MEW/MWE of 243,200 kg, add the interior to the various between operators to make the OEW around the 280,000-290,000 kg mark. Compare a green A380 to a green 747-8i, and the MEW/MWE ratio to the MZFW would surprise you. Put the same interior standard in the 747-8 as what airlines are installing in the A380 (not the Boeing marketing numbers which use a seat pitch of 61” in first and 39” in business, no crew rest, and not enough galleys and toilets for todays service standards) and the OEW of the 747-8i is much higher that what is being projected by Boeing marketing.
Originally Posted by Going Boeing
in comparison, the B747-8 wing/fuselage is designed/optimised for the current version, ie they will not be carrying around any excess weight (probably in excess of 100 tonnes) and thus will almost certainly have better fuel/payload/kilometre figures. Some people deride the B747-8 as being old technology but as it has an entirely new wing, partial fly-by-wire controls, GENX engines & associated systems etc, I believe that its operational performance will stack up very competitively with the A380.
Boeing have conceded that the wing on the 747-8 is not as optimised as it should be. It has kept the same sweep, planform and the location of the structure (inc engine spanwise location) as the 747 classic. It has retwisted and relofted the wing section and added the raked wingtip. This is inefficient for modern supercritical wing section, it should have a higher aspect ratio and lower sweep, and engines in different positions for the bow wave change.
Additionally the GEnx was not optimised for the 747-8, they made it work, but it does not have the same propulsive efficiency as the engine on the 787 due to the smaller fan size and the engine inlet had to be redesigned to the increased operating speed. It does not have the same thermal efficiency due as the engine is not being bleedless. It is also larger with more wetted area, hence drag rise.
What you have also neglected to mention is the advances that both RR and EA have brought to the table since they both flew their A380 engines, both have reduced their TSFC down a few percent leveraging technology from the GEnx/Trent 1000 for the 787 and are still improving. The A380 is also dropping a couple more tonne as more GLARE is being used on the fuselage after MSN024.
The 747-8 has lost its propulsive competitive advantage by being so late. Boeings original business plan had 60% of the 747-8 sales as being passenger models, the market has responded with years of silence with no further passenger sales since LH ( know about the handful of VIP aircraft)
My understanding is they only aspect of the 747-8 that is FBW is the spoilers, none of the primary flight controls, they remain they same conventional control system as found on the 747-400 with 80% parts commonalty with the 747-400.
Originally Posted by stillalbatross
Of course the 747-8 will be on schedule, it's just a couple of plugs and a pair of winglets, how hard can that be?
The 747-8 is already well late as well. At this stage the "simple" derivative looks like it may exceed the 18 months the A380 was late getting to SQ. Some customers are now looking at walking away from their 747-8 commitments as the airframe has now exceeded the 12 month delayed barrier, and they can cancel without penalty.
This was the original 747-8 plan.
The 747 was a magic girl, but the sun is going down on her.