CF188A From , joined Dec 1969, posts, RR: Posted (6 years 3 months 1 week 5 days 14 hours ago) and read 2943 times:
Apologies if already posted under a different title. I did a search and scanned recent threads so apologies if this has been posted. I thought it was quite interesting . Nothing out of the ordinary (info wise) , for those who read these forums daily. However just being in the aircraft (video wise) , and really getting the idea of its massive structure... I thought was pretty cool. Thought I would share
Racercoup From United States of America, joined Jan 2007, 89 posts, RR: 0 Reply 1, posted (6 years 3 months 1 week 5 days 14 hours ago) and read 2904 times:
An interesting quote concerning that media flight.....in the International Herald Tribune.
"Richard Aboulafia, an aircraft analyst at the Teal Group in Fairfax, Virginia, said the slogan for the flight could have been, "Come see the future, as it once was." He predicted that Airbus would sell only 300 of the planes; Leahy said sales would be between 800 and 900".
Gbfra From Germany, joined Sep 2006, 448 posts, RR: 1 Reply 3, posted (6 years 3 months 1 week 5 days 7 hours ago) and read 2584 times:
Well, Aboulafia was not on board. At least, I didn't see him there.
(Just for the record: Aboulafia was co-author of a very critical study of the A380, which was published in 2004. There's of course nothing wrong with critical studies in general, but there was a serious problem with this one: It was financed by Boeing.)
Lostturttle From Bermuda, joined Dec 2006, 140 posts, RR: 0 Reply 4, posted (6 years 3 months 1 week 5 days 4 hours ago) and read 2439 times:
What I still find amazing is the amount of wing flex the A380 has, especially on that bumpy landing! Still, I look forward to seeing the "Whalejet" soon, and maybe even flying on it.
Racercoup From United States of America, joined Jan 2007, 89 posts, RR: 0 Reply 5, posted (6 years 3 months 1 week 5 days 4 hours ago) and read 2420 times:
Quoting Gbfra (Reply 3): Well, Aboulafia was not on board. At least, I didn't see him there.
(Just for the record: Aboulafia was co-author of a very critical study of the A380, which was published in 2004. There's of course nothing wrong with critical studies in general, but there was a serious problem with this one: It was financed by Boeing.)
Never said he was aboard........and just because Boeing financed the study doesn't mean it was distorted, most of what I've read seems to make sense. Also Airbus has changed expected sales figures and breakeven estimates so often I certainly don't trust their estimates.........
KFLLCFII From United States of America, joined Sep 2004, 3262 posts, RR: 33 Reply 8, posted (6 years 3 months 1 week 5 days ago) and read 2277 times:
Quoting Lnglive1011yyz (Reply 7): Quoting LASOctoberB6 (Reply 6):
i find it very odd that the A380 will only use two engines for reversers, not all four. it actually kinda bugs me....
Why?
I'll answer that...For safety.
Considering that 4 out of the 20 main landing gear wheels on the A380 don't even have brakes, you would have thought they'd devise a way to utilize outboard reversers, perhaps in a manner that only blew in a certain direction to prevent FOD kick-up. (Or simply added brakes to the four remaining wheels.)
Why?
Because you've got an aircraft that is potentially heavier than a 747 on landing, utilizing the same amount of ground surface area for stopping power as the 747 (16 wheels), while only being able to use half its available thrust for reverse power (vs. the 747 being able to use all of its available thrust for reverse power). In other words, for an aircraft approximately 1/3 heavier than a fully-loaded 747 at worst-case scenario, it has less total power to stop within the same distance as the 747 does at 1/3 less weight. (Even taking into consideration the fact that the A380's engines are more powerful than the 747's, the A380 still comes away with less total reverse thrust with two engines than the 747 with four. Do the math.)
Safe?
Or only the bare minimum for certification?
You be the judge.
"About the only way to look at it, just a pity you are not POTUS KFLLCFII, seems as if we would all be better off."
CirrusDriver From United States of America, joined Nov 2006, 141 posts, RR: 0 Reply 9, posted (6 years 3 months 1 week 5 days ago) and read 2257 times:
CirrusDriver From United States of America, joined Nov 2006, 141 posts, RR: 0 Reply 10, posted (6 years 3 months 1 week 5 days ago) and read 2232 times:
As far as the reverse thrust, I thought I read somewhere that the reason for the inboards only was because of how the wings would overhang the runways at some airports and kick up a massive cloud of debris. This design would allow the A380 into more airports. Very, very possible that I am only immagioning things
WingedMigrator From United States of America, joined Oct 2005, 2025 posts, RR: 56 Reply 11, posted (6 years 3 months 1 week 4 days 23 hours ago) and read 2184 times:
KFLLCFII From United States of America, joined Sep 2004, 3262 posts, RR: 33 Reply 12, posted (6 years 3 months 1 week 4 days 21 hours ago) and read 2144 times:
Quoting WingedMigrator (Reply 11): considering that takeoff and landing speeds are about 85% that of a 747.
...To which the 747-400 has an approximately 30% greater amount of available reverse thrust for only a 15% increase in landing speed. Not to mention the fact that at max gross, it's about a third lighter than the A380.
So I ask again:
Is it safe?
Or is it only the bare minimum for certification?
"About the only way to look at it, just a pity you are not POTUS KFLLCFII, seems as if we would all be better off."
EI321 From Iraq, joined Jul 2009, 0 posts, RR: 0 Reply 13, posted (6 years 3 months 1 week 4 days 18 hours ago) and read 2013 times:
Quoting KFLLCFII (Reply 8): Considering that 4 out of the 20 main landing gear wheels on the A380 don't even have brakes
Maybe the A380s brakes are more powerful than those on the 747, so I needs less stopping power from the thrust reversers.
Quoting KFLLCFII (Reply 12): ...To which the 747-400 has an approximately 30% greater amount of available reverse thrust for only a 15% increase in landing speed. Not to mention the fact that at max gross, it's about a third lighter than the A380.
Now im no expert in reverse thrusters, but are you assuming the engines max power in your calculations, can thrust reversers use the engines max power?
KFLLCFII From United States of America, joined Sep 2004, 3262 posts, RR: 33 Reply 14, posted (6 years 3 months 1 week 4 days 17 hours ago) and read 1976 times:
Quote:
Taking into consideration that reverse thrust is often barely used and in some place even forbidden.
Exactly one of my original points:
Quoting KFLLCFII (Reply 8): Or simply added brakes to the four remaining wheels.
There are 4 extra main landing gear wheels that don't utilize brakes. Why didn't they simply add the four wheels into the braking system now, rather than wait for the freighter version? Especially knowing full well that what you said is true. Sounds like they cut everything down that they could during development for the bottom line.
Quoting EI321 (Reply 14): Quoting KFLLCFII (Reply 8):
Considering that 4 out of the 20 main landing gear wheels on the A380 don't even have brakes
Maybe the A380s brakes are more powerful than those on the 747, so I needs less stopping power from the thrust reversers.
Brakes on 16 wheels can only be so powerful until the wheels simply lock up. And that, of course, is controlled by the anti-skid system. But if you add four more wheels providing stopping power into the equation, it's that many more providing useful stopping power up until they all reach the threshold for lock-up.
Quoting EI321 (Reply 14): Now im no expert in reverse thrusters, but are you assuming the engines max power in your calculations
No, hence why it's listed in terms of a percentage of available reverse thrust, not total thrust.
[Edited 2007-02-13 12:04:58]
"About the only way to look at it, just a pity you are not POTUS KFLLCFII, seems as if we would all be better off."
Scouseflyer From United Kingdom, joined Apr 2006, 3254 posts, RR: 10 Reply 15, posted (6 years 3 months 1 week 4 days 16 hours ago) and read 1900 times:
Quoting KFLLCFII (Reply 12): To which the 747-400 has an approximately 30% greater amount of available reverse thrust for only a 15% increase in landing speed
Except isn't kinetic energy dependant on the square of the velocity?
As a very rough example we have a 1 kilo object travelling at 100 m/s (our 747) this would have a KE of
0.5 *(100*100)*1 = 5 000 J
for the "A380" say it's 1.4 times the mass of the 747 but lands at 85 m/s:
0.5*(85*85)*1.4 = 5057 J
So that's very slightly more energy with the same braking power (from the brakes) - it's not weight or speed that's important but a combination of the two....
Sebolino From France, joined May 2001, 3667 posts, RR: 5 Reply 16, posted (6 years 3 months 1 week 4 days 16 hours ago) and read 1887 times:
Quoting KFLLCFII (Reply 12): ...To which the 747-400 has an approximately 30% greater amount of available reverse thrust for only a 15% increase in landing speed. Not to mention the fact that at max gross, it's about a third lighter than the A380.
So I ask again:
Is it safe?
15% decrease in landing speed, means 28% less kinetic energy to dissipate.
Wingman From Trinidad and Tobago, joined May 1999, 1838 posts, RR: 5 Reply 17, posted (6 years 3 months 1 week 4 days 15 hours ago) and read 1806 times:
Wingman From Trinidad and Tobago, joined May 1999, 1838 posts, RR: 5 Reply 18, posted (6 years 3 months 1 week 4 days 15 hours ago) and read 1806 times:
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