chornedsnorkackActually, taking the pure thrust you could think of an A380 with three engines.
3x GE90-115 make even a little bit more thrust than the 4x RR Trent 900. But I guess adding a GE90 in the fuselage might be a little difficult.
Four engines have structural advantages for large flexible aircaft. Guess why Boeing started hanging engines under the wing.
What were the engines of MD-XX like? Mind you, MD went for 4 engines on MD-12… though it would be interesting to see a MD-12 quinjet!
However: civilian twins are severely constrained in performance when having 1 engine out. The more engines, the less the performance penalty of losing one of them. Of course, larger number of smaller engines for the same thrust weigh more, burn more fuel and take more maintenance – but for some reason, B-52 is still an octjet and has not been reengined to be a quad or a twin.
Anyway, the outboard engines of a quad are rather far from centerline. Nuisance if an outboard engine fails…
chornedsnorkackYou have to blame in part our aviation industry for making so many mistakes during development of aircraft.
The only real success story was the Vickers Viscount which was developed to meet many airlines needs especially the american market, however, the VC10,Vanguard, Trident were never great sellers as they were tailor made for BOAC and BEA. the makers made a huge mistake in not offering different versions acceptable to other non British airlines. With Concorde, a replacement should have been on the drawing board within 5-10 years of its first commercial service,
There were. Concorde B. ATSF/Alliance.
Yes, Concorde became a little unreliable towards the end of its life and we can all moan or dream for one to fly again, but it wont happen.
I think the main argument here is that the UK along with France had an SST transport in service from 1976 to 2003, and now there is no SST, its as if we have taken a giant leap backwards, I think this is what angers people the most.I think we all have to accept, Concorde will never fly again, and as a previous poster said, ” airbus have more important things to think about than helping to get a concorde flying again.”
There were about as many Tu-144s as Concordes. And the Tu-144s were never as reliable as Concorde at the end of its life.
Well, nearly 20 years after the end of scheduled services, there were enough Tu-144s in good condition to make a return to flight for the NASA supersonic testing.
Why cannot Concordes do the same?
chornedsnorkackSo something new then.
Frankly there would be better things for Beriev to invest their money, I don’t think they would find the market to justify the investment.
The market is supposed to be the Russian Navy.
1000 tons of payload over 10 000 km at 500 km/h or more would compare well with conventional ships (less than 50 km/h). And unlike conventional landplanes like Il-76 or An-124 which require runways, Be-2500 as an amphibian could be unloaded where no airports of adequate size have been built or where such runways are denied by enemy action… It would help projecting force.
chornedsnorkackBe-2500
This
http://forum.keypublishing.co.uk/showthread.php?t=63548
appears to be a Navy initiative, too.
chornedsnorkackAnd can please anyone here explain me who needs an aircraft with more than 100 tons payload for any useful military purpose? Possibly for some out-sized cargo stuff, but that ain’t a market you need to go. Normal civil freighter operations are not the business of C-5 or An-124, they have at least doubled cost per ton-mile.
Most civil freighters are either conversions or versions of passenger airliners. This means that the height of the cargo volume is constrained by the height of a man+overhead bins – roughly 240 cm for widebodies. The rear of a 747 has a bit more height by omitting ceiling and attic otherwise wasted on passenger version – but still not much over 300 cm. Front of 747 and whole A380 have a structurally requires upper deck, so no extra headroom. Also the main decks are structurally needed – cannot remove the deck to join underbelly hold with main deck for extra height. In short, the fuselage cross-section is optimized for passengers, less than optimal for cargo.
Airbus Beluga and Boeing 747-400LCF are narrowly specialized to outsized payloads – again less than optimal.
C-5 and An-124 could be a good compromize to transport moderately large items at a reasonable cost.
chornedsnorkackThe TU154 is not a training aircraft, WD means your average Piper or Cessna (I assume),
Ah, I see. What WD stated above was that only aerobatic aircraft were capable of stable spin…
when you start talking about T tailed & swept wing aircraft you are in a different ball game, T tails are prone to “Deep” stall, which is virtually irrecoverable, the tail is blanketed by the wing wash which destroys the laminar flow making control authority near impossible,
Indeed, they are notorious for this. Like the BAC 1-11 prototype, or the recent Caribbean MD-80 crash where the pilots stalled the plane.
Whereas the “normal” tailed planes ensure that if the main wing stalls, the tail is in clear airflow beneath the wing wash… and turns the airplane to normal, unstalled AoA.
chornedsnorkackCould Lockheed (for example) not buy the plans from Mr Antonov and build the aircraft in the US?
Lockheed has the plans of their own C-5 Galaxy, and L-500 (which the An-124 was based on). Can they deliver more frames of Galaxy? What about upgrades or stretches?
chornedsnorkackAs for a stabilized spin. Other than aerobatic aircraft I don’t think it’s possible to have a stabilized spin in an airplane unless the CG is out of limits. Airplanes are too stable to permit a stable spin.
Then how does a plane come down from FL390 in 3 and half minutes or so? This is roughly 200 km/h… If spin weren´ t stable, you would expect some sort of recovery over 3 and a half minutes…
Just by letting off the controls in any training aircraft and the airplane will eventually right itself in no more than a turn or two. Most airplanes are so stable it can be a chore to get them into a spin for training purposes.
What about Tu-154? Attempted to climb over a thunderstorm near or above ceiling, then something like an attempt to turn or a gust provided the upset… It did not right itself in a couple of turns (and inside the thundercloud they were attempting to avoid to start with) – it continued all the way to the ground. Or so the explanation of the Pulkovo Airlines crash goes.
chornedsnorkackThis is just the lead into the incipient autorotation stage not while the spin is fully developed. Try not to get ahead of the game.
The question in the first post was why spin is a stable state – so referring to fully developed spin. After all, a logical way of looking what happens in incipient autorotation is to look at what happens at fully developed spin, and figure out what happens in between.
chornedsnorkackThe yaw moment comes in because of the differential drag betwen the down-going (more stalled) and up-going (less-stalled) wing.
..and I don’t start PoF until next Monday, D 😉
In which frame of reference is the less stalled wing going up? I suspect that the whole airframe, including the less-stalled wing, is going down, very fast, in a spin…
chornedsnorkackBasically because the aircraft is stalled, not flying
It’s worth reading this.
http://en.wikipedia.org/wiki/Spin_%28flight%29
Moggy
Yes, that was interesting… but it did not clarify well where the yawing couple comes from.
It was explained with the drag differential. Well, the inside wing might have higher coefficient of drag because of higher angle of attack – but then again, it surely has much slower or indeed negative airspeed….
chornedsnorkackA forced water landing will always be catastrophic except for some cases (like overrun of runway). And this is not talking: I know the people handling the ditching requirements at Airbus and if you ask them how high they rate the chances of an aircraft ditching: minimal if on open waters.
What are the chances of a seaplane ditching on open waters?
Seaplanes are built to ditch, and take off from water. They normally take off from sheltered waters near shore – but this might be because the destinations are often on land.
Can seaplanes deliberately take off from open waters? Especially important would be search and rescue missions on high seas – can a plane land in the middle of ocean in foul weather, pick up passengers, take off and fly away?
Also, what is harder to do in a seaplane – ditch or take off? Can a seaplane find that they can ditch safely but are unable to take off and have to wait for better weather?
chornedsnorkackWindow placement
managed to grab a few shots at SOU last Wednedsay.
Such as
http://forum.keypublishing.co.uk/attachment.php?attachmentid=142582
I looked at the window pitch. I could count 11 windows on the right side in front of the exit (the foremost window is to the rear of letter e), 1 on the exit, 14 between exit and winglet, 1 behind the winglet. The other pictures show that there is 1 window covered on that image by winglet – so the total is 16 behind exit, 1 on exit, 11 in front of exit – 28 windows on the right.
How many seat rows – has the number been disclosed?
chornedsnorkackIf that was so Boeing wouldn’t even bother with its countless and, even more importantly, persistent designs which are continuously refined.
Does Boeing persist with the giant designs, or small ones?
Of course, thicker wing means more drag, but at the same time we have smaller fuselage section for less drag.
But we do not get people into the wing until it has stand-up thickness. Plenty of drag before this.
BWB is favourable for big planes, which can have thick wings anyway.
chornedsnorkackJunkers
Whenever BWB designs are mentioned as a possible replacement for tube with wings design – they always talk about large airliners, 400-500 or even 800 pax numbers. They list the benefits of design then when it comes to flaws of the design two of the main complaints always are:
1. passengers are not used to fly in seating arrangements where we’d have 3-4 aisles and where most of PAX would be seated far away from windows.
2. BWB tend to have larger wingspans than tube planes of same pax capacity, for which many of the terminals on airports would need to be redesigned and rebuilt.
But, what happens if we apply BWB for next gen replacement for b737 and a320?
1. Instead of current 20-30 rows of 6 abreast we could have two aisle 3-5-3 arrangement to which pax are familiar with as those are used in b747 and will be used in a380. Distance from windows would be pretty much the same. If we wanna live on the edge, even 3-6-3 configuration could be used for economy class. 25 x 6 is 150 pax, 150:11 would mean 13,5 rows in BWB plane, roughly cutting the requiered cabin length in half and making it very suitable for requirements of BWB design.2. Though larger wingspan may be required than from current 737/320, even a projected 45 m wingspan would still make usable on most of current terminals that are today used for the likes of b757, 767 or a300, a310. Granted, that would take away free space for those models but we are talking about short term measure. What is needed for BWB is a way it can start operating commerical to show its potential. One of the things preventing it is exactly investments needed in change of infrastructure before it can even appear at the airports. But if we forget for a moment about jumbo jets and concentrate on smaller planes, such a bwb design can be readily used at existing airports.
Then later on, given they have proven their worth and fuel consumption is indeed 20-40% lower as theory would have us believe, commercial aviation sector would gladly pay for redesign of airport terminals so they are better suited to BWB. Furthermore, any new thing takes its time to get accustomed to. Getting to experience BWB on smaller planes first, passengers may get used to such seating arrangements despite indeed less window coverage as BWB planes get larger and in some future time they may accept BWBs at any size. I know i would gladly pay 25% less for a plane ticket if i had a chance in exchange of never even seeing a window on a plane.
There was a commercial, in-service BWB with about 45 m wingspan.
It is Junkers/Mitsubishi G38. Passenger capacity 28 in fuselage, 6 in wings. And there are actually windows looking directly forwards in the leading edge of wing.
However, there is a reason small why passenger BWB-s do not work very well. The stand-up cabin constrains wing thickness. Junkers G-38, precisely because of its thick wing, has relatively high drag – it is out of optimum proportion. The more successful propliners of comparable wingspan, like Lockheed Constellation or DC-7 or B-377, have much thinner as well as narrower wings.
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