I think Boeing should develop a new aircraft with new seat configuration for aviation market. That is B777-400, it should carry 400 pax with three class operation (F/C/Y). Definately sales orders will come from the airlines like Singapore Airlines, AirIndia, ANA, Thai ....
Bit unfair Lucifer - I suspect that Boeing have in mind just such a response to the A350-1000: another stretch of the fuselage and push the GE90s to 125k/lb (I think that's the max for engine out controllability?). Should give another 30 - 40 seats and move closer to where the 744 was plus complement the 748i while capping the A350-1000. I think that Lankana might be a smidgen off the mark with four engines though - why re-invent the A340-600? Come to think of it, why invent the A346 in the first place?!
I think that Lankana might be a smidgen off the mark with four engines though - why re-invent the A340-600? Come to think of it, why invent the A346 in the first place?!
And what was 777-200 in the first place, other than A330-300 reinvented?
Bit unfair Lucifer - I suspect that Boeing have in mind just such a response to the A350-1000: another stretch of the fuselage and push the GE90s to 125k/lb (I think that's the max for engine out controllability?).
But stretching the fuselage also stretches the leverage for fin.
Actually, 4 engines does include an outboard engine - which has long leverage for asymmetric thrust. Wasnīt Boeing 777 originally intended to be a trijet? Trijet does not have any outboard engines, while the wing engines have less thrust each than the engines of a twin would have... so better for engine-out controllability.
There are all sorts of arguments, regularly aired on PPRuNe, as to the the merits of two vs four engines but, for commercial aircraft, it's purely a question of economics. If you can do the job with two engines rather than three or four then two will be better from an economics perspective. I don't know what the maximum thrust available for a twin installation is from a practical point of view but assume that there will be issues of fan size, ground clearance, gear length etc and I imagine that a 125k/lb thrust GE90 on a "777-400" is probably about it.
Wasn't Boeing 777 originally intended to be a trijet?
Not in anything but the earliest design phases. Boing dropped any ideas for a tri 777 when it became clear that the tri design had lost out in the court of public opinion, and when the company's 75 and 76 had clearly paved the way for Boeing ETOPS. Whether deserving or not, DC-10s became synonymous with major aircraft accidents in America. That footage of UA232 turning into a fireball on landing in Sioux City was the death knell for the future of trijets in the American passenger market. MD lost big on the -11, and the L-1011 was another disappointment. Boeing didn't want their next flagship going that way, and thought they could do better selling a more efficient, modern-seeming twin. Seems to have gone okay...
... and the development of more efficient & powerful engine technology meant that you could power a DC-10/TriStar-sized a/c happily on two donks with enough safety margin for, say, losing one beyond V1. Plus the ETOPS experience as mentioned.
engine performance is the key. The early heavies were restricted by engine performance -with the tri jets available power from the RB 211 and US types restricted the design performance under the old certification rules - the politics is a known story with RR
factor in the operating economics and it became a problem - the 2% over predicted economic fuel ratios sunk the MD11 (during the oil crisis).
the evolution of the freighter market, curtsey of Fred Smith changed that- Lufthansa argued strongly against the closer of the MD11 F line as the only competition was the B747F (and derivatives); No competition = fixed prices. thatís changed - take a look at the offerings from both sides of the Atlantic.
ETOPS with the old rules didnít allow too much variation in operating structure. this has changed, but have you seen the B777 engine failure rates? Take a look at the recent FAA AD that grounded most of Singapore airlines fleet recently.
On a design note - do you have any idea how much of a P.I.T.A. having an engine sitting above the rear fuselage is?
Last edited by Thirty Eight South; 16th Feb 2007 at 21:41.
Lucifer - do you think that you are in some way superior to the rest of us?
I don't think there was anything wrong with the original question - it makes a perfectly valid point & I speak as an aviation consultant with over a decade's experience in market forecasting and airline economics. If it is ok for me what makes you so special? (But then if all you do is fly Tridents in FS2004 I'm not surprised)
To the original poster, the 777-400 would be a great replacement for the 747-400 if engine-power and structural issues do not get in the way. For example, could the landing gear take the additional weight; would an even longer stretch cause problems with tails scrapes etc - these are questions I could not answer but from an economics point of view you would get a considerable seat-mile cost advantage over the 747.
Going to 4 engines would not be a go-er as the whole airframe would have to be redesigned which would be very expensive and it would not be any different to the 747.
I suspect a further stretched 777 will not happen as Boeing do not want, at this stage, to create a competitor to the 747.
I think both Lockheed and Douglas would have preferred twins if technology and opinion had been fully on their side. A fin mounted engine adds weight and asks for strength where it is rather unwelcome. This was the view of my father who left de Havilland for Douglas and Douglas for Airbus. He was a severe critic of Airbus wing design, the A330 losing out on advantages in wing/engine/fuselage integration for the A340 to have four pods. Then it emerged that the physics had been imperfectly understood requiring redesign effort anyway. Airbus have hardly covered themselves with glory in their A340-500/600 range with its larger wing, different sweep. Once in service there has had to be some unexpected tinkering with c of g and flight dynamics but to be fair you can't always get it right first time. However talk of "optimisation" is spin doctor speak. My father railed at his and others inability to get the speed, cleanliness and economy that was desired. So someone somewhere coined the phrase "optimisation" and Leahy had his slogan. Whereas most of Boeing's trials and tribulations have been of the "sex scandal and shopping" variety Airbus have an irritating knack of snatching defeat from the jaws of victory lately. Whether right or wrong the large twin seems to have inevitableness written all over it and in this context the trijet was a stopgap response, a page in history that has been turned. But Sir Isaac Newton tells us why an apple falls down from the sky and by this law it seems quite fair, a plane without engines won't stay up in the air. If two part company, three's not a crowd but surely these days four is a bore.
I'll declare an interest. I work for a certain company but it might not be the one that you think!
I think both Lockheed and Douglas would have preferred twins if technology and opinion had been fully on their side. A fin mounted engine adds weight and asks for strength where it is rather unwelcome.
Sure. But outboard wing engine?
Once twins were given up, what would have been the second best for Lockheed and Douglas - trijet or quadjet?
Sure a trijet 777X, a la 727 could be done, would it be useful, which is to say economic NO! Structures would be heavy everywhere, including wings.
The FARs and public opinion when the 727 and the heavy tri-jets were also an important factor in addition to engine power. In the sixties, there was a strong bias against twins, take-off weather requirements in 121 were a big element in Eastern and United wanting a tri-jet 727. Twins, I don't believe, could use low mins and a take-off alternate, they had to have a mile viz or landing minimums The "public", meaning media and opinion thought flying across the US, let alone oceans, demanded four engines, going to three was a leap of faith. Privately, the engineers at the airlines were reluctent to buy less than three for long-range in fear of the public rejecting them. Remember airlines were moving from Connies and DC-7s, so everyone associated flight with FOUR engines unless you were puddle-jumping in a Convair or Martin. We forget now that in mid-Eighties, going outside of 60 minutes with a twin was a "there they be dragons" kind of operation.
Hell, getting down to TWO crewmembers was a real effort! The original 767s had an F/E.
The biggest all-tail jets are the quads VC10 and Il-62.
Problems with tail engines include having the centre of gravity of airframe behind the centre of gravity of payload, and needing structural support to carry the weight from tail through the rear fuselage and into the wings.
Nevertheless, tail engines are the favourite arrangement for small regional and private jets.
There was the famous VC-10 trijet, with ordinary pair of low-bypass jets on one side, and a big high-bypass turbofan opposite. Would it make sense to reengine a VC10 to be a twinjet (another big turbofan instead of the other pair of low-bypass jets)?