No, you really can't. Even if it were the same size a dramatically more powerful engine would need a larger "tail" to maintain control in case of an engine out scenario. But a 50% more powerful engine is also likely to be much bigger meaning that major components like the landing gear (and everything around them). A 50% more powerful engine is also likely to be much heavier necessitating its support structures (a.k.a. the wing or tail) be redesigned.
The 737 MAX suffered a number of bad design decisions to accommodate its newer, more powerful engines. Its engines topped out at about 8% more powerful than the 737 NG engines.
Look at thrust on the 737 Max vs thrust on the original 737.
There's a lot of other changes, of course, but more powerful wing engines let you build a bigger plane in the same kind of shape. Changes in flight rules are also significant; if twin jets can't serve all your routes, you most likely want trijets to cover the routes that can't be served by twins and don't demand a quad ... with current flight rules and current engines, twin engine covers pretty much everything.
Essentially every new design is a twinjet, so it's clearly possible to make appropriate decisions in that design space. And both Boeing and Airbus have given up on quadjets.
The MD-11 isn't a new design. It's a stretched version of a first generation widebody whose design dates back to the mid-1960s. Before the MD-11 was developed, McDonnell-Douglas toyed with the idea of a dual engine variant before settling on a three engine version of the DC-10. Trijets in general came about because the engines of the day were too unreliable and too small to work in twin engine configuration at that scale.
The plane which ended up being the final nail in the MD-11's coffin, the 777, didn't start development until the 90s. Of its three initial engine choices, two were derivatives of engines that were around when the trijets came to be. The initial version of that Rolls Royce engine was so late (and so unreliable) that it essentially killed the Lockheed trijet. The third option, the GE90, was the largest turbofan engine at its introduction until it was succeeded in 2020 by the GE9X.
Scaling these earlier engines up to fit an MD-11 sized twin was never an option.
>both Boeing and Airbus have given up on quadjets.
It is possible “to make appropriate decisions” up to a certain size. They didn’t stop making new quadjets because the design doesn’t work as well as a twin engine, but because airlines don’t need/want aircraft that large. You wouldn’t build a successor to the A380 as a twin engine.
No, you really can't. Even if it were the same size a dramatically more powerful engine would need a larger "tail" to maintain control in case of an engine out scenario. But a 50% more powerful engine is also likely to be much bigger meaning that major components like the landing gear (and everything around them). A 50% more powerful engine is also likely to be much heavier necessitating its support structures (a.k.a. the wing or tail) be redesigned.
The 737 MAX suffered a number of bad design decisions to accommodate its newer, more powerful engines. Its engines topped out at about 8% more powerful than the 737 NG engines.
It wasn’t about the engines being powerful but about the fan being bigger and therefore more efficient
The effects of a bigger fan are the same: the engine is bigger and more powerful necessitating changes to the airframe.
> just make the wing engines 50% more powerful
You realize this is not quite how aerospace engineering works, right?
Look at thrust on the 737 Max vs thrust on the original 737.
There's a lot of other changes, of course, but more powerful wing engines let you build a bigger plane in the same kind of shape. Changes in flight rules are also significant; if twin jets can't serve all your routes, you most likely want trijets to cover the routes that can't be served by twins and don't demand a quad ... with current flight rules and current engines, twin engine covers pretty much everything.
Essentially every new design is a twinjet, so it's clearly possible to make appropriate decisions in that design space. And both Boeing and Airbus have given up on quadjets.
The MD-11 isn't a new design. It's a stretched version of a first generation widebody whose design dates back to the mid-1960s. Before the MD-11 was developed, McDonnell-Douglas toyed with the idea of a dual engine variant before settling on a three engine version of the DC-10. Trijets in general came about because the engines of the day were too unreliable and too small to work in twin engine configuration at that scale.
The plane which ended up being the final nail in the MD-11's coffin, the 777, didn't start development until the 90s. Of its three initial engine choices, two were derivatives of engines that were around when the trijets came to be. The initial version of that Rolls Royce engine was so late (and so unreliable) that it essentially killed the Lockheed trijet. The third option, the GE90, was the largest turbofan engine at its introduction until it was succeeded in 2020 by the GE9X.
Scaling these earlier engines up to fit an MD-11 sized twin was never an option.
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>both Boeing and Airbus have given up on quadjets.
It is possible “to make appropriate decisions” up to a certain size. They didn’t stop making new quadjets because the design doesn’t work as well as a twin engine, but because airlines don’t need/want aircraft that large. You wouldn’t build a successor to the A380 as a twin engine.
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It would be way cheaper to replace the airplane with a modern twin-engine plane than to retrofit new engines onto an old plane.
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Now it is, yes. At the time, it would have required 4 total engines, which is a different matter altogether.