Success in so many things is all about getting the timing right.

This is as true for airplane design/development as it is for just about everything else.

Airbus Fires the First Shot in the New A320/737 War with Boeing - part 3 of 4 New Engine Issues too, and How Airbus and Boeing Could Respond
	An open rotor jet engine prototype (the front is on the left).  These will revolutionize engine technology when deployed. Part 3 of a series on the needed evolution of the Airbus/Boeing A320/737 aircraft. Click the links at the bottom to read through the other three articles in the series.

The thing we think of as an airplane is comprised of two major subsystems - the airframe - the fuselage and wings; and the engines that power the plane.

Engine technology is as much a factor in overall plane operational economics as is airframe design.

Current enhancements in engine technology, and projected likely future enhancements complicate how Boeing and Airbus can time the development of new airframes - an outrageously costly and very time consuming process.

Not Just New Airframe Technology; New Engine Technology Too

We've been talking in large part about airframe design and evolution.  But that is only half the puzzle.  The other half revolves around the engines on the plane - engine technology is also steadily advancing all the time, and each new generation of airplane engines generally offer greater efficiency, cleaner operation, and quieter sound levels.

A new plane usually has new engines as well, for two reasons.  Firstly, because each plane has a specific set of performance requirements for its engines, and so it makes sense to custom design an engine to suit the plane (the same as how different cars and trucks have different engines too).

The second reason is simply to take advantage of the latest state of the art capabilities in engine design as well as in airframe design, to make the overall combination of airframe and engine more appealing in the market.

It is possible to re-engine an existing airframe.  If you re-engine your car, you might have some derivative issues too - you might need heavier suspension, a stronger transmission, and if it is a more powerful engine, perhaps you need to upgrade the brakes as well.

The same analogy applies to a plane.  Maybe you need some changes to the wing design, maybe you need greater fuel tanks (or maybe smaller ones will do), maybe you need stronger undercarriage and brakes, and probably you need some changes to the avionics that control the engine due to the different 'flight envelope' characteristics of the re-engined plane.  You might even need things such as a new tail to compensate for more powerful engines and the plane operating in a single engine scenario.

These costs associated with re-engining a plane are far from trivial (potentially a billion or two dollars), and of course, they pre-suppose a willing engine manufacturer who will invest in the development of the new engine (many billions of dollars).  So planes don't change engines with a great deal of frequency.

Furthermore, there's the temptation to add other features at the same time, eg 'If we're going to add a better engine, why don't we stretch the fuselage a bit as well to take advantage of the extra engine power' and before you know where you are, a 'simple' re-engining task has become a complete new model airplane.

The new competing planes will be equipped with the latest and greatest in western engine technologies.

Reversing the past Russian practice of handicapping perfectly good airframes with appallingly bad Russian engines, the new Russian Irkut MS-21 will have a latest generation Pratt & Whitney PW1400G engine.

The new Chinese Comac C-919 will have a latest generation CFM LEAP-X engine.

Both these engines promise about 15% less fuel consumption than comparable current generation engines, and their presence on these 'foreign' airframes also gives the airplanes as a whole a great deal more credibility.

A complete new type of jet engine technology

There is another twist to developing engine technologies.  There is a radical new type of jet engine design - the 'Open Rotor' design - expected to become available in the 2020 - 2025 time frame - a game changing new type of jet that will massively increase engine efficiency.

Open rotor engines will add about another 20% fuel saving over the 15% or so saving offered by replacing current generation engines with the new generation engines scheduled for the Russian and Chinese planes.

This level of saving becomes compelling and will require most airplane models to be re-engined to stay competitive.

Airplane manufacturers are factoring in this new development and its time frame for implementation into how they stage their development and release of new airframes.  It would be unfortunate to design a new airframe and then only a handful of years later, to have to redesign it for new engines - the preference is, instead, to do it all at once rather than in two stages.

The Choices Airbus and (lesserly) Boeing Have

On the face of it, Airbus and Boeing could do one of two things - they could take a big step and design a new airframe, and match that with new engines, or they could take a half-way step, leaving the airfare essentially as it is, but adding new engines to it.

The benefit of the latter approach is that it would be quick and easy (comparatively speaking) to implement, and most of all, it would not cost the airplane manufacturer(s) a great deal of money, shifting most of the cost onto the engine manufacturer instead.

The benefit of a complete new airplane is that it would offer two areas of improvement - a lighter better design of airframe as well as a matching new design of engine.  The downside is that the cost would be massively greater and the lead time to get the plane to market much greater too (and don't forget the pending arrival of the new type of open rotor jet engines).

There's another disadvantage too, and understanding this is key to understanding what Airbus has now announced and what Boeing must do in response.

If either airplane manufacturer proceeds to design a complete new airframe today, it will be doing so with today's material technologies.  The company will hope for a family life for the new airplane series to be anywhere from perhaps 20 to 40 years.

But with the rapidly evolving knowledge of how best to use composite materials, any such airframe developed today risks becoming technologically obsolete in maybe ten years time, possibly even less.  Neither company wants to commit to a new family of airplanes, costing billions of dollars to develop, but which might only have a short life in the marketplace before having to be replaced yet again.

So, on the face of it, simply re-engineering the present airframes seems like a safer more prudent step to take, as long as this will both be sufficient to address the threat posed by new competitors, and as long as the other company doesn't respond not just with a re-engineering but a total new airframe design as well.

This is part 3 of a series on the needed evolution of the Airbus/Boeing A320/737 aircraft.  Please see also the other parts of this series :

1.  The vital importance - and growing problems - of the A320 and 737 families of airplanes
2.  Why Airbus and Boeing don't want to - but must - update their aging airplane series
3.  Engine issues and what Airbus and Boeing could do
4.  Boeing's big problems

If you liked this, you might also enjoy our multi-part series 'Where is Boeing Going'.

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Originally published 24 Dec 2010, last update 30 May 2021

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.