Airport operations

Could twin-engine airliners be aviation’s silver bullet?

Since man first walked on the moon, the Boeing 747 has been in the skies. However, that is set to change in the coming years as the age of the four-engine airliner comes to an end. Rather than mourning their demise, Virginia Lee of Airports Council International Europe tells Andrew Tunnicliffe the next generation of aircraft could have many of the answers to today’s aviation challenges.

The Boeing 747 was a marvel when it was launched at the beginning of the 1970s, and still is today. Carrying as many as 600 passengers and crew (depending on the variant), it lays claim to having transported more than 3.5 billion people from one part of the world to another. But, after more than half a century in service it seems time might be up for the 747, and indeed other four-engine airliners.

Since the 747’s launch, Boeing has sold more than 1,500 of the aircraft, with a further 17 on order. But the end of the runway for this, and its Airbus rival the A380, is approaching.


The demise of the four-engine jumbo

Although the order books for the 747 still show double digits, the aviation giant has been faced with questions about its plans for the future of the jumbo. In the middle of the last decade the company itself fuelled speculation that production would end, yet it continues today. However, for commercial use at least, its future might be out of Boeing’s hands. Perhaps reading the writing on the wall, Airbus announced some time ago that it would be closing its A380 production line in 2021.

The news shouldn’t be met with great surprise, as airlines around the world have been slowly removing the 747 from their fleet. In recent years orders have been in steady decline; Airbus was said to have come to its decision because of falling demand. The demise has largely been put down to technological advances, and more precisely the evolution of twin-engine aeroplanes. 

However, for Airports Council International (ACI) Europe spokesperson Virginia Lee, there are benefits for everyone as the twin-engine alternatives begin to dominate. “The maintenance costs are lower and the amount of space you need to maintain the aircraft is smaller,” she says. “At every point in this chain, things just speed up.”

In addition to maintenance advantages, decreased operational costs, greater efficiencies and reductions in fuel burn are all notable reasons for airlines' growing appetite for the twin-engine.

The maintenance costs are lower and the amount of space you need to maintain the aircraft is smaller

Twin-engines could be the answer

On the face of it, the decision by the manufacturer to stop producing an airliner only affects the airline, but Lee says that is far from the case. “If we take one step back and look at what those bigger picture issues are for airports across Europe, there are two that really come out,” she says. “These are the issues around connectivity and capacity. These are really big challenges in Europe.”

She says ACI Europe believes that the shift to twin-engine aircraft might have a positive impact, even helping the industry address such issues. “I think it falls very much into three main areas: with a lighter aeroplane you can increase the number of movements, you can reduce the time between those movements because of the vortex changes, and if you do those things you can increase capacity.”

For the association, capacity concerns are critical and becoming even more pressing as time goes by. Lee says the growing popularity of twin-engine designs could go some way to addressing the "capacity crunch". The factors hindering capacity are many and varied, from geography to finance, airport footprints to environmental concerns. However, some of the more tangible ones, Lee says, are air traffic management and what she labels “outdated slot allocation regulations”.

‘A light aircraft means as things move faster the connectivity between the more regional airports and hubs becomes smoother,” she says. “So you increase the degree to which you can move between existing ports and start to connect these vital regional airports in a way that hadn't previously been possible, or wasn't commonplace. The two-engine aircraft feed, in a positive way, to all of these things. You get to utilise what you have much more efficiently.”

For the wider sector, Lee says this shift will also prove positive. "Anything that makes better use of the existing capacity is going to be a benefit," she says. "It benefits business, passengers and the airlines themselves. It just helps the whole infrastructure to make better use of what's there." One of the advantages is greater runway capacity. Thanks to the reduced wake vortex, smaller separations between landing and take-off could potentially mean more flights using the same runway. This would increase capacity without the need for any significant infrastructure changes.

From a sustainability perspective, the gains are also evident. Lee says twin-engine aeroplanes could help the sector meet its targets and net-zero 2050 goals thanks to greater efficiency and fuel economy. "It’s a helpful part of the jigsaw," she says, "It's about efficiency and the longer I’m around these issues, the more I think about how interconnected they really are."

A light aircraft means as things move faster the connectivity between the more regional airports and hubs becomes smoother

The rise of the twin-engine is here to stay

A significant factor in the growing number of twin-engine aircraft was changes to regulations. Introduced in the 1980s, Extended Range Operation with Two-Engine Airplanes (ETOPS) guidance required carriers to only use twin-engine craft on routes that were within 90 minutes of airports, in case of emergency. As engine technologies advanced those regulations were eased, heralding the introduction of twin-engine long haul flights by the middle of the following decade.

Because two engines were more efficient and cost-effective than four, and with those change in regulations, more and more airlines opted to use them. Doing so opened up new routes that had never before been considered. Now that the industry and wider world is more aware of the impact of climate change, their popularity will only grow.

It seems the four-engine passenger plane could be flying into the sunset. Speaking to USA Today as far back as 2017, one industry insider saw the demise coming, his reasoning was simple: "Why do with four when you can do with two? It’s going to be simpler and less expensive." His assertion that airlines would increasingly turn to two-engine is proven,  as you only need to look at the order books and listen to what the world’s two largest manufacturers are saying to see that.

For the 747 at least, the chances of seeing it in the sky will remain for some time to come. Boeing believes it still has a future as a cargo plane, taking the so-called ‘Queen of the Skies’ back to her roots. For passenger travel though, the future isn’t so clear. It seems the 747 is saying a long goodbye, and so too are four engines.

Boeing believes [the 747] still has a future as a cargo plane

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