The Boeing replacement for the 737 may end up as the most hotly speculated about aircraft in history. This aircraft was first delivered in 1967 as a 737-100 seating about 100 people. In fact, it was an exceptionally slow seller for most of the 1970s. It’s now nearly 45 years old and the largest of the currently family, the 737-900ER, can seat potentially as many people as 200. The first 737s had a range of about 1600 miles and the current longest range 737 can fly about 3000 miles.
This aircraft has doubled its size and range over its life in what has been really 3 model ranges over that lifespan: The original -100/200 aircraft, the -300/400/500 and then the -600/700/800/900. There are over 6000 of this type delivered with more than 2000 still on order and it possesses possibly one of the best records out there for reliability.
Replacing this aircraft is no small task and Boeing gets one chance to do it right.
It’s all about efficiency and the low cost per available seat mile that can be obtained. Airlines want to see a replacement that gives them not just a good gain upon delivery but which also affords them the best advantage over the life of ownership.
Capacity: Most likely we’ll see an airliner family that seats from 150 to 210 people. Airlines are already seeing the value of switching from the -700 model to the -800 model because they can fill the seats without really any additional cost. (This was the main reason why the -600 never really took off: airlines could fly the -700 for about the same costs and enjoy more flexibility.) In addition to a robust passenger range, I expect that we’ll see the lower cargo area designed to accomodate a bit more payload than the present airliner. While this aircraft will never be an uber freight hauler, the present 737 has always been a bit constrained both in volume and payload weight. An improvement in that area will be desired.
Fuselage: Boeing has already expressed doubt that their approach with CFRP for the 787 won’t necessarily scale down to a 737 type replacement. That’s probably true but that approach is already several years old and don’t rule out some sort of plastic airliner for this development. New materials are developed every year and the big advantage to this approach for such an airliner is that it helps with maintenance. There would be reduced corrosion over the life of the aircraft and reduced fatigue as well. Whether it is a composite barrel or plastic panels on a metal skeleton, it’s liable to be plastic of some sort. In addition to reduced maintenance, it will also lighten the airframe even a small amount and reduced weight translates into carrying more payload a farther distance.
Range: The base range for the next replacement will be, at the least, somewhere between 3000 and 3500 nautical miles. In other words, expect North American transcontinental range at minimum. Will it be designed to fly a 757 style mission across the Atlantic to Europe? That’s anybody’s guess but I think probably not. I don’t see a 5000nm range being designed into this aircraft as it really pushes the weight of the airframe in directions that designers are unlikely to want go in. The 757 was an anomaly in aircraft design because engines available for that aircraft during its design were uncharacteristically robust. Generally speaking, engines have to be pushed to meet such requirements.
Engines: I don’t see a twin tail, open rotor design. Instead, I see a relatively conventional layout with engines on the wings. I do, however, expect two engine choices on the next design. Why? Because so many will be ordered that two engine manufacturers can enjoy good economies of scale and buyers like choice when it comes to engines.
I think we’ll see engine thrusts starting somewhere between 20,000lbs to 22,000 lbs and ranging upwards to somewhere around 30,000lbs to 32,000lbs with bypass ratios in excess of 6 .0. These engines will have big fans and they will drive the aircraft to be higher off the ground. That’s OK because the typical airline using this aircraft today is nothing like the typical airline who used it originally. Airports and airlines are better equipped and while loading will require equipment by default, it will still be easy to turn around this aircraft. I expect we’ll see some cargo hold innovation to speed loading and unloading in this aircraft.
I believe the engine suppliers will be CFM(or, perhaps, just GE) and Pratt & Whitney. Rolls Royce has never played well in the single aisle market and their basic Trent 3-spool design just appears to be too cumbersome to scale down for this aircrafts needs. A Rolls engine in that approach would be heavier and less optimal for the typical flights. In addition, Rolls Royce has done very little innovative work for these kinds of engine requirements.
Wings: Boeing has always done a good job of giving its aircraft enough wing for growth. That won’t be any different here and this is where I think we’ll see some real gains in fuel efficiency. Wing design has come along way at Boeing and they’ll push their technology quite a bit in this area. I think we’ll see raked wing tips rather than winglets in the next aircraft. They’ll likely resemble the 787 more than anything else although without quite the gull-like appearance in flight due to being shorter. I think they’ll be largely plastic and I think they’ll retain good short airfield performance to keep the LCC airlines happy since they have a habit of flying into smalller, more obscure airports as a rule.
Twin Aisles: I doubt it. It’s a concept that has received attention but, at the end of the day, a wider fuselage to accomodate two aisles translates into a wider fuselage. A wider fuselage translates into more drag and that means more fuel to power it through the air. What I do expect is an ever so slightly wider fuselage that is likely more “round” a la Airbus.
What I do think we might see is some sort of innovative approach to making it possible for the airline to load and unload from front and rear doors on a regular basis. LCC’s like their fast turn-arounds and offering the ability to do this in a more self-contained, efficient manner will only make them happier.
Passenger cabins: I expect Boeing will certainly work hard to design an open and pleasant passenger environment that resembles their approaches with the 777/787/747 as well as their new signature Sky Interior. We might even finally see some suggested seating innovation but no one owns this domain very well. Boeing works with outside suppliers on behalf of its customers rather than supplying the seating themselves.
When: I expect a target for initial entry into service of 2019 to 2020. Anything past that offers Airbus too much opportunity to steal customers. It can be done and it is going to require quite a few resources. That’s OK because this kind of effort should be flawless in meeting both requirements as well as in its execution. This is potentially an airliner that sells in excess of 10,000 aircraft. You can’t let Airbus continue to fill needs for customers (especially customers who have blended Boeing fleets a la United and Delta) while you dither around waiting for the perfect opportunity. Once another guy’s airliner is purchased, it can take from 15 to 25 years to have another opportunity to fill that need.
It will be a more revolutionary aircraft than evolutionary certainly but expect it to not look entirely different from what it does today.
Filed under: Aircraft Development by ajax
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