By Bjorn Fehrm
March 20, 2026, ©. Leeham News: We have started a series of articles on the Blended Wing Body (BWB) as a potentially more efficient design for passenger-carrying airliners than the classical Tube And Wing (TAW) configuration.
In the first article last week, we established that it’s not about getting more lift during the efficiency-deciding cruise phase; it’s about reducing the drag that must be countered by engine thrust.
The drag in cruise is essentially decided by the air friction drag against the aircraft’s outer skin, called the wetted surface of the aircraft, and the induced drag, which is decided on how wide the aircraft is where there is lift generated. The reason is the high pressure below the wing will push air towards the wingtips to circulate to the low pressure above the aircraft, causing the global circulation around the wingtips of an aircraft.
Figure 1. The JetZero Z4 Blended Wing Body 250 passenger concept. Source: JetZero.
The drag of a Blended Wing Body airliner compared to a Tube and Wing design
We will now look at the drag of a Blended Wing Body compared to the classical Tube and Wing aircraft. Let’s do the analysis for JetZero’s Z4 in Figure 1, a 250-seat aircraft and a smaller variant designed in 2019 by the same core team then called DZYGN Technologies Inc., with JetZero’s CTO and founder, Mark Page, as a member.
The smaller aircraft is a BWB presented in a DZYGN report as the Ascent1000 (Figure 2).
Figure 2. The DZYGN Ascent1000 165 seater BWB. Source: DZYGN Technologies Inc.
It has a passenger capacity of 165 seats, the same as the MAX 8 when using the US Domestic cabin comfort standard. We get a bit more data from that paper than what is officially known about the JetZero Z4 in Figure 1.
Air Friction Drag
The air-friction drag is proportional to the wetted area when we assume turbulent flow for the aircraft (which is the normal state; laminar-flow assumptions are for optimists).
The Ascent1000 actually has a 12% larger wetted area than the MAX 8 in Figure 3, which is surprising. We will discuss why in the following Corners. It has to do with the problematic takeoff and landing characteristics of a BWB.
Figure 3. The 737 MAX 8 in 3D views. Source: Boeing.
After designing the Ascent1000, the JetZero team increased the cabin size of the JetZero Z4 to 250 US Domestic seats, matching the capacity of the Boeing 767-300. The Z4 then has a wetted area that is 16% smaller than the 225-seat 767-200, Figure 4, and 24% smaller than that of the 265-seat 767-300.
Figure 4. The JetZero Z4 superimposed on a Boeing 767-200. Source: JetZero and Leeham Co.
Induced drag
Induced drag is determined by the total wing span, which resists the global circulation around the aircraft. This includes any wingtip devices. Not because these affect the wingtip vortices, as many writers assume. The extension of a wingtip into a winglet simply adds a tripway for air to circulate around before it reaches the lower-pressure area above the wing.
Structures that are vertical, like winglets, are a bit less effective at affecting this circulation compared with raked wingtips, such as those on the Boeing 787, or low-profile winglets, such as the A350 Sharklets.
The Z4 has an effective wingspan of 57.6 m when we count the winglets/vertical tailplanes, versus the 767’s effective wingspan of 50.6m with winglets. So the induced drag will be lower for the Z4, given that these would have similar cruise weights. Neither of these airliners fit in the common 36m gates; they have to use Widebody gates.
For an airliner that shall fit in the 36m gates of the A320 series or the 737 NG/MAX, a BWB like the ASCENT1000 at 150ft/46m would not fit. It’s why it has folding wingtips that limit the gate width to 115ft (35m, the light gray vertical line).
We are now comparing a future BWB airliner with an existing MAX 8. The future BWB would use folding wingtips to take the 150-ft wingspan down to the gate width of 36m. So would a future Tube-And-Wing (TAW) replacement for the MAX 8, using a 150ft wingspan with folding wingtips, so given the cruise weight would stay the same, we would not see any induced drag advantage of a BWB versus a TAW single-asile replacement.
The fact that we must measure induced drag at the same weight to get comparable drag is because, as we can call the drag due to wetted area the drag due to aircraft size, the induced drag can be called the aircraft drag due to weight. Of the two, the size stays constant during the mission, whereas the weight varies as the aircraft burns off fuel, and thus the induced drag varies as well.
Conclusion
It seems there is a scaling problem with BWBs. The many projects that have studied BWBs since 1990 have all focused on large examples with seating at or above the Boeing 747 levels. When Page designed the Ascent1000 with the same passenger capacity as the MAX 8, the BWB shows no drag advantage if we equipped both with folding wingtips.
The next project, the Z4, was therefore increased in size so that the comparison would be with the rather old and inefficient 767, which is known for its low-aspect-ratio wing. We will explore this scaling problem more as we dig deeper into BWBs.
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