737 or Airbus A320 class, which makes up roughly a third of the current fleet. We named this concept the “D Series” because of its “double bubble” fuselage cross-section. The other aircraft, which we call the “H Series” for hybrid-wing-body, is defined for international routes. This latter design, envisioned as a Boeing 777 aircraft replacement, features a triangular hybrid wing body that blends into the wings, accommodation of 350 passengers in a multiclass configuration with cargo, and a range of at least 7,000 nautical miles.
Double-Bubble (D Series): modified tube and wing with lifting body
Hybrid Wing Body (H Series)
The D Series configuration was calculated to meet fuel burn, engine emissions, and runway length targets, and to provide a substantial step towards achieving the noise target. The H Series was calculated to meet engine emissions and runway length targets,
Baseline: B737-800 Domestic size
NOISE
NOISE 100% of N+3 goal
and is markedly improved compared to current aircraft for fuel burn and noise.
Baseline: B777-200LR International size
75% 50%
RUNWAY LENGTH
NOISE
RUNWAY LENGTH
For both designs, the engines ingest the rela-
50% 75%
tively slower moving air from the fuselage boundary layer (the air flowing next to the
NOISE
100% of N+3 goal
NOX EMISSIONS
NOX EMISSIONS
aircraft’s body), providing a higher propulsive efficiency and, thus, an advantage from a fuel burn perspective. However, the flow into the engines consists of fluid from both within and outside of the boundary layer, so there is a non-uniform velocity into the engines. This is different from current engines, which hang in front of the wing and thus encounter virtually uniform flow. Integration of the aircraft and this unconventional propulsion system is one of
Rendering and performance assessment of two MIT aircraft designs relative to the four N+3 NASA targets. The circles on the small graphs represent the 50 percent, 75 percent and 100 percent target levels targets, and the solid symbols indicate the performance of the concept aircraft.
the main technical challenges. The D Series flies about 10 percent slower than the 737, so the wings on the former, which have a much higher aspect, or length-to-width, ratio (29 vs. 10), require less sweepback than those on the latter. (The sweepback is to address deteriorations
Subsonic Civil Transport Aircraft for 2035
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