Sailplane-Like Boeing Cruises on SUGAR

Dean Sigler Electric Powerplants, Hybrid Aircraft, Sustainable Aviation Leave a Comment

Boeing has sustained a decade-long program to develop aircraft that reduce the use of fossil fuels or eliminate it altogether.  SUGAR (Subsonic Ultra Green Aircraft Research) program designers have resorted to configurations that were a part of early high-performance sailplanes, those craft that soar on the energy of the very air around them. Sailplane designers know that longer wings give a lower span loading: the weight of the airplane and its payload is spread over a greater span.  On powered craft, low span loadings give greater rate of climb for the same power and enable throttling back to get the same cruise speeds.  Longer spans usually lead to heavier structures, though.  Spars end up weighing more and wings are subject to twisting in the wind.  To get around these problems, early designers used highly-tapered wings to move the bending moment on the wings inward, and strut bracing to reduce the cantilevered segment of the wing.  Hawley Bowlus used these methods …