National Geographic : 1988 Aug
Daedaluswing bends in a test (below) of its graphite epoxy spars at the MIT-Lincoln Laboratory Flight Facility near Boston. As structural engineer Juan R. Cruz checks for stress, water filled bottles simulate air loads encountered during flight. Two aircraft were built with funds donated by United Technologies Corporation and named for their year of construction, hence Daedalus87 and Daedalus88. Each revolution of the pedals (top right) was translated by gearboxes into one and a half revolutions of the propeller. An upper gearbox-this one from a Daedalusprototype (bottom right)-transmits power directly to the propeller. A technician's index finger points to a bell crank that enables the pilot to adjust the propeller's pitch to regulate the "bite" of air it takes during flight: low pitch for power on takeoff, higher pitch for endurance during cruise. The aerodynamic design of Daedalus was by Mark Drela (middle right), an MIT assistant professor of aeronautics and astronautics, who uses Kevlar yarn to lash fuselage tubes made of sheets of a superlight, super stiff graphite epoxy that are lay ered, shaped, and baked in an oven. The thickest graphite piece, a section of the hollow main wing spar, consists of 12 layers but is as thin as a dime. Surely the gods smiled at Dae dalus, in flight (right) over the Aegean between the com mand boat and one of the inflat ables. And mortals can almost count the 102 wing ribs, each precisely cut from 3 /16-inch-thick polystyrene foam. The fuselage pod is suspended beneath a 29-foot boom, which supports the 11-foot propeller turning at about 105 revolutions per minute. The airplane's skin is Mylar, a thin plastic film. With a small control stick in his right hand, the pilot maneu vers the rudder and elevator. Except for a few metal screws, everything in the airplane has been handcrafted and meticu lously screened for weight even the glue was weighed. Director of engineering Har old H. Youngren wagered "a roast pig" that the airplane would not come in under 70 pounds. He lost. Flight-ready, Daedalus88 weighed in at 68.5 pounds.