PALO ALTO, Calif. -- March 26, 1970 -- A wide-winged, strangely silent aircraft developed by Lockheed Missiles & Space Co.
PALO ALTO, Calif. -- March 26, 1970 -- A wide-winged, strangely silent aircraft developed by Lockheed Missiles & Space Co. was demonstrated for newsmen today at the Palo Alto Municipal Airport.
If ground watchers had not been searching the sky, listening intently for the slightest sound, they would never have known the craft called Q-Star was above them. It ghosted over observers with scarcely a whisper.
A small, single engine, general aviation aircraft that flew as part of the demonstration contrasted dramatically with the silent flight of the other airplane.
Developed to research the techniques of quiet flight, the Q-Star is a strange looking craft with its engine mounted behind the pilot. A 10-foot shaft passes from the engine over the cockpit to a pylon which rises from the airplane's nose to support a slow-turning, multi-bladed, wooden propeller.
Q-Star's silence and unconventional structure are matched by the propeller, which looks more like a Dutch windmill than a legitimate descendent of the Wright Brothers' experiments.
F. David Schnebly, Lockheed's manager of Airborne Systems, said that despite Q-Star's unusual appearance, the plane incorporates many of the same silencing techniques Lockheed pioneered in developing the Army's quiet reconnaissance aircraft, the YO-3A.
"A clean design, a slow-turning, multi-blade prop, a Lockheed-designed muffler and low power requirements are the four major factors in our quiet flight," he said.
He added that knowledge Lockheed has gained in these areas might someday have application to small, general aviation aircraft, but he doubted that any strong public motivation existed today for quieting such airplanes.
"Today's major research efforts in airplane acoustics are in the area of large passenger jets, not the small, low powered craft we're talking about," he said. "While we may someday supply information on quiet airplanes to general aviation aircraft manufacturers, our prime interest at present is military reconnaissance."
Q-Star originally flew with a conventional aircraft engine, but the airplane was demonstrated today with a rotary combustion Wankel-type engine developed by Curtiss-Wright Corp. The craft is the first in this country of fly with a Wankel-type engine.
Schnebly said that because of Lockheed's interest in quiet flight and because of Curtiss-Wright's desire to measure the engine's applicability to small aircraft, the two companies have joined in a research program.
Schnebly explained that the mechanical operation of a rotary combustion engine is inherently much quieter than the standard reciprocating engines used on conventional, small aircraft and automobiles. The engine also puts out a high degree of power compared to its relatively small size and weight. This makes the engine an attractive possibility for small aircraft.
The origins of Q-Star are in the design of a two-place, high performance sailplane manufactured by Schweizer Aircraft Co. in New York. Lockheed made extensive changes to convert the craft to powered flight.
"One requirement for quiet flight is an efficient aerodynamic design," said Schnebly. " sailplane's clean structure is one of the most efficient aerodynamic designs available, so the sailplane gave us an excellent point of departure."
Because Q-Star possesses an efficient design. despite the engine hump behind the cockpit, relatively little power is needed to keep the craft aloft.
"The low power requirement is an important factor in Q-Star's low noise emissions," said Schnebly. "The less power you need, the less noise you make."
To accommodate the additional weight of an engine. fuel tanks and radio equipment in Q-Star's development, sections of the sailplane fuselage and both wings were strengthened. Modifications also included a conventional tricycle landing gear in place of the sailplane's belly wheel and tail skid.
Tests with Q-Star have included many experiments with propellers. which are a major source of airplane noise, according to Schnebly. Three, four and six-bladed props have been flown on the Q-Star program. Two different engines have been used in the Q-Star--the Curtiss-Wright Wankel. and a four-cylinder, 100-horsepower conventional aircraft engine.
Schnebly said Lockheed has been doing acoustical tests with Q-Star and its predecessors for over four years. Because noise emissions from Q-Star and the Army's YO-3A are so slight, Lockheed has performed most of the testing at lonely air strips in California's central valley where background noise levels are much lower than in metropolitan areas.
He said current testing with the Curtiss-Wright engine is nearly concluded and that future research with Q-Star would depend on data gathered from flight tests with the rotary combustion engine and different propeller designs.