Volume 5, Number 4     July/August 1997

Aerospace Technology Development

Tests Could Cut Aircraft Fuel Costs

ASA RESEARCHERS HAVE BEGUN TESTS they hope will lead to improved commercial aircraft efficiency and $140 million annual fuel cost savings by minimizing aerodynamic drag.

Drag is the aerodynamic force from air pressure and friction that resists passage of an aircraft as it flies through the air.

Adaptive Performance Optimization experiment tests will obtain data on putting an aircraft's control surfaces in the best position to reduce drag. Dryden Flight Research Center (DFRC) began tests in May using a modified Lockheed L-1011 TriStar operated by Orbital Sciences Corp. of Dulles, Virginia.

This Lockheed L-1011 TriStar aircraft is the subject of new flight research developed to improve the efficiency of large transport aircraft.

Langley Research Center is sponsoring the tests as part of its Advanced Subsonic Transport Aircraft Research Program.

"A drag reduction of only one percent translates into an equivalent saving in fuel usage and fuel costs, a major factor in airline operations when you improve the efficiency of transport aircraft by minimizing aerodynamic drag," said DFRC's Glenn Gilyard, the experiment's principal investigator and flight-test director. Project officials hope for drag reductions of up to three percent.

The research team will fly the aircraft three or four times each year over the next two or three years. Most of the tests will be flown at speeds of about Mach 0.83 and at altitudes of 30,000 to 40,000 feet.

Gilyard said all aircraft are designed to operate most efficiently at a single point in their flight profile. Unfortunately, they often do not fly at that design point, and therefore, fly at reduced efficiency, he said.

The NASA/McDonnel Douglas X-36 remotely piloted tailess aircraft takes off for the first time in May.

"The experiment is designed to improve aircraft performance during a given flight condition, based on real-time, in-flight measurements and analysis," Gilyard said.

An engineering team designed a software program for the aircraft's research computer that reduces the aircraft's drag by changing the positions of its aerodynamic control surfaces. The program incorporates airspeed, altitude, engine measurements, and other data to make instant adjustments to the aircraft's control surface positions for greatest aircraft efficiency at each flight profile point.

Engineers also developed flight-research systems that will record test data and permit on-board flight test engineers to make decisions and analyze research data in-flight.

"We are trying to achieve savings based on the difference between what the manufacturer designed the airplane to be and what the airplane actually is," said Gilyard. "The bottom line is how much fuel goes into that airplane over the course of a year."

Potential fuel cost savings could be $130,000­ $150,000 per year per aircraft depending on its type.

For more information, contact Fred Brown at Dryden Flight Research Center.
Call 805/258-2663 E-mail: fred.brown@dfrc.nasa.gov

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