TESTS BEGUN TO STUDY DECREASE IN AIRCRAFT DRAG; MAY PRODUCE SUBSTANTIAL FUEL COST REDUCTIONS FOR AIRLINES

TESTS BEGUN TO STUDY DECREASE IN AIRCRAFT DRAG; MAY PRODUCE SUBSTANTIAL FUEL COST REDUCTIONS FOR AIRLINES

Dwayne Brown, Fred Brown

NASA researchers have begun tests on an experiment they hope

will improve the efficiency of commercial aircraft by minimizing

aerodynamic drag. This, in turn, could mean a savings of up to

$140 million annually in commercial fuel costs.

Drag is the aerodynamic force resulting from air pressure and

friction that acts to resist the passage of an aircraft as it

flies through the air.

Called the Adaptive Performance Optimization experiment, the

tests will obtain data on applying an aircraft’s control surfaces

in the optimal position to reduce drag. The tests, which began

last week, will be conducted on a modified Lockheed L-1011 TriStar

by NASA’s Dryden Flight Research Center, Edwards, CA.

NASA’s Langley Research Center, Hampton, VA, is sponsoring

the testing, which is part of the Advanced Subsonic Transport

Aircraft Research program led by the Airframe Systems Program

Office at Langley.

“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 Dryden engineer

Glenn Gilyard, principal investigator and flight-test director for

the experiment.

“There are lots of data to indicate that a one percent

improvement is achievable,” Gilyard said. “The trick is

identifying very small changes in drag,” he added. Project

officials are hoping for drag reductions of up to three percent.

The modified Lockheed L-1011 TriStar jetliner is operated by

Orbital Sciences Corp. of Dulles, VA. The research team plans to

fly the aircraft approximately three or four times each year over

the next two or three years in both the current and follow-on

phases of the experiment. The follow-on phases could incorporate

the TriStar’s flaps into the system, as well as second-generation

computer software using artificial intelligence. 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 pointed out that 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.

“The experiment is designed to improve aircraft performance

during a given flight condition, based on real-time in-flight

measurements and analysis,” Gilyard said.

For the experiment, a team of engineers designed a software

program for the aircraft’s research computer that reduces

aerodynamic drag of the entire aircraft by changing the positions

of the aerodynamic control surfaces. The program incorporates

data such as airspeed, altitude, engine measurements and other

parameters to make instantaneous decisions on adjusting the

position of the control surfaces for the greatest aircraft

efficiency for each point in the flight profile.

In addition to developing the software, NASA engineers

developed flight-research systems that will record test data and

will allow on-board flight test engineers to make decisions and

analysis of research data while the flights are in progress.

“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. The

potential fuel cost savings for a single MD-11 in regular service

could be $130,000 per year and for a Boeing 747, the savings could

approach $150,000.”

These tests mark the beginning of programs that will reflect

the enabling technology of one of NASA’s major aeronautics goals –

– to reduce the cost of air travel by 25 percent within ten years

and by 50 percent within 20 years.

-end-

A Photographic image is available to news media to illustrate this

release by calling the Headquarters Imaging Branch at 202/358-

1900. The photo numbers are:

97-HC-365

97-HC-366