National Full Scale Aerodynamics Complex (NFAC) Test Engineer Al Lizak surveys the large rotor test apparatus test rig prior to tunnel. NFAC recently reached its first major milestone–that of achieving full operational capability for rotocraft testing. A Defense Advanced Research Projects Agency (DARPA) helicopter is scheduled
this spring to be the first test with this capability since the facility reopened in 2006. (Photo by Dominic Hart)
In this image, an engineer is dwarfed by NASA's Mars Science Laboratory's parachute, which holds more air than a 3,000-square-foot house and is designed to survive loads in excess of 36,000 kilograms (80,000 pounds). The parachute, built by Pioneer Aerospace, South Windsor, Conn., has 80 suspension lines, measures more than 65 feet in length, and opens to a diameter of nearly 55 feet. It is the largest disk-gap-band parachute ever built and is shown here inflated in the test section with only about 12.5 feet of clearance to both the floor and ceiling of the world’s largest wind tunnel at National Full-Scale Aerodynamics Complex. The parachute is attached to a launch arm mounted on a swivel-base that allows the test item to pitch and yaw under simulated conditions of subsonic entry into the Martian atmosphere. (Photo courtesy of NASA/JPL and Pioneer Aerospace Corp.)
The National Full-Scale Aerodynamics Complex wind tunnel facility located at NASA Ames Research Center in Moffett Field, Calif., is operated by the U.S. Air Force's Arnold Engineering Development Complex. In 2006, the Air Force signed a lease with NASA to reopen NFAC after the facility closed in 2003 due to budget pressures. Full operational capability ocurred in early 2008.
NFAC is a unique facility primarily used for determining aerodynamic characteristics of large-scale and full-scale rotorcraft and powered-lift V/STOL aircraft, as well as tesing of wind turbines, parachutes, trucks, and other non-traditional types of testing. The facility is composed of two large test sections and a common, six-fan drive system. The 40-by-80 foot wind tunnel circuit is capable of providing test velocities up to 300 knots. The 80-by-120 foot test section is the world's largest wind tunnel and is capable of testing a full size Boeing 737 at velocities up to 100 knots. A system of moveable vanes can be positioned so that air either drawn through the 80-by-120 foot test section and exhausted into the atmosphere, or driven around the closed circuit through the 40-by-80 foot test section. A passive air exchange systems is utilized in the 40-by-80 circuit to keep air temperatures below 125 degrees Fahrenheit. A wide range of available model support systems combine with this unique facility to allow successful completion of aerodynamic and acoustic experiments that cannot be achieved anywhere else.
The 40-by-80 foot wind tunnel was built in 1944. In 1987, it became NFAC after the 80-by-120 foot test section was added and the fan drive system was replaced. The new fan drive system is composed of six variable-pitch fans, each 40 feet in diameter arranged in two rows of three. Each fan has 15 laminated wood blades and is powered by a 22,500 horsepower electric motor. The six fans rotate together at 180 rpm drawing 106 megawatts of electricity at full power while moving more than 60 tons of air per second.
Unique, test specific requirements are explored with each customer to guide the experiment design and new systems are integrated into the facility as needed. Utility support systems that have been used for testing powered vehicles and components include variable frequency electrical power, hydraulic power units, cooling water, 150 and 400 Hz electrical power and jet fuel systems. Rotor test beds incorporating electric motors and rotor balance systems are available for testing complete rotor and hub systems independent of the flight vehicle.
Data Systems The NFAC Data Acquisition System is a distributed computing system connected by both a real-time network using reflective memory, and a switched Ethernet and Local Area Network within the NFAC control room. Major Components consist of the Basic DAS, Dynamic DAS, Safety of Flight DAS, Real-Time Processor and Post-Point Processor.
Additional features include:
-- Calibrations traceable to National Institute of Standards and Technology standards.
-- Support for dynamic acquisition of analog inputs. Basic DAS and Dynamic DAS data are acquired synchronous to rotor position for rotorcraft testing or by a common clock for non-rotor testing.
-- Real-time calculations and engineering unit conversions with results instantly available to the user for review and diagnostics.
-- Standard equations library available in the Real-Time Processor and Post-Point Processor to meet most aerodynamic test computational requirements. Full support of test dependent equations to meet unique customer requirements.
-- Multiple, continuous near real-time displays for monitoring measured and computed parameters in table and plot format.
-- Post-point data reduction, analysis, and plotting.