The Langley 14 X 22 Foot Subsonic Tunnel Brochure

14 X 22 Foot Subsonic Tunnel

NASA Langley Research Center

The Langley 14- by 22-Foot Subsonic Tunnel is currently used for low-speed tests of powered
and unpowered models of various fixed- and rotary-wing civil and military aircraft.

Test Section and Performance

14 X 22 Foot Subsonic Tunnel Characteristics

The Langley 14-by 22-Foot Subsonic Tunnel (14x22) is an atmospheric, closed return tunnel with a test section 14.5-ft high, 21.75-ft wide, and 50-ft long that can reach a velocity of 348 ft per sec with a dynamic pressure of 144 psf. The Reynolds number per foot ranges from 0 to 2.2 x10⁶. The flow in the closed test section configuration is relatively uniform with a velocity fluctuation of 0.1 percent or less. When the test section is not in the fully closed configuration, the test section velocity is lower and the turbulence level is higher. Test section airflow is produced by a 40-ft diameter, 9-bladed fan powered by a 12000-hp solid state converter with synchronous motor. This main drive motor was installed in 2001. The tunnel has a set of flow control vanes to maintain close control of the speed for low-speed testing.

Speed, foot per second	348
Reynolds number, per feet	0 to 2.2 x10⁶
Test gas	Air
Test section size, feet	14.5 x 21.75
Length, feet	50
Drive power, horsepower	12,000

High-Pressure Air and
Cooling Capability

High-pressure air and cooling water lines are available at the test section for connection to model components.

Low Noise Tiltrotor configuration

Instrumentation

Model force and moment measurements are typically made with 6-component strain-gage balances. Multiple pressure measurements are made with an electronically scanned pressure (ESP) system, and iron-constantan thermocouples are typically used to measure temperatures.

Data Acquisition and Processing

Static and dynamic data acquisition systems are available. The static system is comprised of three Open Architecture Data Acquisition Systems (OADAS). This OADAS is based on the Compaq Computer Corporation's AlphaServer line of computers. One system is dedicated to the tunnel and the other two are for the model preparation area (MPA). Each is capable of handling input from 128 analog, 32 digital, and up to 2048 pressures from ESP module channels. The digital inputs can be configured to support a combination of 24-bit BCD, binary, datex, tachometer, resolver, RS-232, and GPIB device interfaces. The dynamic system can handle 72 channels with a 0- to 20-kHz bandwidth. All channels can be digitized in real time (16 bits for a 90-dB dynamic range), and stored on removable disk drives.

Facilities Available to Users

Six model carts complete with model support systems are available for model assembly and disassembly in the six buildup test sites of the MPA or in the rotor test cell. Common instrumentation interfaces are provided with quick connections at all sites. In addition, static tests of powered models can be performed at these sites.

Safety and Design Criteria

Langley’s LAPG 1710.15 Wind Tunnel Model System Criteria is the guideline for model design and fabrication. Model installation and any exceptions to this document must have the approval of the 14x22 Safety Head on a case-by-case basis to assure personnel and tunnel hardware are not exposed to risk.

Model Supports		Test Techniques
Models are typically mounted on carts for all tests, including ground-effects, high angle-of-attack, rotorcraft, forced oscillation, or semispan testing. The facility has six large model carts with varying capabilities to support a variety of testing. Models are typically assembled and disassembled on these carts in the MPA, which has several static test areas, as well as the rotor test cell. Two carts have the capability of vertical traverse for ground-effects testing with ranges of 24 deg in pitch and 170 deg in yaw for one cart and 190 deg in yaw for the other. Another cart can accommodate a vertical strut support system with pitch (-10 deg to 50 deg) and elevation (near 0 to 87 in. above floor) capabilities. The facility also has a unique support system with a 3-joint rotary sting, which keeps the model center at the test section centerline. This system has a pitch range of 32 deg, a yaw range of 30 deg, and a vertical traverse of 6 ft. The carts can also be lowered 2 ft below the test section floor to accommodate acoustical treatment, a microphone traverse system, or the third component of the laser velocimetry system.		Flow visualization techniques available at the facility include a laser light sheet, smoke flow, titanium dioxide oil flow, and fluorescent minitufts. Additional capabilities and test techniques are being developed for the 14x22, primarily in the form of new or modified model carts. There are three techniques formerly used at the Langley 30- x 60-Foot Full-Scale Tunnel are available in the 14x22. These are (1) the small model, high angle-of-attack technique, (2) free-flight testing, and (3) forced oscillation testing. A new model cart is currently being developed for the forced oscillation technique. In addition, motorsports and vehicular tests have been conducted in cooperation with Old Dominion University.
Semi-span mount of Trapezoidal Wing model with acoustical array mounted on tunnel sidewall.
Type of Testing		Test Request Procedures
Transport Model in Tunnel	The tunnel (initially named the V/STOL Tunnel and later the 4- by 7-Meter Tunnel) was constructed in 1970 to provide an improved understanding of the aerodynamics of vertical/short takeoff and landing (V/STOL) aircraft configurations. This facility addresses the distortion of the tunnel flow that results from the strong downwash generated by the V/STOL model lift fans or jets and the interaction of the floor boundary layer with the vertical or forward-facing propulsion flow components from the model. Tunnel configurations include a fully closed test section, and an open test section closed only on the floor. A boundary layer removal system and moving-belt ground plane prevent the formation of a floor boundary layer in the test section and provide a uniform vertical velocity distribution for ground-effects testing. The 14x22 is also ideally suited for low-speed tests to determine high-lift stability and control, aerodynamic performance, rotorcraft acoustics, turboprop performance, motorsports, and basic wake and flow-field surveys. An extensive modification was completed in 1984 to improve flow and expand capabilities for both acoustic and rotorcraft testing. In 1999, the facility automation system and new model carts were added to the facility.	The first step of the test process is to submit a test request form. The form can be filled out electronically or printed for mailing at the NASA Langley aero Compass website. A posttest questionnaire is also available at this site. Our customers are encouraged to provide feedback to the facility for our continuous improvement process.

Document Version 1.0
Trademark Disclaimer: The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration.
For more information contact: The 14 X 22 Foot Subsonic Tunnel Manager -- NASA Langley Research Center -- Hampton, Virginia 23681-2199 phone: 757-864-5068 \| fax: 757-864-8820 \| e-mail: wte+fm_14x22@larc.nasa.gov

NASA Official Responsible For Content: Pete Jacobs

Page Curator: Lori Rowland

Date Last Updated: 07/01/08

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