• The TWT is a continuous flow, variable density facility. Shock attenuation and de-blocking to achieve transonic speeds is accomplished through uniformly perforated test section boundaries, a concept originated and developed at Calspan.
• Maximum clear tunnel Mach number is 1.35 and the tunnel may be operated at stagnation pressures from 0.25 to 3.25 atmospheres.
• Test conditions are set via independent control of Mach number and one other pressure-dependent variable for:
  • Constant Reynolds number
  • Constant static pressure
  • Constant dynamic pressure or
  • Constant total pressure operations
• Under conventional operations (the blue or dark region of the Operating Map), the tunnel can operate continuously at Reynolds numbers up to about 5 million per foot or a dynamic pressure of approximately 800 lb/ft², for most of the Mach number range.
• Ejector augmentation for high Reynolds numbers operating conditions is also available. In this blow down mode and for limited test duration, higher Reynolds numbers up to 12.5 million per foot or a dynamic pressure of approximately 2200 lb/ft², can be achieved using the tunnel's Ejector-augmentation system (the yellow or light region of the Operating Map).
• The entire cooling system of the tunnel maintains the test section total temperature in a range of approximately 65°F to 140°F. The humidity levels of the air stream are typically held below 5000 ppm.

TWT Operating Map
Click for a larger thumbnail image

• Test and data acquisition procedures are integrally keyed to either pause, continuous sweep or Hybrid (Pause/Sweep Combined) operating scenarios in the pitch, yaw, or roll planes.
• " Demonstrated run rates are highly dependent on model configuration and number of runs per configuration (model change) and run type. When comparing run rates, only the Air On Hours (AOH) should be considered since it eliminates the unknown (variableness) it takes for model configuration changes. Also note the run rates for pause testing are inversely proportional to the number of customer desired angles; more discrete angles results in a slower run rate The following AOH run rates are typical at the Calspan TWT.
  
  
• All data reduction computers are contained within the TWT control room that allows the user quick access to data results and provides excellent control over computing program/ presentation changes as required. Calspan's user-friendly plotting routines allow for quick and efficient data evaluation.
• Main balance force and moment (F&M) data, model pressures, as well as all standard facility instrumentation are acquired using Calspan's Data Acquisition System. All acquired data are transferred via Ethernet to Calspan's Data Reduction System.
• Data reduction requirements for the test program are comprised of customer supplied algorithms as well as Calspan's standard data reduction methodologies.
  • Any unique or test specific requirements should be provided with as much advanced notification as possible and include all of the necessary algorithms and data reduction methodologies.
  • Calspan will review these data requirements and formulate a data reduction report for evaluation and approval.
• On typical TWT test programs, after initial verification of data has been completed, fully corrected data is made available in tabular, plotted, and electronic formats immediately after a run is completed.
  • Hard copies of tabular and graphical test data can be provided on-request.
  • Data can also be transmitted electronically to customer-supplied computers on site if required.

• The ISO-9001:2000 certified TWT facility is designed and operated for maximum user flexibility and efficiency.


The Calspan TWT Calibration Model supplements basic (static pipe) tunnel airflow calibration results with repeat entries to demonstrate the repeatability and quality of the test section flow-field. This calibration model:

TWT Calibration Model

• Most test types Calspan can support will utilize the TWT's Sting Cart. The Sting Cart has a vertical strut support and pitch mechanism. The vertical strut is limited to:
  • a maximum 3,500 lbs [15,568 N] and
  • a maximum side force of 1,500 lbs [6,672 N] load at the model.
• The system is capable of wind-off angle-of-attack ranges of ±18.25°, ±20.5° or ±24.5° depending on the selected center of rotation (COR) point of the support's pitch mechanism.
  • These angle ranges are increased during wind-on test operations when balance/sting deflections are introduced.
  • All angle ranges can be biased with the addition of fixed or variable angle adapters.
• The pitch mechanism can be operated in a point pause, continuous-sweep, or hybrid mode. The pitch rate in a continuous-sweep mode can be set anywhere between 0.25º/sec to 2.0º/sec and has been optimized to 1.25º/sec.
• To set yaw angles, TWT typically utilizes its Double Roll Mechanism (DRM) and the sting cart model support system. The DRM contains two roll actuators, each with a roll angle range of ±180°, joined together within an aerodynamic fairing at a 10° included angle. The arrangement allows model yaw angles to be set ranging over ±10° in a wings-horizontal orientation.
• Typical wind-on run rates for pitch variable runs range from 7 runs per hour in the pause mode to 30 runs per hour or more in the sweep mode.
• Yaw and roll sweep rates of 15 and 20 runs per hour, respectively, are typical
• All rates are subject to model size, instrumentation/data requirements, and tunnel operating conditions.
• For even greater angle ranges, Calspan has a high angle-of-attack, Single Roll Mechanism (HISRM) system that can be installed on the Sting Cart.
• The HISRM has a double-clutched, pitch adjustment feature that can bias the pitch range of the Sting Cart up to 45°.
• A model can be tested from -5° to +40° and then from +40° to +85° in one installation for a total angle-of-attack range of -5° to +85°.

• Free-to-Roll (FTR) wind tunnel testing is used identify the potential for un-commanded lateral motions in air vehicles. The data from this test technique coupled with traditional force and moment (F&M) data can:
  • Determine the severity of the motions
  • Assess the impact of unsteady and nonlinear aerodynamics (rate and amplitude)
  • Determine dynamic aerodynamic data (roll damping).
  
  The FTR rig is designed to accommodate typical wind tunnel test articles, instrumentation and support stings.
  
  
  • Locking bars are included in the design to allow switching between FTR testing and standard (static) F&M testing.
  
  
  
  
• Braking control logic is designed to interrupt unsafe roll accelerations and divergences of the test article and to gently decelerate the test article without overloading F&M measuring systems.
  
  
• The FTR rig is compatible with Calspan's Double Roll Mechanism (DRM).

o Store Freestream
o Flow Field Grid & Captive Trajectory Simulation
o Ejector stroke simulation
o Variable restrained motion
o Auto-pilot
o Rail launches
o A/C maneuvering
o A/C roll due to store release
o Pull-up / Push-overs
o Captive Loads Testing
o Simultaneous testing of multiple metric stores
o Weapons Bay Acoustics
o Weapons bay/store interactions
o Static & dynamic pressure monitoring
o Support of aero-acoustic suppression devices

• 6 DOF aircraft and store motions are computer controlled
o Theta or Z-traverses in customer defined coordinate systems
• System Optimized for High Productivity
o Automatic store / A/C positioning
o Infrared proximity sensors
o Collision detection system
o Opto-Trak 6-DOF position monitoring



Calspan Transonic Wind Tunnel Weapons Integration Capabilities Handout

o Testing semi-span force, pressure and flutter models
o Isolated large scale model components (wings, tails, etc.)
o Full scale APUs.
o Can be easily configured to meet other specialized mounting or test requirements

o Incorporates a 7.25-feet (2.2-m) diameter turntable
o Provides for ±180° angle excursion
o Utilizes swept leading edges that are elevated 4 inches above the primary tunnel floor to place the reflection plane out of the tunnel floor's boundary layer

o This chamber, easily accessible during model configuration changes, can accommodate complex pressure instrumentation, remotely operated control surface mechanisms, or high-pressure air lines for cold jet simulations

Derivative Assessment Testing using Calspan's Island Fairing Cart

• The Island Fairing (IF) or super-blade cart is employed primarily to study after-body distortion and sting effects on the aerodynamics of a model configuration


• It is used solely for incremental-type testing.
• The IF cart provides:
o A constant wetted-area blade support fro model mounting
o A high fineness ratio fairing conceals a three-component (NF, PM, AF) balance and a pitch mechanism
o A pitch mechanism with a range of ±16.5°
o The capability to attach dummy stings to the moving support mechanism to aid in investigating sting tare effects

Inlet Optimization & Jet Effects

Inlet Optimization & Jet Effects

For testing requiring the use of "cold" auxiliary gas, the Calspan TWT has the necessary control system to deliver dry, metered, high pressure air to the customer's model.
• Can provide approximately 2000 psi air at mass flow rates of 2 lbm/sec or less
o Mass flow rates up to 15 lbm/sec provided at proportionally lower pressures
• Three independently controllable primary air-flow systems
o 1 lbm/sec
o 4 lbm/sec
o 15 lbm/sec
• A supplemental, dual channel air delivery system for secondary or tertiary flows


o Capable of open or closed loop control
o Flows ranging from 0.02 to 0.2 lbm/sec
o At pressures ranging from 20 to 100 psi.
o Set points to within ±1.0% and measurement accuracies to within ±0.1%

• Calspan maintains an inventory of rear entry stings to support the models in Calspan's model support system. Factors influencing sting selection include:
  • structural integrity,
  • flexibility
  • aerodynamic interference
  • exit clearance
  • location in the test section and
  • accommodation for cables and utilities.
• Calspan will use customer model specifications such as model drawings to determine if a sting in our inventory can be utilized. We can also use a sting provided by the customer or, if no sting exists, Calspan can design and fabricate a sting at additional cost.

• Integrity of the models and their suitability for testing in the TWT will be verified by the Calspan design staff.
• The models must be stressed to a minimum safety factor of five.
  • A stress analysis report for the models and model support hardware must contain sufficient detailed loads data to assess model integrity.
  • This report is required a minimum of three weeks prior to the test start date for Calspan review.
  • A lower safety factor (minimum of four) may be utilized provided substantiation is provided in the stress report for Calspan approval.
• All new models tested at the TWT undergo a detailed inspection by Calspan's on-site inspection laboratory, to determine the main balance location and alignment relative to a known reference point on the model.

• When identifying an appropriately sized model for testing in the TWT, Calspan follows model-sizing guidelines generally accepted by the industry for transonic wind tunnels with ventilated test section walls.
• These guidelines are summarized in below:

Model Sizing Guidelines for TWT

• The TWT has also had great success testing models that have exceeded these guidelines. Although not recommended for validation testing, larger models have proven useful for programs quantifying incremental effects.
• Model length is also subject to limitations. The overall model length must be within the region of uniform Mach number distribution for the maximum test Mach number. In addition, the model base should be a reasonable distance forward of the aft tunnel station listed to avoid possible interference effects due to the model support system.
• Calspan will recommend an appropriate support sting length to ensure proper model placement in the TWT test section.