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writer. Inputs can be entered from the high speed paper so that any variable used by the reduction program may
tape reader at 300 characters per second, from either mag­ be displayed. The computer controls the timing for up­
netic tape unit, from the control-teletypewriter’s paper tape dating the displays.
reader at 10 characters per second, or from the control­ Stored data are recorded in raw form on one magnetic
teletypewriter’s keyboard in response to interrogation from tape and may be stored also in coefficient form on the sec­
the computer. ond magnetic tape. The data system is able to generate
Up to 12 digital data channels and 55 analog data chan­ coefficient data from recorded raw data at any time after
nels are input to the computer through a multiplexer. The obtaining the data.
six-component balance data, pitch, and yaw angles, and PROPULSION UNITS - Two auxiliary systems are used
four model component position indicators are displayed on to power simulated propulsion units within the models. The
the control console and also fed into the digital multiplexer first system, an Allis-Chalmers air compressor consisting
Three wind tunnel airflow parameters and 49 analog chan­ of two centrifugal multistage sections having maximum out­
nels are directed to the analog multiplexer and the analog puts of 100 and 375 psig, is capable of supplying 20 lb/sec
to digital converter. Of the 49 analog channels, as many at 300 psig. The second is a motor-generator system which
as 14 may be used for reading scanivalve transducers. The provides variable frequency electrical power.
remaining analog channels may be used for reading mul- AIR SYSTEM - The air supply system consists of two
livolt outputs from strain gages, transducers, thermocouples, centrifugal compressors connected in series and driven through
and so forth. speed increasing gears by a 4500 hp synchronous motor.
Scanivalves are used to acquire pressure data, and nor­ This air system could be used with ejectors to vary the air­
mally 48 tubes can be connected to each valve to transmit flow through the grille region and around the engine cavity
data electrically through one transducer. The scanivalve to determine variable airflow effects on the car. All air
control unit steps the valves in response to signals from the supply equipment is controlled from a panel located in the
computer timer. The transducer reference pressures are electrical equipment room or from the main Wind Tunnel
monitored for calibration purposes on a precision pressure Control Console.
balance which supplies analog signals to the Data Acquisi­ The air supply system is capable of receiving 18,000 cfm
tion System. Approximately 650 local surface pressures of air at atmospheric pressure at a temperature range from
may be recorded with this scanivalve system. a maximum of 100 F to 10 F, 50% relative humidity, and
The computer can output to either magnetic tape unit, delivering this air free of oil or other contaminants to the
a 120 character per second paper tape punch, a 300 line models at 318 psia pressure. If the desired inlet volume
per minute line printer, and nine 11 in. x 17 in. point plot­ is less than 18,000 cfm, a correspondingly higher discharge
ters. The control-teletypewriter is reserved solely for two- pressure up to a maximum of 375 psia can be obtained.
way communication with the computer. Silica gel dessicant dryers rated at 20 lb/sec at 300 psig
Fifteen four-digit-plus-sign displays are mounted in the are available to provide output air at -60 F dew point. The
DAS rack. A two digit digi-switch is associated with each dryer system consists of two units, so that one unit is being
display. Each of the 67 input channels is assigned a number electrically heated for regeneration while the other unit
which, when dialed on the digi-switch, will display that is on line.
channel in the associated display windows. Digi-switch POWER - Two ideal model power motor-generator sets
positions may also be assigned through a FORTRAN program supply power to receptacles at either the low speed test sec­
tion or V/STOL test section. A variety of model motors
may be connected to these receptacles depending on size
and type of model and test configuration. Control and moni­
toring of the model power systems are performed at the main
Wind Tunnel Control Console.
Each model power system consists of a generator driven
by a squirrel cage induction motor through an eddy current
coupling. Output frequency of the generator is controllable
from 60-400 cps by adjusting coupling excitation and thus
generator speed. The volts-per-cycle ratio can be regu­
lated from 0.4-2.0 throughout the frequency range with a
maximum limitation of 400 v output. Each generator is
capable of supplying 240 hp to four identical three phase
induction motors.
The model motors are started individually and accelerate
to a minimum speed corresponding to a buss frequency of
60 cps. In the event of overheating, emergency stopping
of the motor is possible. Control of the model power sys­
Fig. 10 - Line printer and plotters tems is performed from the remote control console. Motors