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tip diameter qf 39 ft. The outer 2 in. portion of the fan 160 deg to either side of the wind tunnel centerline. The
blades is balsa, and serves to break away in the event foreign /aw drive provides rates of l/4 and 4 deg/sec.
articles are blown around to the fan section. On the turning The balance systems are capable of measuring and re­
vanes in front of the fan is a 1 in. mesh stainless steel wire motely indicating forces and moments as defined in Table 1.
screen, which should prevent any large damaging materials DATA ACQUISITION SYSTEM - The wind tunnel data
from getting to the fan. The blade leading edges are cov­ acquisition system supplied by Space Craft Inc. is physically
ered with a soft polyurethane film to protect the blades located in two rooms on the operating floor of the wind tun­
against abrasion from dust and other small particles in the nel. One of the more impressive features of this system is
airstream. its ability to read, reduce, record, and plot the data from the
Five fixed counter-rotation vanes are installed down­ test on a real time basis, so there is no waiting for answers
stream of the fan to remove the rotational velocity com­ to be used in test evaluation. The high speed paper tape
ponent of the airstream emanating from the plane of the reader and punch, off-line teletypewriter, magnetic tapes,
fan. In addition, the vane fairings serve as motor and nacelle disk, and computer main-frame are located in the com­
support structure, and as ducts for cooling air for the totally puter room. The control-teletypewriter/line printer, plot­
enclosed drive system, as well as ducts for entrance of elec­ ters, digital displays, and control console are located in
tric, water, and oil lines into the drive system components. the control room shown in Figs. 9 and 10. The two rooms
MEASURING EQUIPMENT - Two nominally identical, ' are separated by approximately 33 ft.
pyramidal external balance systems designed by TEM En­ The computer is controlled from the control-teletype-
gineering Ltd. are provided for use at the facility, with one
balance installed under each of the two test sections. Each
balance separates and measures independently tne basic
Table 1 - Balance Force And Moment Ranges
aerodynamic components of lift, drag, and side force, and
pitching, yawing, and rolling moment. Both balances
Centerline Floor Mounted
will carry the loads developed by two classes of models un­
Component Mounted Model Model
der test, either models supported on the strut system near
the center of the test section or models attached to the bal­ Lift, lb -5000- +10,000 -1500- 3000
ance at or just above the wind tunnel floor. Drag, lb -1500- 1500 -5000- 10,000
Models in either test section are attached to and posi­ Side Force ±5000
tioned by the support system which transmits model loads (that is, lift on
to the balance. The entire model support system is mounted l/2 model), lb
on the balance turntable, which is driven in yaw within the Pitching Moment, ft-lb ±5000
balance moments frame. The moments frame is one of Rolling Moment, ft-lb ±5000 ±30,000
the four major structure portions of the balance shown in Yawing Moment ±3000 ±10,000
Fig. 8, and it senses moments about the tunnel centerline. (that is, pitching mo­
The other parts are the turntable, supporting the models; ment for l/2 model),
the forces frame, which senses model forces; and the earth ft-lb
frame, which is a nonmetered structure supporting the whole
system. The balance turntable may be rotated more than
*1

MOMENT CENTER

£4^ ........

Fig. 8 - Balance schematic Fig. 9 - Digital displays