Summary of Methods of Measuring Angle of Attack on Aircraft Page: 7 of 30
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NACA TN 4l51
a direct indication of the angle of attack is desired, a pressure-ratio
type of instrument must be employed.
Data from wind-tunnel tests of differential-pressure sensors having
hemispherical nose shapes are presented in figures 3 and 4. The sensor
shown in figure 3(a) was about iL inches in diameter with two orifices
-4-
spaced 900 apart. The data for this sensor were from a report of limited
availability by G. F. Moss and N. K. Walker of the British Royal Aircraft
Establishment. The tests were conducted at a Mach number of about 0.11
through an angle-of-attack range of 200. The variation of 4p/q with
a for these test conditions is given in figure 3(b). The two sensors
shown in figure 4(a) were 1/2 inch in diameter and were tested by the
Engineering Physics Department at Cornell Aeronautical Laboratory, Inc.
The orifices of one of the tubes were spaced 600 apart and those of the
other, 900 apart. The tests covered a range of Mach number of 0.5 to
0.8 and an angular range of 00 to 200. Sample results of the tests at
M = 0.55 and 0.60 are presented in figure 4(b). These data show that
the tube with the orifices spaced 900 apart is more sensitive to angle
of attack than the tube with orifices spaced 600 apart. The data also
show the sensitivity of both tubes to decrease as the Mach number
increases. A comparison of the data in figures 3 and 4 shows the sensi-
tivity of tube A in figure 4 to be greater than that of the tube shown
in figure 3 despite the fact that the orifices on both of the tubes are
spaced 900 apart. The Mach number trend shown in figure 4 does not
account for this difference and no other explanation for the difference
can be found in the reports of these two tests.
The use of conical nose shapes for measurements at supersonic speeds
has received considerable attention because the measurement of total pres-
sure at the nose of the cone, in combination with the pressures on the
surface of the cone, can provide indications of Mach number and static
pressure as well as angles of attack and sideslip. Wind-tunnel tests to
determine the accuracy with which Mach number and angle of attack can be
calculated from the pressures on a 150 cone at M = 1.99 are reported
in reference 9.
Wind-tunnel data of conical-nosed tubes having apex angles of 300,
400, and 500 were also made at the Cornell Aeronautical Laboratory, Inc.
The body diameter of each tube was 1/2 inch and the orifices on each of
the tubes were located 2/3 of the cone length behind the apex. (See
fig. 5(a).) The tests were conducted at M = 0.30 to 0.65 through an
angle-of-attack range of 00 to 200. Sample calibrations of the tubes
at M = 0.55 and 0.60 are presented in figure 5(b). These curves show
the sensitivity of the tubes to decrease as the apex angle decreases.
For the range of Mach numbers covered by the tests, the effect of Mach
number on the sensitivity is small for the 500 probe and negligible for
the 500 and 400 probes.
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Gracey, William. Summary of Methods of Measuring Angle of Attack on Aircraft, report, August 1958; (https://digital.library.unt.edu/ark:/67531/metadc57244/m1/7/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.