XV-15 litho - NASA's History Office

close formation to a quiet research aircraft (the Lockheed YO-3A) which was
equipped with microphones and recording equipment. By maintaining the YO-
3A microphone location at a fixed distance and position with respect to the XV-
15 proprotor (shown in figure 60) corresponding to a microphone location in the
test section of the wind tunnel, and by operating at the same proprotor operating
condition, a direct comparison (with corrections for the second proprotor)
between the flight data and wind tunnel test data was obtained. This experiment
was conducted by Ames researchers. The tests 48 involved a Bell flight crew in the
XV-15, and a NASA flight crew in the YO-3A.
Composite Proprotor Blades
From the very beginning of the TRRA project the proprotor blades were of special
concern to the Government Project Office. The metal blades used on the XV-
15 were designed in the late 1960s under Bell’s IR&D funding for the predecessor
tilt rotor aircraft, the Bell Model 300. This aircraft had a design gross weight
of 12,400 pounds, 600 pounds lighter than that of the XV-15. The concern was
48 The results of the 1995 terminal area and in-flight acoustics tests are presented in: Michael A.
Marcolini, Casey L. Burley, David A. Conner, C. W. Acree, Jr., “Overview of Noise Reduction
Technology in the NASA Short Haul (Civil Tiltrotor) Program,” SAE International Powered Lift
Conference, Jupiter, Florida, November 18-20, 1996.
Figure 60.
The XV-15 flying in close
formation with the YO-3A
for acoustics data.
(Ames Photograph
AC95-0438-15.1)
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