Determination by the Free-Fall Method of the Drag and Longitudinal Stability and Control Characteristics of a Canard Model at Transonic Speeds Page: 5 of 47
This report is part of the collection entitled: National Advisory Committee for Aeronautics Collection and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
.mS
NACA RM 150D04
The center of gravity of the model was located 81.7 percent of the
mean aerodynamic chord (mean geometric chord) ahead of the leading edge
of the mean aerodynamic chord. The model had a wing loading of 150 pounds
per square foot and a moment of inertia about a lateral axis through the
center of gravity of 531 slug-feet squared. The total horizontal control-
surface deflection was from 00 to 120 trailing edge down. The total
aileron deflection obtainable was 200 right and 80 left (right aileron
100 up, 40 down; left aileron 40 up, 100 down).
Control Systems
The automatic control systems and internal instrumentation used in
this model are shown schematically in figure 5. An automatic pilot
sensitive to normal acceleration was used to control the model in pitch.
The automatic pilot operated in such a manner as to attempt to control
the normal acceleration at approximately 1/2g. When the acceleration
exceeded the desired 1/2g, the automatic pilot moved the horizontal
control surface at a constant rate in the nose-down direction, and, in
a like manner, when the acceleration fell below 1/2g, the automatic
pilot moved the horizontal control surface in the nose-up direction.
A 11-second time delay between control motion in one direction and the
2
other was incorporated in the automatic pilot. This time delay elimi-
nated any possibility of dynamic instability of the automatic pilot-model
combination. This objective is accomplished by preventing any adverse
phase relationship between motions of the horizontal control surface and
the model.
In addition, a time delay of approximately 12 seconds was employed
to prevent the automatic pilot from operating during the initial part of
the drop. Use of the 12-second time delay allowed the model to increase
in speed while at zero lift since the horizontal control surface was
initially set at zero deflection. The increase in speed prior to control
operation was desirable because the combination of a high wing loading
and the low dynamic pressure at release might have resulted in a stall
of the model.
Another automatic control system was used in attempt to control the
rate of roll of the model. (See fig. 5.) The ailerons were connected
by linkages to a rate gyro. The gyro restraining springs were preloaded
to give a moment corresponding to the precessional moment produced by the
gyro at a rate of roll of 1/10 rps. Since no roll existed at release,
the ailerons were held by the spring preload at maximum deflection in the
direction to produce right roll and remained so deflected until a rate of
roll of approximately 1/10 rps was obtained, after which the gyro moved
the ailerons in a direction to oppose further change in the rate of roll.
The variation of processional moment with rolling velocity for the gyroa
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Kraft, Christopher C., Jr. & Mathews, Charles W. Determination by the Free-Fall Method of the Drag and Longitudinal Stability and Control Characteristics of a Canard Model at Transonic Speeds, report, August 25, 1950; (https://digital.library.unt.edu/ark:/67531/metadc58452/m1/5/: accessed May 30, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.