SAWE Report - Cal Poly San Luis Obispo

10 Stability and Control
To initially size the horizontal tail, tail volume coefficients from historical aircraft were
analyzed. This was done in an attempt to determine the rough size of the horizontal and vertical
tail surfaces prior to addressing stability and control issues. The tail volume coefficients are
unitless parameters defined by geometric values relating the size of the empennage surface to the
aircraft. The horizontal and vertical tail volume coefficients are defined in the following
equations.
V
H
=
SHTL
c S
W
HT
W
V
V
=
SVT
L
b S
W
VT
W
Because the demands for most supersonic cruising aircraft are considered similar to a certain
extent, the historical values of tail volume coefficients are used to back out the planform areas
for the horizontal and vertical surfaces. Similar aircraft and their tail volume coefficients are
presented in Table 10.I.
AIRCRAFT
Table 10.I - Historical Aircraft Tail Volume Coefficients
TAIL VOLUME COEFFICIENTS
V H
V V
Boeing SST (2707-300) 0.36 0.049
Concorde n/a 0.080
GD F-111A 1.28 0.064
Rockwell B1B 0.80 0.039
TU-22M 1.11 0.087
TU-144 n/a 0.081
AVERAGE 0.58 0.067
Using the average tail volume coefficient for these similar aircraft yielded a horizontal stabilizer
area of 386 ft 2 . This is rather large and may be attributed to the fact that these vehicles require
large robustness in CG travel without the use of a flight control augmentation system (CAS).
Likewise, the vertical tail would require 196 ft 2 of area. This number is driven slightly larger due
to the fact that some of the larger historical tail volumes are inflated because these aircraft’s
verticals are mounted on booms which extend aft. These booms allow for greater moment arms
and make the vertical more effective.
The effects of horizontal tail area on longitudinal static stability were looked at in an attempt to
determine what the driving factors for horizontal tail area are. A Roskam class II method was
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