Lab 8 Notes – Basic Aircraft Design Rules
Nomenclature
x, y longitudinal, spanwise positions
S reference area (wing area)
b wing span
c average wing chord ( = S/b )
AR wing aspect ratio
CL lift coefficient
Υ wing dihedral angle
β sideslip angle
φ bank angle
R turn radius
Sh horizontal tail area
Sv vertical tail area
ℓh horizontal tail moment arm
ℓv vertical tail moment arm
ARh horizontal tail aspect ratio
Vh horizontal tail volume coefficient
V
v vertical tail volume coefficient
B spiral stability parameter
α angle of attack
V velocity
Role of Simple Design Rules
Aircraft must have a certain amount of inherent stability and controllability to be flyable. It
is therefore important to consider these characteristics when designing a new aircraft. Accurate
evaluation of the stability characteristics of any given aircraft is a fairly complicated process, and
is not well suited for preliminary or intermediate design. Fortunately, we have alternative criteria
which give reasonable estimates and are vastly simpler to apply.
The criteria involve basic dimensions, shown in Figure 1. Longitudinal x locations are typically
S
cg
x
v
Sh
S
c
b
xnp
l h
lv
c
MAC
x
y
Figure 1: Lengths, areas, and angles used in simple stability criteria.
1
