Transcript Engineering 310

Aero Engineering 315
Lesson 36
Stability and Control
Longitudinal Static Stability
So what’s so important about
aircraft stability?
Lesson 36 Objectives
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Draw a stability curve (Cm vs a) for tail and wing
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Draw a curve for positive, negative and neutral stability
Understand tail and wing contributions to stability
List factors that contribute to longitudinal static stability
State criteria for positive long-stat stability
Identify trim AoA and velocity
Predict changes in stability with changes in tail area,
moment arm, incidence angle, camber, CG, etc.
Define neutral point and static margin
Know criteria for positive long-stat stability WRT CG and
static margin
Moments for “Natural” Stability
Mc
g
Mcg decreases
with increasing a
aVmax
Associated with
high speed limits
atrim
astall
aa
Criteria for Longitudinal Static
Stability and Balance
CM
cg
CM
∂CM
cg = C
M
∂a
a
Steeper slope (more negative) =
more stable (stronger restoring moment)
0
a
atrim
Aircraft is Longitudinally Statically Stable if:
Thus, to balance it at a useful CL:
CM < 0
CM > 0
0
a
Changing Variables*
C
M cg
CMo _____
change
CMa No
_____
atrim _____
Vtrim _____
C
M cg
change
CMo No_____
CMa _____
atrim _____
Vtrim _____
a
a
Slow Down (c. g. constant)
* In Handout Package
Move c. g. Aft
Next Lesson (37)…
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Prior to class
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Read/review sections 6.1 - 6.3
Review long-stat stability handout
In class
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Finish discussing longitudinal (pitch)
stability