Post on 01-Apr-2015
transcript
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Lecture 7: Stability & Control
Jason Mickey
For AE 440 A/C LectureSeptember 2009
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S&C Responsibilities
• Select/design/size all control surfaces, e.g. horizontal tail, vertical tail, etc. (sizes to aerodynamics & configuration
• Determine/Ensure static margin range for all flight conditions
• Evaluate longitudinal and lateral stability (suggest needed changes to configuration)
• Specify avionics and any digital control system (weight/size to internal configuration)
• Evaluate dynamic stability (phugoid & short period) and evaluate flying qualities (e.g. with a flight simulator)
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Control Surface Sizing
• Horizontal tail, elevator
• Vertical tail, rudder
• Ailerons
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Longitudinal Moments
Raymer, Fig. 16.3
cg cg acw w w f fus
h ach cg t p cg p
M L X X M M f M
L X X Tz F X X
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Tail and Control Surface Sizing
vt W Wvt
vt
c b SS
L Wht W
htht
c C SS
L
(Raymer)
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Neutral Point
W
PahL
W
hthL
PP
Paachh
LW
hthmacwL
np
qSF
aa
CSS
C
Xaa
FXaa
CSS
CXC
X
aha
ahafusa
(Raymer)
Find such that for all aX 0aMC
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Yaw and Roll Moments
wing w a fus acv cg
p p p cg p
N N N a N F X X
TY DY F X X
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Stability and Handling Qualities
• Static stability
• Dynamic stability
• Handling qualities
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Tail and Control Surface SizingTable 5.2.1 Horizontal Tail Dimensions
Configuration Area (ft2) Span (ft) Mean Chord (ft)
Pusher 26.75 10.7 2.5
Tractor 22.83 9.13 2.5
Twin-Boom 19.41 7.31 2.5
Table 5.2.2 Vertical Tail Dimensions
Configuration Area (ft2) Span (ft) Mean Chord (ft)
Pusher 12.84 5.14 2.5
Tractor 13.7 5.55 2.5
Twin-Boom 15.07 4.38 2.5
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Static Margin
Table 5.41 Power-Off Static Margin (%)
Configuration 1 Pilot 2 Pilots
Pusher 1.93 9.60
Tractor 3.33 6.98
Twin-Boom 4.17 5.99
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Suggestions for CR
• Determine tail-type(s)• Finish sizing tail and control surfaces• Determine elevator reqt. for takeoff & landing• Determine trim points• Determine static margin range• Investigate static stability• Trade studies, e.g. tail size/location vs. trim
elevator deflection