D & C PDR #1
AAE451 – Team 3
November 4, 2003
Brian CheskoBrian HronchekTed LightDoug MousseauBrent RobbinsEmil Tchilian
2
AAE 451Team 3Team 3 Aircraft Walk Around
•Low wing – Clark Y
•Tricycle Gear
•Conventional Tail – NACA 0012
•Pusher
•Wing Span = 14 ft
•A/C Length = 10 ft
3
AAE 451Team 3Team 3 Introduction
• Dihedral angle• Determine tail boom length• With boom length, find rotation angle• Determine horizontal stabilizer size
– Is this realistic?
• Determine vertical tail size– Is this realistic?
• Calculate static margin based on sizing• Future Work
4
AAE 451Team 3Team 3 Dihedral Angle
Recommendations
• Survey of Roskam data on homebuilt & agricultural low-wing aircraft: ~5°
• McCombs “Wing and Tail Dihedral…”– RC w/ailerons (for max maneuverability, low
wing): 0-2° EVD (Equivalent V-Dihedral ≈ dihedral)
– Free Flight Scale model low wing: 3-8° EVD
5° dihedral is a good compromise
5
AAE 451Team 3Team 3 Tail Boom Length Trade Study
• Used to determine optimum (lightest weight) tail boom length
• Goal: minimize weight of tail system (boom, horizontal tail, vertical tail) based on location of tail
6
AAE 451Team 3Team 3 Tail Boom Length Trade Study
• Assumed rectangular boom cross section based on maximum bending stress
• Horizontal and vertical tail size determined based on 1st order tail sizing
• Multiplied boom and tail volumes by respective density to get weight
7
AAE 451Team 3Team 3 Tail Boom Length Trade Study
• Logic– Tail moment needed for stability– Moment = distance x force– Tail boom length increases Boom Weight Increases
Tail Weight Decreases
– Tail boom length decreases Boom Weight Decreases Tail Weight Increases
Assumptions
•Boom Material: Bass Wood
•Boom Geometry: Solid Rectangular Cross Section
•Tail Construction: Foam Core / Fiberglass Shell
8
AAE 451Team 3Team 3 Tail Boom Length Trade Study
• Optimum tail boom length gives a total aircraft length of ~14.1 ft
• Aircraft Length Limit: 10 feet– Based on transportability constraint– If length is greater than 10 ft, A/C will be
difficult to transport in a conventional vehicle
• Weight gain: ~0.5 lbf
9
AAE 451Team 3Team 3 Tail Boom Length Trade Study
10
AAE 451Team 3Team 3 That’s great, what about rotation angle?
• 12 degrees of rotation based on:
• Gear height of 1.0 foot
• Rear gear located below rear spar (60% of the chord of main wing)
• Is 12o enough? Not sure yet. Looking into it.
~12o of available rotation
11
AAE 451Team 3Team 3 Class 2 Tail Sizing
• More Analytical than Initial Estimates from Class 1 method
• Use different Horizontal and Vertical Tail Areas to calculate valuable characteristics of aircraft
• Compare to Class 1 estimates for both Tail Sizes:
Sh 8.8 ft2
Sv 3.5 ft2
12
AAE 451Team 3Team 3 Class 2 Horizontal Tail Sizing
• Horizontal Tail important factor of Longitudinal Stability Equations for aircraft– Calculate Center of Gravity and Aerodynamic Center of
aircraft for a range of Horizontal Tail Area values
• Center of Gravity of Aircraft– Weight of Horizontal Tail changes with area
9
1i i
iAircraft
Total
W xCG
W
20.44HT HT
lbsW Area
ft
Note: 0.44 lbs/ft2 based on aircraft sizing code
13
AAE 451Team 3Team 3 Class 2 Horizontal Tail Sizing
15% 20%
ac cgX XSM
c
• Aerodynamic Center as a function of Horizontal Tail Area
• Desired Static Margin
1
1 1
wing hh
Aircraft
h
h hac L ac
ach h
L
d SX C X
d SX
d SC
d S
Roskam Eq 11.1
ac ac wingX X c 0.49hd
d
15.8degh
LC
Raymer Fig 16.12
14
AAE 451Team 3Team 3
8 9 10 11 12 13 14 153
3.5
4
4.5
Horizontal Tail Area (ft2)
Pos
ition
of
Airc
raft
=>
x(f
t)
Figure 1 - Position of Aircraft vs. Horizontal Tail Area
Aerodynamic Center
Static Margin Boundary (15% - 20%)
AircraftCenter of Gravity
Horizontal Tail X-Plot• Compares Area of Horizontal Tail to Position of Center of
Gravity in Respect to Aerodynamic Center
211HTS ft
3.5AircraftCG ft
4.0AircraftAC ftBest Position
15
AAE 451Team 3Team 3 Horizontal Tail Sizing
• CGAC/ACAC analysis does not cover full breadth of operating envelope
• Use Takeoff Rotation to analyze Horizontal Tail potential to rapidly increase angle of aircraft on runway
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AAE 451Team 3Team 3 Horizontal Tail Sizing
• This sizing based on angular acceleration during take-off rotation
Ref. Roskam 421 book, pg 288-290
Variable defintiions found in above reference
max
2
( ) ( ) ( )
( )( )
( )( )
g g g g g g g g
g g wf g g wf mgg g
g h g g gh gground
cg mg g cg g mg g D cg cg T
wf mg ac g cg g mg ac yy
hL h rotate ac mg g mg g cg
W x x z z D z z T z z
L x x z z M IS ft
C q x x z z
17
AAE 451Team 3Team 3 Horizontal Tail Sizing
12 12.2 12.4 12.6 12.8 13 13.26
7
8
9
10
11
12
13
14
15
16
The
ta D
oubl
e D
ot a
t In
stan
t of
Rot
atio
n (d
eg/s
ec2 )
Horizontal Tail Area (ft2)
• values for different values of Horizontal Tail Area at instant time of rotation
Concrete
Long Grass
0.02g
0.10g
g Wheel-Ground Friction Coefficient
For lighter airplanes:210 12deg sec
For our concrete runway:212.5HTS ft
18
AAE 451Team 3Team 3 Horizontal Tail Sizing
• Need to iterate between both methods– Use results for Horizontal Tail area from Takeoff
rotation method to find a new Center of Gravity and Aerodynamic center
– Use new CG and AC values for aircraft in Takeoff rotation problem
• Results used for Vertical Tail Analysis:
212HTS ft
3.5AircraftCG ft
4.0AircraftAC ft
17.8%SM
19
AAE 451Team 3Team 3 Class 2 Vertical Tail Sizing
• Vertical Tail sized from Coefficient of Yaw Moment due to Sideslip
wb v
n n L V VC C C S S x b
1
0 57.3wb f sW
n n n N R f fC C C K K S l Sb
Due to Wing and Fuselage:
Roskam Eq 11.8Vol 2
Roskam Eq 10.42Vol 6
5.8v
LC
5Vx ft 240S ft 14b ft
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AAE 451Team 3Team 3 Class 2 Vertical Tail Sizing
• Overall level of directional stability must be
• To meet coefficient value
10.0010degnC
nC
22.4VS ft
21
AAE 451Team 3Team 3
• Need to compare calculated horizontal tail size to historical data
• Use Tail Volume Coefficient method to check
Does Tail Size Make Sense?
2
2
5.7 120.58
40 2.8h h
HT
x S ft ftc
Sc ft ft
2
2
5.7 2.40.02
40 14v v
VT
x S ft ftc
Sb ft ft
> Homebuilt value of 0.50
< Homebuilt value of 0.04
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AAE 451Team 3Team 3 C.G. and A.C. of Aircraft
Center of Gravity
Aerodynamic Center
•Center of gravity of aircraft is 3.5 feet behind the nose
•Aerodynamic center is 4.0 feet behind the nose
•Static margin ~ 0.17
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AAE 451Team 3Team 3 Quick 3-View
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AAE 451Team 3Team 3 Future Work
• Control surface sizing
• Continue working with Predator code– Many constants already estimated, still need
to verify some
• Look into advantages / disadvantages of moving horizontal tail into prop wash
• Stall characteristics?
• Necessary rotation angle
25
AAE 451Team 3Team 3 Questions?
Ref. http://roger.ecn.purdue.edu/~andrisan/Miscellaneous/Isle_Royale/IsleRoyale1/IsleRoyale1.html
That’s a fine looking airplane!
Airplane not to scale
That’s pimp Dad!
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AAE 451Team 3Team 3 Dihedral Angle
EVD = A + kB
A = 0°
k = f(x/(b/2)) = 0.98
B = EVD / k ≈ EVDA=0°
B
X
CL
Source: McCombs, William F. “Wing and Tail Dihedral for Models.”