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

16

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

20

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

22

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

23

AAE 451Team 3Team 3 Quick 3-View

24

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!

26

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.”