the albatross design report

7/26/2019 The Albatross Design Report

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SOBIN SANTHOSH, PEARL MARY JACKSON, BENNET JOSE

THE ALBATROSS DESIGN

REPORT


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Contents

List of figures......................................................................................................................................... 2

OBJECTIVE......................................................................................................................................... 4

INSPIRATION...................................................................................................................................... 5

ROADMAP............................................................................................................................................ 6

AIRCRAFT MATERIALS..................................................................................................................... 7

AIRFOIL SELECTION.......................................................................................................................... 8

WING DESIGN.................................................................................................................................... 12

HORIZONTAL STABILIZER DESIGN............................................................................................. 15

VERTICAL STABILZER DESIGN..................................................................................................... 17

FUSELAGE AND PRIMARY STRUCTURE..................................................................................... 19

STRUCTURAL WEIGHT ESTIMATION.......................................................................................... 23

MOTOR AND PROPELLER............................................................................................................... 24

Propeller ............................................................................................................................................ 25

Fixed wing.................................................................................................................................... 25

Lift propellers: Multirotor............................................................................................................. 26

Electronic Speed Controller .............................................................................................................. 26

PRIMARY BATTERY SELECTION....................................................................................................... 27

FLIGHT PERFORMANCE.................................................................................................................. 28

Stability ............................................................................................................................................. 30

CONTROL SURFACES...................................................................................................................... 33

ACTUATORS: SERVO MOTORS...................................................................................................... 36

LANDING GEAR................................................................................................................................ 38

MODULAR DESIGN FOR EASE OF TRANSPORT......................................................................... 40

PLACEMENT OF EQUIPMENT........................................................................................................ 42PAYLOAD BAY.................................................................................................................................. 44

FINAL DESIGN................................................................................................................................... 45

MAINTENANCE................................................................................................................................. 46

OPERATION........................................................................................................................................ 47

CONCLUSION..................................................................................................................................... 48

FINAL DRAFT...................................................................................................................................... 49


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List of figuresFigure 1: The majestic wandering albatross........................................................................................... 5

Figure 2: Performance of Albatross Opt Foil and NACA 0012............................................................ 11

Figure 3: Albatross in cruise................................................................................................................. 12

Figure 4: The wing design in XFLR5................................................................................................... 13

Figure 5: Wing Design.......................................................................................................................... 14

Figure 6: Anhedral of the Wing adapted from the albatross................................................................. 14

Figure 7: HTP design in XFLR5........................................................................................................... 15

Figure 8: Horizontal tail plane.............................................................................................................. 16

Figure 9: Preliminary CFD Analysis revealed an ineffective horizontal stabilizer in a conventional

empennage............................................................................................................................................ 16

Figure 10: Vertical Tail design in XFLR5............................................................................................ 17

Figure 11: T- tail was chosen for better effectiveness and stability...................................................... 18

Figure 12: Fuselage requirement - space for given components........................................................... 19

Figure 13: Primary Structure................................................................................................................ 19Figure 14: Structural Stress Analysis in ABAQUS.............................................................................. 20

Figure 15: Cross section of carbon fibre tube in the nose..................................................................... 20

Figure 16: Cross section of carbon fibre tube in the main structure and arms...................................... 21

Figure 17: Cross section of carbon fibre tube in the wing spars and horizontal tail............................. 21

Figure 18: Final design of the Albatross............................................................................................... 22

Figure 19: Final assembly of the Albatross.......................................................................................... 22

Figure 20: Tiger motor U11 120 KV Brushless DC Motor.................................................................. 25

Figure 21: Mejzlk 26x14 inch propeller for fixed wing....................................................................... 25

Figure 22: Mejzlk 26x15 inch propeller ................................................................................................ 26

Figure 23: T-MOTOR FLAME80A Electronic Speed Controller........................................................ 26

Figure 24: Max Amps Li Po 16,000 12S 44.4v Battery Pack............................................................... 27

Figure 25: Hover Performance.............................................................................................................. 28

Figure 26: Performance of the fixed wing mode.................................................................................. 28

Figure 27: Motor characteristic in hover mode..................................................................................... 29

Figure 28: Motor Characteristics in fixed wing mode.......................................................................... 29

Figure 29: Motor Partial Load ............................................................................................................... 29

Figure 30: The Albatross modelling in XFLR5.................................................................................... 30

Figure 31: Lift, drag and moment over the wing.................................................................................. 30

Figure 32: Rudder design (in mm)........................................................................................................ 33Figure 33: Elevator design (in mm)...................................................................................................... 34

Figure 34: Alieron design (in mm) ......................................................................................................... 35

Figure 35: Aileron in Sky Surfer V2 ....................................................................................................... 35

Figure 36: Position of the Rudder Servomotor Figure 37: Position of the elevator servomotor...... 36

Figure 38: Servo placement on the ailerons.......................................................................................... 37

Figure 39: JR DS8921HV Ultra High Torque Digital Servo................................................................ 37

Figure 40: Control horns....................................................................................................................... 37

Figure 41: Landing Gear Design........................................................................................................... 38

Figure 42: Comparison of various materials for the landing gear cap.................................................. 39

Figure 43: Assembling component....................................................................................................... 40Figure 44: Joining two components for assembly ................................................................................ 41


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Figure 45: Parts after joining ................................................................................................................. 41

Figure 46: Payload bay (in grey) and the payload ................................................................................. 44

Figure 47: Payload Bay .......................................................................................................................... 44

Figure 48: The Albatross...................................................................................................................... 48


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OBJECTIVE

The objective of this project is to design a UAV capable of VTOL and fixed wing motion satisfying the

following conditions

The design shall be capable of vertical takeoff and landing The aircraft shall include at least one fixed wing for forward flight Maximum takeoff mass (MTOM) shall be below 25 kg The maximum wing span shall be below 5 meters and the maximum aircraft length shall be

below 4 meters The aircraft shall be modular for the ease of transportation. The maximum length of the individual parts shall not be longer than 2 meters Payload range requirement:

o 5 kg payload: > 60 km rangeo 3 kg payload: > 100 km range

Minimum payload bay dimension shall be 450 x 350 x 200 mm

The cruise speed in fixed wing mode shall be at least 80 km/h Max speed shall not exceed 194 km/h The aircraft shall use at least 4 direct drive lift rotors/propeller but not more than 10 direct drive

lift rotors/propellers For energy storage off the shelf rechargeable batteries shall be used Have reserved weight, space and power for the items outlined in the Ignition Kit Capable of sustained flight in all flight states while experiences 10 m/s head and cross wind Weather conditions:

o -30 to 50Co Moderate rain


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INSPIRATION

The design of the albatross as the name suggests is inspired by one of natures largest flying bird the

albatross. The weight, wingspan and aerodynamic conditions of the required UAV and the albatross are

comparable. The team firmly believes that nature is the best teacher and one should draw inspiration

from the same for innovative solutions. The albatross makes use of dynamic soaring and uses the

velocity gradients of the atmospheric boundary layer for a very efficient flight. Our team wishes to

incorporate dynamic soaring in the future to be as efficient as possible.

Based on an extensive literature survey the aerodynamic characteristics of natures largest bird was

incorporated into our design as a tribute towards the marvels of Mother Nature.

Figure 1: The majestic wandering albatross


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ROADMAP

The Albatross

Design

DesignParameters

Wing

Stabilizers

Flight Dynamics

Control Surfaces

Material Selection

Control and PowerSystem

Autopilot Components

Battery

Motor andPropeller

ESC

Servo Motors

Payload

Module Design

Objective

Final UAV


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AIRCRAFT MATERIALS

Material Selection is the first step towards the design as it helps in the preliminary weight estimation.The various properties that must be considered while selecting an appropriate material are:

Hardness and Strength Density Fatigue life Conductivity Thermal Expansion

The most important parameter is specific strength in order to make the aircraft as light as possible.

Table 1: Properties of Materials

SlNo MaterialYoungs

Modulus(G Pa)

Density(Kg/m3)

Compressive

/TensileStrength(M Pa)

Shear

Modulus(G Pa)

PoissonRatio

Thermal

Expansion(10-6m/K)

1 Balsa 3 130 7 0.23 0.38 6.5

2CarbonFibre

T300/5208181 1600 1500 7.17 0.28 0.41

3EPS Foam(Shah &

Topa, 2014)3 12.75 0.055 1.4 - 120

4 EPP Foam1 1.2 16 0.077 0.041 0.1 362, 683

Based on experience and many iterations of designing, the following materials were selected:

Main structure: Truss- Carbon Fibre T300/5208

Substructure : EPP Foam

1

JSP ARPRO Ultra Low density foam2-40 C to 20 C320 C to 80 C


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AIRFOIL SELECTION

The wing is one of the most crucial aspects of the design as it is the lift producing part and at the same

time has to bear most of the stress acting on the airplane. Therefore the design is a careful compromise

of performance, easiness to manufacture and economy. Airfoil is a device that provides reactive force

when in motion relative to the surrounding air; can lift or control a plane in flight. Hence airfoil selection

is the most important aspect in the design.

Assumptions:

MTOW: 25 Kg

Wing Span: 5m

Cruise velocity between 20-30 m/s

Reynolds number: 900,000 to 1,000,000

Criterion for selection was based on:

Higher CL at lower angles of attack

Higher CL/ CDratio at lower angles of attack

Ease of fabrication

Scope for reinforcement

Based on a literature survey and experience, a list of airfoils was chosen for comparison.

NACA 4412

CLARK Y

CLARK Z NACA 2412

NACA 23012

AG03

MH45

MH60

NACA 0012

NACA 0006

List of airfoils


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NACA 0012 in XFLR5

Albatross optimized Airfoil

MH60 was found to be the best airfoil for the given conditions, therefore it was chosen as the base for

optimization. NACA 0012 was selected for the vertical and horizontal stabilizer over NACA 0006 to

accommodate structural reinforcements.


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Figure 2: Performance of Albatross Opt Foil and NACA 0012

The airfoil was optimized to give:

CD0 = 0.004636

CL max= 1.46 at 14

CL/CD at CL cruise = 64.46


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WING DESIGN

The wing is one of the most crucial aspects of the design as it is the lift producing part and at the same

time has to bear most of the stress acting on the airplane. Therefore the design is a careful compromise

of performance, easiness to manufacture and economy. The procedure is adopted on the basis of the

performance requirements of the aircraft. The current design involved modification of operating high

wing aircraft to carry more loads and provide more endurance.

Inspiration: The wing design was based on that of the albatross, the largest bird capable of flight.

Weight: 10 kgAspect Ratio: 11Cruise speed: 16 m/sGlide ratio: 18.4Wingspan: 3 mGeometric Angle of Attack: 2 degrees

Figure 3: Albatross in cruise


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The albatross is able to fly very efficiently because it makes use of dynamic soaring of the atmosphericboundary layer. We decided to incorporate the wing characteristics of the albatross in facilitate the useof the same principle for our UAV in the future.

Requirements of the mission:

Total weight: 25 Kg

Wing loading: 10 Kg/m2 (Structural constraints)

Wing Span: 5m

Chord length: 0.5

Aspect Ratio: 10 (inspired by albatross)

There is a significant similarity in the operating conditions too.

The anhedral, taper ratio and sweep of the albatross wing were incorporated into the wing design.

Wingspan: 5mRoot Chord: 0.62m

Tip chord: 0.170m

Anhedral at 1.4m: -10

Sweep at 1.4m: 8.8

Geometric angle of attack: 1.6

Figure 4: The wing design in XFLR5

The Oswald factor was calculated was estimated to be 0.76.


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Figure 5: Wing Design

Figure 6: Anhedral of the Wing adapted from the albatross

A high wing designwas chosen mimicking that of the albatross. Moreover, high wing adds tostability due to the dihedral effecti.e. increase in Cl. Additionally, it preventsthe disturbancesin

the flowarising due to presence of the motorsfrom affecting flow over the wing.


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HORIZONTAL STABILIZER DESIGN

Stability is an important characteristic in an aircraft. The characteristic is achieved by the means of the

tail of an aircraft. The horizontal stabilizer is associated with longitudinal stability. Aspect ratio, span,

chord and tapering are the important characteristics calculate on the basis of the wing used. A symmetric

airfoil is used as the forces on both sides are to balance in a steady state without the need for trimming.

AIRFOIL:

A symmetric airfoil with ease to be fabricated had to be chosen. Therefore based on a literature survey

of the current trend and lower cost of fabrication NACA 0012 was chosen as the airfoil. Compared to

NACA 0006, the former has a higher thickness enhancing the opportunity for reinforcement.

CALCULATIONS

Based on the data in the Aircraft Design - A Conceptual Approach by Raymer, the various parameter

of the horizontal tail were calculated.

Figure 7: HTP design in XFLR5


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Figure 8: Horizontal tail plane

Figure 9: Preliminary CFD Analysis revealed an ineffective horizontal stabilizer in a conventional empennage

A T-Tail configuration is preferred so as isolate the disturbances in the flow in different planes. This

is improve the efficiency of the horizontal stabilizer.


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VERTICAL STABILZER DESIGN

The vertical stabilizer is associated with directional stability. Aspect ratio, span, chord and tapering are

the important characteristics calculate on the basis of the wing used. A symmetric airfoil is used as the

forces on both sides are to balance in a steady state without the need for trimming.

CALCULATIONS

Based on the concepts in the Aircraft Design - A Conceptual Approach by Raymer, the various

parameter of the vertical tail were calculated.

Figure 10: Vertical Tail design in XFLR5


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Figure 11: T- tail was chosen for better effectiveness and stability


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FUSELAGE AND PRIMARY STRUCTURE

Requirements for the fuselage design:

Payload bay: 450 x 350 x 200 mm

Space and position requirements of the given components.

Separation distance between the motors for non-interference of flows

Position of vertical and horizontal stabilizers: T-tail

Position of the wing

Preventing disturbed flow over the wing and tail.

Structural rigidity and strength

Modularity

Figure 12: Fuselage requirement - space for given components

Figure 13: Primary Structure


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Figure 14: Structural Stress Analysis in ABAQUS

The primary structure was optimized to withstand various stresses acting on aircraft. The various

forces and moments acting on the main structure were:

Weight: Net weight 25Kg

Max Thrust in VTOL mode: 130N per motor

Max thrust in fixed wing mode: 130N

Lift acting on the wing: 25 x 1.1x 9.81 : 270 N

Max load on the vertical stabilizer: 85 N

Max load on horizontal stabilizer: 80 N

Carbon fibre pipes of the following cross sections were used to optimize the structure:

Figure 15: Cross section of carbon fibre tube in the nose


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Figure 16: Cross section of carbon fibre tube in the main structure and arms

Figure 17: Cross section of carbon fibre tube in the wing spars and horizontal tail

After many iterations, the weight of the primary structure was reduced from 3.976 Kg to 1.699Kg.

This primary structure will be covered by EPP foam to obtain an aerodynamic shape. The wing, HTP

and the VTP will also be made of EPP foam reinforced by 2 carbon fibre pipes.


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Figure 18: Final design of the Albatross

Figure 19: Final assembly of the Albatross


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STRUCTURAL WEIGHT ESTIMATION

The primary structure was optimized to be 1.9 Kg. The secondary structure is to be made of EPP

Foam whose density is 16 Kg/m3.

Table 2: Component weight estimation with safety margin4

Component Wingspan

(in m)

Chord length (in

m)Ka5 Mass6

Wing 5 0.5 0.6 1.5

HTP 2 0.26 0.6 0.31

VTP 0.751 0.53 0.6 0.24

Component Max length (in m) Max Width (in m) Mass (in kg)

Primary Structure 3.625 2 1.9

Wing 5 0.5 1.5

HTP 2 0.26 0.31

VTP 0.751 0.53 0.24

Fuselage 3.625 0.6 0.35

Additional Mass 0.5 0.4 1.2

Total Mass 5.5

The overall structural weight was optimized to be 5.5 Kg.However in order to account for the

manufacturing errors, we decide to give it an additional margin of 25%.So the structural weight used

in calculations would be 7Kg.

The EPP foam was also found to withstand the shear loads produced way below its failure stress as

desired.

4Safety margin 1.13 added to account for the plastic coating on the surfaces for waterproofing them5

Correction factor for airfoil area: http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-01-unified-engineering-i-ii-iii-iv-fall-2005-spring-2006/systems-labs-06/spl10b.pdf6Weight= density*wingspan*chord length*thickness*Ka*1.13(Safety margin)


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MOTOR AND PROPELLER

BRUSHLESS DC MOTORS

The primary advantages of brushless D.C. motors are:

Reliability

Lasts 10 times as long as motors with commutators and brushes

Less noisy(no electronics and frictional loss)

Smaller in size and lighter in weight

More efficient to operate

No arcing

Faster dynamic response and higher speed ranges

Higher torque-to-size ratio

Simpler to maintain No commutator or brushes to wear out

Ideal for use in small devices

Reduced requirements for heat dissipation

Parameters for motor selection:

Low power consumption

High Thrust

Low weight

Waterproof

Based on a vast literature survey, the Tiger RC U11 120Kv Motor was selected.

Specifications:

KV: 120

Configuration: 12N14P

Shaft Diameter: 15mm

Motor Dimension (Dia.*Len): 8050mm

Weight (g): 730g

Idle current (10) at 10V (A): 0.7ANo. of Cells (Li Po): 6-12S

Max Continuous current (A) 180S: 80A

Max Continuous Power (W) 180S: 4000W

Internal resistance: 57m

Thrust: 13559g

The electronic speed controller was chosen on the basis of the manufacturer requirements. The motor

will operate at 44.4 V.


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Figure 20: Tiger motor U11 120 KV Brushless DC Motor

Propeller

Fixed wingRequirements:

Thrust> 12.5 Kg thrust/motor

High thrust to weight ratio Power should not exceed

Should not over heat

For thrust> 12.5 Kg thrust/motor, a Mejzlk 26 x 14 inch propeller was selected.

The pitch speed: 97km/hr. Tip speed: 563 km/hr. Static Thrust:13559g/ 478.3oz Revolutions maximum: 4525 rpm Stall Thrust:10387g/ 366.4oz

Thrust @ 90 km/h:925 g Weight< 94g

Figure 21: Mejzlk 26x14 inch propeller for fixed wing


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Lift propellers: MultirotorRequirements:

Thrust> 12.5 Kg thrust/motor

High thrust to weight ratio: 10 m/s crosswind and headwind

Power should not exceed Should not over heat

Figure 22: Mejzlk 26x15 inch propeller

Based on numerous iterations a 26x15 inch propeller was chosen. It gives the following

performance:

Maximum Tilt: 42

Maximum Speed: 52km/h

Rate of climb: 6.1m/s

Thrust to weight ratio: 1.6

Custom propellers from the Mejzlk Company are to be obtained for clockwise and anti-

clockwise propellers.

Electronic Speed Controller

The ESCs were chosen as per the manufacturer requirements as well as the maximum current in the

motors. They will be placed inside the fuselage

Figure 23: T-MOTOR FLAME80A Electronic Speed Controller


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PRIMARY BATTERY SELECTION

Criterions for selecting batteries for a UAV are:

Light weight

Reliability Storage time

Activation time

Maintenance

Availability

The Max Amps Li Po 16,000 12S 44.4v Battery Pack was chosen because of it high battery specific

energy.

16,000mah capacity

12S 44.4 volts

True 20C rating

Lifetime warranty

5C fast charge capable

Waterproof

12AWG Deans Ultra wire

138mm x 50mm x 252mm, 3708g

Figure 24: Max Amps Li Po 16,000 12S 44.4v Battery Pack


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FLIGHT PERFORMANCE

Required performance:

100 Km with 3Kg payload

60 Km with 5 Kg Payload

VTOL

Cruise Altitude: 300 Ft.

Hover: 2 minutes

Loiter: 5 minutes

Stability

The aircraft is take-off vertically as a multi rotor and transit into a fixed wing in 1 minute.

For primary flight performance, both fixed wing and multi rotor modes performances were estimated

first independently.

Stall velocity: 10.47 m/s

Cruise velocity: 25m/s

In case of headwind: 35 m/s

From experience, a reliable platform e-Calc was used to perform the initial performance of both the

modes. The following results were obtained:

Figure 25: Hover Performance

Figure 26: Performance of the fixed wing mode


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Figure 27: Motor characteristic in hover mode

Figure 28: Motor Characteristics in fixed wing mode

Figure 29: Motor Partial Load


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Stability

The natural aircraft stability analysis was performed on XFLR5.

Figure 30: The Albatross modelling in XFLR5

Static Stability:

Center of Gravity PositionBody axis

CoGx= -0.0170 m

CoGy= 0.0000 m

CoGz= -0.1793 m

Neutral Point position= 0.35818 m

Figure 31: Lift,drag and momentover the wing


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Static Margin: 70%

Dynamic stability:

Stability Analysis was performed using XFLR5.

Wings as thin surfacesRing vortices

Neumann boundary conditions for wingsDirichlet boundary conditions for the body

Ref. area = 2.499 mRef. span = 5.000 mRef. chord = 0.532 m657 panel elementsMass= 24.970 kg

Inertia - Body Axis - CoG OriginIbxx= 6.355 kg.mIbyy= 11.04 kg.mIbzz= 15.29 kg.mIbxz= -1.423 kg.m

Inertia - Stability Axis - CoG OriginIsxx= 6.632Isyy= 11.04Iszz= 15.01Isxz= -2.104

Longitudinal derivatives

Xu= -0.77494 Cxu= -0.02845Xw= 6.9711 Cxa= 0.25592Zu= -27.537 Czu= -0.00028397Zw= -130.95 CLa= 4.8076Zq= -82.878 CLq= 11.445Mu= -0.38827 Cmu= -0.026808Mw= -49.134 Cma= -3.3924Mq= -201.94 Cmq= -52.446

Lateral derivatives

Yv= -11.855 CYb= -0.43522Yp= 9.4809 CYp= 0.13923Yr= 25.949 CYr= 0.38107Lv= 6.0384 Clb= 0.044336Lp= -182.6 Clp= -0.5363Lr= 61.127 Clr= 0.17953

Nv= 27.118 Cnb= 0.19911Np= -22.158 Cnp= -0.065079Nr= -68.852 Cnr= -0.20222


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State matrices

Longitudinal state matrix

-0.031035 0.279179 0 -9.81

-1.102820 -5.24439 14.477 0-0.0351635 -4.44974 -18.29 00 0 1 0

Lateral state matrix

-0.47476 0.379692 -16.7565 9.810.352937 -28.3232 11.1686 01.7572 2.49436 -6.15284 00 1 0 0Longitudinal modes

Eigenvalue: -11.77+ -4.69i | -11.77+ 4.69i | -0.01124+ -0.5371i | -0.01124+ 0.5371iEigenvector:1+ 0i | 1+ 0i | 1+ 0i | 1+ 0i70.85+ -19.49i | 70.85+ 19.49i | -0.1288+-0.006474i | -0.1288+ 0.006474i-38.18+ -14.17i | -38.18+ 14.17i | 0.02937+ 0.002439i | 0.02937+-0.002439i3.213+ -0.07643i | 3.213+ 0.07643i | -0.005684+ 0.05456i | -0.005684+ -0.05456i

Lateral modes

Eigenvalue: -29.49+ 0i | -2.844+ -4.917i | -2.844+ 4.917i | 0.2247+ 0iEigenvector: 1+ 0i | 1+ 0i | 1+ 0i | 1+ 0i-16.47+ 0i | 0.04349+ 0.137i | 0.04349+ -0.137i | 0.1419+ 0i1.685+ 0i | 0.1279+ 0.2934i | 0.1279+ -0.2934i | 0.331+ 0i0.5585+ 0i | -0.02471+-0.005447i | -0.02471+ 0.005447i | 0.6312+ 0i


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CONTROL SURFACES

Flight control surfaces are hinged (movable) airfoils designed to change the attitude of the aircraft

during flight.

These surfaces are divided into three groups:

1) Primary

2) Secondary

The primary group of flight control surfaces includes

1) Ailerons

2) Elevators

3) Rudders

Required performance:

10 m/s crosswind: Rudder sizing

10 m/s headwind: Elevator sizing to counter increase in moment due to increased ground speed.

The various aspects of the control surfaces were calculated based on the concepts in the Aircraft Design

- A Conceptual Approach by Raymer and Aircraft Design: A Systems Engineering Approach by M.

Sadraey.

Rudder:

C rudder: 0.13 m

L rudder: 0.751 m

Figure 32: Rudder design (in mm)


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Elevator:

C elevator: 0.13 m

L elevator: 2 m

Figure 33: Elevator design (in mm)

Aileron:

C aileron: 0.130 m

L aileron: 0.820 m

Distance from COG: 1.89m

Max deflection: 20

Cl delta l: - 0.85


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Figure 34: Alieron design (in mm)

The control surfaces are to br formed out of the main surface while manufacturing as in the case of

famous RC Aircrafts like Sky Surfer and Super Sky Surfer. This reduces the need for an additional

hinge, there reducing the points of failure as learnt from our experience.

Figure 35: Aileron in Sky Surfer V2


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ACTUATORS: SERVO MOTORS

A servomotor is arotary actuator that allows for precise control of angular position, velocity and

acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also requires a

relatively sophisticated controller, often a dedicated module designed specifically for use with

servomotors.

Servomotors are generally used in UAVs as actuators.

Requirements:

High torque: Heavy aircraft

Low weight

Small size

High response rate

Max deflection > 20

As per the requirements the RJX FS-0521HV Metal Gear Digital Servo was selected for the controlsurface actuation. Its specifications are as follows:

Operating Voltage: 6.0~8.4V

Torque: 19.5kg/cm at 7.4V

Speed: 0.055sec/60 at 7.4V

Frequency: 333Hz

Gear Type: All metal gear

Motor Type: CorelessPlug Type: JR

Dimensions: 40x20x37mm

Weight: 68g

Figure 36: Position of the Rudder Servomotor Figure 37: Position of the elevator servomotor
http://en.wikipedia.org/wiki/Rotary_actuatorhttp://en.wikipedia.org/wiki/Rotary_actuator


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Figure 38: Servo placement on the ailerons

Figure 39: JR DS8921HV Ultra High Torque Digital Servo

Control Horns (X-LARGE) 60x30mm was selected for connecting the control rod to the control

surface.

Length: 60mm

Height: 30mm

Figure 40: Control horns


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LANDING GEAR

The landing gear has the following requirements:

Withstand high compressive stress

Withstand shock loads

Should not transmit vibrations to the main structure

Light weight

Weatherproof

Protect propellers: determines height

Based on the above requirements the landing gear was designed with carbon fibre pipe of 3cmdiameter, thickness of 3mm and length 20cm.

Figure 41: Landing Gear Design

For high shock absorption, a cap made of Sorbothane is to be attached at the end of the landing gear.It absorbs up to 94.7% of the impact shock. The cap is to be of 3cm diameter, 5mm thick and 4cmlength.


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Figure 42: Comparison of various materials for the landing gear cap7

7http://www.sorbothane.com/shock-absorbing-material.aspx


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MODULAR DESIGN FOR EASE OF TRANSPORT

The aircraft has 8 major preassembled components:

Front fuselage

Rear fuselage

Left Wing (1.8*0.6*0.3)

Right Wing (1.8*0.6*0.3)

Quadcopter arms4 (0.9*D0.02) with propeller

They can be easily assembled using butterfly nuts and safety bolts.

Figure 38: The splitting of the Albatross for modularity

In disassembled form they can be carried in 3 boxes:

Front fuselage box

Rear fuselage and battery box Wings and Quadcopter arm box

Figure 43: Assembling component


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The assembling component consists of two carbon fibre plates of dimensions 10cm by 4cm of

thickness 2mm. They are used to attach wing components and the fuselage components together.

They sandwich the joint by using 5mm diameter safety bolts and butterfly nuts.

The wings are joined together by the following steps:

The main wing and the attachment can be joined easily as a 10cm rod of diameter 1.9 cm

protrudes from the spars of the main wing.

This can be easily slided into spar of the attachment.

Place the upper panel directly above the predrilled holes in the wing through the front spar

Insert the bolts into the holes

Repeat the same for the rear spar

Attach the lower panel to the end of the bolts

Secure the bolts using butterfly nuts

The fuselage and the motor arms are also joined similarly.

Figure 44: Joining two components for assembly

Figure 45: Parts after joining


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PLACEMENT OF EQUIPMENT

The following list of avionics had to be placed in the fuselage

Sl No Equipment Length [mm] Width[mm]

Heigh

t

[mm]

1 Flight Control Computer 170 180 80

2 Internal Measurement Unit 100 30 40

3 ADS-B Transponder 89 46 18

4 Antennas and external mounted Systems -/- -/- -/-

5 Flight Termination Parachute 280 120 50

6Flight TerminationSystem/Launcher

200 55 55

7 Camera System 97 95 97

8 Communication System 57 98 86

9 Air data system 42 78 49

The fuselage was designed to accommodate all the components as shown in the figures below.

Figure 40: Position of the various components in the fuselage, the yellow box is the payload


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Figure 41: Front view showing the placement of the components

Figure 42: Side view of the equipment placement, the battery is kept directly in front of the payload

bay for easy accessibility


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PAYLOAD BAY

The payload bay is located directly below the aerodynamic centre of the wing.

The payload is fastened to the payload bay by means of Velcro straps

The payload bay is of attached to the main structure. There is a panel below the fuselage to facilitate the access to the cargo bay.

It is secured by butterfly nuts.

Dimensions of payload bay

o Outer:460 x 360 x 210 mm

o Inner :454 x 354 x 204 mm

Figure 46: Payload bay (in grey) and the payload

Figure 47: Payload Bay

The payload is placed in the payload bay and is secured using Velcro straps. The payload bay is then

pushed into the slot in the fuselage and is secured using Velcro straps arising from the upper beams of

the main structure of the aircraft. The lower panel made of foam and surrounded by rubber ring is used

to seal the fuselage. There are four plastic bearing in the panel through which bolts arising from the

lower beams of the fuselage passes through. The panel is then secured by butterfly nuts. Therefore the

mechanism is failsafe. The aircraft can operate even when one of then fails.


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FINAL DESIGN

The final design was optimized for minimum weight and maximum performance. The major features

of the design are:

Comprises four motors which are equidistant from the centre of gravity

Four U11 100KV Tiger motors are used vertical take-off and landing

One U11 100KV Tiger motors for the fixed wing mode.

The motors arms are of circular cross section to minimize drag o Airfoil in the arms would

affect the stability of the aircraft due to lift at high angles of attack

Weight reduction

Ease of maintenance

T-tail configuration: Smooth flow over the wing and HTP

Spherical nose cone to maximize the camera field of view


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MAINTENANCE

The aircraft components can be divided into the following categories:

Safe Life

Damage tolerant

Structure

The aircraft is made of a carbon fibre primary structure which is unlikely to get damaged unless in

case of a catastrophic failure.

Motor bearing

The motor, U11 Tiger motor is a military grade system, therefore the bearing is tolerant to wear.

All the servos used are metal gear servos, which has a very long life its plastic alternates.

Damage Tolerant

The secondary structure made EPP foam can be easily repaired using glass fibre tapes in case of dents

or slight damages.

Since the aircraft is modular the damage part can be easily replaced in case of a major damage.In case of failure

In case of power loss and rapid deceleration the parachutes will be deployed. The parachute systems

are connected to the primary structure as the secondary structure may not be able to withstand such

high loads. The parachute tube will be connected to the

The aircraft is naturally stable, therefore the aircraft can land safely manually even in case of the

failure of the autopilot system.

Waterproofness

The motors -Tiger RC U11 are water proof. The ESCs and the major components would be inside thefuselage. The only component that might be exposed to water is the battery, which as per the

manufacturer is 100% waterproof.

The EPP Foam is covered with an extremely thin coating of plastic which makes it waterproof. Ease

of handling.


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OPERATION

Requirement: 20 minute turnaround between max-distance missions

The major delay in turnaround is payload loading and unloading and the replacement of batteries.

These delays are avoided by use of butterfly nutsto securethe payload bay. This avoids the

requirement of a screw driver, Allen wrench etc. and reducesthe timeto fasten and unfasten the

bolts.

A singleMax Amps Li Po 16,000 12S 44.4v Battery Pack is used instead of a multiple batteries. It is

located right in front of the payload bay, thereby increasing the ease of accessibility. So the battery is

easily swappable.

Operating conditions: -30 to 50C with moderate rain

These conditions were taken into account during material selection. The materials chosen i.e. carbonfibre and EPP foam have low thermal expansion coefficients.

The water absorption coefficients are also very low for both the materials.

The aircraft is designed and sized to fly comfortably with 10 m/s crosswind and 10m/s headwind.

Human Factors and Safety Provisions

Considering the fact that human error is responsible for majority of the UAV crashes, safety boltsare

to be used while assembling the UAV in order prevents the components from detaching in flight.

Butterfly nutsare to be used to easily assemble and disassemble the components.

In order to avoid electrical connection error, the electronics bay is not easily accessible unlike the

battery and the payload bay.

Figure 43: Butterfly nut

Limit timeon ground with rotors spinning: The Albatross has maximum rate of climb of 7.9 m/s and

the thrust to weigh ratio is 1.7. Therefore the Albatross can reach an altitude of 60ft in 4.64s.


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CONCLUSION

The Albatross is a high endurance hybrid unmanned aerial vehicle and satisfies the requirements of

the competition.

Figure 48: The Albatross


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FINAL DRAFT

the albatross design report

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