VISVESVARAYA TECHNOLOGICAL UNIVERSITY Jnana Sangama, Belgaum, Karnataka-590 014
A PROJECT REPORT ON “DESIGN AND ANALYSIS OF AIR TO AIR REFUELLING PROBE SUPPORT STRUCTURE” Project Report submitted in partial fulfillment of the requirement for the award of the degree of
BACHELOR OF ENGINEERING IN MECHANICAL ENGINEERING Submitted by Melvin George 1NH15ME726 Navaneeth RN 1NH15ME732 Vijay P 1NH16ME428 Zuber J 1NH16ME433
Work was carried out in Aeronautical Development Agency, Bangalore
Under the guidance of Internal Guide External Guide’s Mr. Rajesh A Mr. M Raghu Mr. Girish B Assistant Professor SC/ENGG ‘E’ SC/ENGG ‘G’ Dept. of Mechanical Engineering AF Dept. ADA AF dept, ADA
NEW HORIZON COLLEGE OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING BANGALORE-560 103 2018-19
DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE It is certified that the Project work entitled “Design and Analysis of Air to Air Refueling Probe Support Structure” carried out by MELVIN GEORGE (1NH15ME726), NAVANEETH RN (1NH15ME732), VIJAY P (1NH16ME428), ZUBER J (1NH16ME433), the bonafide students of New Horizon College of Engineering, Bengaluru, in partial fulfillment for the award of Bachelor of Engineering in Mechanical Engineering of the Visvesvaraya Technological University, Belgaum during the year 2018-2019. It is further certified that all corrections/suggestions indicated for internal assessment has been incorporated in the report deposited in the department library. The Project has been approved as it satisfies the academic requirements in respect of Project Work prescribed for the Bachelor of Engineering degree.
Signature of the Guide Signature of the HOD Signature of the Principal Mr. RAJESH A Dr. M S GANESHA PRASAD Dr. MANJUNATHA Assistant Professor Dean, Prof. and HOD-ME Principal Dept. of Mechanical Engineering. Dept. of Mechanical Engineering. NHCE
Name(s) of the student: University Seat Number: Melvin George 1NH15ME726 Navaneeth RN 1NH15ME732 Vijay P 1NH16ME428 Zuber J 1NH16ME433
External Viva Examiner Signature with date: 1. 2. ABSTRACT
Aerial refueling allows the receiver aircraft to remain airborne for the longer time. It will increase the range and as Fighter jets can fly for only 2-3 hours doing a regular mission. The receiver aircraft can be topped up with extra fuel in the air, air refueling can allow a takeoff with a greater payload. It also increases the effectiveness of surveillance and patrol aircraft by allowing them to remain in the air longer
The main aim of the project is to design a support structure that can withstand the load of the probe when it is engaging and disengaging with the refuelling drogue which is located on the mother aircraft and uniformly distribute the load to it. The various constraints faced while retrofitting are the space availability on the aircraft to accommodate the probe, also the LRU’s placed on various floor’s had to be moved around in order to accommodate the mounting bracket that holds the probe in place.
v CONTENTS
COLLEGE CERTIFICATE i COMPANY CERTIFICATE ii ACKNOWLEDGEMENT iii DECLARATION iv ABSTRACT v CONTENTS vi LIST OF FIGURES viii LIST OF TABLES xi NOMENCLATURE xii
1. INTRODUCTION ...... 1 1.1. Fixed Air to Air Refueling Probe ...... 1 1.2. Fuel Tanks ...... 2 1.3. Aerial Refueling ...... 3 1.3.1. Few Facts ...... 3 1.3.2. Objective of AAR System ...... 4
1.3.3. Disadvantages of AAR ...... 4 1.4. Indian Air Force Transport Aircrafts...... 5 1.5. Types of Refueling Systems ...... 6 1.5.1. Probe and Drogue ...... 7 1.5.2. Flying Boom ...... 11 2. LITERATURE REVIEW ...... 13 3. NUMERICAL ANALYSIS ...... 19 3.1. Moment Values About Fixed Point ...... 19 3.2. 1st load case moment values for θ = 0° using analytical approach ...... 21 3.3. Verification of the moment 1st load case θ = 0° through Nastran & Patran ...... 24 3.3.1. HyperMesh v13.0 (Pre-processor) ...... 24 3.3.2. Nastran v2016 (Solver) ...... 25 3.3.3. Patran v2016 (Post-processor) ...... 25 4. CAD MODEL ...... 27 4.1. Introduction to CATIA ...... 27 4.2. CATIA Model of Probe and Mounting Bracket ...... 27 5. FINITE ELEMENT ANALYSIS ...... 31 5.1. Introduction to Finite Element Analysis ...... 31 vi 5.2. Basic Concepts in Finite Element Analysis ...... 31 5.2.1. Major Element Types ...... 31 5.2.2. Degrees of Freedom ...... 32 5.2.3. Boundary Conditions ...... 32 5.3. FE Model Description ...... 32 5.4. Bolt Connections ...... 33 5.5. Material Description ...... 33 5.6. Loads...... 34 5.7. Boundary Conditions ...... 35 5.8. Analysis Results ...... 36 5.8.1. Normal Mode Analysis Result ...... 36 5.8.2. Natural Frequency Analysis Result ...... 37 5.8.3. Max-Displacement Result ...... 38 5.8.4. Reaction Forces ...... 39 5.8.5. Bar Forces ...... 40 5.8.6. Von Mises Stress Results ...... 41 5.8.7. Max Principal Stress Results ...... 43 6. CONCLUSION ...... 44 7. SCOPE OF FUTURE WORK...... 45 REFERENCES ...... 47
vii LIST OF FIGURES
FIG NO TITLE PAGE NO
1.1 LOCATION OF THE FIXED AIR TO AIR REFUELING PROBE 1 1.2 THE VARIOUS FUEL TANKS LOCATED ON A FIGHTER JET 2 1.3 DROP TANK 3 1.4 THE BERIEV A-50 IS A SOVIET AIRBORNE EARLY WARNING 5 AND CONTROL (AEW&C) 1.5 ILYUSHIN IL-76-TRANSPORT AIRCRAFT IAF 6 1.6 ILYUSHIN IL-78MKI HAS A REFUELING RATE OF 500-600 6 LITRES A MINUTE, CAN FERRY UP TO 118 TONS OF FUEL 1.7 FLOWCHART SHOWING THE VARIOUS METHODS OF FUEL 7 RECEIVING METHODS ON THE RECEIVING AIRCRAFT 1.8 F-35B WITH A RETRACTABLE PROBE REFUELING THROUGH 7 PROBE AND DROGUE 1.9 MIRAGE 2000 WITH A FIXED PROBE REFUELING THROUGH 8 PROBE AND DROGUE 1.10 F-35A 8 1.11 MIRAGE 2000 9 1.12 PROBE AND DROGUE SYSTEM 10 1.13 F-22 RAPTOR 11 2.1 MIRAGE 2000 - FIXED AAR PROBE (SIDE VIEW) 13 2.2 MIRAGE 2000 - FIXED AAR PROBE (TOP VIEW) 13 2.3 RAFALE - FIXED AAR PROBE (SIDE VIEW) 14 2.4 RAFALE - FIXED AAR PROBE (SIDE VIEW) 14 2.5 RAFALE - FIXED AAR PROBE (SIDE VIEW) 15 2.6 RAFALE - FIXED AAR PROBE (FRONT VIEW) 15 2.7 AERMACCHI M-345 - FIXED AAR PROBE (SIDE VIEW) 16 2.8 AERMACCHI M-345 - FIXED AAR PROBE (SIDE VIEW) 16 2.9 AERMACCHI M-345 - FIXED AAR PROBE (FRONT VIEW) 16
viii 2.10 F18 WITH RETRACTABLE AERIAL REFUELING PROBE 17 2.11 PANAVIA TORNADO WITH AERIAL REFUELING PROBE 17 2.12 TYPHOON WITH RETRACTABLE AERIAL REFUELING PROBE 18 2.13 GRIPEN JAS 39 WITH RETRACTABLE AERIAL REFUELING 18 PROBE 3.1 PROBE COORDINATE SYSTEM FOR LOADING 19 3.2 SIDE VIEW 19 3.3 FRONT VIEW DIMENSIONS 20 3.4 VISUALIZATION OF THE FORCES ACTING ON THE PROBE 20 3.5 YZ FRONT VIEW OF 1D PROBE 24 3.6 ISOMETRIC VIEW OF 1D PROBE 24 3.7 NASTRAN RESULTS 25 3.8 THE VISUALIZATION OF MOMENTS ALONG X, Y & Z AT THE 26 FIXED-POINT CAN BE SEEN 3.9 VISUALIZATION OF THE TRANSLATIONAL DISPLACEMENT 26 ALONG Y DIRECTION CAN BE SEEN 4.1 SIDE VIEW OF PROBE 28 4.2 ISOMETRIC VIEW OF THE MOUNTING BRACKET 28 4.3 ASSEMBLY OF MOUNTING BRACKET ALONG WITH THE 29 PROBE FLANGE 4.4 EXPLODED VIEW OF THE ASSEMBLY 30 5.1 1D ELEMENTS 31 5.2 2D ELEMENTS 31 5.3 3D ELEMENTS 32 5.4 FEM MODEL OF PROBE ALONG WITH THE MOUNTING 32 BRACKET 5.5 BOLT CONNECTIONS ALONG WITH THE VISUALIZATION OF 33 A SINGLE STEEL BOLT 5.6 LOADS ACTING IN X, Y AND Z DIRECTION 34 5.7 THE VARIOUS BOUNDARY CONDITIONS DEFINED FOR THE 35 MESHED MODEL
ix 5.8 NATURAL FREQUENCY FOR PROBE WITH MOUNTING 37 BRACKET 5.9 Deformation of the probe assembly during Natural 38 Frequency 5.10 MAXIMUM DISPLACEMENT 39 5.11 BOLT LOCATION’S 40 5.12 IN-PLANE AND TENSILE BAR FORCES ACTING ON THE SIX 41 BOLTS 5.13 VON-MISES STRESS DISTRIBUTION 42 5.14 STRESS DISTRIBUTION 44
x LIST OF TABLES
TABLE NO TITLE PAGE NO
3.1 VARIOUS LOAD CASES 20 3.2 MOMENT CALCULATIONS ALONG X, Y & Z DIRECTION 22 3.3 CRITICAL LOAD CASES 23 5.1 MATERIAL PROPERTIES OF ALUMINIUM AND STEEL 33 5.2 FREQUENCY VALUES FOR FREE – FREE 36 5.3 NATURAL FREQUENCY VALUES 37 5.4 DEFLECTION IN X, Y AND Z DIRECTION 38 5.5 REACTION FORCES AT FASTENER LOCATION 39
xi NOMENCLATURE
SYMBOL NAME OF QUANTITY NOTATION IN SI UNITS
N FORCE N/m2 M MOMENT N-mm kg MASS Kg m LENGTH metre s TIME second V VOLUME m3 litre LITRE 10-3 m3 θ ANGLE degree D DIAMETER mm Y YOUNG’S MODULUS MPa ρ DENSITY g/cm3 f FREQUENCY Hz g ACCELERATION DUE TO GRAVITY m/sec2
xii
ACKNOWLEDGEMENTS
We thank the Lord Almighty for showering His blessings on us.
It is indeed a great pleasure to recall the people who have helped us in carrying out this project. Naming all the people who have helped us in achieving this goal would be impossible, yet we attempt to thank a selected few who have helped use in diverse ways. We wish to express our sincere gratitude to Dr. Manjunatha, Principal, NHCE, Bangalore, for providing us with facilities to carry out this project. We wish to express our sincere gratitude to Dr. M S Ganesha Prasad Dean, Prof. & HOD-Mechanical Engg., for his constant encouragement and cooperation. We wish to express our sincere gratitude to our external guides Mr. M Raghu, Sc/Engg ‘E’ and Mr. Girish B, Sc/Engg ‘G’ in the Airframe Department, ADA, for their valuable suggestions, guidance, care & attention shown during the planning, conduction stages of this project work. We wish to express our sincere gratitude to our teacher and internal guide Mr. Rajesh A, Asst. Professor in the Department of Mechanical Engg., NHCE, for his valuable suggestions, guidance, care & attention shown during the planning, conduction stages of this project work. We express our sincere thanks to Mr. Divij and Mr. Dev project assistants at ADA, for helping us get familiarized with the software’s that were used in our project We express our sincere thanks to project coordinators, all the staff members and non-teaching staff of Department of Mechanical Engg., for the kind cooperation extended by them. We thank our parents for their support and encouragement throughout the course of our studies.
iii Scanned by CamScanner
DECLARATION
I hereby declare that the entire work embodied in this dissertation has been carried out by me and no part of it has been submitted for any degree of any institution previously.
Date: 26-05-2019 Place: Bangalore
NAME USN SIGNATURE MELVIN GEORGE 1NH15ME726 NAVANEETH RN 1NH15ME732 VIJAY P 1NH16ME428 ZUBER J 1NH16ME433
CERTIFICATE
This is to certify that the above declaration made by the candidate is correct to the best of my knowledge and belief.
Place: Bangalore Date: 23-05-2019 Mr. Rajesh A Assist. Prof, Department of Mechanical Engg, N.H.C.E, Bangalore.
iv Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
CHAPTER 1
INTRODUCTION
1.1. Fixed Air to Air Refueling Probe
Fixed Air to Air Refueling Probe is an external protuberance that exists in a fighter aircraft at the front fuselage region on the star board side ahead of the canopy region. The probe is located between Station 1 and Station 2 as shown in Fig 1.1. It is used for mid-air refueling of the aircraft to enhance its endurance capability. During mid-air refueling the probe gets engaged to the drogue (fuel basket) of the mother aircraft. As a consequence, the refueling probe and the supporting structure experiences engagement/disengagement loads.
Fig 1.1 Location of the Fixed Air to Air Refueling Probe
The subject of AAR is very important for the Alliance forces because out of area operations require those kinds of aircrafts that are capable of accomplishing their mission to be far from their service distance.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
1.2. Fuel Tanks
1.2.1. Internal Tanks
1.2.1.1. Integrated Fuel Tanks
On several aircrafts, espacially transport class and high performance aircraft’s, part of the structure of the wings or fuselage is sealed with a fuel resistant two-part sealant to create a fuel tank. The sealed skin and structural members offer the highest volume of space available with the least possible weight. This type of tank is termed as an integral fuel tank since it forms a tank as a unit within the airframe structure
Fig 1.2 The various fuel tanks located on a fighter jet
1.2.2. External Tanks
1.2.2.1. Drop Tanks
Drop tanks, wing tanks, pylon tanks or belly tanks are all terms used to describe auxiliary externally mounted fuel tanks. Drop tanks were originally designed to be dropped off when empty or in the event of combat or emergency in order to reduce drag and weight, increasing maneuverability and range. External tanks are common place on modern military aircraft Dept. of Mechanical Engg, NHCE, Bengaluru Page 2
Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.3 Drop Tank
1.3. Aerial Refueling
Aerial refueling system is taken as a method to allow the receiver aircraft to remain airborne for the longer time. It will increase the range and loiters time on station. Fighter jets can fly for only two to three hours during a regular mission. Allows surveillance aircraft to fly for longer times without landing. The receiver aircraft can be topped up with extra fuel in the air, air refueling can allow a takeoff with a greater payload which could be weapons, cargo, or personnel.
1.3.1. Few Facts
• The normal refueling altitude is 25,000ft (Refueling envelope). • An aerial refueling takes about three to four minutes for small fighter aircraft. • Currently this aerial refueling system is used by thirty-four countries air force including India. • Commercial aircrafts cannot be refueled mid-air as Aerial refueling is inherently very unstable it is not a good idea to allow two planes, one fully loaded with fuel and the other with passengers, to come so close.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
1.3.2. Objective of AAR System:
The objective of AAR operations is to enhance combat effectiveness by extending the range, payload or endurance of receiver aircraft. Successful AAR depends on 3 major factors: a. Equipment Compatibility - It is essential that aircraft requiring AAR are fitted with probes/receptacles and fuel systems compatible with the characteristics of the tanker aircraft employed, e.g. drogue/boom system, fuel surge pressures, fuel type etc. b. Performance Compatibility - It is essential for tanker and receiver aircraft performance to be compatible in terms of AAR speeds and altitudes c. Procedural Compatibility - It is essential for tankers and receivers to employ pre- planned and compatible procedures for rendezvous, making contact, fuel transfer and departure. It permits the introduction of fighter, electronic warfare, reconnaissance, and other aircraft into worldwide theater operations within a matter of hours. In addition to improving range of tactical aircraft, it is also cost effective. By reducing the number of aircraft needed to maintain a combat air patrol (CAP), it reduces the number of maintenance personnel needed as well as the amount of time aircraft spend on the ground. Air refueling missions require added emphasis on situational awareness and flexibility. Often, missions do not go exactly as briefed. The WD must be aware of what is happening and be able to react to any contingency. This reference text will acquaint you with the basics of air refueling. It does not cover all situations or techniques.
1.3.3. Disadvantages of AAR During aerial refueling there is a major time limitation. During this time both, the tanker and the receiver has a limited maneuver capability and the number of receivers due to the fact the tanker has limited fuel transfer capability. To refuel a multi ship formation takes a relatively long time, volume of air space and long route. Also needs continues
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019 control and protection of that airspace to ensure mission success and to prevent losses due to accident or action taken by enemy. Because of these effects, a big AAR formation is very vulnerable during its AAR mission. This is the reason to plan major AAR missions out of enemy air space when it is possible. To plan AAR mission is one of the most complex operational planning activities and very challengeable due to high cost air assets. The loss of one of this asset could affect deeply to the success of operation
1.4. Indian Air Force Transport Aircrafts with mid-air Refuelling capability
The Indian Air Force operates 24 Il-76s, including 17 Il-76MDs, 6 Il-78MKIs, and three Beriev A-50 for AEW&C.
Fig 1.4 The Beriev A-50 is a Soviet airborne early warning and control (AEW&C)
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.5 Ilyushin Il-76-Transport Aircraft IAF
Fig 1.6 Ilyushin Il-78MKI has a refueling rate of 500-600 litres a minute, can ferry up to 118 tons of fuel.
1.5. Types of Refueling systems
The refueling systems are mainly classified into two types, they are Probe and Drogue and Flying Boom. In Probe and Drogue method the probe gets engaged to the boom of the mother aircraft, the probe can be of retractable or fixed type. In the Flying Boom method, the boom which is a rigid, telescoping tube with movable flight control surfaces that a boom operator inserts into the receptacle on the receiving aircraft
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.7 Flowchart showing the various methods of fuel receiving methods on the receiving aircraft
1.5.1. PROBE AND DROGUE METHOD
It uses a trailing hose with a basket attached on the other end. Pilots can guide the probe on their aircraft into the basket to attach with the hose. The hoses are retracted when not in use. It is simple to adapt to existing aircraft
Though the crew has less control of the drogue, which can still cause damage, there is less danger to the aircraft than from a boom, and it could allow the aircraft to stay further away from the tanker.
The probe and drogue system can only pump 833 to 1098 liters per minute.
Fig 1.8 F-35B with a retractable probe refueling through probe and drogue
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.9 Mirage 2000 with a fixed probe refueling through probe and drogue 1.5.1.1. Types of Probes
1.5.1.1.1. Retractable Probe
Are used when space is not a constraint and when there is sufficient space available in the front fuselage to house the retreating mechanism.
Fig 1.10 F-35A
1.5.1.1.2. Fixed Probe
A non-retractable probe takes up less space in the forward fuselage compared to the retractable one also the nose isn't big enough or has no space to house the mechanism next to a big radar.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.11 Mirage 2000
Advantages of Probe and drogue System
• It has simpler tanker design. • Tankers can also be equipped with buddy pod which makes it possible to refuel more than one aircraft. • This system can also be equipped with helicopters and light combat aircraft. • No boom operator is needed.
Disadvantages
• It has lower flow rate as compared to flying boom all due to its limited hose diameter. • It needs modification in the fuselage for higher fuel flow rate. • It is highly susceptible to turbulence and aerodynamic forces during refuelling.
1.5.1.2. Elements of Probe and Drogue System: The tanker trails a hose; the free end of the hose terminates in a reception coupling and a conical shaped drogue. Receiver aircraft are fitted with an AAR probe which terminates in a fuel nozzle; the receiver aircraft is flown to engage the probe into the drogue.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 1.12 Probe and Drogue system System Description The tanker hose is carried on a power driven hose drum (or reel).To trail the hose, the hose drum brake is released and air drag on the drogue pulls the hose, at a controlled rate, into the airstream. When the hose is at full trail, a winding-in torque (response system) is applied to the drum; this counter the air drag of the drogue. The controlled balance between winding-in torque (response system) and air drag absorbs the impact of the receiver making contact; it also damps any tendency for the hose to whip as contact is made, provided excessive receiver closure rates are avoided.
When contact is made the probe engages coupling latches, which grip the probe to make a fuel tight joint; fuel valves in the coupling and probe then open. The receiver continues to move forward, pushing the hose back onto the drum. When sufficient hose has rewound onto the drum, the main fuel valve in the AAR equipment opens and fuel can be pumped to the receiver.
After making contact the forward movement required of the receiver to open the fuel valve is typically about 2 m (6 ft); however, the distance varies according to AAR equipment type. Most systems afford a considerable range of fore and aft hose
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019 movement within which fuel will flow to an in-contact receiver. A range of movement from the valve open position to 7 m (20 ft) forward of this, is typical. On some equipment, the fuel valve closes if the hose is pushed in too far.
When AAR is complete, the receiver pilot makes a small power reduction and drops back slowly to stabilize in the pre-contact position. As the hose nears the full trail position, the AAR equipment fuel valve closes. When the hose reaches full trail, the probe begins to pull out of the reception coupling; the coupling and probe fuel valves close, then the coupling latches release the probe. If a Breakaway is commanded, the receiver drops back quickly. A sensor in the AAR equipment detects the high rate of hose movement and the hose drum brake is automatically applied; this achieves a swift, positive disconnect and occurs well before the hose reaches full trail.
1.5.2. FLYING BOOM METHOD (FOR FASTER FUEL TRANSFER)
Fig 1.13. F-22 Raptor
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
The boom is a telescoping, rigid tube that an operator on the tanker aircraft extends and inserts into a receptacle on the aircraft being refueled. which is "flown" by an operator in coordination with the pilot in order to make a connection with a receptacle on the second aircraft. The boom is retracted when not in use.
Though it can do damage if it comes in contact with an aircraft, the operator can quickly move the boom if needed
The boom can also pump a lot more fuel: 3331 liters per minute.
Advantages of Flying Boom System
• It has higher fuel flow rate up to 1000 US gallons that are equal to 3800 litres, due to the large diameter of the pipe.
• It is less prone to receiving aircraft pilot error and fatigue.
• It is less dangerous to refuel in adverse weather conditions.
• It can also be convertible to multisystem refuel methods.
Disadvantages of Flying Boom System • A boom operator needs to control it. • only one receiver aircraft can be refueled at a time. • Fuel flow rate needs to be reduced as military fighter aircraft cannot allow fuel at the boom maximum flow rate
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
CHAPTER 2
LITERATURE REVIEW
This chapter shows the location of the air to air refueling probe on various fighter aircrafts
Literature Survey of Fixed Air to Air Refueling Probe System
Dassault Mirage 2000’s refueling probe is mounted on the front fuselage of the aircraft between station 1 and station 2. The length of the probe is short and also has a slow fuel flow rate.
Fig 2.1 Mirage 2000 - Fixed AAR Probe (Side View)
Fig 2.2 Mirage 2000 - Fixed AAR Probe (Top View) Dept. of Mechanical Engg, NHCE, Bengaluru Page 13
Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Dassault Rafale’s refueling probe is also mounted on the front fuselage of the aircraft between station 2 and station 3. The length of the probe is longer when compared to Mirage 2000 and it also has a faster fuel flow rate
Fig 2.3 Rafale - Fixed AAR Probe (Side View)
Fig 2.4 Rafale - Fixed AAR Probe (Side View)
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 2.5 Rafale - Fixed AAR Probe (Side View)
Fig 2.6 Rafale - Fixed AAR Probe (Front View)
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Aermacchi M-345’s refueling probe is also mounted on the front fuselage of the aircraft between station 3 and station 4. The length of the probe is long and it also has a faster fuel flow rate
Fig 2.7 Aermacchi M-345 - Fixed AAR Probe (Side View)
Fig 2.8 Aermacchi M-345 - Fixed AAR Probe (Front View)
Fig 2.9 Aermacchi M-345 - Fixed AAR Probe (Side View)
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Literature Survey of Retractable Air to Air Refueling Probe System This system is designed with mechanism as to extend & retract during refueling operation. The F18’s refueling probe is mounted on the front fuselage of the aircraft between station 1 and station 2. The length of the probe is short and also has a faster fuel flow rate.
Fig 2.10 F18 with Retractable Aerial Refueling Probe
The Panavia Tornado’s refuelling probe is mounted on the shoulder region of the aircraft between station 8 and station 9. The length of the probe is long, but it has a slower fuel flow rate
Fig 2.11 Panavia Tornado with Aerial Refueling Probe
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Eurofighter Typhoon’s refueling probe is mounted on the front fuselage of the aircraft between station 2 and station 3. The length of the probe is short, but it has a faster fuel flow rate.
Fig 2.12 Typhoon with Retractable Aerial Refueling Probe
Saab JAS 39 Gripen’s refueling probe is mounted on the shoulder of the aircraft between station 6 and station 7. The length of the probe is long and also higher fuel flow rate.
Fig 2.13 Gripen JAS 39 with Retractable Aerial Refueling Probe
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
CHAPTER 3 NUMERICAL ANALYSIS
3.1. MOMENT VALUES ABOUT FIXED POINT
Specifications
The actual aircraft axis (Right hand co-ordinate system) and the corresponding sign convention for the application of the probe loads are shown in Fig 3.1 Probe Axis System: X – Positive AFT Y – Positive STBD Z – Positive UP
Fig 3.1 Probe coordinate system for loading
Fig 3.2 Side View
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Load Case Fx (kg) Fy (kg) Fz (kg)
1 1000 500 -
2 1000 - 500
3 -500 500 -
4 -500 - 500
Table 3.1 Various Load Cases
Fig 3.3 Front View Dimensions
Fig 3.4 Visualization of the Forces acting on the Probe
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Distances
X = 1000mm, Y = 350mm, Z = 450mm
Engaging forces
Fx = 1000kg, Fy = 500kg, Fz= 500kg
The radial load (FY or FZ) act on the probe with some angle, and these angles varies from 0° to 360°.
For every 5° we calculate loads for cos and sine.
3.2. 1st load case for θ = 0° Moment values using analytical approach
Resolved Forces with respect to their angles
Fx = 1000kg * 9.81 = 9810N
휋 Fy = −500푘푔 ∗ cos (휃 ∗ ) ∗ 9.81 180 = - 4905N
휋 Fz = 500푘푔 ∗ sin (휃 ∗ ) ∗ 9.81 180
= 0 Moment Calculations
Mx = (-Fy * Z) + (Fz * Y) ……… (3.1) = (4905 * 450) + (0 * 350) = 2207250 N-mm
My = (Fx * Z) + (Fz * X) .……... (3.2) = (9810 * 450) + (0 * 1000) = 4414500 N-mm
Mz = (-Fx * Y) + (-Fy * X) ……….. (3.3) = (-9810 * 350) + (4905 * 1000) = 1471500 N-mm
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Table 3.2 Moment calculations along X, Y & Z direction Dept. of Mechanical Engg, NHCE, Bengaluru Page 22
Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Graph
Moment at different angles 12000000
10000000
8000000
6000000
4000000 mm) - 2000000
0 0 10 20 30 40 50 60 70 80 90100110120130140150160170180190200210220230240250260270280290300310320330340350360370380
Moments (N Moments -2000000
-4000000
-6000000 Mx (N-mm)
-8000000 My (N-mm) Mz (N-mm) -10000000 Angle (Degrees)
From the above graph, the critical load cases are identified and tabulated as shown in Table 3.3 and the critical load case is 90◦ and it Is used for 3D - FE analysis.
Angle My (N- Mz (N- Fx (N) Fy (N) Fz (N) Mx (N-mm) (∘) mm) mm) Critical 7567373. 40 9810 -3757.45 3152.873 2794357.23 323947.993 MX 23 1261626. 220 9810 3757.448 -3152.87 -2794357.23 -7190948 77 Critical 90 9810 -3E-13 4905 1716750 9319500 -3433500 MY 270 9810 9.01E-13 -4905 -1716750 -490500 -3433500
Critical 360 9810 -4905 0 2207250 4414500 1471500 MZ 180 6.01E-13 9810 4905 -2207250 4414500 -8338500
Table 3.3 Critical Load cases
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
3.3. Verification of the 1st load case when θ = 0° moment values through Nastran & Patran
3.3.1. HyperMesh v13.0 (Pre-processor) HyperMesh is used to model the 1D element of the probe. • Nodes were created with coordinates (0,0,0), (-320,350,450), (-1000,350,450) • 10 nodes were created in between the line connecting the fixed point to the 1st coordinate and another set of 10 nodes were created in between the line connecting the 2nd and the 3rd coordinate • For the 1D element Aluminum is selected and its Youngs Modulus, density and other properties are specified • Radius of the probe is given as 25mm. • Beam property CBEAM is set with element type. • The Load Collector card is defined by specifying the SPC and forces o The Origin is constrained by selecting that node i.e. origin and then selecting ALL DOF o The forces acting along X, Y & Z are applied on the free end by selecting Force option under Analysis and the force values are given by selecting the respective direction. • The Load Step card is defined by selecting the SPC force and by changing the analysis type to live static. • The 1D element with the forces acting at the free end is exported using the Solver Deck option to get the BDF file which can be run in Nastran.
Fig 3.6 isometric view of 1D probe
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3.3.2. Nastran v2016 (Solver) • The BDF file from HyperMesh is being imported to Nastran for solving the model with forces acting on it. • After solving, from the F06 file was checked for fatal error (error that it encountered while solving due to any missing boundary conditions) • In the F06 file the resultant moment can be viewed under OLOAD RESULTANT
Fig 3.7 Nastran Results
The analytical values of forces and moments matches with the FE results obtained from the F06 file.
3.3.3. Patran v2016 (Post-processor) Patran is the world’s most widely used pre/post processing software for fine element analysis (FEA), providing solid modeling, meshing, analysis setup and post processing for multiple solvers including MSC Nastran, Abaqus, ANSYS, and Pam crash.
• The new database file with the extension .db is created. • The BDF file is finally imported to Patran, to visualize moments across X, Y and Z directions and also the translational displacement along Y direction
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
Fig 3.8 The visualization of moments along X, Y & Z at the Fixed point can be seen
Fig 3.9 Visualization of the translational displacement along Y direction can be seen
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CHAPTER 4
CAD MODEL
4.1. Introduction to CATIA CATIA is a 3D designing package the core surface represented by NURBS and it is a parametric solid/surface-based package and has a several workbenches that provide KBE support. Commonly used 3D Products are conceptualization manufacturing (CAM). Design (CAD), and engineering (CAE). In engineering CATIA is used for surfacing & shape design, mechanical engineering, CATIA is also used for reverse engineering, creating drafts, sketches, creating 3D sketches, 3D parts, part modelling assembly or composites etc. This provides functional tolerance of kinematics definition.
CATIA tool can be applied to any industry from automotive, shipbuilding, plant design, construction, architecture to defense and aerospace. CATIA v4, CATIA v5, NX (formerly known as uni-graphics), Pro/ENGINEER, and Solid Works are the dominant systems.
CATIA offers many workbenches that can be loosely termed as modules. A few of the important workbenches are
• Part design • Generative shape Design • Assembly • Kinematic simulation
4.2. CATIA Model of Probe and Mounting Bracket
Initially a CAD modeling of probe and mounting bracket is modeled using CATIA V5 software which is shown in fig 4.1 and fig 4.2 and is then imported through IGES file and then meshed using HyperMesh V13 software.
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Fig 4.1 Side View of Probe
Fig 4.2 Isometric view of the mounting bracket
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
• Mounting bracket is generally a supporting structure for the probe and it is designed in such a way that the probes flange is connected to the Mounting bracket. • The Probe is a major part in fueling of the aircraft, as the probe comes in contact to the drogue of the mother aircraft. • Mounting bracket has a bath tub structure where the flange of the probe is fixed. • The mounting bracket and the probe consist of six bolt holes in common and it fastened together by means of fasteners.
Procedure Carried out in CATIA: -
• The bathtub structure of the mounting bracket is created as per the dimensions. • The bathtub structure is been designed with fuel sealing o ring from its bottom surface and is connected to the mid floor in the airfoil structure. • The whole mounting bracket is been fastened to the top floor. • As per the probes length measurements a probe is created with a hollow structure in it for the fuel to flow. • Once the probe is modelled the flange is been created according to the bathtub structure of the mounting bracket.
Fig 4.3 Assembly of Mounting bracket along with the probe flange
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Fig 4.4 Exploded view of the assembly
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CHAPTER 5
FINITE ELEMENT ANALYSIS
5.1. INTRODUCTION OF FINITE ELEMENT ANALYSIS
FEA allows detailed visualization of where structures bend or twist, and indicates the distribution of stresses and displacements. The software provides a wide range of simulation options for controlling the complexity of both modelling and analysis of a system. FEA allows entire designs to be constructed, refined, and optimized before the design is manufactured.
This powerful design tool has significantly improved both the standard of engineering designs and the methodology of the design process in many industrial applications. The introduction of FEA has substantially decreased the time to take products from concept to prototype and manufacture. It is primarily through improved initial prototype designs using FEA that testing, and development have substantially improved delivery times and also greater confidence in the structural performance of a product.
5.2. BASIC CONCEPTS IN FINITE ELEMENT ANALYSIS 5.2.1 Major element types
1D (Line element) Mainly of three types: 1. Linear (2 Noded per side) e.g. Beam, truss
2. Quadratic (3 Noded per side) e.g. Beam
3. Cubic (4 Noded per side) e.g. Beam Fig 5.1 1D elements
2D (Area element) Mainly of three types: 1. Linear (2 Noded per side) e.g. Plane stress 2. Quadratic (3 Noded per side) e.g. Plane strain
3. Cubic (4 Noded per side) e.g. Plate and shell Fig 5.2 2D elements Dept. of Mechanical Engg, NHCE, Bengaluru Page 31
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3D (Volume element) Mainly of two types: 1. Linear 2. Quadratic Fig 5.3 3D Elements 5.2.2 Degrees of Freedom (DOF):
• DOFs are the unknown quantities associated with a node, or the things that must be solved for mathematically. • Associated loads are loads of the same direction and type as the DOFs. • For structural FEA the DOFs are displacements (or rotations) and the associated loads are forces (or moments).
5.2.3 Boundary Condition (BC):
A boundary condition for the model is the setting of a known value for a displacement or an associated load. For a particular node you can set either the load or the displacement but not both.
5.3. FE MODEL DESCRIPTION
Fig 5.4 FEM model of Probe along with the mounting bracket Dept. of Mechanical Engg, NHCE, Bengaluru Page 32
Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
• The model is idealized using CTETRA10 solid elements with size 10mm • Total Number of elements is 1.9 Lakhs • Total Number of nodes is 2.9 Lakhs • Total FEM mass is 23.5kg (Probe = 15.16kg and Mounting Bracket = 8.7kg)
5.4. BOLT CONNECTIONS
Fig 5.5 Bolt Connections along with the Visualization of a single steel bolt
There are totally six steel bolts having diameter of 12mm shown in Figure 5.5, idealized as CBAR element type connecting the Mounting Bracket and probe flange with RBE2 element at each end.
5.5. MATERIALS DESCRIPTION • Probe’s Mast and the Mounting Bracket is assigned with Aluminum material • The bolts are assigned with Steel material.
DESIGN ALUMINIUM DESIGN STEEL ALLOWABLE ALLOWABLE Young’s modulus, E 70000 Young’s modulus, E 210000 (MPa) (MPa) Ultimate strength 465 Ultimate strength 1200 (MPa) (MPa) Density (ρ), (g/cm3) 2.71 Density (ρ), (g/cm3) 7.75 Poisson’s ratio 0.3 Poisson’s ratio 0.3
Table 5.1 Material Properties of Aluminium and Steel
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5.6. LOADS
Fx = 9.81e+03
Fz = 4.91e+03
Fig 5.6 Loads acting in X, Y and Z direction
The loads that are being used for Finite Element Analysis have been taken from table 3.2 where the maximum moment value corresponds to My and hence the corresponding loads for My have been used.
Critical Loads applied in
X-axis = 1000kg * 9.81 = 9810 N Y-axis = 0 휋 Z-axis = 500푘푔 ∗ sin (90 ∗ ) ∗ 9.81 180 = 4905 N
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5.7. BOUNDARY CONDITIONS
Fx = 9.81e+03
Fz = 4.91e+03
Tx=Ty=Tz=0
Fig 5.7 The various Boundary Conditions defined for the meshed model
The translational motions are constrained to transmit the loads to the Airframe when the probe engages with the drogue (fuel basket). It’s constrained at special bolt location which transmits the loads to the longerons and also at the fastener locations
All the translational motions are constrained at the 10 defined locations shown in Figure 5.7 above
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5.8. ANALYSIS RESULTS
5.8.1. Normal Mode Analysis Result
Mode No. Frequency (Hz)
1 0
2 0
3 0
4 0
5 0
6 0
7 121.5487
8 141.2508
9 233.7344
10 245.4763
Table 5.2 Frequency values for Free – Free
From Table 5.2 The first six are rigid body modes having natural frequency value equal to 0. This tells us that the model is stable
The 7th mode of frequency having the magnitude of 121.5487Hz. Which is within the accepted range
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5.8.2. Natural Frequency Analysis Result
Natural Frequency, also known as Eigen frequency, is the frequency at which a system tends to oscillate in the absence of any driving or damping force. The motion pattern of a system oscillating at its natural frequency us called the normal modes.
If the oscillating system is driven by an external force at the frequency at which the amplitude of its motion is greatest (close to natural frequency) this frequency is called resonant frequency
Mode Frequency No. (Hz)
1 27.99793
2 35.06329
3 112.7709
4 151.6929
5 367.2321
6 479.4975
7 680.7666
8 746.1400
9 836.7615
10 864.1591
Table 5.3 Natural Frequency values Fig 5.8 Natural Frequency for probe with Mounting bracket
From Table 5.3 the natural frequency for the 1st Mode is found to be 27.99Hz which is the side bending mode
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Fig 5.9 Deformation of the probe assembly during Natural Frequency
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5.8.3. Max-Displacement Result
Load Deflection Deflection Deflection Case’s in x – in y - in z – direction direction direction (mm) (mm) (mm) critical 19.4 0.5 51.4
Table 5.4 Deflection in X, Y and Z direction
Max. Displacement = 54.104mm
Fig 5.10 maximum displacement
The displacement along x, y and z direction is found to be 19.4 mm, 0.5 mm, 51.4 mm. From Figure 5.9 The resultant Max Displacement is found to be 54.104mm at the Probe tip
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5.8.4. Reaction Forces
Bolt No. Resultant (N) Rx (N) Ry (N) Rz (N)
1 26316.91 -3802.91 20643.6 15873.13
2 17112.14 -4464.13 15120.44 6653.53
3 14516.53 -4669.56 11946.00 6798.38
4 13899.11 -5197.87 11422.27 5974.87
5 16823.41 -3859.13 -3058.69 16086.60
6 8282.00 -3462.74 -4275.14 6190.65
7 8102.88 -3446.99 -3563.20 6409.25
8 7566.70 -3571.35 -4703.37 4730.62
Table 5.5 Reaction Forces at Fastener Location
FD 1 5
2 6
3 7
4 8
Fig 5.11 Bolt Location’s
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
5.8.5. Bar Forces
Fig 5.12 In-Plane and Tensile Bar Forces acting on the six bolts
Steel Bolt UTS = 1200MPa Allowable Tensile load = 1200 * 훱 ∗ 푟2 = 1200 * 훱 ∗ (6)2 = 135648 N (13.56 tons) Maximum Bar Force = 6.73 T
퐴푙푙표푤푎푏푙푒 푇푒푛푠푖푙푒 퐿표푎푑 13.56 Reserve Factor (R F) = = = 2.01 i.e. > 1 푀푎푥 퐵푎푟 퐹표푟푐푒 6.73
Since the Reserve Factor of the bolt is greater than one, hence the bolts can withstand the loads.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
5.8.6. Von mises Stress Results
Von Mises stress is a value used to determine if a given material will yield or fracture. It is mostly used for ductile materials, such as metals.
1
Max stress = 505.470MPa 2
Max stress = 541.575MPa Fig 5.13 Von Mises Stress Distribution
Figure 5.12 shows the study of the Von-Mises stress and it is evident that the max stress is found to be 505.470MPa at location 1 and 541.575MPa at location 2. These stresses are higher than the UTS of the aluminum alloy as mentioned in Table 5.1
Hence Neuber correction is used to evaluate the corrected stress at these locations and are presented below.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
5.8.6.1. Neuber Correction done to correct the stress
Using the Neuber Plot to Account for the Effects of Scatter, Corrosion and Welding in Strain-Life Fatique Test Data
F.A. Conle and J.J.F. Bonnen
Calculation for Limit and Ultimate Load With Result as Reserve Factor (RF)
1) At location 1
2) At location 2
427 N/mm2
Therefore, the corrected stresses are well within the allowable stress limit
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
5.8.7. Max Principal stress Results
The failure of a material or component will take place when the max value of stress exceeds the max value of stress exceeds the limiting value of stress
푌푖푒푙푑 푠푡푟푒푠푠 푝푒푟푚푖푠푠푖푏푙푒 푠푡푟푒푠푠 = 퐹푂푆
We can reduce the value of working stress so that it does not go into the maximum stress condition
Max. Principal stress = 314 MPa
Fig 5.14 Stress Distribution
From Figure 5.13 Max Principal stress is found to be 314MPa at the fillet of the probe flange
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
CHAPTER 6
CONCLUSION
Probe interface mounting bracket is designed with 6 tension bolts. Mounting bracket is supported at floor. Additional support at mounting bracket is provided to transfer loads to the Longerons. Linear static analysis carried out with drogue contact loads. FE Mass of the probe(15.16kg) and mounting bracket (8.7kg) is found to be 23.5kg. From the analysis it is concluded that the Von-mises and max principal stresses are within the allowable limit. From the result’s it is observed that the structure is safe from strength point of view.
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Design and Analysis of Air to Air Refuelling Probe Support Structure 2018 - 2019
CHAPTER 7
SCOPE OF FUTURE WORK
Studies are going on to
1) Find the optimum number of bolts required and the diameter of bolts 2) Find the most optimum pattern of bolt arrangement for more uniform load distribution 3) To increase the stiffness of the mounting bracket to control probe tip deflection and also to improve the frequency 4) Finally, to reduce the overall weight of the probe assembly
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REFERENCES
1) Carmelo J. A. Bastos-Filho, Augusto C. S. Guimarães, “Multi Objective Fish School Search”, July 2015. 2) MIL-V-18634B3 April 1981 UPERSEDING MIL-V-18634A6 February 1967. 3) Darrol Stinton, “The Anatomy of the Aeroplane”, Published 1999 4) Finite element method and applications in engineering using ANSYS by Erdogan. Madenci Ibrahim Guvenn The University of Arizona, 2006 by Springer Science Business Media, LLC. 5) Material selection through the military standards, special materials for aerospace applications. 6) ring design, installations, and applications by Busak ShambanIn 1999. 7) THREADED FASTENERS provides full detail design of fasteners Joseph E. Shigley Professor Emeritus the University of Michigan Ann Arbor, Michigan. 8) “Aircraft Flying Handbook”, U.S. Department of Transportation, Federal Aviation Administration, 2004
WEBSITES
• https://en.wikipedia.org/wiki/Aerial_refueling • https://www.aiaa.org/microlesson37/ • https://www.quora.com/How-is-aerial-refueling-done-How-do-the-tanker-and- receiver-maintain-the-altitude-How-do-they-connect-themselves-What- technology-is-used • https://www.quora.com/What-are-the-advantages-of-different-types-of-aerial- refueling
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