Construction of a retractable single-strut undercarriage in fiber composite design for the motorized sailplane “Valentin Taifun 17E”

Table of Contents

1. INTRODUCTION AND PRESENTATION OF THE TYPE OF PROBLEM

1.1 Valentin Taifun 17E

1.2 Standard carriage of the Taifun 17E, its problems and task of the thesis

2. FUNDAMENTALS OF THE MANUFACTURE OF SANDWICH-STRUCTURED COMPOSITES

2.1 Fundamentals

2.2 Showcase of manufacture of a sandwich constructed fuselage plate

3. BOUNDARY CONDITIONS

3.1 Determination of position of the landing gear in the extended position

3.1.1 Determination of center of mass under consideration of different load conditions

3.1.2 Determination of the horizontal landing gear position under disregard of plane inclination

3.1.3 Comparison with available space

3.1.4 Adaption of the landing gear position

3.1.5 Provision for the start-kick

3.1.5 Further considerations

4. LOAD ASSUMPTION OUT OF THE JOIN AVIATION REQUIREMENTS 22

4.1 Level landing condition

4.2 Lateral load conditions

4.3 Lever control

4.4 Limit maneuvering load factor

4.5 Wheel

4.6 Factors of Safety

5. CONSTRUCTION POSSIBILITIES

5.1 Version 1 – Description and Evaluation

5.2 Version 2 – Description and Evaluation

5.3 Version 3 – Description and Evaluation

6. CONSTRUCTION AND STRESS ANALYSIS VERSION 3

6.1 Wheel

6.1.1 Experimental set-up

6.1.2 Calibration

6.1.3 Execution

6.1.4 Selection of the tire pressure

6.2 Axle

6.2.1 Forces on the axle by “normal landing load case”

6.2.2 Forces on the axle by “lateral load case”

6.2.3 Contact pressure between axle and fit bushing

6.3 Bushings

6.3.1 Execution of the bushings

6.3.2 Bearing Pressure between spherical plain bearing and bushing

6.3.3 Bearing pressure between bushing and roving truss

6.3.4 Implementation of the brake

6.4 Gear swing

6.4.1 Framework

6.4.2 Bending truss

6.4.3 Bending truss with shear field

6.3.4 Compression strut - behavior during compression

6.5 Framework trusses 1 and 2

6.5.1 Framework truss 1

6.5.2 Framework truss 2

6.5.3 Console wall

6.6 Connection of the framework trusses 1 and 2

6.7 Connection of framework truss 1 with the wheel and the gear swing

6.8 Bolt mechanism

6.8.1 Requirements of the single components

6.8.2 Execution and assembly

6.8.3 Improvements

6.9 Lever mechanism – extending and retracting

6.9.1 Requirements and execution

6.9.2 Actuating force

6.10 Bench face – Holm mounting

6.10.1 Contemplation and determination of loads transferred by axle

6.10.3 Thickness for perpendicular/lateral loads

6.10.4 Adhesive bonded joint

6.11 Connection of the holm mounting with the gear swing and framework truss 2

6.11.1 Manufacturing and assembling

6.11.2 Stress analysis of the “bench face axle”

7. EVALUATION AND FURTHER PROCEDURE

Objectives & Thematic Focus

The primary objective of this diploma thesis is to calculate, interpret, and design a retractable one-wheel landing gear system for the "Valentin Taifun 17E" motorized sailplane, emphasizing a construction that is lighter, simpler, and more stable than the original design, while utilizing advanced fiber composite materials.

• Aerodynamic and structural integration of a one-wheel landing gear system within the existing fuselage constraints.
• Determination of load assumptions based on JAR 22 aviation standards, including level landing and lateral load cases.
• Development of a weight-efficient and durable construction using sandwich-structured composites and fiber-reinforced roving trusses.
• Implementation of a reliable retraction and extension lever mechanism with integrated locking functionalities.

Excerpt from the Book

Summary of Chapters

1. INTRODUCTION AND PRESENTATION OF THE TYPE OF PROBLEM: This chapter introduces the Valentin Taifun 17E aircraft and defines the problem with its current landing gear, setting the goal for a simpler, one-wheel construction.

2. FUNDAMENTALS OF THE MANUFACTURE OF SANDWICH-STRUCTURED COMPOSITES: This section covers the theoretical basis of sandwich materials and provides a step-by-step procedure for manufacturing fuselage plates using vacuum infusion and resin.

3. BOUNDARY CONDITIONS: This chapter focuses on determining the optimal geometry for the landing gear, including center-of-mass calculations and ground clearance requirements.

4. LOAD ASSUMPTION OUT OF THE JOIN AVIATION REQUIREMENTS 22: The chapter outlines the specific structural and safety criteria from JAR 22, including kinetic energy absorption and maneuvering load factors.

5. CONSTRUCTION POSSIBILITIES: This chapter evaluates three different design versions, ultimately selecting the third version for its balance of weight, ease of assembly, and simplicity.

6. CONSTRUCTION AND STRESS ANALYSIS VERSION 3: This core chapter details the stress analysis for all components, including the wheel, axle, bushings, framework trusses, and the bolt locking mechanism.

7. EVALUATION AND FURTHER PROCEDURE: This concluding chapter summarizes the design process and outlines the recommended procedure for building and flight-testing a prototype.

Keywords

Valentin Taifun 17E, Landing Gear, Retractable Landing Gear, Fiber Composite Design, Sandwich Structure, JAR 22, Structural Analysis, Finite Element Analysis, Gear Swing, Roving Truss, Mechanical Design, Aviation Engineering, Stress Analysis, Bearing Pressure, Lever Mechanism.

Frequently Asked Questions

What is the core focus of this diploma thesis?

The thesis focuses on the structural design and engineering calculation of a retractable one-wheel landing gear for the Valentin Taifun 17E motor glider, with an emphasis on using fiber composite materials.

Which standard does the landing gear design comply with?

The construction follows the JAR 22 requirements, which define the necessary load assumptions for utility aircraft and sailplanes.

What is the primary goal of the new design?

The goal is to improve upon the existing complex tricycle gear by creating a more robust, lightweight, and easily maintainable one-wheel landing gear.

What analytical methods are utilized for the structural verification?

The author performs analytical stress calculations and uses external software tools, such as the Java-based TM-Interaktiv, to handle over-determined systems and determine force distributions.

What does the main construction chapter cover?

Chapter 6 provides detailed stress analyses for the wheel, axle, bushings, and framework trusses, ensuring that all parts remain within the permissible stress limits for both normal and lateral landing conditions.

Which keywords best describe this engineering work?

Key terms include landing gear construction, fiber composite design, JAR 22 compliance, sandwich-structured materials, and kinematic retraction mechanisms.

How is the landing gear locked in the retracted position?

The design utilizes a specialized bolt mechanism, actuated by a Bowden cable, to secure the landing gear safely during flight.

Why was the "fitting bushing" approach selected?

After comparing different configurations, the fitting bushing approach was chosen because it allows for lower shear forces on critical components compared to the spherical plain bearing version.