11493 - Aircraft and Aerospace Design

Learning outcomes

At the end of the course, the student knows the main rules of representation of the assemblies and parts. They can read a technical drawing. They know the standard components representation and their use. They understand the design solutions typical of the aerospace industry, and they know how the realization technologies can impact the design of a component. They possess the fundamental skill to realize a 2d drawing from a three-dimensional one, both in terms of representing it on the sheet and about the choice of materials and manufacturing technologies.

Course contents

Drawing sheets and standardization of formats; reproduction of drawings. Folding of drawing sheets. Title block. Representation scales. Pencils and leads. Rulers and set squares. Compasses, French curves, and templates. Standardization of line types and their use, lettering and numerical characters, practical recommendations. Reduction factors.

General concepts and historical background of national and international standardization bodies. Projection methods. Views: first-angle projection (E) and third-angle projection (A), arrow method, auxiliary views, partial views, local views, and revolved views.

Sections according to a single plane, two or more consecutive planes, parallel planes, and cylindrical surfaces with a specified directrix; partial sections and sections of symmetrical parts; revolved sections in place or nearby; successive sections; components that are not sectioned. Hatching conventions for representing materials in sections. Special representation conventions. Criteria for representing filleted and blended parts.

General dimensioning principles, dimension and extension lines, arrangement and interpretation of dimensions. Dimensioning systems (chain dimensioning, parallel/baseline dimensioning, superimposed dimensions, combined dimensioning, Cartesian coordinates, and polar coordinates). Special dimensioning conventions (solids of revolution, circles, spherical surfaces, squares, chamfers and fillets, regularly and irregularly spaced elements). Criteria for selecting reference features and general rules for proper dimensioning. Dimensioning in axonometric views. Dimensioning of standardized components.

Overview of technological tests for material characterization: tensile testing, hardness testing, and impact toughness. Classification and designation systems, with an introduction to application criteria in the aerospace sector for the following materials: steels, cast irons, copper alloys, aluminum alloys, magnesium alloys, titanium alloys, and composite materials (glass fiber, carbon fiber, Kevlar). Introduction to the main heat treatments and their indication on technical drawings.

Application of dimensional, quality, and supply-condition standards in detail and assembly drawings. Renard series. Dimensional tolerances: introduction, definitions, and the ISO system of tolerances. Indication of tolerances and general tolerances on drawings. Criteria for tolerance selection. Basic shaft system and basic hole system. Fit problems and applications: recommended fits. Chains of toleranced dimensions and evaluation of the resulting tolerance. Criteria for determining deviations and tolerances in functional dimension chains when the functional condition limits are known, or for evaluating the tolerance of the functional condition when the limiting dimensions of the chain elements are known.

Introduction to microgeometric and macrogeometric errors. Surface roughness: definitions and relationship between manufacturing processes and roughness. Surface finish indication. Geometric tolerances: general principles, datums, graphical symbols, and rules for their specification. Maximum Material Principle.

General concepts of rigid and elastic joints (friction joints, form-fit joints, combined friction and form-fit joints, fusion joints, and adhesive joints). Threaded fasteners: definitions and principal standardized thread systems (metric, BSP/GAS, Whitworth). Standards for the representation and dimensioning of screws, nuts, bolts, and blind tapped holes. Examples of threaded joints: through bolts, set screws, studs, etc.; tolerances for threaded fits. Bolts and strength classes. Incomplete threads and relief grooves for internal and external threads. Clearance holes for screws. Locking devices to prevent self-loosening.

Shaft-hub connections using tapered elements; taper and cone angles. Dimensioning and tolerance indication for tapered elements; introduction to taper tolerance systems; application examples (Morse tapers, etc.). Direct force-fit joints. Connections using locking rings (locking assemblies), taper pins, dowel pins, and compensating rings. Connections using keys (parallel, tapered, square-ended, round-ended, concave, gib-head, tangential). Connections using feather keys (parallel, tapered, square-ended, round-ended, Woodruff keys). Cylindrical and tapered shaft ends. Connections using cylindrical splines with parallel flanks and involute splines. Complete and simplified representation, tolerances. Connections using retaining rings. Riveted joints (cold riveting). Welded joints.

Rotary motion guides: plain bearings. Criteria for material selection. Influence of operating and lubrication conditions on design. Lubrication methods for plain bearings (intermittent lubrication: ball oilers, Stauffer grease cups, hexagonal-head grease fittings; continuous lubrication: spring lubricators, drip-feed oilers, wick-feed oilers). Closed lubrication systems (splash lubrication, ring lubrication, forced circulation).

Rolling rotary guides: rolling-element bearings. General concepts, nomenclature of standardized types, and designation. Criteria for selecting bearing type and dimensional fit tolerances with bearing seats. Criteria for evaluating geometric tolerances and surface roughness. Assembly issues. Mounting of ball and roller bearings, angular contact ball bearings, tapered roller bearings, single-direction and double-direction thrust bearings. Lubrication and protection criteria for rolling-element bearings and their influence on technical drawings.

Gear transmissions (definitions, conventional representation, standardization, and application examples). Metric trapezoidal threads. Power transmission by screw-and-nut mechanisms, cams, and crank-slider mechanisms (definitions, standardization, representation, and application examples).

Aerospace components: rivets, solid rivets, screws, aircraft fasteners, aircraft latches, seat tracks, toggle switches, aircraft seat attachment elements, and vibration isolators.

Readings/Bibliography

Lecture notes delivered during the course, accessible on the University page to the students of the University of Bologna who selected the exam in the study plan (website: virtuale.unibo.it).

Further resources helpful to students interested in a deeper analysis of the course topics:

- Manfè, Pozza, Scarato - Disegno Meccanico – Principato Editore, Milano, Voll. 1, 2, 3

-Chirone, Tornincasa – Disegno Tecnico Industriale – Edizione Capitello, Torino, Voll. 1, 2

- UNI M1, Norme per il disegno tecnico, UNI, Milano.

- Megson, Aircraft Structures for Engineering Students, Fourth Edition (Elsevier Aerospace Engineering)

Teaching methods

The course consists of 6CFU, corresponding to 60 hours, of which 30 are lectures (module 1) and 30 are practical drawing exercises (module 2). Practical exercises are carried out in the classroom, which is equipped with drawing tables, and in the computer room. Practical lessons aim to teach students technical drawing by hand. The aspects related to the drawing, the setting of dimensional/geometric tolerances (GD&T), and roughness are also dealt with by revealing how these are managed in the CAD codes.

In consideration of the teaching methods adopted in this course unit, all the students must attend Modules 1 and 2 on Health and Safety (https://www.unibo.it/en/services-and-opportunities/health-and-assistance/health-and-safety/online-course-on-health-and-safety-in-study-and-internship-areas) in e-learning mode.

Assessment methods

The final course examination is designed to assess the achievement of the learning objectives with respect to both the theoretical and practical contents:

• Knowledge of the main rules for representing assemblies and individual parts.
• Ability to read an assembly drawing and a manufacturing drawing of a component.
• Correct drafting of a technical drawing from a three-dimensional component view or an assembly.

The final grade awarded to the student is based on the results achieved in both the written and oral parts of the examination. The written examination consists of producing a manufacturing drawing of a component starting from an assembly drawing, while the oral examination consists of 3 questions concerning either theoretical topics or the drawing of specific mechanical components.

To be admitted to the written examination, students must have completed approximately 20 drawing excercises, which are assigned and solved on the blackboard during the practical sessions. Students are required to bring drawing paper and manual drafting instruments to the written examination.

The written examination lasts 1 hour and 15 minutes. After the papers are collected, the instructor reviews and corrects the exercise on the blackboard. Approximately 30 minutes after the end of the written examination (depending on the number of students taking the exam), each student is individually called to the instructor's desk to review the corrected paper and receive the result of the written part.

Once all written papers have been reviewed, the oral examinations begin. These are completed on the same day or, in the case of a large number of candidates, on subsequent days.

The final grade is the sum of the scores obtained in:

• Written examination: 15 points
• Oral examination: 12 points
• Oral Discussion and comments of the drawing exercises completed by the student: 3 points

Detailed information on the examination procedures is provided to students on the first day of class.

The use of AI tools during the exam is strictly prohibited in any form, including chatbots, text generators, advanced translators, content synthesizers, and tools integrated into devices. Any use of AI is considered a violation of the principles of honesty and integrity outlined in the Policy and may result in the exam being annulled by the instructor, who remains responsible for verifying the exam's validity. Students are required to place smartphones and any other electronic devices inside backpacks or cases, which must be left at the classroom entrance. To take the exam, you must bring the following items: two A3-sized sheets of gridded/bordered paper, a soft-grade pencil (e.g., HB), a hard-grade pencil (e.g., H), an eraser, a 30/60° set square, a 45° set square, a ruler (at least 40 cm long), a circle template, a compass, and the drawing plates completed during the course.

Teaching tools

The teaching material presented in class will be available to the student in electronic format via the web. Please visit: virtuale.unibo.it to obtain the educational material. The material is reserved for the students of the University of Bologna who include the course in the study plan and is for personal use only.

Any student unable to attend can find the drawings to be done by hand (including a possible solution) on the virtuale.unibo.it website.
The website includes both drawings to be done by hand and a summary of the theoretical topics covered in the course.

Office hours

See the website of Alessandro Ceruti