FEA Finals

Structure

is something that has been arranged or organized to support loads or maintain shape

Structure

refers to a framework, maintains the shape of an aircraft, and more importantly supports and transmits loads during flight and ground operations

1. Lightweight yet strong

2. Stiff yet flexible

3. Durable yet efficient

4. Aerodynamic yet structural

5. Simple yet optimized

6. Strict yet safe

6. An aircraft structure must be

Primary Structures

are the main load-bearing components of an aircraft that are essential to its flight safety and structural integrity

Primary Structures

are designed to carry and transfer significant aerodynamic, inertial, and ground loads experienced during all flight and landing conditions

Secondary Structures

are the non-critical components of an aircraft that do not carry primary flight or ground loads but play key roles in aerodynamics, accessibility, maintenance, and performance

Secondary Structure

their failure does not directly endanger the structural integrity or safety of the aircraft

1. Powerplant

2. Wing

3. Empennage

4. Landing Gear

5. Fuselage

5 Primary Structures

ATA 100 Specification (as defined by the Air Transport Association of America)

ATA of the Zoning System for Large Aircraft

ATA 100 (Zoning System)

provides a standardized way to identify and locate different sections of an aircraft for maintenance, repair, and inspection

ATA 100 (Zoning System)

divides the aircraft into major zones, each represented by a unique three-digit number

Zoning System (ATA 100)

its primary purpose is to streamline communication, improve efficiency, and ensure safety by allowing technicians to quickly pinpoint specific areas of components

Wings

• Generates Lift: the main upward force opposing the aircraft’s weight

• Supports the other structures: fuel tanks, engines (on some designs), and control surfaces such as ailerons and flaps

• Acts as a beam: transferring aerodynamic loads to the fuselage

1. Cantilever Wing

2. Braced Wing

3. High-, Mid-, and Low-Wing

4. Tapered/Swept/Delta Wings

4 Wing Designs

Cantilever Wing

• no external bracing

• internal spars and ribs carry all loads (common in modern aircraft)

Braced Wing

• uses external struts or wires to support loads (common in older or light aircraft)

High-, Mid-, and Low-Wing Configurations

• determined by the vertical position on the fuselage, affecting stability and ground clearance

Tapered/Swept/Delta Wings

• aerodynamic shaping based on speed and efficiency requirements

Full Cantilever

in page 24 of the pdf, what is the heaviest

Wire braced biplane/Long struts braced with jury struts

in page 24 of the pdf, what is the lightest

High Wing

provide better downward visibility and ground clearance, are often used on cargo planes for easy loading, and have better visibility in cruise flight,

Low Wing

offer better upward visibility, simplify fuel systems, and are often more stable in turbulence

Dihedral Wings

wings angle upward from the fuselage, providing roll stability and returning the aircraft to a level flight path, which is common in commercial and general aviation planes.

Anhedral Wings

sacrifices stability for increased maneuverability, making them common in fighter jets and high-performance aircraft that need to be more agile

Biplane

a fixed-wing aircraft with two main wings stacked one above the other

Monoplane

a fixed-wing aircraft configuration with a single main wing

1. Lift-induced bending moments

2. Torsional Loads

3. Shear Loads

4. Fuel Weight and Inertial Loads

4 Main Loads Experienced by the Wings

Lift-induced bending moments

load experienced when wing flexing upward

Torsional Loads

load experienced when twisting from aerodynamic moment or aileron deflection

Shear Loads

load distributed along the span

Fuel Weight and Inertial Loads

load experienced during maneuvers or turbulence

1. Spars

2. Ribs

3. Stringers

4. Wing Skin

5. Control Surfaces

5 Wing Subcomponents

Spars

main longitudinal beams carrying bending loads

Ribs

cross-sectional frames that maintain airfoil shape and distribute loads to the skin

Stringers

longitudinal stiffeners to prevent buckling of the skin

Wing Skin

forms the aerodynamic surface and carries shear and part of bending loads

Control Surfaces

ailerons, flaps, slates for roll control and lift augmentation

Fuselage

serves as the central body of the aircraft that connects all major components: wings, tail, landing gear, engines

Fuselage

houses passengers, cargo, and avionics, while withstanding internal pressurization and external aerodynamic forces

1. Truss-Type

2. Monocoque

3. Semi-Monocoque

4. Composite Fuselage

4 Design Types of a Fuselage

Truss-Type

framework of steel or aluminum tubes (light aircraft, older models)

Monocoque

skin carries most of the load

• minimal internal structure

Semi-Monocoque

combination of load-bearing skin with frames and stringers (standard in modern aircraft)

Composite Fuselage

uses carbon fiber-reinforced polymers for lighter weight and strength

1. Bending Loads

2. Shear and Torsional Loads

3. Internal Pressurization Loads

4. Payload and Landing Impact Loads

4 Main Loads Experienced by the Fuselage

Bending Loads

loads experienced from wings, tail, and landing gear attachments

Shear and Torsional Loads

loads experienced from asymmetric aerodynamic forces

Internal Pressurization Loads

loads experienced in cyclic loads expanding the fuselage skin outward

Payload and Landing Impact Loads

loads experienced from the weight of passengers, cargo, and gear reactions

1. Frames/Bulkheads

2. Stringers/Longerons

3. Skin

4. Floor Beams

4 Subcomponents of a Fuselage

Frames/Bulkheads

circular or oval cross-sections that define shape and transfer loads

Stringers/Longerons

longitudinal stiffeners that resist bending

Skin

load-bearing outer shell resisting tension and shear

Floor Beams

support cabin loads and distribute them to frames

Pressure Bulkheads

seal the pressurized cabin ends

Empennage

provides stability and control in pitch and yaw

Empennage

counteracts aerodynamic moments from the wings and fuselage to maintain steady flight

1. Conventional Tail

2. T-Tail

3. V-Tail

4. Cruciform Tail

4 Design Types of Empennage Tails

Conventional Tail

horizontal and vertical stabilizers at the rear of the fuselage

T-Tail

horizontal stabilizer mounted atop the vertical fin

V-Tail

combines horizontal and vertical stabilizers into two diagonal surfaces

Cruciform Tail

cross-shaped layout for improved aerodynamics

1. Aerodynamic Loads

2. Bending and Torsional Loads

3. Inertial Loads

3 Main Loads Experienced by the Empennage

Aerodynamic Load

load experienced from stabilizing forces and control surface deflection

Bending and Torsional Loads

load experienced due to lift/drag on stabilizers and rudder movement

Inertial Loads

load experienced from tail mass during pitch/yaw maneuvers

1. Horizontal Stabilizer

2. Vertical Stabilizer

3. Spars and Ribs

4. Skins and Stringers

5. Control Surfaces

5 Empennage Subcomponents

Horizontal Stabilizer

provides pitch stability and house elevators

Vertical Stabilizer

provides yaw stability and houses the ridder

Spars and ribs

carry aerodynamic and bending loads

Skins and Stringers

distribute shear stresses and maintain shape

Control Surfaces

elevator and rudder for maneuver control

Landing Gear

supports the entire aircraft weight on the ground

Landing Gear

absorbs impact energy during landing

Landing Gear

provides stability and steering during taxi, takeoff, and landing

1. Tricycle Gear

2. Taildragger (Conventional)

3. Retractable Gear

4. Fixed Gear

4 Landing Gear Designs

Tricycle Gear

two main gears and a nose gear (most common)

traildragger (conventional)

two main gears and a tailwheel

Retractable Gear

can be folded into the fuselage or wings to reduce drag

Fixed Gear

simplified, always exposed configuration (small/light aircraft)

1. Wheels

2. Skid-Type “Sled”

3. Legs and Pads

3 Types of landing Gear

1. Static

2. Retractable

2 Types of Wheel Landing Gear

Static (Flat-terrain Only)

lightweight and simple solution but generates a lot of drag in flight

• popular among eVTOL

Retractable (Flat-Terrain Only)

heavier and more complex than static wheels. 

• completely hidden in flight

• used on modern airliners

Skid-Type “Sled” (Multi-terrain)

simpler solution but generates drag in flight

• Pontoons can be added to skids for water landings

Legs and Pads (Multi-Terrain)

specialized in land in very soft terrain like sand and snow

• easily configured to be retractable

1. Vertical Impact Loads

2. Braking and Drag Loads

3. Side Loads

4. Inertial Loads

4 Main Loads Experienced by the Landing Gears

Vertical Impact Loads

load experienced on touchdown

Braking and Drag Loads

load experienced during deceleration

Side Loads

load experienced during turning or crosswind landings

Inertial Loads

load experienced from retraction and extension mechanisms

1. Shock Struts (Oleo Struts)

2. Wheels and Tires

3. Braking System

4. Torque Links and Actuators

5. Attachment Fillings

5 Subcomponents of Landing Gears

Shock Struts (Olea Struts)

absorb and dissipate impact energy

Wheels and Tires

provide rolling contact with the ground

Braking System

slows down the aircraft after landing

Torque Links and Actuators

control retraction/extension

Attachment Fillings

connect gear to fuselage or wings

Engine Nacelles and Pylons

securely attach engines to the fuselage or wing structure

Engine Nacelles and Pylons

transfer thrust and vibration loads safely without affecting structural integrity

Nacelles

are streamlined enclosures that house aircraft engines

• designed to reduce drag and protect engine components