AAE 400/401: Aircraft Design and Classification

• AAE 400/401 covers the subject of aircraft design
• Engineer Abdulbaqi Jinadu of Kwara State University's Faculty of Engineering and Technology, in the Aeronautical/ Astronautical Department is in charge of AAE 400/401

Aircraft Classification

• Aircraft can be classified according to purpose, aerodynamic configuration, number of wings, engine type, landing gear, and takeoff/landing mode

According to Purpose (Civil Passenger)

• Short-range flights are less than 2,000 km
• Medium-range flights are less than 4,000 km
• Long-range flights are less than 9,000 km
• Intercontinental flights are greater than 11,000 km

According to Purpose (Cargo)

• Light cargo planes carry up to 10 tons
• Medium cargo planes carry up to 40 tons
• Heavy cargo planes carry more than 40 tons

According to Purpose (Special)

• Special-purpose planes include ambulances, agricultural, reconnaissance (ice patrol, fish search), fire prevention, aerial photography, and trainers

Aerodynamic Configuration (Classic)

• Good forward view, safest for civil transport, and easy flight control
• Horizontal stabilizer provides negative lift, reducing total lift, operation of horizontal stabilizer is disturbed by the wing

Aerodynamic Configuration (Canard)

• Horizontal stabilizer operates in undisturbed flow, aids stability by providing positive lift, aerodynamic center is backwards making it faster and easier to control
• Induced drag is more than classic, dangerous takeoff/landing due to close ground proximity, and downward view is poor

Aerodynamic Configuration (Tailless)

• High wing stiffness for torsion aids aeroelastic abilities and maneuverability
• Absence of elevators makes control less easy.

Aerodynamic Configuration (Flying Wing)

• Lowest air drag, structural weight is lowest, destabilizing moment on its vertical axis is minor with no fuselage
• Most challenging control, automating flight control is needed

Number of Wings (Bi-Planes)

• They contain 2 wings, one over the other; the bottom wing is pushed back with respect to the top
• Mass is low, and wing loading is reduced
• Drag is high when speeds increases

Number of Wings (Bi-Plane Benefits)

• Reduces drag interference
• Provides center of gravity
• Good downward view is provided

Number of Wings (Monoplanes)

• They have one wing broken into 2 with a fuselage in the middle
• Drag is reduced and mass is increased

Low-Wing Monoplanes

• Screening helps with takeoff and landing
• Lower landing gear support height provides less weight and is easier to store
• Due to the protection the wing supplies, safety is improved during touchdown
• In the event of an accident, the wing helps to create buoyancy, extending the evacuation period
• Engine upkeep is simple

Low-Wing Monoplanes draw backs

• Increases drag interference
• Poor downward vision
• Foreign objects will be sucked into the engine's air intakes due to its closeness to the runway
• Likelihood of the engine hitting the runway during bank landing due to being under the wing

Mid-Wing Monoplanes facts

• Interference drag has been reduced
• A freight compartment space is provided beneath the fuselage's wing load
• Rearward view is poor

High-Wing Monoplanes facts

• Interference drag has been lowered
• A good downward view
• The design of the passenger compartments has been made to be easier
• Loading and unloading the aircraft has been made to be easier, which reduces the chance of wing damage
• Engine upkeep is simple

High-Wing Monoplanes draw backs

• Arrangement for landing gear supports is complicated
• Complexity of engine maintenance due to placement on wings

Cantilever/Semi-Cantilever construction

• Cantilever monoplanes attach to the fuselage on the root section
• Semi-cantilever monoplanes connect in a similar manner yet have a brace for more strength
• Low mass
• Restricted to slow aircraft

Parasol Construction

• Wings are positioned above the fuselage and supported by a brace system

According to Engine Type

• Aircraft can have a propeller or jet.

According to Landing Gear

• Tail wheel landing gear
• Nose wheel landing gear
• Bicycle landing gear
• Multi-wheel landing gear.

According to Take Off and Landing Mode

• VTOL (Vertical Take-off and Landing) includes Helicopters and Quadcopters
• HTOL (Horizontal Take-off and Landing) includes Fixed-wing Aircraft
• Spacecraft

General Structure requirements

• The general requirements for the aircraft include stiffness, strength, manufacturing, operational, reliability, survival, ecological and having a minimum mass requirements

Aerodynamic Requirements

• Structures must have specific coefficients for CD, CL, and k
• Unit surfaces have small roughness
• Original unit shape does not change under load
• It cannot have bumps
• Fasteners cannot interfere with unit edges
• Units used in certain modes should have minimal effect on C♭ and CL when operational
• Units need to be hermetic at high velocities to prevent airflow disturbances and stalls

Hatch and Panel Requirements

• Hatches and access panels used for inspection and maintenance cannot be at pressure or refracted zones
• Units without aerodynamic load must to be removed from airplanes

Stiffness and Strength Requirements (General)

• Aircraft must resist all loads when taking off, landing and staying on the runway based on aviation rules
• Unit placement removes the possibility of dangerous oscillations
• Stress on items cannot go beyond the materials' elastic limit values
• Elastic deformation cannot cause malfunction during operation

Strength Requirements

• Strength requirements: Aircraft's ability to withstand external loads.
  • Employ High-Strength materials
  • Reduce of stress concentration
  • Surface layer hardening on units
  • Apply of special high resource fasteners
  • Apply of a specific coating for structural parts

Stiffness Requirements.

• Stiffness Requirement: Aircraft's ability to resist deformation when subjected to external loads.
  • Usage of materials with high elasticity modulus
  • Choosing constrictive members, with semi-finished items
  • Apply install special stiffness
• Low stiffness can result in large deformations like sags, twists, and buckling which causes
  • Changes in form
  • Aircraft stability deterioration
  • Dangerous vibrations

Manufacturing Requirements

• Easy and quick to produce materials, lowering the amount of labor and expenses

Operational Requirements

• Ease of unit and assembly inspection for repair and replacement
• Possibility of observation and connections for hatchets and doors
• Removable units and assemblies
• Possibility of units and assemblies lifting and movement
• Integration of units and assemblies

Possibility of quick loading and unloading.

• Hatch ladder installations
• Overhead track hoist
• Conveyor installations
• Adjusting of undercarriage leg height. The ability to handle operation under conditions while in open environment is a must for in service life

Reliability and Survival Requirements

• Reliability is the structural ability to maintain operations and service life with constant Inspections and use of redundant application and duplication
  • Determined by structural complexity-
  • Manufacturing Quality
  • Operating Conditions
• Survivability is the ability to maintain with partial part damage
  • Rational construct and bearing schemes
  • Divide parts into units
  • Divide load bearing dispersal

Ecological Requirements

• Goals are to lower the impact an aircraft has on the environment by reducing noise and pollution

Minimum Mass Requirements

• Competent designer will want to incorporate all the components and units to have very little in mass making it the upmost important but difficult
• All the requirements are hard to meet since they tend contradict so a comprise is needed
• Post design is finished it tested and certified for use

Mass equations for aircraft

mo = mk + Mep + mf + Meq + mc + mcr

Mk = aircraft structure Mep = Propulsion system mass Mf = Fuel mass Meq = Equipment mass Mc = Useful load cargo Mcr = Crew Mass Then divide then mass equation with mo and subtract

Aircraft wings:

• Wings are an array of airfoils that cause lift, and they also provide stability and steering.

Aircraft Wing Requirements

• Aerodynamic drag needs to be kept to a minimum
• Greatest Coefficient from high lift products
• Provide stability and command in all phases of flight
• Gradual, smooth changes that are not abrupt
• The average aerodynamic center should be minimized to ensure stability, controllability, and efficiency throughout various flight conditions

Geometrical Parameters

• Wing Chord: b
• Wing Area: Sw
• Sweep Angle: x
• Wing Span: l
• Root Chord: br
• Tip Chord: bk
• Wing aspect Ratio: ƛ
• Wing taper ratio: ŋ
• Mean aerodynamic chord: ba
• Specific wing loading: Po

Exterior Wing shapes

• Wing shape affects assignment of airplane and remains a vital assignment component.
• Wings are designed to be symmetrical

Rectangular wings benefits

• Common in general aviation
• Manufacturing is simple

Elliptical wings benefits

• Most appropriate for aerodynamic characteristics
• High Lift-to-Drag ratio

Tapered wings benefits

• Very common for air characteristics

Swept Wings Benefits

• Airplanes that are subsonic and low supersonic must use wings

Delta Wing Benefits

• High supersonic speeds that are capable in such flight

Airfoil

• streamline over its total area and are divided into 3 Classes

Airfoil Class Thickness

• 12% is Thick
• 12% - 6% mean
• Less then 6% thin

Aerofoil facts

• 8..20% is used for subsonic and 3..9% is used for supersonic

Airfoil Types

• Convex: exhibits high aerodynamic performance at moderate subsonic speeds, when air compressibility is negligible
• Convex-Concave: high lift ability used for slower flights
• Laminar Flow: requires a pristine wing surface
• Symmetrical: exhibit minimum drag a high speeds (Used in small airplane)
• Wedge Shaped: Minimum drag very high speeds
• Double wedge: Highly efficient at speeds faster then sound
• Lenticular airfoils have acute edges
• Supercritical

Wing Load Aerodynamics

• Wings interacting produces the air flow from Application of aerodynamic load is created with forces X and Y

Formula

Aerodynamic load = P = Y = mgne f. M = Aircraft mass ne = maneuvering load f = safety margin

Formula 2

• PER UNIT LENGTH MASS LOAD (effective at 0.45 chords) = qM = mMgne f/ S b

STRUCTURAL Load Bearing requirements

Structure load barring transmission comes with

• Quantity
• Arrangement
• Member dispersal Other requirements are SPECIFIC STRENGTH
• MINIMUM MASS
• shape, rigidity, reliability

Load Bareing requirements

• Longitudinal with spars/ false spars, stringers framework
• Longitudinal framework with ribs and bulkheads

Spar

Spar is longitudinal that bares loads from M♭ ,Q, and 𝗠𝗍.

Span Types

• Beam: Can be monolithic/modular.
• Types: Use rib nose, mid rang tail piece with out puts for stringers of structural loads
• Cantilevers can uses normal enforce concentrated forces on engine mounts points, and landing gear struts
• Rib 200 500mm ranging

Struts and Braces

• Truss Types: Has and members that will operate with tension and compression
• Used during light load intensities

False Spar is the weaker of all of caps and takes torque and force not moment are and come as a Monolithic or Modular component

Components that support structural loads

• Skin: is the main support of the wing for shape
• Stringer: is a tensile and compressive support which ranges from 100 400mm
• Panel: the load barring support

Types of supports (Modular Panel)

• Low mass, high aerodynamic surface
• Great Durability

Types of supports (Monolithic Panel)

• Great aero tightness
• low stress

Types of supports (sandwich Panel)

• Light weight
• Great Aerodynamics
• High Thermals

Load carrying structures of wings

They can use an assembly that can be determined by arrangement number and part level Those can be in parts of;

a- spar type wings b- torsion box swings c- Monoblock wings

Spanwing

• More practical with lows loads intensity
• The low loss surability caused by lift destruction can be an issue

Torsion swing

• High surability and are great to torque

Monoblock swings are degenerated and their fails can be

• Degeneration
• Deconstruction Sweptback wings are useful for planes near the speed of light, but are not reliable in aircraft of high sound The wings are designed so air runs along them but if designed for RAM it gets more complex.

Sweepforward wings

• The benefits and the draw backs of using this is an increase in pressure and stability but less value force.
• Benefit is to the aircraft

Components of the airplane

• Large chords
• High Multi-spare design
• Lower Coefficient.

Pivoted wings

• Used for take off which benefits Clmar at low speeds.
• Better fuel consumption, maneuverability
• Can be cause is a lower stifness or increase complexity

Ailerons (Aerodynamic)

Control surfaces on wings that are designed to balance aircraft load force