ATAC 205 Aviation Technician Aerodynamics

• ATAC 205 is an Aviation Technician Aerodynamics course.

Course Outline

• The course includes a review of flight theory for both fixed and rotary wing aircraft.
• Mechanical flight control systems design and maintenance is covered.
• Hydraulic flight control systems description and operation for fixed and rotary wing are included.
• Fly-by-wire and fly-by-light flight control systems are examined.
• Basic autopilot systems are also reviewed.

Accessing Course Materials

• Course materials for ATAC 205 can be found on eCentennial.
• Videos on YouTube help explain the movement of control cable systems.
• A video demonstrates primary flight controls with the link: https://youtu.be/AiTk5r-4coc. -Another video explains the Elevator Tim Tab System with the link: https://youtu.be/3UDRN9uMNVM.
• The course includes weekly lectures in a virtual classroom format, with a 20-minute break halfway.
• eCentennial course content updates frequently, and virtual class sessions are recorded with added links.

Evaluation Breakdown

• Assignments account for 20% of the final grade, consisting of 4 assignments worth 5% each.
• The midterm exam is worth 30%
• The final test is worth 50%
• The final total is 100%

Online Assignments

• Online assignments constitute 20% of the final grade.
• There will be 4 online assignments for completing.
• Assignments are based on PowerPoint presentations from previous weeks.
• Assignments are available for a limited time during weeks 2, 3, 5, and 6, such as Monday at 9:00 am to Friday at 5:00 pm.
• Assignments are timed, with a 10-minute limit for multiple-choice.
• Only one attempt is allowed for each assignment within the provided time slot.

MidTerm Exam

• The midterm exam is valued at 30% of the final grade.
• Due to Transport Canada requirements, the exam must be completed using the Lockdown Browser on campus.
• The midterm covers material from weeks 1, 2, and 3, taking place at the beginning of week 4 and given 60 minutes to complete.

Final Exam

• The final exam contributes 50% to the final course grade.
• As per Transport Canada, the exam must be completed using the Lockdown Browser on campus during a scheduled session.
• The exam covers all materials from all six weeks as well as taking 100 minutes to complete.
• There will be an equal numbers of questions from each topic area, having more questions from the material discussed after the mid-term.

Lab Projects

• A practical task, designated 205-A, requires determining the correct autorotative rpm from a given autorotative chart.
• Mandatory Project #205-1 involves inspecting a typical cable type and push tube (control rod) flight control system.
• Project #205-2 focuses on rigging a cable type primary flight control system.
• Project #205-3 consists of repairing a control cable.

New Course Format

• Presentations will be posted by Saturday midnight before the Virtual class
• Attendance is recorded during theory and lab classes, at the beginning and after a mid-session break, and manually entered into the eCEntennial Gradebook.
• Every Saturday night by midnight, a new PowerPoint with audio narration will be uploaded.
• The presentations will be reviewed during the two classroom sessions each week.

Weekly Breakdown of Course Content

• Week 1 covers fixed wing theory of flight, primary and secondary flight controls, F/W auxiliary flight control system elements, and control cable repair.
• Week 2 includes Assignment 1, helicopter theory of flight, helicopter and rotor system design, and checking control surface travel.
• Week 3 involves Assignment 2, FW mechanical control components and operation, and RW control system description and operation.
• Week 4 focuses on the midterm exam covering weeks 1-3, FW hydraulic flight control system, and RW hydraulic flight control systems.
• Week 5 covers Assignment 3, hydraulic fly-by-wire control systems, and autopilot system basics.
• Week 6 includes Assignment 4 with autopilot systems.
• Week 7 concludes with the final exam.

Fixed Wing Theory of Flight Terminology

• Elements include lift, drag, thrust and weight; aerofoil shapes; chord; angle of incidence; relative wind; angle of attack; centre of pressure; stall; and span.

Four Forces of Flight

• Lift, weight, thrust, and drag are the four forces acting on an aircraft.
• Balanced forces mean thrust equals drag (constant velocity) and lift equals weight (constant altitude).
• Unbalanced forces bring about ascend, descend, acceleration, and deceleration.
• Effects of an Imbalance of Forces include acceleration, deceleration, ascending, descending and equilibrium.

Wing Dimensions include:

• Camber: Upper & Lower
• Chord Line
• Leading Edge
• Trailing Edge
• Relative wind
• Angle of Attack
• Angle of Incidence: angle between the chord line of the wing and a reference axis along the fuselage

Lift Calculation / Factors

• Factors include angle of airflow, shape of wings (airfoil), air density, flight airspeed, and wing surface area.
• Lift is proportional to the square of speed. Lift = CL 1/2pv² A

Coefficient of Lift

• Calculated into one total lift force. Angles and forces (vectors) of lift and drag produce a resultant force.
• Greater speed brings greater lift as more air is sent under/over the wings.
• Increasing the angle of attack until the stall point raises lift.
• The pilot uses control pressures to apply aerodynamic force to the tail plane or control surface.
• Centre of Pressure: Single force vector representing total lift and direction.

Coefficient of Drag

• More angle of attack leads to more drag
• Drag on airfoil increases as angle of attack increases.
• A wing's shape impacts the drag. Thicker shapes or straight wings add drag
• Induced drag is an unavoidable byproduct of lift, increasing with the angle of attack.
• Newtonian or dynamic drag is inertia of air. Pressure Induced Drag occurs when the AOA is too large, & airflow becomes turbulent, disturbing airflow, increasing drag & lead to stall

Parasite Drag

• Skin-friction drag is caused by the friction between outer surfaces of the aircraft and the air through which it moves.
• Form drag is due to the shape of the object moving through the air. Interference drag is generated by the mixing of airflow streamlines between airframe components.

Airflow

• Boundary Layer: Thin layer of air that adheres the aircraft's surface, tending to flow smoothly.
• Laminar Flow: Promotes lift generation; aided by flush rivets and laminar flow kits.
• Turbulent Flow: Loss of energy that causes lifting and turbulence; smooth laminar flow and lift are lost.
• Stall is is when the turbulence affecting the boundary layer increases to the point that it breaks away from the surface.
• It’s airflow separation, called a burble with air no longer creates lift according to Bernoulli's principle.
• The wing's Critical Angle of Attack causing is where the stall occurs. Stalling Speed: The slowest speed before stall.

Stall Strips

• Stall strips are protrusions fixed to the leading edge of a wing, usually inboard, to ensure the wing root stalls before the wing tips. - They can be installed later on or designed in at the outset.
• Spin occurs when one wing is "more stalled" than the other, causing the aircraft to yaw/roll quickly.
• The aircraft's attitude can change quick rapidly and the nose pitches downward

Wingtip Vortices

• Occurs when air passing over and under wing meet trailing edge, higher pressure flows upwards to lower pressure, causing turbulence.
• The spiral or vortex of air is strongest when flying slowly, and larger on larger aircraft.
• Known as wake turbulence, and are very dangerous for aircraft, especially on final landing.
• Tip tanks, sharklets and drooped wingtips reduce wingtip vortices.

Boundary Layer Control

• Achieved by keeping a wing's surface as smooth as possible.
• It is important to keep clear of debris, dirt, and ice.
• Icing is critical to manage because of the fundamental function of wing is lost.
• Boundary layer may also be controlled by ducting and managing airflow.

Aircraft Stability

• Positive stability is when the aircraft immediately returns to straight and level flight when flying straight and it pitches up
• Static stability is the aircraft's initial response during disruption.
• The time it takes to regain equilibrium is dynamic stability.
• Dynamic stability refers to how an aircraft responds to disturbance over time with oscillations; involving the oscillations that typically occur.

Static Stability

• Positive: Returns to position
• Neutral: Remains in displaced position
• Negative: Continues in direction
• Dynamic Stability- Aircraft's long-term characteristics.

Positive Dynamic Stability:

• Aircraft disturbed in level flight pitches and immediately returns to straight and level flight.
• In this case, there is little or no hunting or oscillations as the aircraft finds its level.

Dynamic Stability - Negative Dynamic Stability

• Oscillations increases
• Aircraft pitches up or down until equilibrium is found increasing same when oscillating nose up.
• This is Porpoising.

How do we get Stability?

• Longitudinal (Pitch) Stability using a horizontal stabilizer.
• With the centre of Gravity (CG) forward of the centre of Lift, the nose of the aircraft will want to pitch nose down.
• Horizontal stabilier provides downward push on tail to keep aircraft in level attitude.
• Lateral (roll) stability using Dihedral Design

Lateral Stability

• When airplane is banked without turning, sideslip or slide downwards
• Air strikes lower wing at greater angle of attack, lifting bringing aircraft axis in vertical direction.
• Keel Effect: c of G below wing acts as pendulum, returning mass of fuselage to center.

Yaw Stability

• Vertical stabilizer (like a weather vane) returns aircraft to straight forward direction.
• Offset counteract "Corkscrew Slipstream

Axes of Control

• Aircraft control has 3 axes: rolling, pitching, and yawing.
• The longitudinal axis runs from nose to tail, centered in the fuselage where movement is called "Rolling".
• The lateral axis runs from wing tip to wing tip, where movement is called "Pitching".
• The vertical axis passes vertically through the center of the aircraft at its CG, where movement is called "Yawing".

Primary Flight Control Input Devices

• Control wheel (yoke) allows the pilot move the Aileron and ROLL the aircraft
• Control Column allows the pilot move the ELEVATOR and PITCH up/down the aircraft.
• Rudder Pedals allows the pilot controls the RUDDER's move to Yaw airplane left or right
• Control Stick move both Ailerons for ROLL & the ELEVATOR for PITCH

Primary Flight Control Surfaces

• Aileron - Hinged controls trailing edge moved from cockpit by control
• They move differentially in opposite directions. When control wheel turned left, the left aileron moves up+right aileron moves down and right is reverse.

Elevator

• A surface hinged to trailing edge of horizontal Varies the tail attitude of the aircraft.
• Elevator is linked cable to the control column, the ELEVATOR goes Up for aircraft pitch up.

Rudder

• A vertical control surface hinged of vertical stabilizer and for Yaw aircraft to moments.
• Movement of the rudder controlled by foot. Push of the right pedal turns the aircraft to the right.

Detailed look at Alternate Types of Primary Flight Controls is as follows:

• High & Low Speed Ailerons: Primary flight controls provides roll.
• Some turbine aircraft use two sets of ailerons, outboard of the flaps.
• Outer ailerons not operated at high because stress to high on wing.

Adverse Yaw

• The Downward aileron gives more drag turning the aircraft in wrong directions.

Counter Acting Adverse Yaw include:

• Frize Aileron with hinge line set back from leading so air makes parasite drag. Differential Aileron with Up/Down have with parasite reduces the drag causing the adverse yaw.
• Roll spoilers cause descending wing to deflect upwards, producing drag decrease life .

Pitch Control Device: Elevator

• Elevators govern movement in lateral axis, attached to horizontal stabilizer/rear spar.
• When aircraft is pushed, the elevators move down using 'air flow generated that raises the tail to lowers the nose..

Stabilator – Pitch Control Device

• Complete all moving horizontal stabilizer can adjust the control column for generate generate lift alter the total
• Stabilators combine a stabilizer and an elevator

Alternative Controls

• Subsonic aircraft use horizontal stabilizer and elevator setups; supersonic aircraft use stabilators.

Elevon-Pitch & Roll Control Device

• Controls a dual function- Elevator- ailerons the to elevator, it moves in it will in a similar Ruddervator – Pitch & Yaw Control Device Ruddervator – Pitch & Yaw Control Device

Auxillary Devices

• Wing Fences: Flat metal plates to prevent entire wing stalling.
• Saw Tooth/Notched Leading Edges: functions similar to the wing fence

Winglets

• at wingtip provides control produces and reduce the drag from the wing. increase by increasing decreasing by of drag

Auxillary Devices-Vortex Generators

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