CH 5 Aircraft Systems(INCOMPLETE, STUDY PAPER PACKET and tab 10 in smaller binder) (5)

Aircraft Aerodynamics and systems

Four forces of Flight

Four Forces act upon an aircraft in flight : Lift, Weight, Thrust, Drag

Lift and weight act in directions opposite of eachother, while thrust and drag also act in opposite directions.

Lift

upward force created by air flowing over and under the wing.

Parts of the Wing

• Leading Edge – Front of wing, meets airflow first

• Trailing Edge – Rear of wing, airflow reunites

• Chord – Straight line from leading to trailing edge

• Camber – Curvature of wing surface (upper/lower); helps generate lift

AOA

Angle of attack. As Lift increases with AOA up to a critical angle — beyond that point, airflow separates from the wing's upper surface and the wing stalls, regardless of airspeed or attitude.

Induced Drag vs Parasite Drag

Induced drag — caused by producing lift (wingtip vortices); increases as speed decreases.

Parasite drag — caused by moving through air (form, friction, interference); increases as speed increases.

L/D Speed

(L/Dmax) — the airspeed that gives the best lift-to-drag ratio, where total drag is at its minimum.

• Produces the greatest glide distance per unit of altitude lost

• Used for best-glide speed during an engine-out emergency

• Occurs where the induced drag and parasite drag curves intersect

Axes of an Airplane

• The longitudinal axis runs from nose to tail, movement about this axis is called roll

• The Lateral axis runs from wingtip to wingtip, movement about this axis is called pitch

• The CG is the point which the 3 axis intersect

Primary Flight controls

Aileron — controls roll (bank) about the longitudinal axis; located on the trailing edge of each wing, moving opposite each other (one up, one down).

Elevator — controls pitch about the lateral axis; located on the trailing edge of the horizontal stabilizer.

Rudder — controls yaw about the vertical axis; located on the trailing edge of the vertical stabilizer.

inboard vs outboard aileron

Inboard aileron — near wing root; used at high speed, less wing twist.

Outboard aileron — near wingtip; more roll authority, used at low speed (often locked out at cruise on larger aircraft).

Flight Spoiler vs Ground Spoiler

Flight spoilers — deployed in flight to increase drag and reduce lift symmetrically or asymmetrically (working with ailerons for roll control); used for descent control or speed reduction while airborne.

Ground spoilers — deploy fully and symmetrically only after touchdown (or during a rejected takeoff), dumping lift to plant the aircraft on the wheels and boosting brake/wheel-friction effectiveness.

Rudder

Rotates the plane around the yaw axis. Rudder does not turn the plane. Primary purpose of rudder is to counteract the effects of aileron drag(adverse yaw). Improves the quality of a turn.

Trim tab vs control tab vs Servo Tab vs anti servo tab

Trim tab — small movable surface on a primary control surface, adjusted by the pilot to relieve control pressure and hold a desired attitude hands-off.

Control tab — linked to the cockpit controls (not the main control surface), moves opposite the desired control deflection; aerodynamic force on the tab then moves the main surface. Used to reduce pilot effort on large aircraft.

Servo tab — similar to a control tab; the pilot moves only the tab, and the tab's aerodynamic force deflects the main control surface. Common on large/heavy aircraft where direct control forces would be too high.

Anti-servo tab — moves in the same direction as the control surface (opposite a normal trim tab's effect), increasing the force needed to move it. Used mainly on stabilator-equipped aircraft to prevent overly sensitive pitch control.

high lift devices

leading or trailing edge of wing. Primary purpose of all high life devices is to increase lift at low speeds, High life devices work by increasing camber of wing.

Effects of forward/rearward CG within limits

Forward CG

• Increases stall speed

• More stable

• Take off distance increases

• Drag and fuel consumption increase

Rearward CG

• Stall speed decreases

• Drag and fuel consumption decrease

• longitudinal stability decrease

Best rate of climb

Jet aircraft have best rate of climb at speeds greater than L/Dmax

Relationship between bank angle/airspeed with rate and radius of turn

In level turn coordinated turn with a constant airspeed

• increasing bank angle decreases the radius of turn and increase rate of turn

• Decreasing bank angle increase radius of turn and decrease rate of turn

In a level, coordinated turn with a constant bank angle

• increasing airspeed decreases the rate of turn and increase the radius of turn

• Decreasing airspeed increases the rate of turn and decreases the radius of turn

Mach Speed Flight

Mach 1 is the speed at which the speed of sound is reached. The actual speed in knots varies with altitude and temp. Commercial airline fly between subsonic and transonic.

Critical Mach Number

Critical mach number is important because shock wave caused by local supersonic flow greatly increase drag and can cause control problems. Even when flying slower than the speed of sound, airflow over parts of wing can exceed mach 1

Swept wing aircraft characteristics

• Shock induced airflow seperation near the wing root causes a severe pitch down movement called mach tuck

• Major disadvantage is that the wingtips tend to stall before the wing root

Two Critical Considerations in weight and balance

• The total weight of the aircraft must be no greater than the max gross weight determined by manufacturer

• The center of gravity must be maintained within the allowable range for the weight of aircraft

Increasing an aircraft’s weight

• Longer takeoff runs and higher takeoff speeds

• Reduced rate and angle of climb

• reduced altitude capability

• reduced range

• higher stalling speed

• longer landing roll

Basic Empty weight

Basic empty weight (BEW) — the weight of the aircraft structure, engines, and all permanently installed equipment, plus unusable fuel and full engine oil. It does not include crew, passengers, cargo, or any usable fuel. This is essentially the aircraft "as manufactured," serving as the baseline for all other weight calculations.

Dry operating weight

Dry operating weight (DOW) — BEW plus everything needed to operate the flight that isn't fuel or payload: flight crew and cabin crew, their baggage, catering supplies, potable water, and other standard operating items. Still excludes usable fuel and revenue payload (passengers/cargo).

Zero Fuel weight

Zero fuel weight (ZFW) — DOW plus payload (passengers, baggage, and cargo), but before any usable fuel is loaded. This represents the maximum weight the aircraft can carry before fuel, and it matters structurally because fuel in the wings actually relieves bending stress on the wing spar — so there's a maximum ZFW limit separate from the maximum takeoff weight.

Take off weight

Takeoff weight (TOW) — ZFW plus the usable fuel on board at the point of brake release for takeoff. This is the weight used to calculate takeoff performance: runway length required, climb gradient, and obstacle clearance.

Taxi weight

Taxi weight (ramp weight) — TOW plus the fuel that will be burned during taxi, engine start, and runup before the takeoff roll actually begins. Since that fuel is consumed before liftoff, taxi weight is always slightly higher than takeoff weight.

Where can limits for a specific airplane are found in which manual

Airplane Flight Manual (AFM)

You can never plan to land an aircraft that would exceed max landing weight because

Because it risks structural damage to the landing gear, wing spar, and fuselage — they're only certified for touchdown loads up to that weight.

Flight planning ensures landing weight (TOW minus fuel burn) stays at or under the limit by arrival.

Center of pressure

Center of pressure — the point on the chord line where the total lift force is considered to act. It moves forward as AOA increases and aft as AOA decreases.

Reference Datum

Reference datum — an imaginary vertical plane from which all arm measurements (for weight and balance) are taken.

Arm

Arm — the horizontal distance from the reference datum to an item's CG, measured in inches (positive aft, negative forward).

Moment

Moment — the product of weight × arm; represents that item's turning effect on the aircraft's balance.

Mean Aerodynamic Chord

Mean aerodynamic chord (MAC) — the average chord line of the wing, used as the reference for expressing CG position (often as %MAC).

Ground Deicing/Antiicing

Ground deicing — removing existing frost, ice, or snow from the aircraft surfaces before flight, typically using heated fluid (Type I).

Ground anti-icing — applying a protective fluid film (usually Type II, III, or IV) after deicing to prevent new ice/frost/snow from forming or adhering before takeoff, for a limited holdover time.

Key points:

• Holdover time (HOT) — the estimated time anti-icing fluid prevents ice/frost formation under given weather conditions; if exceeded, the aircraft must be reinspected or retreated before takeoff.

• Deicing and anti-icing are often done together (a "two-step" procedure) in active precipitation.

• Contamination on lifting surfaces disrupts airflow and can drastically reduce lift and increase stall speed — even a thin layer of frost is hazardous.

Clean Aircraft Concept

the principle that an aircraft must have no frost, ice, or snow adhering to critical surfaces (wings, control surfaces, tail, and other specified areas) at the time of takeoff.

Key points:

• It's a regulatory requirement, not just a guideline — takeoff is prohibited if contamination is present on critical surfaces.

• Applies even to small amounts of contamination (e.g., frost) since it can disrupt airflow and significantly degrade lift and stall margins.

• Compliance is achieved through deicing/anti-icing procedures and pre-takeoff contamination checks (visual or tactile inspection) within the fluid's holdover time.