Aerodynamics Flashcards
What is Adverse Yaw (Aileron Drag)
occurs when ailerons are used, for example during a turn, the downward aileron creates more lift as a result causes more drag, which slows down the wing. From the pilot’s perspective, the yaw is opposite the direction of the bank
What are the types of drag are there?
1) Induced drag - B/c lift is always perpendicular to relative wind.When the aircraft creates downwash from the wing tip vortices, your lift vector points more back, thus causing induced drag. Induced drag is an inevitable consequence of lift
2) Form - aircraft’s shape (engine cowlings, antennas; air has to seperate and flow around it)
3) Intereference - collision of airstreams (wing and fuselage air merging and colliding)
4) Skin - rough/ragged surface (air moves faster in certain areas)
What are the (4) left turning tendencies?
1) P-factor - propeller is a spinning wing, in a climb, descending blade will create more THRUST, than the ascending blade, resulting in a yaw towards the left. (in a Straight & level flight, descending and ascending blades, creates the same amount of thrust)
2) Spiraling slipstream - Air pushed backwards from the propeller, as it gets pushed back, it strikes the rudder, causing the aircraft to yaw LEFT (why we step on the right rudder)
3) Torque - Propeller turns clockwise, Newton’s Third Law states for every action there is an equal and opposite reaction. Therefore, with a clockwise rotating propeller, there is an opposite force wanting to yaw the roll the airplane LEFT. (why we step on the right rudder)
4) Gyroscopic Precession - the result of a DEFLECTIVE FORCE being applied to a rotating body, like a propeller. Resultant action occurs 90 degrees later into the rotation of the turn.
What are trim tabs?
supporting surfaces that helps alleviate pilot controls. (fixed trim tabs, bent tail, is preset on the ground). (hinged trim tabs are controlled in flight via the trim wheel)
Due to gyroscopic precession, pitching up in a propeller-driven airplane will also cause:
A yaw to the right.
Pitching upwards is equivalent to pushing forwards on the bottom of the propeller disc. The force acts 90° ahead in the direction of rotation, so it pushes forward on the left side of the propeller disc, yawing the airplane to the right.
What is a tailplane stall, how it can occur, and how to recover?
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Tail plane stall is a hazard of structural icing, a tailplane stall describes how sharp-edge surfaces are more susceptible to collecting ice than large blunt surfaces. For this reason, the tailplane may accumulate ice before the wings, and may accumulate ice faster.
- How it occurs: occurs when the critical angle of attack is exceeded. Since the horizontal stabilizer’s job is to stabilize and counter the natural nose down tendency by the center of lift of the main wing, the airplane will react by pitching down, sometimes uncontrollably, when the tailplane is stalled. Application of flaps can aggravate or initiate the stall. Pilots are to use caution when applying flaps during approach if there is possibility of icing on the tailplane.
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Recovering: retract flaps & maintain or reduce thrust. Undo what you just did
- Pull yoke back (opposite to action for wing stall recovery) this reduces the angle of attack of the tailplane and moves it away from the critical angle
- Retract flaps
- Maintain or reduce thrust
What are the two conditions are necessary for structural icing in flight?
- the aircraft must be flying through visible water such as rain or cloud droplets
- the temperature at the point where the moisture strikes the aircraft must be 0° C or colder. Aerodynamic cooling can lower temperature of an airfoil to 0° C even though the ambient tempera-ture is a few degrees warmer.
Aircraft Category speeds?
- Category A: Speed 90 knots or less.
- Category B: Between 91 and 120 knots.
- Category C: Between 121 and 140 knots.
- Category D: Between 141 knots and 165 knots.
- Category E: Speed 166 knots or more.
What are Flaps?
Increases lift by increasing the camber of the wing, flaps also offer advantages such as:
1) decrease stalling speed
2) decrease distance for takeoff
3) steeper approach without and increase it airspeed
4) better visibility during approach
Slotted flaps explained
By opening a slot between the wing and the flap, high pressure air from the bottom of the wing flows through the slot into the upper surface. This adds energy to the wing’s boundary layer (area where friction slows down the airflow), delays airflow separation, and produces less drag. The result? Lots of additional lift, without the excessive drag.
What is a differential frise type aileron?
Differential ailerons = the deflection of the upwards aileron on the lowered wing is greater than that of the lowered aileron on the upward wing, this produces an increase in drag on the descending wing, which reduces adverse yaw
Frise = the aileron that is being raised pivots on an offset hinge. This projects the leading edge of the aileron into the airflow and creates drag. It helps equalizethe drag created by the lowered aileron on the opposite wing and reduces adverse yaw
What are the Secondary flight controls?
Trim, Flaps, & slats
What are the Primary Flight controls?
Aileron, Rudder, & Elevator
What are Slots & Slats?
Devices on the leading edge of the wing that improve laminar flow over the wings at low speeds
Does the C172 skyhawk have a stabiliator or a stabilizer?
It has a Stabilizer, which the horizontal stabilizer is fixed, the elevator and trim moves with hinges attached to it.
The seminole has Stabilator, which is a ONE piece horizontal stabilizer pivoting from a central hinge point.
What is a Horn balance?
helps reduce aerodynamic forces on the rudder and ease movements of the pedals
What are the 4 phases of a spin?
1) Entry - where the pilot intentionally/unintentionally stalls the a/c while losing coordination
2) Incipient - 4-6 seconds or 2 turns
3) Developed - airspeed, vertical speed & rate of rotation stabilized. (approx. 500 ft/ 3 sec.turn)
4) Recovery - P.A.R.E (Power Idle, Ailerons Neutral, Rudder opposite spin, Elevator forward)
