Aerodynamics 1.1

Speed is said to be stable if after it has been disturbed from its trimmed state. it returns naturally to its original speed. the speed divergence continues, resulting in a negative speed stability.

What is Mach number?. is a true airspeed indication, given as a percentage relative to the local speed of sound. is a true airspeed indication, given as a percentage relative to the local speed of light. is a true airspeed indication, given as a percentage relative to the cruising level.

What is the critical Mach number (Mcrit)?. Mcrit is the aircraft’s Mach speed at which the airflow over a wing becomes sonic. Mcrit is the aircraft’s TAS speed at which the airflow over a wing becomes sonic. Mcrit is the aircraft’s Mach speed at which the airflow under a wing becomes sonic.

What characteristics can we experience when flying critical Mach number (Mcrit)?. Initial Mach buffet, increase in drag, nose-down change in attitude (Mach tuck) and possible loss of control. Initial Mach buffet, decrease in drag, nose-up change in attitude (Mach tuck) and possible loss of control. Initial Mach buffet, increase in drag and nose-up change in attitude (Mach tuck).

When flying Mcrit the center of pressure moves _________ on a swept wing. rearward. forward. do not change.

(Regarding Mcrit) The shock waves on the wing’s upper surface occur toward the _________ because of the greater chamber, which creates the greatest airflow velocity to be experienced at this point. wing root. wing tip.

The swept wing tends to experience the shock-wave effect at the _________ part of the wing first, causing a loss of lift inboard, and therefore, the lift force now predominantly comes from the outboard part of the swept wing. thick root. thin root.

What is Mach tuck?. Mach tuck is the nose-down pitching moment an aircraft experiences as it passes its critical Mach number (Mcrit). Mach tuck is the nose-up pitching moment an aircraft experiences as it passes its critical Mach number (Mcrit). Mach tuck is the nose-down pitching arm an aircraft experiences as it passes its critical Mach number (Mcrit).

What is the purpose of a Mach trimmer?. to automatically compensate for Mach tuck (longitudinal instability) above Mcrit. to manually compensate for Mach tuck (longitudinal instability) above Mcrit. to automatically compensate for Mach tuck (longitudinal instability) below Mcrit.

Mach trimmers allow for an aircraft’s normal operating speed range to be. above its Mcrit. below its Mcrit. above its Mmo.

In the event of a Mach trimmer failure, there is usually an imposed reduced _________ value so that a margin is retained below the Mach speed at which the onset of instability occurs. Mmo. Vmo.

The critical Mach number or Mcrit that's the Mach number where the first __________ flow starts to show up somewhere on the airplane, generally on the upper surface of the wing. supersonic. subsonic. transonic.

The chord line is a. straight line from the leading edge to the trailing edge of an aerofoil. line from the leading edge to the trailing edge of equidistance on the upper and lower surfaces of an aerofoil. line from wingtip to wingtip.

The mean chamber line. is a line from the leading edge to the trailing edge of equidistance on the upper and lower surfaces of an aerofoil. is straight line from the leading edge to the trailing edge of an aerofoil. from wingtip to wingtip.

The angle of incidence. is the angle between the aerofoil’s chord line and the aircraft’s longitudinal axis. is the angle between the chord line of an aerofoil and the relative airflow. is the angle between the chord line and the horizontal.

The angle of attack. is the angle between the chord line of an aerofoil and the relative airflow. is the angle between the chord line and the horizontal. is the angle between the aerofoil’s chord line and the aircraft’s longitudinal axis.

The pitch angle. is the angle between the chord line of an aerofoil and the relative airflow. is the angle between the aerofoil’s chord line and the aircraft’s longitudinal axis. is the angle between the chord line and the horizontal.

Washout is a. decrease in the angle of incidence from the wing root to the tip. increase in the angle of attack from the wing root to the tip. forward movement of the airfoil center of pressure.

Washout causes the root of the wing will fly at a ________ angle-of-attack than the wing tip so the root will reach the critical angle-of-attack sooner than the tip, and it will stall first. higher. lower.

Coefficient of lift. it depends on the shape of the wing section and the angle of attack. is angle between the chord and the relative wind. is the lift vs drag ratio.

Center of pressure is. a single point acting on the wing chord line at a right angle to the relative airflow where wing’s lifting force is produced. the point through which the total weight of a body will act. where the total weight of the aircraft lies when in ground.

A center of gravity forward of the center of pressure has a __________ pitching moment. nose-down. nose-up.

Profile drag is greatest at. high speeds. low speeds.

Induced drag is greatest at. low speeds. high speeds.

What speed has the lowest total drag penalty?. Vmd = minimum drag speed. Vlof = lift of speed. Vmp = minimum power. Vsl = stall speed in a specific configuration.

An increase in thrust on an aircraft with engines mounted under the wing will cause a __________ pitch as thrust is increased. nose-up. nose-down.

Wing-tip vortices. are created by spanwise airflow over the upper and lower surfaces of a wing/aerofoil that meet at the wing tips as turbulence and therefore increase induce drag. are caused by the shock waves on the upper surface of the wing as the aircraft approaches Mcrit. are tiny wings and create mini wingtip vortices, which spiral through the boundary layer and free-stream airflow.

Spanwise flow. reduced aileron (wing control surface) efficiency. results in nose-down change in attitude. moves center of pressure rearward.

Vortex generators. accelerates the airflow on the upper section of the wing delaying the boundary layer separation keeping control surfaces effective at low speeds and high speeds. creates spanwise airflow over the upper and lower surfaces of a wing/aerofoil that meet at the wing tips as turbulence and therefore increase induce drag. are caused by the static pressure differential between the accelerated supersonic air flow being decelerated.

Winglets are aerodynamic efficient surfaces located at the wing tips. They are designed to. reduce induced drag. decrease the boundary layer separation. reduce the nose-down pitching moment due thrust changes.

What causes wing tip stalling on a swept wing?. Downwash and spanwise flow. Upwash design. Forward movement of center of pressure.

Which of these statements on shock wave stall is correct?. Shock wave stall is caused by sudden loss of lift due to a rise in load factor. Shock wave stall is a stall due to flow separation caused by a shock wave. Shock wave stall is a stall due to flow separation at high angles of attack.

Which statement with respect to the speed of sound is correct?. Varies with the square root of the absolute temperature. Increases always if the density of the air decreases. Doubles if the temperature increases from 9° to 36° Centigrade.

A shock wave occurs when. the upper section of the wing airflow moves at or faster than the speed of sound. The airflow expands when passing the aerofoil. The airflow changes direction.

To reduce wing shock waves at high speeds. vortex generators are installed on the upper section of the wing. wingtips are installed. speed must be increased.

To reduce stabilizer shock waves. vortex generators are installed on the lower section of the wing. vortex generators are installed on the upper section of the wing. there is no possibility of shock waves on the stabilizer.

To mitigate aileron shock waves,. spoilers are use when flying at high speeds. there is no possibility of shock waves to form on the ailerons. speed must be increase.

The speed of sound (LSS) is affected by one thing and that's. temperature. density. pressure.

Mach number is the. true airspeed (TAS) of an aircraft, given as a percentage relative to the local speed of sound. indicated airspeed (IAS) of an aircraft, given as a percentage relative to the air density. calibrated airspeed (CAS) of an aircraft, given as a percentage relative to the total temperature.

Absolute temperature formula: C° + 273K° = KELVIN (K°). TAS / LSS = MN. F° + 273K° = KELVIN (K°).

Coffin corner is. where stall IAS and the Mcrit values are equal. where the aicraft can still climb 50 fpm. flying at supersonic speeds.

One of the reasons straight wings stall first at the root because of. washout wing. upwash airflow. downwash airflow.

An aircraft will stall. at a constant angle of attack. at the same speed. at a variable angle of attack.

Regarding stall speed. As weight increases, stall speed will. increase. decrease. be the same no matter the weight.

Low speed stall: When the tips stall on a swept wing the center of pressure. moves forward. moves rearward. remains at the same position.

High speed stall: When the root stall on a swept wing the center of pressure. moves rearward. moves forward. remains at the same position.

The load factor is the ratio of the. lift of an aircraft to its weight. drag of an aircraft to its thrust. weight of an aircraft to its drag.

Which is true regarding effective weight/center of gravity position? (assuming CG is forward of the CoP). The most forward CG the greater effective weight. The most rearward CG the greater effective weight. The most rearward CG the less effective weight.

Stalling speed increases as the. square root of the load factor. air density increases. percentage of the TAS.

A deep stall has two distinct characteristics: 1. A nose-up pitching tendency 2. An ineffective tailplane. 1. A nose-down pitching tendency 2. An ineffective tailplane. 1. A nose-up pitching tendency 2. An ineffective elevator.

Stall strips: avoid the situation where the entire upper surface of the wing stalls simultaneously and with little warning. help to reduce wingtip vortices. increases airflow of the boundary layer delaying stall to higher speeds.

YAW is. a rotation movement around the vertical axis. a rotation movement around the longitudinal axis. a rotation movement around its lateral axis.

ROLL is a rotation movement around the. longitudinal axis. vertical axis. lateral axis.

PITCH is a rotation movement around the. lateral axis. longitudinal axis. vertical axis.

Dutch roll is an. oscillatory instability associated with swept-wing jet aircraft. lift instability associated with straight-wing jet aircraft. oscillatory instability associated with straight-wing jet aircraft.

Yaw damper: corrects Dutch roll oscillatory instability and coordinates turns. only coordinates turns. actuates in the ailerons.

The increase in stall speed (IAS) with increasing altitude is due to: compressibility effects. an increase in TAS. exceedance of Mcrit.

Which of the following statements about stall speed is correct?. Decreasing the angle of sweep of the wing will decrease the stall speed. Increasing the angle of sweep of the wing will decrease the stall speed. Use of a T-tail will decrease the stall speed.

Which combination of design features is known to be responsible for deep stall?. Swept back wings and a T-tail. Straight wings and a T-tail. Swept back wings and wing mounted engines.

The stall speed: increases with an increased weight. decreases with an increased weight. does not depend on weight.

The stalling speed in IAS will change according to the following factors: Increase during turn, increased mass and forward c.g. location. Decrease in a forward c.g. location, higher altitude and due to the slip stream from a propeller on an engine located forward of the wing. Increase with increased load factor, icing conditions and an aft c.g. location.

When extending the flaps you manage to fly straight and level flight and a constant IAS, the lift coefficient will eventually: remain the same. decrease. increase.

A symmetrical airfoil, when positioned in the airflow at a small angle of attack, will produce: both lift and drag. lift but no drag. neither lift nor drag.

Shock wave separation results in: decreasing lift. constant lift. decreasing drag.

The most important problem of ice formation on a transport aeroplane during flight is: reduction in CLmax. increase in drag. increase in weight.

As the Mach number increases in straight and level flight, a shock wave on the upper surface of the wing will: move towards the trailing edge. not move. move towards the leading edge.

Which statement with respect to the speed of sound is correct?. Varies with the square root of the absolute temperature. Increases always if the density of the air decreases. Is independent of altitude.

During which type of stall does the angle of attack have the smallest value?. High speed stall (Shock stall). Deep stall. Low speed stall.

Two methods to increase the critical Mach number are: thin aerofoils and sweepback of the wing. thick aerofoils and dihedral of the wing. positive cambering of the aerofoil and sweepback of the wing.

Transonic speed range is from mach. 0.8 to 1.2. 1.2 to 5.0. 0.5 to 1.2.

The speed range from approximately M=1.3 to approximately M=5.0 is called the: supersonic range. subsonic range. hypersonic range.

Mcrit is increased by: sweepback and thin aerofoils. sweepback, area ruling and high aspect ratio. sweepback, dihedral and thin aerofoils.

How you must a high-speed aircraft wing be?. thinner and swept wings. thicker and swept wings. only swept wing.

How can Mcrit can be increased?. with swept wings. with straight wings. more engine power.

What are the advantages of a swept wing?. higher Mach cruise speeds and more stability in turbulence. produces less lift, higher stall speed, tailstrike possibility, increase takeoff and landing distances, MAC TUCK, increases wing structural weight and reduces fuel capacity.

What are the disadvantages of a swept wing?. produces less lift, higher stall speed, tailstrike possibility, increase takeoff and landing distances, MAC TUCK, increases wing structural weight and reduces fuel capacity. higher Mach cruise speeds and more stability in turbulence.

What are the disadvantages of a swept wing?. produces less lift. higher stall speed. tailstrike possibility. increase takeoff and landing distances. MAC TUCK. increases wing structural. reduces fuel capacity. higher Mach cruise speeds. more stability in turbulence.

What are the advantages of a swept wing?. produces less lift. higher stall speed. tailstrike possibility. increase takeoff and landing distances. MAC TUCK. increases wing structural. reduces fuel capacity. higher Mach cruise speeds. more stability in turbulence.

Where does the swept wing stall first at low speeds?. at the wing tips. at the wing root. at the center of pressure.

Where does the swept wing stall first at high speeds?. at the wing tips. at the wing root. at the center of pressure.

A stall at the wing tip causes the center of pressure to move. inboard and forward. outboard and aft. outboard and forward.

A shock wave (high speed stall at the wing root) produces. less aileron effectiveness. pitch-down. the center of gravity to move forward.

A low speed stall at the wing tip produces. less stabilizer effectiveness. pitch-up. the center of gravity to move rearward.

A shock wave (stall at the wing root) causes the center of pressure to move. inboard and forward. outboard and aft. outboard and forward.

What is the center of pressure?. is a single point acting on the wing chord line at a right angle to the relative airflow, through which the wing’s lifting force is produced. are various points acting on the wing chord line parallel to the relative airflow, through which the wing’s lifting force is produced. is a single point acting on the center of gravity range through which the weight of the airplane acts.

Concerning the center of pressure, for a greater angle of attack,. moves forward towards the leading edge. moves aft towards the trailing edge. remains at the same position.

Concerning the center of pressure, for a lower angle of attack,. moves forward towards the leading edge. moves aft towards the trailing edge. remains at the same position.

Which of these statements is true concerning profile drag. Profile drag increases as speed increases. Profile drag decreases as speed increases. Profile drag increases as speed decreases.

Which of these statements is true concerning induced drag. Induced drag increases as speed increases. Induced drag decreases as speed increases. Induced drag increases as speed decreases.

Minimum drag speed (VMD) is the speed at which. induced and profile drag values are equal and is the speed that has the lowest total drag. induced and profile drag values are equal and is the speed that has the highest total drag. induced and profile drag values are not the same and is the speed that has the highest total drag.

Regarding the pitching moment associated with the thrust-drag couple. An increase in thrust on an aircraft with engines mounted under the wing will cause a. nose-up pitch as thrust is increased. nose-down pitch as thrust is increased. no change in pitch as thrust is increased.

Wing-tip vortices are created by spanwise airflow over the. upper and lower surfaces of a wing/aerofoil that meet at the wing tips as turbulence and therefore profile drag. upper and lower surfaces of a wing/aerofoil that meet at the wing tips as turbulence and therefore induce drag. lower surface of a wing/aerofoil and create turbulence and therefore induce drag.

What are the effects of spanwise airflow over a wing?. wing-tip stall (increases disturbed airflow on the wing’s upper surface at the tip). creates wing-tip vortices. reduced aileron efficiency. increased aileron efficiency. moves center of pressure aft.

What does the shock wave temperature effective gradient affects the angle of attack in a air density loss compensation with the relative disturbance?. It requires a low specific gamma angle of attack. The air density does not compensate for temperature loss. I am a pilot of channa so I don´t care what the fuck happens!.

Test data indicate that ice, snow, or frost having a thickness and roughness similar to medium or coarse sandpaper on the leading edge and upper surface of a wing can. reduce lift by as much as 30 percent and increase drag by 40 percent. increase drag and reduce lift by as much as 25 percent. reduce lift by as much as 50 percent and increase drag by as much as 50 percent.