POF Q34 - Principles of High Speed Flight Flashcards
The Mach number:
Select one:
a.is the ratio between the IAS of the aeroplane and the local speed of sound.
b.increases at a given TAS, when the temperature rises.
c.is the ratio between the TAS of the aeroplane and the local speed of sound.
d.is the ratio between the TAS of the aeroplane and the speed of sound at sea level.
c.is the ratio between the TAS of the aeroplane and the local speed of sound.
Which statement with respect to the speed of sound is correct ?
Select one:
a.Increases always if the density of the air decreases.
b.Is independent of altitude.
c.Doubles if the temperature increases from 9° to 36° Centigrade.
d.Varies with the square root of the absolute temperature.
d.Varies with the square root of the absolute temperature.
The speed of sound is affected by the:
Select one:
a.humidity of the air.
b.temperature of the air.
c.density of the air.
d.pressure of the air.
b.temperature of the air.
The flight Mach number is 0.8 and the TAS is 400 kts. The speed of sound is:
Select one:
a.480 kts
b.320 kts
c.600 kts
d.500 kts
d.500 kts
When the Mach number is slowly increased in straight and level flight the first shockwaves will occur:
Select one:
a.on the upper surface at the wing root.
b.somewhere on the horizontal tail.
c.on the lower surface of the wing.
d.somewhere on the fin.
a.on the upper surface at the wing root.
The formula for the Mach Number is:
Select one:
a.M= TAS / a
b.M= a / TAS
c.M = a / IAS
d.M= IAS / a
a.M= TAS / a
A normal shock wave:
Select one:
a.can occur at different points on the aeroplane in transonic flight
b.is a discontinuity plane in an airflow, which is always normal to the surface
c.is a discontinuity plane in an airflow, in which the temperature drops suddenly
d.is a discontinuity plane in an airflow, in which the pressure drops suddenly
a.can occur at different points on the aeroplane in transonic flight
Which statement is correct about a normal shock wave ?
Select one:
a.The airflow changes from supersonic to subsonic
b.The airflow expands when passing the aerofoil
c.The airflow changes direction
d.The airflow changes from subsonic to supersonic
a.The airflow changes from supersonic to subsonic
When the air has passed through a normal shock wave the Mach number is
Select one:
a.lower than before but still greater than 1.
b.less than 1.
c.equal to 1.
d.higher than before.
b.less than 1.
When the air is passing through a shock wave the static temperature will
Select one:
a.increase.
b.decrease and beyond a certain Mach number start increasing again
c.decrease.
d.stay constant
a.increase.
When the air is passing through a shock wave the density will
Select one:
a.increase.
b.decrease and beyond a certain Mach number start increasing again
c.stay constant.
d.decrease.
a.increase.
When air has passed through a shock wave the local speed of sound is:
Select one:
a.increased
b.not affected
c.decreased and beyond a certain Mach number start increasing again
d.decreased
a.increased
The loss of total pressure in a shock wave is due to the fact that
Select one:
a.the friction in the boundary layer is higher.
b.the speed reduction is too high.
c.kinetic energy in the flow is converted into heat energy.
d.the static pressure decrease is comparatively high.
c.kinetic energy in the flow is converted into heat energy.
The critical Mach Number of an aeroplane is the free stream Mach Number, which produces the first evidence of:
Select one:
a.buffet.
b.supersonic flow.
c.local sonic flow.
d.shock wave.
c.local sonic flow.
Air passes a normal shock wave. Which of the following statements is correct?
Select one:
a.The static temperature increases
b.The static pressure decreases
c.The velocity increases
d.The density decreases
a.The static temperature increases
When comparing a rectangular wing and a swept back wing of the same wing area and wing loading, the swept back wing has the advantage of:
Select one:
a.Greater strength
b.Lower stalling speed
c.Increased longitudinal stability
d.Higher critical Mach number
d.Higher critical Mach number
Vortex generators on the upper side of the wing surface will:
Select one:
a.increase the critical Mach Number.
b.increase the magnitude of the shock wave.
c.decrease the span wise flow at high Mach Numbers.
d.delay the shock wave induced air separation.
d.delay the shock wave induced air separation.
Which of the following (1) aerofoils and (2) angles of attack will produce the lowest Mcrit values?
Question 18 Select one:
a.(1) thin and (2) large.
b.(1) thin and (2) small.
c.(1) thick and (2) small.
d.(1) thick and (2) large.
d.(1) thick and (2) large.
To increase the critical Mach number a conventional aerofoil should
Select one:
a.have a large camber.
b.have a large leading edge radius.
c.be used with a high angle of attack.
d.have a low thickness to chord ratio.
d.have a low thickness to chord ratio.
The critical Mach number can be increased by
Select one:
a.a T-tail.
b.positive dihedral of the wings.
c.an increase in wing aspect ratio.
d.sweepback of the wings.
d.sweepback of the wings.
What are the key characteristics of a Supercritical Aerofoil?
PICK ALL THAT APPLY
a.Negative camber on the lower surface
b.Extreme positive camber at the trailing edge
c.Flat Top
d.Low Thickness to chord ratio
a.Negative camber on the lower surface
b.Extreme positive camber at the trailing edge
c.Flat Top
What is the purpose of a supercritical aerofoil?
a.To eliminate stalling characteristics
b.To increase the margin between MCRIT and MDRAG DIVERGENCE
c.To make the onset of wave drag occur earlier
d.To produce a predictable movement of the separation point
b.To increase the margin between MCRIT and MDRAG DIVERGENCE
Which of the following statements about Mach Buffet in modern aircraft is true?
a.Mach buffet is felt above MMO due to the turbulent air ahead of the normal shock wave
b.Mach buffet can occur in modern day aircraft and results in a shock stall past MMO
c.Mach Buffet will not occur in modern day aircraft
d.Mach Buffet can occur after MMO and poses a threat to the structural integrity of the aircraft
d.Mach Buffet can occur after MMO and poses a threat to the structural integrity of the aircraft
MDRAG DIVERGENCE occurs
a.A small margin after MCRIT
b.at M1.0
c.at MCRIT
d.before MCRIT
a.A small margin after MCRIT
Transonic flow defines the speed at which
a.all local mach number’s are less than M1.0
b.some local mach numbers at greater than M1.0 and some are less than M1.0
c.The free stream flow is M1.0
d.All local mach numbers are greater than M1.0
b.some local mach numbers at greater than M1.0 and some are less than M1.0
