High Speed: FINAL 4040 Flashcards
An aircraft’s critical mach number is the speed at which airflow somewhere on the aircraft starts to exceed mach one
true
false
true
How does the coefficient of parasitic drag act in the subsonic speed regime?
It is characterized by a gradual increase until reaching a velocity of approximately 50% of the critical mach number, then it decreases.
It is characterized by a gradual increase as velocity increases
It is characterized by a gradual decrease as velocity increases
It is basically a constant
it is basically a constant
The dividing line between the subsonic and transsonic speed regimes is the critical mach number of the aircraft
true
false
true
How does the coefficient of parasitic drag act in the transsonic speed regime?
It rapidly increases shortly after passing the critical mach number and levels again when all of the airflow is supersonic.
It rapidly increases shortly after passing the critical mach number and level approximately at mach one.
It rapidly increases shortly after passing the critical mach number and peaks approximately at mach one. It then decreases to a point where it is well below its peak but well above its level at subsonic speeds.
It rapidly increases shortly after passing the critical mach number and peaks approximately at mach one. It then decreases to a point where it is below its level at subsonic speeds.
It rapidly increases shortly after passing the critical mach number and peaks approximately at mach one. It then decreases to a point where it is well below its peak but well above its level at subsonic speeds.
How does the coefficient of parasitic drag act in the supersonic and hypersonic regimes
The coefficient of drag increases throughout the supersonic regime and then is basically a constant in the hypersonic regime.
The coefficient of drag decreases in the supersonic regime and then once again increases entering the hypersonic regime.
The coefficient of drag is basically a constant throughout the supersonic and hypersonic regimes.
The coefficient of drag is basically a constant in the supersonic regime and then once again starts to increase throughout the hypersonic regime.
The coefficient of drag is basically a constant in the supersonic regime and then once again starts to increase throughout the hypersonic regime.
The airflow behind a normal shockwave is always supersonic
true
false
false
What are the two ways shockwaves create drag.
Boundary Drag
Shockwave drag
Mach Stall
Transsonic drag
shockwave drag
mach stall
Mach stall is characterized by boundary layer separation under certain conditions. Match those conditions with their proper descriptors.
True Airspeed
Angle of attack
high
small
How do you minimize the effects of increased drag on aircraft as it flies at high mach numbers?
Put winglets on its wings
Streamline the shape of its fuselage
Design the aircraft with fanjet engines
Design the aircraft with a high MCR airspeed
Design the aircraft with a high MCR airspeed
What are some of the ways that one can increase MCR?
Increase wing dihedral
Use a wing with low camber
Decrease the wing’s chord
Add an aerodynamic twist to the wings
Increase the wing’s thickness
Use a supercritical wing
Lower a wing’s thickness/chord ratio
Use swept wings
use a wing with low camber
use a supercritical wing
lower a wing’s thickness/chord ratio
use swept winds
Swept wing aircraft have the following disadvantages.
Trailing edge controls are less effective
The have a greater tendency to experience mach stall
For the same wing area and aspect ratio, swept wings have more mass
There is a strong tendency for the wingtips to stall first
They increase the amount of parasitic drag generated by the aircraft
Trailing edge controls are less effective
For the same wing area and aspect ratio, swept wings have more mass
There is a strong tendency for the wingtips to stall first
What problem does a high speed, subsonic aircraft encounter as it climbs higher in altitude?
Due to decreased air density, laminar flow of air on the wings tends to detach
Parasitic drag increases
Stall speeds decrease
They get caught in “coffin corner”
They get caught in “coffin corner”
In supersonic flight, normal shockwaves _________.
Double in size
Disappear
Detach from the wings
Double in number
Disappear
In supersonic flight, shockwaves become oblique.
true
false
true
Above Mach 1.0, there are _______ pair of shockwaves.
1
2
3
4
2
The airflow behind a normal shockwave is ___________. The airflow behind an oblique shockwave is _________.
Subsonic / subsonic
Subsonic / supersonic
Supersonic / Supersonic
Supersonic / Subsonic
Subsonic / supersonic
The primary drag problem with supersonic flight is _______________.
the bow wave ahead of the wing.
the trailing oblique shockwave.
the normal shockwave
induced drag
the bow wave ahead of the wing.
The problem with using a supersonic wing for such things as airliners is that ____________.
They have a very low crosswind limitation.
they cause instability around the longitudinal axis of the aircraft.
they have high stall speeds, thus necessitate long runways.
their large wingspan limits the number of gates at airports.
they have high stall speeds, thus necessitate long runways.
In supersonic flight, the aerodynamic center of the wing ________________.
Doesn’t move
moves to the 75% chord point
moves to the 25% chord point
moves to the 50% chord point
moves to the 50% chord point
In order for swept wings to be effective in supersonic flight, they must be swept back at least to the mach angle.
true
false
true
Mach tuck is the tendency of an aircraft to pitch _________ when transitioning from subsonic to supersonic speed.
up
down
down
When an aircraft goes supersonic, movement of the aerodynamic center increases ___________.
yaw stability
longitudinal stability
lateral stability
both yaw and lateral stability
longitudinal stability
A high bypass (fan jet) engine is the most efficient engine for supersonic flight.
true
false
false
Which of these statements is true concerning jet engines and supersonic flight?
Jet compressors are very efficient when the incoming airflow is supersonic.
Compressors are not efficient with supersonic air, therefore the airflow must be slowed to subsonic speed.
Designing a jet diffuser so that an oblique shockwave forms is a good way to slow the airflow down.
Compressors are not efficient with supersonic air, therefore the airflow must be slowed to subsonic speed.
