11.1B High Speed Flight Flashcards by John Watts

What Mach number is equal to the speed of sound?
A. Mach 1
B. Mach 0.5
C. Mach 2

A. Mach 1

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How does the speed of sound at sea level compare to the speed of sound at 36,000 ft?
A. It is the same at both altitudes
B. It is faster at 36,000 ft
C. It is slower at 36,000 ft

C. It is slower at 36,000 ft

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What is the speed of sound at sea level (0 metres) and 15 °C?
A. 340 m/s or 760 mph
B. 295 m/s or 660 mph
C. 300 m/s or 700 mph

A. 340 m/s or 760 mph

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What is the speed of sound at 36,000 ft (10,973 m) and –56.5 °C?
A. 295 m/s or 660 mph
B. 340 m/s or 760 mph
C. 310 m/s or 700 mph

A. 295 m/s or 660 mph

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What does the Mach number represent?
A. The number of engines on an aircraft
B. The speed of the aircraft in km/h
C. The ratio of an object’s velocity to the speed of sound

C. The ratio of an object’s velocity to the speed of sound

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What happens as an aircraft approaches the speed of sound?
A. The aircraft becomes more fuel-efficient
B. Compressibility effects like shock waves and drag occur
C. The aircraft automatically slows down

B. Compressibility effects like shock waves and drag occur

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What type of wave is sound?
A. Electromagnetic wave
B. Mechanical wave
C. Light wave

B. Mechanical wave

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What kind of unit does the Mach number have?
A. Meters per second
B. Miles per hour
C. It has no units

C. It has no units

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What are the three types of aircraft speed regions?
A. Subsonic, Transonic, Supersonic
B. Low, Medium, High
C. Slow, Fast, Ultra-fast

A. Subsonic, Transonic, Supersonic

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Which speed region has Mach numbers less than 0.8?
A. Supersonic
B. Subsonic
C. Transonic

B. Subsonic

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What is the Mach number range for transonic flight?
A. Mach numbers from 0.8 to 1.2
B. Mach numbers from 1.2 to 5.0
C. Mach numbers less than 0.8

A. Mach numbers from 0.8 to 1.2

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What is the Mach number range for supersonic flight?
A. Mach numbers from 0.8 to 1.2
B. Mach numbers from 1.2 to 5.0
C. Mach numbers greater than 5.0

B. Mach numbers from 1.2 to 5.0

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What forms at the leading edge as flight speed approaches the speed of sound?
A. Shock wave
B. Light wave
C. Nothing as it’s at the speed of sound

A. Shock wave

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What happens to the velocity, pressure, and density in supersonic flight?
A. They change gradually
B. They change suddenly and sharply
C. They remain the same

B. They change suddenly and sharply

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What is another name for a shock wave?
A. Sound wave
B. Compression wave
C. Subsonic wave

B. Compression wave

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At subsonic speeds, how is the behavior of air typically approximated?
A. Incompressible
B. Compressible
C. A mixture of both

A. Incompressible

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Why is the assumption of incompressibility useful in subsonic flight?
A. It helps simplify the mathematical analysis of aerodynamic forces
B. It allows aircraft to fly faster
C. It eliminates drag

A. It helps simplify the mathematical analysis of aerodynamic forces

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In subsonic flight, how are changes in air density due to variations in pressure treated?
A. They are significant and must be considered
B. They are relatively small and can be disregarded
C. They are constant throughout the flight

B. They are relatively small and can be disregarded

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What happens when an aircraft travels at transonic speeds?
A. It experiences only subsonic airflow
B. It experiences a combination of subsonic and supersonic airflow
C. It experiences only supersonic airflow

B. It experiences a combination of subsonic and supersonic airflow

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What forms at the upper surface of the wing when an aircraft reaches Mach 1?
A. A compression wave
B. A normal shock wave
C. A light wave

B. A normal shock wave

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What effect does the shock wave have on the aircraft during transonic flight?
A. It causes the aircraft to accelerate
B. It causes the center of lift to shift rearward and leads to a nose-down pitch tendency
C. It stabilizes the airflow around the wing

B. It causes the center of lift to shift rearward and leads to a nose-down pitch tendency

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What is the typical position and angle of the initial formation of a normal shock wave on an aircraft wing?
A. At the leading edge of the wing, at a 60-degree angle to the airflow
B. At the trailing edge of the wing, at a 90-degree angle to the airflow
C. Midway between the wing’s leading and trailing edges, at a 90-degree angle to the airflow

C. Midway between the wing’s leading and trailing edges, at a 90-degree angle to the airflow

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What is the primary challenge of transonic flight?
A. Airflow separation and shock wave effects
B. Inability to maintain altitude
C. Excessive fuel consumption

A. Airflow separation and shock wave effects

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What happens to the shock wave during supersonic flight?
A. It moves to the rear and attaches to the aircraft’s trailing edge
B. It dissipates completely
C. It stays at the leading edge of the wing

A. It moves to the rear and attaches to the aircraft’s trailing edge

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In supersonic flight, what happens to air pressure and density? A. Air pressure and density change significantly B. Air pressure changes without changes in density C. There is no change in pressure or density

B. Air pressure changes without changes in density

What is a consequence of supersonic flight on aerodynamic forces? A. Increase in coefficient of lift and decrease in coefficient of drag B. Reduction in coefficient of lift and increase in coefficient of drag C. Increase in coefficient of lift and drag

B. Reduction in coefficient of lift and increase in coefficient of drag

How does the coefficient of lift in supersonic flight compare to subsonic flight? A. It is higher than in subsonic flight B. It is the same as in subsonic flight C. It is lower than in subsonic flight

C. It is lower than in subsonic flight

What happens to the coefficient of drag in supersonic flight compared to subsonic flight? A. It is lower than in subsonic flight B. It is the same as in subsonic flight C. It is higher than in subsonic flight but lower than in transonic flight

C. It is higher than in subsonic flight but lower than in transonic flight

During supersonic flight, what is the primary characteristic of the airflow around the aircraft? A. The airflow is completely turbulent B. The entire aircraft is subjected to supersonic airflow C. The airflow moves slower than the speed of sound

B. The entire aircraft is subjected to supersonic airflow

What happens to the speed when an aircraft exceeds Mach 5.0? A. The aircraft enters hypersonic flight B. The aircraft slows down to subsonic speeds C. The aircraft experiences no change in speed

A. The aircraft enters hypersonic flight

What is the critical Mach number (MCrit) of an aircraft? A. The speed at which the entire aircraft reaches supersonic speeds B. The lowest Mach number at which airflow over some point of the aircraft reaches the speed of sound C. The highest Mach number at which airflow over 2/3 of a point on the aircraft reaches the speed of sound

B. The lowest Mach number at which airflow over some point of the aircraft reaches the speed of sound

What happens when an aircraft reaches its critical Mach number? A. The entire aircraft becomes supersonic B. Compressibility effects occur, and shock waves begin to form C. The airflow around the aircraft becomes completely subsonic

B. Compressibility effects occur, and shock waves begin to form

What is the "local Mach number" around an aircraft? A. The average speed of sound around the aircraft B. The Mach number at specific points on the aircraft C. The total Mach number of the aircraft

B. The Mach number at specific points on the aircraft

Can an aircraft fly below the speed of sound and still experience local supersonic flow? A. No, the aircraft must be traveling faster than the speed of sound to experience supersonic flow B. Yes, areas like the upper wing surface can experience supersonic flow while the aircraft stays subsonic C. No, the entire aircraft must be supersonic for any flow to be supersonic

B. Yes, areas like the upper wing surface can experience supersonic flow while the aircraft stays subsonic

At approximately what speed is air considered somewhat compressible? A. Mach 0.2 B. Mach 0.4 and above C. Mach 1.9 and above

B. Mach 0.4 and above

Which of the following is not a compressibility effect experienced near MCrit? A. Rise in drag B. Increase in lift C. Buffeting and control problems

B. Increase in lift

What is formed when pressure waves build up as an aircraft reaches the speed of sound? A. Vapor trail B. Bow shock wave C. Engine flame

B. Bow shock wave

What happens to airflow as it passes through a shock wave? A. It speeds up and cools down B. It slows down and heats up C. It stays the same

B. It slows down and heats up

When do shock waves start to form on the wing? A. At subsonic speeds B. When local airflow reaches Mach 1 C. Only above Mach 2

B. When local airflow reaches Mach 1

What kind of drag increases due to shock waves? A. Rolling drag B. Wave drag C. Engine drag

B. Wave drag

What effect can shock waves have on aircraft control? A. Improved control B. No effect C. Reduced control and stability

C. Reduced control and stability

Where does a shock wave form first during transonic flight? A. At the nose of the aircraft B. On the tail C. Over the upper surface of the wing

C. Over the upper surface of the wing

What happens to the shock waves as the aircraft speed increases further? A. They move forward B. They disappear C. They move rearward toward the trailing edge

C. They move rearward toward the trailing edge

What happens to the boundary layer behind shock waves? A. It becomes thinner and more smooth B. It becomes turbulent and thickens C. It turns into ice

B. It becomes turbulent and thickens

What does a shock wave do to air pressure? A. Decreases it B. Keeps it the same C. Increases it

C. Increases it

What type of shock wave forms at right angles to the airflow? A. Oblique shock wave B. Bow wave C. Normal shock wave

C. Normal shock wave

What shape of leading edge helps reduce wave drag by forming an oblique shock wave? A. Rounded B. Blunt C. Sharp or pointed

C. Sharp or pointed

What happens to airflow speed after it passes through an oblique shock wave? A. It drops to subsonic B. It remains supersonic C. It stops moving

B. It remains supersonic

Compared to a normal shock wave, how strong are the pressure and temperature changes in an oblique shock wave? A. Much stronger B. About the same C. Less dramatic

C. Less dramatic

What is one reason a supersonic aerofoil is designed with a sharp leading edge? A. To form a stronger bow wave B. To reduce drag by creating an oblique shock wave C. To prevent airflow from becoming turbulent

B. To reduce drag by creating an oblique shock wave

What type of wave forms at the leading edge of the airflow over the upper surface of a thin flat plate? A. Shock wave B. Expansion wave C. Turbulent wake

B. Expansion wave

What type of wave forms at the leading edge of the airflow under a thin flat plate? A. Expansion wave B. Oblique shock wave C. Normal shock wave

B. Oblique shock wave

In supersonic flight, how does the position of the center of pressure affect the aircraft’s stability? A. It increases the aircraft’s longitudinal stability B. It decreases the aircraft’s longitudinal stability C. It has no effect on the aircraft’s stability

A. It increases the aircraft’s longitudinal stability

In supersonic flight, where is the center of lift typically located on a profile? A. 25% chord position B. 50% chord position C. 75% chord position

B. 50% chord position

In subsonic flight, where is the center of pressure typically located on a profile? A. 50% chord position B. 25% chord position C. 75% chord position

B. 25% chord position

What is wave drag? A. The drag caused by friction between the aircraft and the air B. The portion of total drag caused by shock waves C. The drag from the aircraft's surface roughness

B. The portion of total drag caused by shock waves

What happens when shock waves form at speeds above the critical Mach number (MCrit)? A. Total drag decreases B. Useful energy is converted into heat energy C. The aircraft experiences no drag

B. Useful energy is converted into heat energy

What are the two ways to reduce wave drag? A. Using vortex generators and applying the area rule B. Increasing altitude and reducing speed C. Using air brakes and reducing engine thrust

A. Using vortex generators and applying the area rule

What do vortex generators do on an aircraft? A. Produce a vortex that reduces boundary layer separation B. Increase airflow speed C. Reduce fuel consumption

A. Produce a vortex that reduces boundary layer separation

How do vortex generators affect the shock wave in supersonic airflow? A. They create a larger normal shock wave B. They produce a smaller normal shock wave C. They eliminate shock waves completely

B. They produce a smaller normal shock wave

What is the disadvantage of using vortex generators? A. They reduce fuel efficiency B. They increase parasite drag slightly C. They cause excessive noise

B. They increase parasite drag slightly

What is the main goal of the Area Rule in aircraft design? A. To increase the aircraft's speed B. To reduce drag at transonic speeds C. To improve the aircraft's maneuverability

B. To reduce drag at transonic speeds

What is the ideal shape for minimizing wave drag in supersonic flow? A. Circular body shape B. Sears–Haack body C. Rectangular body shape

B. Sears–Haack body

How does the area rule apply to aircraft design? A. By maintaining constant cross-sectional area from nose to tail B. By changing the aircraft’s cross-sectional area smoothly from nose to tail C. By making the fuselage wider at the rear

B. By changing the aircraft’s cross-sectional area smoothly from nose to tail

What is another term for aerodynamic heating? A. Heat dissipation B. Friction heating C. Thermal expansion

B. Friction heating

At what flight speeds does aerodynamic heating become significant? A. Subsonic speeds B. Supersonic speeds C. Hypersonic speeds

B. Supersonic speeds

What happens to the temperature of an aircraft as the Mach number increases? A. The temperature decreases B. The temperature increases rapidly C. The temperature stays constant

B. The temperature increases rapidly

Why are some parts of the Concorde and military aircraft made from titanium alloy? A. Titanium is cheaper than aluminium B. Titanium alloys can withstand higher temperatures without losing strength C. Titanium is less dense than aluminium

B. Titanium alloys can withstand higher temperatures without losing strength

What is a major concern with aerodynamic heating at high speeds? A. Increased drag B. Loss of aircraft control C. Loss of material strength at elevated temperatures

C. Loss of material strength at elevated temperatures

What happens to the strength of aluminium alloy when its temperature increases to 250°C (482°F)? A. The strength increases by 80% B. The strength remains the same C. The strength decreases by approximately 80%

C. The strength decreases by approximately 80%

Which part of an aircraft experiences the highest aerodynamic heating at supersonic speeds? A. The tail APU and other electrical components B. The fuselage and cargo area C. The leading edge and nose

C. The leading edge and nose

What is the maximum axial velocity a gas turbine engine compressor can accept? A. Mach 1 B. Mach 0.4 C. Mach 0.9

B. Mach 0.4

What must happen to the airflow entering the engine compressor in a supersonic aircraft? A. It must be increased to supersonic speeds B. It must be slowed to subsonic speeds C. It must remain at supersonic speeds

B. It must be slowed to subsonic speeds

What is the primary goal of intake design in supersonic aircraft? A. To maximize the energy loss B. To slow the air with minimal energy loss C. To increase the airflow to supersonic speeds

B. To slow the air with minimal energy loss

What happens when the airspeed entering the compressor section of a supersonic aircraft is too high? A. The compressor blades stall B. The engine gains more thrust C. The engine operates at maximum efficiency

A. The compressor blades stall

What is a normal shock diffuser inlet used for? A. To increase the airspeed entering the engine B. To slow the air to subsonic velocity at low supersonic speeds C. To increase engine thrust at higher speeds

B. To slow the air to subsonic velocity at low supersonic speeds

What happens to supersonic air when it passes through a converging duct? A. The velocity decreases and pressure increases B. The velocity increases and pressure decreases C. The airflow remains constant

A. The velocity decreases and pressure increases

In a diverging duct, what happens to supersonic air? A. The velocity decreases and pressure increases B. The velocity increases and pressure decreases C. The airflow stays the same

B. The velocity increases and pressure decreases

What does a single oblique shock inlet use to slow the supersonic airflow? A. A series of weak oblique shock waves B. A single oblique shock wave C. A normal shock wave

B. A single oblique shock wave

How does the multiple oblique shock inlet slow the supersonic airflow? A. Using a single strong normal shock wave B. Using a series of weak oblique shock waves C. Using a converging duct

B. Using a series of weak oblique shock waves

What is the primary advantage of using a multiple oblique shock inlet design? A. It leads to higher drag B. It results in the highest-pressure recovery with the least waste of energy C. It reduces the engine's thrust

B. It results in the highest-pressure recovery with the least waste of energy

What happens to the strength of the normal shock wave in a multiple oblique shock inlet? A. It becomes stronger B. It stays the same C. It is reduced in strength

C. It is reduced in strength

What is the main benefit of a variable supersonic inlet design? A. Reduces engine noise B. Maintains efficient airflow at different speeds and angles C. Increases drag for stability

B. Maintains efficient airflow at different speeds and angles

How does wing sweep affect the critical Mach number? A. Increases it B. Decreases it C. Has no effect

A. Increases it

What is a primary advantage of increasing the critical Mach number through wing sweep? A. Allows for thicker, structurally efficient airfoils B. Increases drag at high speeds C. Reduces aircraft stability

A. Allows for thicker, structurally efficient airfoils

What aerodynamic phenomenon does wing sweep help delay in supersonic flight? A. Boundary layer separation B. Shock wave formation C. Laminar flow transition

B. Shock wave formation

What is a potential disadvantage of swept wings at low speeds? A. Increased drag B. Reduced lift C. Wingtip stall

B. Reduced lift

What aerodynamic issue is caused by increased spanwise flow on swept wings? A. Reduced drag B. Wingtip stall C. Increased lift

B. Wingtip stall

What is the typical sweep angle for wings on modern jet aircraft? A. 10° B. 20° C. 30°

C. 30°

Which device is used to help control spanwise flow? A. Flaps B. Spoilers C. Wing fences

C. Wing fences

11.1B High Speed Flight Flashcards

(90 cards)