Airfoils, Wings, and Other Aerodynamic Shapes

What is the primary function of a swept-back wing on a subsonic aircraft?

In the context of airfoil nomenclature, what is the 'chord' of an airfoil?

What does the Prandtl-Glauert rule, as described by Equation (5.28), predict about the pressure coefficient (Cp) for subsonic compressible flow?

For a finite wing with an elliptical lift distribution, the induced angle of attack (alpha_i) is given by which formula?

What is the primary cause of the phenomenon known as airfoil stall at high angles of attack?

For a thin airfoil in supersonic flow at a small angle of attack alpha, what is the approximate formula for the wave drag coefficient, cd,w?

According to the discussion on lift generation, what is the fundamental reason that the flow velocity is higher over the top surface of a conventional airfoil compared to the bottom surface?

What is the 'critical Mach number' (Mcr) for an airfoil?

A wing has a wingspan of 15 meters and a planform area of 30 square meters. What is its aspect ratio?

For a finite wing with a general planform, the total drag coefficient (CD) is the sum of which two components, as shown in Equation (5.58)?

An NACA 23012 airfoil is at an angle of attack of 8 degrees. According to the data provided in the text for Example 5.6, what are the section lift and drag coefficients (cl and cd)?

How does the lift slope 'a' of a finite wing relate to the lift slope 'a0' of its corresponding infinite wing airfoil section?

An airplane is flying at 100 meters per second at an altitude of 3 km. The pressure coefficient at a point on the fuselage is -2.2. Given that standard conditions at 3 km are p_inf = 7.0121 x 10^4 N/m^2 and rho_inf = 0.90926 kg/m^3, what is the absolute pressure at that point?

What is d'Alembert's paradox?

An NACA 4412 airfoil has a low-speed lift coefficient (cl,0) of 0.83 at a 4 degree angle of attack. If this airfoil is in a free-stream flow with a Mach number of 0.7, what is its corrected lift coefficient (cl)?

For supersonic flow at Mach number M, what is the formula for the Mach angle, mu?

What is the primary aerodynamic advantage of using a 'supercritical airfoil' on a transonic aircraft?

The zero-lift angle of attack for a cambered airfoil is typically:

What is the primary reason for the precipitous drop in the drag coefficient (CD) of a sphere at a critical Reynolds number of about 3 x 10^5?

An airplane wing has an aspect ratio of 10 and a span efficiency factor (e) of 0.95. At a lift coefficient (CL) of 0.8, what is its induced drag coefficient (CD,i)?

The aerodynamic force on an airfoil can be resolved into components perpendicular and parallel to the chord line. What are these components called?

What is the primary purpose of deploying flaps on an airplane wing during takeoff and landing?

The first person to introduce the concept of a fixed-wing aircraft in 1799, separating the principles of lift and propulsion, was:

Dimensional analysis of the forces on an airfoil reveals that the lift, drag, and moment coefficients are functions of which two primary dimensionless similarity parameters?

An airfoil in a low-speed wind tunnel has a minimum pressure coefficient (Cp,0) of -0.5. Using the graphical method described in the chapter, this value would be used to plot which curve to find the critical Mach number?

For a finite wing with an elliptical lift distribution and an aspect ratio of 6, what is its induced drag coefficient (CD,i) when the lift coefficient (CL) is 0.5?

What is the defining characteristic of the 'aerodynamic center' of an airfoil?

Who were the first to bring order and logic to airfoil design in the United States with their 1933 report on 78 related airfoil sections and the introduction of the NACA four-digit series?

An airplane has a weight of 20,000 N, a wing area of 20 square meters, and is flying at an altitude where the air density is 1.0 kg/m^3. To achieve a lift coefficient of 0.5, what must its velocity be?

An airplane weighs 40,000 N, has a wing area of 20 square meters, and is flying at an altitude where the air density is 1.25 kg/m^3. To achieve a lift coefficient of 0.8 in level flight, what must its velocity be?

On a finite wing, the downward velocity component induced by the wing-tip vortices in the neighborhood of the wing is called what?

What was the designation of the first manned airplane to officially fly faster than the speed of sound?

How does increasing the aspect ratio of a subsonic wing generally affect its induced drag coefficient (CD,i) and its lift curve slope (a)?

A flat plate in supersonic flight at Mach 3 is at an angle of attack of 5 degrees. The lift coefficient is 0.123. What is its wave drag coefficient?

Who is credited with being the 'grandparent of the modern airfoil' for his pioneering work and patents on double-surface, cambered airfoils in 1884?

For a finite wing, the lift slope (a) can be calculated from the infinite wing lift slope (a0) and the wing's aspect ratio (AR) and span effectiveness factor (e1). What is the correct formula?

An airplane with a weight of 160,000 lb, a wing area of 1650 sq ft, and a maximum lift coefficient of 3.0 is flying at sea level (rho = 0.002377 slug/ft^3). What is its stalling speed?

What is the primary aerodynamic design consideration for supersonic wings that is different from subsonic wings?

The minimum drag coefficient for a Northrop F-5 is given as CD,min = 0.015. At what lift coefficient (CL) does this minimum drag occur, according to the drag polar in Figure 6.2?

What is the purpose of the dimples on a golf ball?

The Bell X-1, the first aircraft to break the sound barrier, used a straight, low-aspect-ratio wing with a very thin airfoil section. What was the primary reason for this design choice?

An infinite wing with a lift slope (a0) of 0.1 per degree is used to construct a finite wing with an aspect ratio of 7 and a span effectiveness factor (e1) of 0.9. What is the lift slope (a) of the finite wing?

The X-15 hypersonic research aircraft had wings with a low aspect ratio of 2.5 and a thin airfoil section of 5 percent thickness. Why were these design features chosen?

What is the relationship between the zero-lift drag coefficient (CD,0) and the induced drag coefficient (CD,i) for an airplane flying at the velocity for maximum lift-to-drag ratio?

What fundamental principle of physics is violated by the 'equal transit time' theory of lift, which claims air particles must meet simultaneously at the trailing edge?

An airplane is in a power-off glide. Its minimum glide angle is 4.2 degrees. What is the maximum lift-to-drag ratio (L/D) of the airplane?

Why does a swept-forward wing pose a greater structural challenge than a swept-back wing?

The pressure coefficient over the surface of an airfoil is given by Cp = 1 - (V/V_inf)^2 for incompressible flow. If the local velocity (V) at a point is 1.2 times the free-stream velocity (V_inf), what is the pressure coefficient at that point?

What is the defining feature of a 'delta wing' airplane?

For a propeller-driven airplane, maximum range is achieved when which aerodynamic ratio is at its maximum?