engineering
beginner
10 sample questions
Aircraft Design MCQ Practice Test
Aerodynamics, wing design, and flight mechanics
Q1. For a high-speed civil transport (HSCT) aircraft, which of the following wing designs would minimize the sonic boom intensity while maintaining aerodynamic efficiency?
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A. A swept wing with a high aspect ratio and a low taper ratio ✓
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B. A delta wing with a low aspect ratio and a high taper ratio
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C. A double-delta wing with a high aspect ratio and a high taper ratio
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D. A cranked arrow wing with a low aspect ratio and a low taper ratio
Explanation: A swept wing design with a high aspect ratio and a low taper ratio would minimize the sonic boom intensity while maintaining aerodynamic efficiency. This is because the swept wing design would reduce the pressure gradient along the wing, resulting in a lower sonic boom intensity. Additionally, the high aspect ratio would provide a higher lift-to-drag ratio, while the low taper ratio would reduce the wing's thickness and thereby minimize the sonic boom intensity.
Q2. A supersonic transport cruises at Mach 2.4 at a small, constant angle of attack. Which statement about its wing aerodynamics is correct?
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A. The wing's lift-curve slope is lower than at subsonic speeds because of compressibility effects ✓
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B. The wing's drag is minimized because the angle of attack is constant
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C. The lift coefficient is maximized by holding angle of attack constant
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D. The pitching moment is zero because the wing is symmetric
Explanation: In supersonic flow, thin-airfoil theory gives a lift-curve slope of about 4/sqrt(M^2 - 1), well below the subsonic ~2-pi per radian — lift-curve slope falls markedly at supersonic Mach numbers.
Q3. For a high-speed civil transport (SST) aircraft designed to cruise at Mach 2.4, what is the primary advantage of using a "double-wedge" shock-free airfoil on its wing?
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A. It reduces the risk of shockwave-induced drag at high angles of attack.
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B. It increases the wing's maximum lift coefficient by 15%.
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C. It minimizes the formation of shockwaves on the wing surface, reducing wave drag. ✓
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D. It enhances the wing's stability by increasing the moment of inertia about the longitudinal axis.
Explanation: The double-wedge shock-free airfoil is designed to eliminate shockwaves on the wing surface at high speeds, resulting in a significant reduction in wave drag. This design allows the SST aircraft to maintain efficiency and stability at high Mach numbers.
Q4. An aircraft designer is tasked with creating a high-speed business jet with a cruise altitude of 45,000 ft. The designer wants to minimize the aircraft\u2019s drag while maintaining a high lift-to-drag ratio. Which of the following wing shapes would be most effective in achieving this goal?
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A. A symmetrical airfoil with a high cambered upper surface and a flat lower surface
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B. A wing with a NACA 64-210 airfoil section and a 35\u00b0 sweep angle
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C. A wing with a RAE 2211 airfoil section and a 45\u00b0 sweep angle
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D. A wing with a supercritical airfoil and a 25\u00b0 sweep angle ✓
Explanation: A supercritical airfoil is designed to delay the onset of flow separation, resulting in a higher lift-to-drag ratio. The 25\u00b0 sweep angle also helps to reduce drag by reducing the wing\u2019s exposure to the oncoming airflow.
Q5. Why must a supersonic transport cruising at Mach 2 fly at a low angle of attack?
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A. To keep the shock waves attached and avoid shock-induced boundary-layer separation ✓
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B. To maximize the lift coefficient
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C. To minimize skin-friction drag alone
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D. Because the engines flame out at high lift
Explanation: At high angle of attack the upper-surface shock strengthens and its adverse pressure jump can separate the boundary layer (shock stall/buffet); low alpha keeps the shock weak and attached.
Q6. Why do supersonic aircraft typically have sharply tapered or pointed leading edges?
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A. To weaken bow shocks and reduce wave drag ✓
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B. To increase maximum lift coefficient
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C. To improve low-speed stall behavior
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D. To reduce structural weight
Explanation: At supersonic speed a blunt leading edge creates a strong detached bow shock with high wave drag; a sharp edge produces a weaker attached oblique shock — why supersonic designs use sharp edges.
Q7. For a given supersonic aircraft, the drag coefficient (Cd) is influenced by the shock wave formation on its surface. Which of the following statements accurately describes the effect of shock wave strength on the drag coefficient?
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A. The drag coefficient increases as the shock wave strength increases. ✓
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B. The drag coefficient decreases as the shock wave strength increases.
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C. The drag coefficient is unaffected by the shock wave strength.
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D. The drag coefficient remains constant as shock wave strength varies within the transonic regime.
Explanation: As the shock wave strength increases, the pressure drag also increases due to the stronger pressure jump across the shock wave. This leads to a higher drag coefficient.
Q8. When are an aircraft's wingtip vortices (and induced wake turbulence) strongest?
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A. Heavy, slow, and clean configuration at a high angle of attack ✓
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B. Light and fast at cruise
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C. Zero-lift dive
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D. Parked with engines off
Explanation: Wingtip vortex strength scales with lift (thus weight) and grows as airspeed drops and angle of attack rises — strongest from a heavy, slow, clean aircraft, the basis of wake-turbulence separation rules.
Q9. For a given supersonic aircraft, the shock wave angle is measured to be 40°. If the Mach number is increased to 1.5, which of the following statements regarding the shock wave angle is correct?
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A. The shock wave angle will increase to 45°
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B. The shock wave angle will decrease to 38° ✓
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C. The shock wave angle will remain the same at 40°
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D. The shock wave angle will increase to 42°
Explanation: For a fixed deflection angle, increasing Mach number makes the oblique shock weaker and more closely aligned with the flow (approaching the Mach angle mu = arcsin(1/M)), so the shock angle decreases as Mach rises.
Q10. What is the main aerodynamic trade-off of a 'double-bubble' fuselage cross-section?
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A. Extra wetted area and interference drag, traded against more cabin volume for a given length ✓
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B. A guaranteed 5% drag reduction
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C. A guaranteed 10% drag increase
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D. No aerodynamic effect at all
Explanation: Joining two lobes adds wetted surface and junction interference drag but yields greater usable cross-section (and can enable aft boundary-layer ingestion, e.g., the MIT D8 concept). No fixed percentage applies.
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