T Final Mock Board Exam: Aircraft Structures and Design

1. ___________ can be considered as one of the most powerful aerodynamic considerations.

A. Wingspan

B. Number of spars

C. Number of ribs

D. Wetted area

D. Wetted area

2. A Piper PA-34 Seneca aircraft is flying at a particular altitude, where the ratio of the actual airspeed to the equivalent airspeed is 1.4. What is the density ratio?

A. 0.12

B. 1.89

C. 0.51

D. 0.189

C. 0.51

3. Determine the value of stress produced if the body is subjected to a force of 100 N and a cross-sectional area of 10 sqm.

A. 15 MPa

B. 10 Pa

C. 20 GPa

D. 27 Pa

B. 10 Pa

4. A general aviation aircraft is flying with crew load of 115 lb, payload of 220 lb and fuel weight of 100 lb. Find out the design take-off gross weight of the aircraft, given 95 lb empty weight.

A. 435 lb

B. 241 lb

C. 530 lb

D. 500 lb

C. 530 lb

5. An airplane has a stalling speed of 120 kt in a steady level flight. When the airplane is flying a level turn with a load factor of 2.5, the stalling speed is:

A. 122 kt

B. 190 kt

C. 150 kt

D. 141 kt

B. 190 kt

6. After plotting the bending moment diagram for an aircraft cabin floor beam, a portion of the diagram shows a large "positive" bending moment. What physical deformation does this positive moment dictate within the cross-section?

A. Tension in both upper and lower fibers.

B. Shear flow along the neutral axis.

C. Tension in the upper fibers and compression in the lower fibers.

D. Compression (shortening) in the upper fibers and tension (stretching) in the lower fibers.

D. Compression (shortening) in the upper fibers and tension (stretching) in the lower fibers.

7. In early aviation, aircraft wings were constructed with spars, ribs, and fabric covering. Why did these structures specifically require a diagonal triangular drag/torsion truss inside the wing?

A. Because the fabric covering prevented the aerodynamic center from shifting.

B. To allow the wing to warp freely for roll control without damaging the spars.

C. Because fabric coverings cannot provide reliable torsional resistance; a single- spar fabric surface requires a truss to resist torsion.

D. To provide a rigid mounting point for the landing gear oleo struts.

C. Because fabric coverings cannot provide reliable torsional resistance; a single- spar fabric surface requires a truss to resist torsion.

8. What is the wetted area of a typical tapered wing planform of 500 sq. ft. with an aspect ratio of 9? Assume constant wing airfoil thickness of 12 inches.

A. 1001.5 sq. ft.

B. 1023.4 sq. ft.

C. 1407.1 sq. ft.

D. 1429.0 sq. ft.

A. 1001.5 sq. ft.

9. A civilian aircraft has a maximum lift coefficient of 3. If the wing loading is 120 square meters, find the approach speed of the aircraft. Consider sea- level conditions.

A. 10.50 kph

B. 10.50 m/s

C. 12 kph

D. 120 m/s

B. 10.50 m/s

10. When analyzing the cross-section of a symmetrical I-beam used as a floor joist in an aircraft, an engineer knows the centroid lies exactly on the vertical centerline. Why is this true based on the general principle of moments?

A. The polar moment of inertia cancels out the rectangular moments.

B. The radius of gyration is zero along the plane of symmetry.

C. If a figure is symmetrical with respect to a line, the moments of the parts of the figure on opposite sides are numerically equal but of opposite sign.

D. Symmetrical figures do not experience bending moments, forcing the centroid to the center.

C. If a figure is symmetrical with respect to a line, the moments of the parts of the figure on opposite sides are numerically equal but of opposite sign.

11. When calculating primary stresses in a classical aircraft truss structure, an engineer relies on several foundational assumptions. Which of the following outcomes is a direct result of these assumptions being perfectly met?

A. The structural members will experience combined bending and torsion.

B. All primary stresses are purely axial (tension/compression) without bending or torsion.

C. The structure will develop significant secondary stresses at the joints.

D. The system will act as a mechanism rather than a rigid truss.

B. All primary stresses are purely axial (tension/compression) without bending or torsion.

12. Low wing loading will provide ___________.

A. more space of fuel storage in cabin

B. more space for fuel storage in wing

C. less fuel storage

D. less lift

B. more space for fuel storage in wing

13. You are an aeronautical engineer at an aircraft design company, working under the design engineering department. In a joint meeting between your company and the customers, one of the customer representatives specifically requires and asks you for ways to reduce the empty weight of your proposed aircraft. Among the choices below, what is the best possible way to satisfy the customers' requirement?

A. Opt for an airfoil with a large leading-edge radius.

B. Increase the wing loading.

C. Decrease the wing loading.

D. Increase the wing loading, but keep the wing area fixed.

B. Increase the wing loading.

14. During testing, an aircraft component acting as a simply supported beam is subjected only to a pure concentrated couple applied at mid-span. How does this pure couple affect the vertical shear diagram and the bending moment diagram?

A. The shear diagram drops to zero at mid-span, creating a maximum peak moment.

B. The vertical shear remains constant across the span, while the moment abruptly transitions (jumps) at the point of the couple.

C. The shear diagram experiences a jump at mid-span, while the moment remains zero.

D. Both the shear and bending moment diagrams remain perfectly linear without any jumps.

B. The vertical shear remains constant across the span, while the moment abruptly transitions (jumps) at the point of the couple.

15. A biplane has positive stagger when

A. the upper wing is closer to the nose than the lower wing.

B. the upper wing has the greater angle than the lower wing.

C. the lower wing is closer to the nose than the upper wing.

D. the lower wing has the greater angle than the upper wing.

A. the upper wing is closer to the nose than the lower wing.

16. In a lightweight biplane design, a structural element is designated strictly as a cable-tie rod. What must be assumed about the internal reaction forces provided by this specific element?

A. The reaction must resist torsional moments about the spanwise axis.

B. The reaction from the cable must be collinear with the cable axis due to negligible bending resistance.

C. The cable acts as a rigid support carrying horizontal and vertical shear forces.

D. The reaction direction is strictly normal to the attachment point.

B. The reaction from the cable must be collinear with the cable axis due to negligible bending resistance.

17. The dive speed in a V-n diagram represents _________.

A. hydraulic actuator speed limit

B. maximum manifold pressure of supercharger

C. maximum dynamic pressure

D. rate of climb

C. maximum dynamic pressure

18. An airplane equipped with floats is catapulted into the air from a Navy Cruiser as illustrated in the figure. The catapulting force 𝑃 gives the airplane a constant horizontal acceleration of 3g. The cross weight of the airplane is 9,000 lb and the catapult track is 35 ft long. Find the catapulting force 𝑃 and the reactions 𝑅_1 and 𝑅_2 from the catapult car. The engine thrust is 900 lb.

A. 𝑃 = 26,100 lb ; 𝑅_1 = 20,800 lb ; 𝑅_2 = 29,800 lb

B. 𝑃 = 52,200 lb ; 𝑅_1 = 41,600 lb ; 𝑅_2 = 59,600 lb

C. 𝑃 = 13,050 lb ; 𝑅_1 = 10,400 lb ; 𝑅_2 = 14,900 lb

D. 𝑃 = 17,400 lb ; 𝑅_1 = 13,900 lb ; 𝑅_2 = 19,900 lb

A. 𝑃 = 26,100 lb ; 𝑅_1 = 20,800 lb ; 𝑅_2 = 29,800 lb

19. An aircraft stress analyst is evaluating a structural fitting unit used to react in-plane aerodynamic loads. If a single pin fitting is selected for the attachment, which of the following best describes its structural limitation?

A. It provides zero rotational resistance and cannot resist couples in any axis.

B. It fixes the direction of the reaction as normal to the roller bed.

C. It establishes a line of action for in-plane forces but cannot resist moments about the z-axis through the pin center.

D. It forces loads to pass through the center but is capable of resisting torsional moments about the x-axis.

C. It establishes a line of action for in-plane forces but cannot resist moments about the z-axis through the pin center.

20. A structural engineer initially uses rigid body assumptions to calculate loads on a modern high-speed aircraft with a large wing span. Why must a dynamic analysis subsequently be performed to verify these loads?

A. Rigid body assumptions overestimate the aerodynamic damping of the aircraft.

B. Dynamic effects tend to considerably increase wing forces on some portions of the wing and decrease it on others due to structural vibration.

C. Rigid body analysis cannot determine the center of gravity of an aircraft.

D. Dynamic loading prevents the wing from twisting, simplifying the structural requirements.

B. Dynamic effects tend to considerably increase wing forces on some portions of the wing and decrease it on others due to structural vibration.

21. As a rule of thumb, how much is the least area of the rudder that should be out of the wake generated by the horizontal stabilizer?

A. 50%

B. 15%

C. 66%

D. 33%

D. 33%

22. The beam shown in the figure is subjected to a bending moment of 1500 Nm in a vertical plane. Calculate the maximum direct stress due to bending, stating the point at which it acts.

A. 96 N/mm^2 (compressive)

B. 96 N/mm^2 (tensile)

C. 48 N/mm^2 (compressive)

D. 48 N/mm^2 (tensile)

A. 96 N/mm^2 (compressive)

23. An airliner with take-off gross weight of 2100kg is cruising with fuel weight fraction of 0.280. Then, what will be the weight of fuel?

A. 28 lb

B. 588 lb

C. 90 kg

D. 588 kg

D. 588 kg

24. What do you mean by "scale factor" in terms of a rubber engine?

A. thrust required to thrust available

B. lift to drag ratio

C. thrust coefficient to drag coefficient

D. ratio of thrust required by rubber engine to the actual thrust from selected existing engine

D. ratio of thrust required by rubber engine to the actual thrust from selected existing engine

25. An aeronautical engineer is sizing the skin thickness for a multi-cell wing torsion box. According to the Bredt-Batho theory for multiple-cell thin- walled closed sections, what is the general rule for determining the total internal resisting torque?

A. It equals the sum of the polar moments of inertia of the individual webs.

B. It is equal to the integral of the normal stress over the largest cell's area.

C. It equals the sum of twice each cell's enclosed area times the outer-wall shear flow of that cell.

D. It is calculated by assuming the section acts as an open, thin-plate profile.

C. It equals the sum of twice each cell's enclosed area times the outer-wall shear flow of that cell.

26. During the stress analysis of an unsymmetrical Z-section stringer subjected to bending, it is crucial to determine the principal axes. Which of the following defines a defining property of the principal axes of an area?

A. They are axes where the polar moment of inertia is strictly zero.

B. They are axes about which the moment of inertia is equal to the radius of gyration.

C. They are axes about which the moment of inertia is either a strict maximum or minimum, and the product of inertia is zero.

D. They are axes that are strictly parallel to the applied bending load.

C. They are axes about which the moment of inertia is either a strict maximum or minimum, and the product of inertia is zero.

27. When analyzing a general space (non-coplanar) force system for an aircraft fitting, what is the maximum number of equations that can be utilized specifically for force translation to maintain static equilibrium?

A. Exactly six force equations

B. A maximum of two force equations

C. A maximum of three force equations

D. Exactly one force equation

C. A maximum of three force equations

28. Which is not a best way to improve the stall characteristics of airfoils?

A. Changing the angle of attack of the wing tip airfoils or a different wing tip airfoil.

B. Stall characteristics for thinner airfoils can be improved with various leading-edge devices such as slots, slats, leading-edge flaps, and Krueger flaps.

C. Active methods such as suction or blowing.

D. Increase the leading edge radius.

D. Increase the leading edge radius.

29. According to Prandtl's membrane analogy for the torsion of non-circular cross-sections, how does the shear stress distribute in a solid rectangular bar subjected to twisting?

A. The shear stress is constant at any given radius from the geometric center.

B. The shear stress is maximum at the four corners and zero at the midpoints of the sides.

C. The shear stress is maximum at the ends of the short axis (midpoint of the long sides) and zero at the corners and center.

D. The shear stress forms concentric circular paths of equal magnitude throughout the rectangle.

C. The shear stress is maximum at the ends of the short axis (midpoint of the long sides) and zero at the corners and center.

30. The largest load that is expected to be experienced by aircraft is called __________

A. normal strain

B. normal stress

C. limit load

D. shear stress

C. limit load

31. To simplify complex inertia calculations, engineers often use the concept of "radius of gyration". Conceptually, what does this radius represent for a given structural area?

A. The distance from the centroid to the extreme outer fiber of the cross-section.

B. The distance from the inertia axis to a point where the entire mass or area could be concentrated while retaining the same moment of inertia.

C. The exact center of gravity of an asymmetrical structural member.

D. The distance between the aerodynamic center and the flexural axis.

B. The distance from the inertia axis to a point where the entire mass or area could be concentrated while retaining the same moment of inertia.

32. In aircraft design, the structure must be sized to withstand dynamic inertia forces caused by both pilot maneuvers and atmospheric disturbances. How do the dynamic effects of air gusts typically compare to those of pilot maneuvers?

A. Pilot maneuvers apply loads much more rapidly, creating severe high-frequency flutter.

B. Air gusts apply load far more rapidly, and thus dynamic overstress is more pronounced compared to relatively slow maneuvers.

C. Both maneuvers and gusts apply loads at the same rate, resulting in identical dynamic overstress.

D. Gusts are ignored in dynamic loading because they cancel out over the wingspan.

B. Air gusts apply load far more rapidly, and thus dynamic overstress is more pronounced compared to relatively slow maneuvers.

33. Find the design takeoff weight of the transport cargo aircraft with the following specifications: Pilot = 170 lb Co-Pilot = 165 lb Flight Engineer = 165 lb Maximum Gross Payload = 11,000 lb Empty Weight Fraction = 0.44 Total Mission Weight Fraction = 0.55

A. 2,000,000 lb

B. 1,100,000 lb

C. 1,500,000 lb

D. 1,150,000 lb

D. 1,150,000 lb

34. To calculate the sudden load factor increment during turbulent flight, engineers often use the "sharp edge gust" theory. What is the fundamental physical assumption of a sharp-edged gust striking an aircraft normal to its flight path?

A. It causes a sudden decrease in air density leading to loss of lift.

B. It causes an instantaneous change in the aircraft's forward velocity.

C. It causes a sudden change in angle of attack with no sudden speed change.

D. It causes the aerodynamic center to instantaneously shift to the trailing edge.

C. It causes a sudden change in angle of attack with no sudden speed change.

35. An aircraft is approaching for landing and the pilot deploys the trailing- edge flaps. From a structural loading standpoint, why is this a critical special flight design condition?

A. It causes the center of gravity to shift forward, increasing nose gear loads.

B. It increases the stalling speed of the wing, reducing the margin of safety.

C. Lowering flaps shifts the center of pressure aft, which is critical for the rear shear wall and torsion box.

D. Flap deployment eliminates all aerodynamic drag, forcing the brakes to absorb the entire landing energy.

C. Lowering flaps shifts the center of pressure aft, which is critical for the rear shear wall and torsion box.

36. Consider a NACA 2412 airfoil. It is operating with flow velocity of 100 m/s with chord of 1 m. What should be the maximum thickness of this airfoil?

A. 0.12 m

B. 0.21 m

C. 0.90 m

D. 2.10 m

A. 0.12 m

37. An aircraft is cruising at 250 m/s, and then all of a sudden, it experiences an upward gust with a velocity of 10 m/s. Determine the change in angle of attack due to this upward gust.

A. 2.3°

B. 6.0°

C. 5.6°

D. 9.0°

A. 2.3°

38. The airplane in the figure weighs 14,000 lb. It is flying horizontally at a velocity of 500 mph when the pilot pulls it upward into a curved path with a radius of curvature of 2,500 ft. Assume the engine thrust and airplane drag are equal and collinear with each other. Find the airplane load factor.

A. 8.3

B. 6.9

C. 7.7

D. 3.4

C. 7.7

39. Which best describes the stalling characteristics of fat airfoils?

A. Flow separates near the nose at a very small angle of attack, but reattaches itself so that little effect is felt.

B. Has a thickness to chord ratio less than 0.06

C. The flow separates from the nose at a small angle and reattaches almost immediately.

D. Stall from the trailing edge.

D. Stall from the trailing edge.

40. A short and fat fuselage will have ___________.

A. higher wetted area

B. higher tail arm

C. higher fineness ratio

D. lower tail arm

D. lower tail arm

41. An aircraft's main landing gear utilizes a telescoping oleo strut. Because a single cantilever strut would face severe multidirectional bending and torsion during landing, what specific structural fitting is used to mitigate torsion between the cylinders?

A. A single pin fitting

B. A double-cantilever "nutcracker" torque link

C. A lubricated slot

D. A ball and socket fitting

B. A double-cantilever "nutcracker" torque link

42. According to FAA, general aviation aircraft requires reserved fuel in terms of _____

A. additional cruise fuel of half hour

B. additional climb fuel

C. no provision is mentioned in FAA

D. additional taxi-way fuel of three hours

A. additional cruise fuel of half hour

43. A new wing spar design features redundant internal members to fail-safe against battle damage. How does this redundancy alter the approach required for structural analysis compared to a statically determinate structure?

A. The structure can still be solved using only the static equilibrium equations if internal pins are assumed.

B. The structure requires the application of elastic theory to solve, demanding knowledge of member sizes and material properties to calculate distortions.

C. The redundant members can simply be ignored because they act as zero-force members under limit loads.

D. The structure becomes a mechanism and requires dynamic analysis to determine internal forces.

B. The structure requires the application of elastic theory to solve, demanding knowledge of member sizes and material properties to calculate distortions.

44. In metal-covered airplane wings, primary structures are frequently subjected to severe torsional moments during flight. What aerodynamic action is a prominent cause of this severe wing torsion?

A. Maintaining a constant angle of attack in steady, unaccelerated level flight.

B. Lowering flaps or deflecting ailerons, which shifts the center of pressure (c.p.) aft.

C. Stalling the aircraft, which brings the aerodynamic center perfectly in line with the flexural axis.

D. The symmetrical drag produced by engine nacelles mounted on the leading edge.

B. Lowering flaps or deflecting ailerons, which shifts the center of pressure (c.p.) aft.

45. A control mechanism in an aircraft uses a double pin (universal joint) fitting. A junior engineer assumes this fitting can handle torsional moments similarly to a rigid support. Is this assumption correct, and why?

A. No, because it fixes the reaction direction normal to the roller bed.

B. Yes, because it can resist moments about the y and z axes.

C. Partially, because while forces must pass through the center and it cannot resist y or z axis moments, it is capable of resisting torsional moments about the x-axis.

D. No, because it acts like a ball and socket with zero rotational resistance.

C. Partially, because while forces must pass through the center and it cannot resist y or z axis moments, it is capable of resisting torsional moments about the x-axis.

46. A prop-driven aircraft has a fuel weight of 650kg. Now, the aircraft is taxiing on runway, after which it has a fuel fraction of 0.975. Determine the fuel used during taxing of aircraft, if the takeoff gross weight is 5000 kg?

A. 125 lb

B. 125 kg

C. 200 lb

D. 250 kg

B. 125 kg

47. An engineer has calculated the moment of inertia of a composite bulkhead about its local centroidal axes. To find the moment of inertia of the entire airplane cross-section about the global airplane centerline, which theorem must be applied?

A. The Principal Axis Theorem

B. The Parallel Axis Theorem

C. The Perpendicular Axis Theorem

D. Bredt-Batho Theorem

B. The Parallel Axis Theorem

48. Which of the following is correct?

A. Lift produced by an airfoil is always equal to weight.

B. Drag by sphere is more than the drag produced by an airfoil for similar conditions

C. Drag by sphere is less than that of produced by an airfoil for similar conditions

D. Drag by sphere is equal to the drag produced by an airfoil for similar conditions.

B. Drag by sphere is more than the drag produced by an airfoil for similar conditions

49. During the analysis of a complex coplanar frame used in a fuselage bulkhead, the analyst discovers the system has 4 unknown reaction components, implying indeterminacy. However, there is an internal pin at the crown of the frame. How does this internal pin affect the analysis?

A. It introduces bending moments that require elastic theory to resolve.

B. It acts as a rigid joint, increasing the degree of indeterminacy.

C. It implies the bending moment at that location is zero, providing a 4th static equation and making the system determinate.

D. It prevents translation but allows rotation, creating an unstable mechanism.

C. It implies the bending moment at that location is zero, providing a 4th static equation and making the system determinate.

50. The following statements below best describe the conceptual design phase except:

A. A concrete goal is established toward which the designers are aiming.

B. The overall shape, size, weight, and performance of the new design are determined.

C. Lofting is carried out.

D. Layout of the airplane configuration is produced.

C. Lofting is carried out.