Answers - Aircraft Structures


Fill in the Blanks

1. structural member
2. torsion, shear
3. pounds per square inch, psi
4. full cantilever
5. spanwise
6. longerons
7. web, cap
8. firewall, engine
9. regulate engine temperature
10. lateral, longitudinal, and directional
11. flutter
12. left
13. lateral or horizontal
14. Right
15. fowler
16. AOA or angle of attack
17. spoilers
18. zero station
19. stainless steel
20. up and down, back and forth


True/False

1. false ‐ wing spar
2. false ‐ tension
3. true
4. false ‐ stringers
5. false ‐ skin carries load
6. true
7. false ‐ ribs forward of front spar used for shaping and strengthening leading edge
8. true
9. true
10. false ‐ electrical and hydraulic power
11. false ‐ wing sealed with fuel resistant sealing
12. true
13. false ‐ installed and operate dependently
14. false ‐ winglets
15. false ‐ conventional and tailwheel
16. true
17. true
18. false ‐ tilting the rotor
19. false ‐ flap
20. false ‐ opposite direction of rotation

Knowledge Application

1. Rotors are rotating wings as opposed to propellers and rotating airfoils of an engine.

2. The degree of deformation of a material.

3. The part is shortened or compressed on the inside of the bend and stretched on the outside of the bend. This is a combination of compression and tension stress.

4. They must be streamlined to meet aerodynamic requirements to reduce drag or direct airflow.

5. Members such as beams, struts, bars, and longerons covered with fabric.

6. Maintaining the proper amount of strength while keeping the weight within the allowable limits

7. Monocoque fuselages have heavy structural members located at intervals with no other bracing members, requiring the skin to carry the primary loads. Semi‐monocoque type fuselage uses longerons as longitudinal reinforcements that help support the skin.

8. Metal fatigue is caused by cycling from pressurized to unpressurized and back during each flight as well as withstanding the pressure differential in‐flight.

9. Jury struts subdue strut movement and oscillation on struts that are attached to the wings at a great distance from the fuselage. They are vertical support structures that are attached to the wing and strut.

10. They are the principal structural member and they support all distributed loads as well as concentrated weights (i.e. fuselage, landing gear, engines, etc.).

11. They are located entirely forward of the front spar and they are used to shape and strengthen the wing leading edge. They do not span the entire wing chord.

12. They are streamlined and house the engine and its components. They can sometimes be designed to house the landing gear. All nacelles incorporate a firewall to isolate the engine from the rest of the airframe. They have cowlings which cover areas that can be easily accessed when detached.

13. Lateral‐ elevators, longitudinal‐ ailerons, vertical‐rudder.

14. Camber and lift are increased.

15. Slots direct air over the upper surface of the wing during high angles of attack. They lower stall speed and provide control during slow flight. Slots are located on the outer leading edge of the wing forward of the ailerons.

16. Typically linked directly to the control surface so they move automatically when the control surface moves. Balance tabs aide the pilot in overcoming the force needed to move the control surface.

17. Allows for greater clearance between the propeller, which were longer back then, and loose debris when operating on unpaved runway.

18. The two main wheels are forward of the center of gravity while the tail is aft. If the aircraft swerves on landing the tail can swing out pulling the center of gravity aft of the main wheels allowing the tail to freely pivot.

19. As the plane of rotation of the rotor blade tilts the advancing blade has a greater relative windspeed compared to the retreating blade. This causes a greater amount of lift being developed on the advancing blade resulting in the blade flapping up. The opposite occurs on the retreating side causing the blade to flap down.

20. Stands for “no tail rotor” because it has an engine driven adjustable fan located in the tail boom. As the speed of the main rotor changes, the speed of the NOTAR fan changes as well. Air is vented out of two long slots on the right side of the tail to counteract the torque produced by the main rotor.


Multiple Choice

1. a
Aircraft structural members are designed to carry a load or to resist stress. In designing an aircraft, every square inch of wing and fuselage, every rib, spar, and even each metal fitting must be considered in relation to the physical characteristics of the material of which it is made. Every part of the aircraft must be planned to carry the load to be imposed upon it. The determination of such loads is called stress analysis.

2. c
The term “stress” is often used interchangeably with the word “strain.” While related, they are not the same thing. External loads or forces cause stress. Stress is a material’s internal resistance, or counterforce, that opposes deformation. The degree of deformation of a material is strain. When a material is subjected to a load or force, that material is deformed, regardless of how strong the material is or how light the load is.

3. b
Compression is the stress that resists a crushing force. The compressive strength of a material is also measured in psi. Compression is the stress that tends to shorten or squeeze aircraft parts.

4. c
A single member of the structure may be subjected to a combination of stresses. In most cases, the structural members are designed to carry end loads rather than side loads. They are designed to be subjected to tension or compression rather than bending.

5. a
The spars are the principle structural members of a wing. They support all distributed loads, as well as concentrated weights such as the fuselage, landing gear, and engines.

6. c
The skin, which is attached to the wing structure, carries part of the loads imposed during flight. It also transfers the stresses to the wing ribs. The ribs, in turn, transfer the loads to the wing spars.

7. b

8. a
Often wings are of full cantilever design. This means they are built so that no external bracing is needed. They are supported internally by structural members assisted by the skin of the aircraft.

9. c
The monocoque (single shell) fuselage relies largely on the strength of the skin or covering to carry the primary loads.

10. b

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