Airframe Mechanic Certification Aircraft Structures 5

Question 1

What is the term for the ratio of the ultimate load that causes structural failure to the design limit load an aircraft is expected to experience in service?

Accepted Answer

Safety factor

Answer

The safety factor (typically 1.5 for FAR Part 25 transport aircraft) is the ratio of ultimate load to limit load, providing a margin for uncertainties.

Question 2

Which inspection method is most appropriate for detecting subsurface fatigue cracks in aluminum wing skins without removing the skin?

Accepted Answer

Eddy current inspection

Answer

Eddy current inspection can detect subsurface cracks in non-ferrous metals like aluminum without requiring surface preparation or skin removal.

Question 3

A doubter (doubler) plate installed over a cracked fuselage skin repair serves primarily to:

Accepted Answer

Restore original strength and stop-drill the crack

Answer

A doubler plate bridges the cracked area, restores load-carrying capacity, and distributes stress away from the crack tip after stop-drilling.

Question 4

What structural phenomenon occurs when thin aircraft skin panels buckle under shear loading but still carry additional load through diagonal tension?

Accepted Answer

Wagner field or diagonal tension

Answer

Wagner field (diagonal tension) describes post-buckling behavior where shear-buckled skin carries additional load through diagonal tensile stress fields.

Question 5

When determining the minimum edge distance for a rivet installed in an aircraft skin repair, what is the generally accepted minimum distance from rivet centerline to the sheet edge?

Accepted Answer

2 times the rivet diameter

Answer

FAA AC 43.13-1B specifies a minimum edge distance of 2 times the rivet diameter to prevent shear-out failure of the sheet material.

Airframe Mechanic Certification Practice Test

Airframe Mechanic Certification Practice Test

Airframe Mechanic Certification Aircraft Structures 5