Stress Analysis of Wings and Fuselage Questions and Answers

Answer: A

Correct answer: 180 MPa

Rearranging the margin definition,

Adding 20 per cent of the allowable instead of the applied, or subtracting, gives the wrong figure - the margin is always taken on the applied stress, which is the denominator of the ratio.

Answer: B

Both are true and the second explains the first. Direct stress from bending and shear flow from torsion act at the same point in the skin, and only combining them through a failure criterion gives a meaningful strength check.

Answer: C

Both statements are true and the second is the reason for the first. Hydrostatic stress changes volume without distorting the material, and experiment confirms that metals can sustain very large hydrostatic pressures without yielding.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the purpose of the convention. Quoting the plain ratio would require every entry in a stress report to be compared mentally with unity; subtracting one puts the break-even at zero, so the sign alone says whether the member passes. Scanning a long table for negative numbers is far quicker and far less error-prone than scanning it for values below one.

Answer: A

Both statements are true and the second is the reason for the first. The effect grows with the number of rows and with any stiffness mismatch, and tapering the sheet thickness towards the joint ends is one way of evening the sharing.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the justification. A simple member in tension carries a load that can be calculated with confidence; a fitting introduces eccentricities, uneven fastener load sharing, local bending and stress concentrations that the analysis represents only approximately. The fitting factor of about 1.15 covers that additional uncertainty, and it multiplies a load that already includes the ultimate factor of 1.5.

Answer: C

Both statements are true and the second is the reason for the first. The distributed reaction balances the applied load close to where it acts, so the real moments are far smaller than a free-ring idealisation predicts.

Answer: D

Both are true and the second gives the statistical meaning behind the first. Where a member's failure would be immediately critical, the more conservative A-basis value at ninety-nine per cent survival is required instead.

Answer: A

Both statements are true and the second is the reason for the first. Inertia relief and greater structural depth both moderate the effect, but neither is enough to move the critical section outboard on a conventional wing.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the mechanism. The wing delivers its entire bending moment, shear and torque into the fuselage at a handful of attachment points, and that concentrated load must be spread into a shell of two or three millimetres without overstressing it locally. Diffusing it needs heavy machined fittings, thick doublers and closely spaced frames - which is why the centre section is among the heaviest parts of the aircraft per unit volume.