A symmetric flight load case is one in which
Answer: C
Symmetric cases such as a pull-up or a vertical gust load both wings alike and are analysed on a half model. Asymmetric cases, including rolling manoeuvres, engine failure and rudder reversals, load the two sides differently and require the whole aircraft to be considered.
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A rolling pull-out is a demanding load case because it combines
Answer: D
Superimposing roll on a high-g pull raises the load on the down-going wing well above the symmetric value, and the aileron loads and wing torsion rise with it. It is one of the cases that most often sizes the outer wing and the aileron attachments.
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Engine failure on a wing-mounted installation produces a structural load case because
Answer: A
The remaining engine's thrust must be balanced by rudder, and that side load is reacted through the fin, its attachment and the rear fuselage in torsion. The case is checked at the critical speed and is frequently what sizes the fin.
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A dynamic landing analysis is used rather than a static one because
Answer: B
The impact is a transient in which the oleo, tyres, gear structure and airframe all interact, so the peak loads depend on their dynamic response rather than on a single static equilibrium. Drop tests of the complete gear are used to validate the model.
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Buffet loads on a wing arise from
Answer: C
Separated flow produces fluctuating pressures that shake the structure, and the resulting vibration contributes both to fatigue and to the definition of the usable flight envelope. The buffet boundary is one of the limits that bounds a transport's cruise altitude and speed.
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Two engines each of \( 120 \) kN thrust are mounted \( 8 \) m from the centreline. With one failed, the yawing moment to be trimmed is
Answer: D
The live engine produces \( 120 \times 8 = 960 \) kN m about the centre of gravity. The rudder must generate an equal and opposite moment, and the side load needed to do so is what sizes the fin and its attachment structure.
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A fin \( 6 \) m from the centre of gravity must trim a yawing moment of \( 960 \) kN m. The side load it must produce is
Answer: A
Dividing the moment by the arm, \( 960/6 = 160 \) kN. That load is reacted through the fin spars into reinforced rear fuselage frames, and the shell carries the resulting torsion forward, which is why the rear fuselage of a twin is so noticeably strengthened.
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Assertion (A): The engine-out case frequently sizes the fin of a twin-engined transport.
Reason (R): The rudder must trim a yawing moment equal to the live engine's thrust times its lateral arm.
Select the correct answer from the options below.
Answer: B
Both are true and the second explains the first. For engines set well outboard the moment runs to hundreds of kilonewton metres, and the side load needed to balance it exceeds anything the fin meets in ordinary flight. It is checked at the critical speed with the aircraft near the ground.
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Assertion (A): A rolling pull-out loads the down-going wing more heavily than a symmetric pull-up would.
Reason (R): The rolling motion adds an asymmetric increment on top of the symmetric load factor.
Select the correct answer from the options below.
Answer: C
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the mechanism. A rolling pull-out superimposes the rolling manoeuvre’s asymmetric load on the symmetric pull-up load, and on the down-going wing the two add. The outer wing and the aileron attachments are usually what this case sizes.
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Consider the following statements about asymmetric load cases:
1. A rolling pull-out combines symmetric and asymmetric loading.
2. Engine failure produces fin and rear fuselage loads.
3. Asymmetric cases can be analysed on a half model.
Which of the statements given above is or are correct?
Answer: D
The first two are correct. The third is false and is the defining difficulty of these cases: because the two sides are loaded differently, the whole aircraft must be modelled, which is considerably more work than the symmetric cases allow.
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