A supersonic transport cruises at \( M = 2.0 \) with a leading-edge sweep of \( 65 \) degrees. Its leading edge is
Answer: A
At Mach 2 the Mach angle is 30 degrees, so a sweep beyond 60 degrees hides the edge inside the cone. At 65 degrees it is comfortably subsonic, which is why Concorde could use a rounded leading edge on its ogival delta and recover useful leading-edge suction in cruise.
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Assertion (A): Sweeping a wing back raises the Mach number at which drag divergence occurs.
Reason (R): Only the velocity component normal to the leading edge governs the section's behaviour.
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Answer: B
Both are true and the second explains the first. That component is smaller than the free stream by the cosine of the sweep, so the section behaves as though flying more slowly and the local supersonic pocket appears later. Every high-subsonic transport is built on this single result.
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Assertion (A): Swept wings tend to stall at the tip before the root.
Reason (R): Sweep drives boundary-layer fluid outboard along the span.
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Answer: C
Both statements are true and the second is the reason for the first. The thickened, low-energy layer that collects near the tip separates early, costing maximum lift and, worse, aileron authority. Fences, vortilons, washout and leading-edge devices all exist to fight this tendency.
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Assertion (A): A supercritical aerofoil eliminates supersonic flow over its upper surface.
Reason (R): A supercritical section has a relatively flat upper surface.
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Answer: D
The assertion is false and the reason is true. The flat crest does not prevent the supersonic pocket; it keeps the local Mach number modest over a long run so the shock that closes the pocket is weak. The section manages supersonic flow rather than avoiding it.
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Assertion (A): The fuselage of a transonic aircraft is often waisted where the wing joins it.
Reason (R): Transonic wave drag depends on the distribution of total cross-sectional area along the aircraft.
Select the correct answer from the options below.
Answer: A
Both are true and the second explains the first. The wing adds area over its own length, so narrowing the fuselage there keeps the total distribution smooth. The F-102 could not exceed Mach one until this was done, and could comfortably afterwards.
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Assertion (A): A rounded leading edge is acceptable on a wing swept well behind the Mach cone.
Reason (R): The velocity component normal to such an edge is subsonic.
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Answer: B
Both statements are true and the second is the reason for the first. With a subsonic normal component the edge behaves as it would in subsonic flow, developing leading-edge suction without forcing a detached bow shock. Ahead of the cone the edge must be sharp instead.
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Assertion (A): Increasing aspect ratio is as valuable supersonically as it is subsonically.
Reason (R): Induced drag varies inversely with aspect ratio.
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Answer: C
The assertion is false and the reason is true. Induced drag does fall with aspect ratio, but at supersonic speed it is a much smaller share of the total, and a longer span pushes the tips outside the Mach cone and adds wave drag. Supersonic wings are therefore short and highly swept.
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Assertion (A): Slender delta wings continue to produce lift well beyond a conventional stalling angle.
Reason (R): Their sharp swept leading edges shed stable vortices that suck on the upper surface.
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Answer: D
Both are true and the second explains the first. The vortex cores hold strong low pressure over the upper surface, and the increment grows nonlinearly with incidence. The consequence is the very nose-high approach attitude such aircraft adopt rather than a conventional stall.
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Assertion (A): The aerodynamic centre of a wing moves aft as it accelerates through the transonic range.
Reason (R): Supersonic chordwise loading is much more uniform than subsonic loading.
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Answer: A
Both statements are true and the second accounts for the first. Subsonic loading is concentrated forward, placing the centre near the quarter chord, while supersonic loading is spread along the chord and places it near mid-chord. The resulting trim change is large and must be managed, as Concorde did by moving fuel.
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Assertion (A): Variable-sweep wings have largely fallen out of favour in new designs.
Reason (R): The pivot mechanism imposes a substantial weight and complexity penalty.
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Answer: B
Both are true and the second explains the first. The aerodynamic case for varying sweep is real, but the pivot is heavy, expensive and a maintenance burden, and modern high-lift devices and thrust-to-weight ratios have narrowed the benefit enough that fixed wings now usually win.
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