Instruction
- Total number of questions : 20
- Time allotted : 30:00 Minutes:Seconds.
- Each question carry 1 mark, no negative marks.
- DO NOT refresh the page.
- All the best
Aerodynamics [ Question No: 1 To 4 ] :
In a closed-circuit supersonic wind tunnel, the convergent-divergent (C-D) nozzle and test section are followed by a C-D diffuser to swallow the starting shock. Here, we should have the
Doubling the free-stream velocity over a flat plate in fully laminar flow changes the total friction drag force by a factor of
The minimum possible angle an oblique shock can make with the oncoming flow is
Consider the following statements about applying thin airfoil theory to a flapped section:
1. The flap deflection is treated as a change to the mean camber line.
2. The effect of the flap can be superposed on that of the basic section.
3. The flap moves the aerodynamic centre aft of the quarter chord.
Which of the statements given above is or are correct?
Aerospace Structures [ Question No: 5 To 9 ] :
Which statement about plate buckling is INCORRECT?
A finite element model reports reactions summing to \( 47.9 \) kN against an applied load of \( 48.0 \) kN. This indicates
An open channel and a closed box of the same wall material differ in torsional stiffness typically by a factor of order
The shear centre of a thin-walled angle section lies at
An aircraft of mass \( 50\,000 \) kg touches down at \( 3 \) m/s sink rate. The kinetic energy the gear must absorb is
Aerospace Vehicle Design [ Question No: 10 To 11 ] :
The thrust-to-weight ratio used on a constraint diagram is conventionally evaluated at
A composite fuselage allows a cabin altitude of 6000 feet rather than the usual 8000 feet, raising the cruise pressure differential accordingly.
What is the principal structural consequence?
Aircraft Instrumentation [ Question No: 12 To 14 ] :
A safety department finds that unstable approaches at one airport occur at four times the rate seen elsewhere in its network, from routine recorded data across several thousand flights.
What is the appropriate use of this finding?
Engine vibration monitoring is used principally to detect
The erection system of an attitude indicator works by
Aircraft Propulsion [ Question No: 15 To 17 ] :
Match each parameter in List I with its correction in List II.
List I
A. Rotational speed
B. Mass flow
C. Thrust
D. Fuel flow
List II
1. Divided by the square root of the temperature ratio
2. Multiplied by root temperature and divided by pressure ratio
3. Divided by the pressure ratio
4. Divided by pressure ratio and root temperature ratio
Select the correct match.
Consider the following pairs of arrangement and its rationale:
Twin spool - Front and rear stages run at different speeds
Geared fan - Fan and low pressure turbine each run at their preferred speed
Mixed exhaust - Small gain in fuel consumption and noise
Separate exhaust - Required for low bypass ratio engines
How many of the pairs given above are correctly matched?
Consider the following statements about streamtube behaviour:
1. At static conditions the streamtube is larger than the intake and contracts.
2. At high subsonic cruise it is smaller than the intake and expands.
3. Spillage drag arises when the intake captures more than the engine demands.
Which of the statements given above is or are correct?
Aircraft Stability and Control [ Question No: 18 To 19 ] :
Two fins of \( 5 \ \mathrm{m^2} \) each replace one of \( 9 \ \mathrm{m^2} \). The change in total fin area is
Consider the following pairs of effect and cause:
Nose up pitch with power on underslung engines - Thrust line below the centre of gravity
Mach tuck - Rearward shift of the aerodynamic centre
Nose down moment in the flare - Reduced downwash in ground effect
Mach tuck - Loss of elevator hinge moment
How many of the pairs given above are correctly matched?
Engineering Mathematics [ Question No: 20 To 20 ] :
The mass of a solid of variable density \( \rho(x,y,z) \) is
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Aerodynamics [ Question No: 1 To 4 ] :
In a closed-circuit supersonic wind tunnel, the convergent-divergent (C-D) nozzle and test section are followed by a C-D diffuser to swallow the starting shock. Here, we should have the
Your Answer : (Not Answered)
Correct Answer : B
The diffuser throat must be larger than the nozzle throat, with the shock located downstream of the diffuser throat.
During starting, a normal shock passes through the test section at the test Mach number. The total pressure loss across it means the diffuser throat must pass the same mass flow at a lower stagnation pressure, so it needs a larger area: \(A_{t2}/A_{t1} = p_{01}/p_{02} \gt 1\). A diffuser throat the same size as the nozzle throat would choke and the shock could not be swallowed.
Once swallowed, the shock passes through the diffuser throat and settles in the diverging part just downstream of it, where it is weak and its position is stable. A shock held exactly at the throat is unstable: a small disturbance pushes it upstream and the tunnel unstarts. That rules out the two 'just at the diffuser throat' options.
Doubling the free-stream velocity over a flat plate in fully laminar flow changes the total friction drag force by a factor of
Your Answer : (Not Answered)
Correct Answer : C
The drag goes as \( C_F \times V^2 \), and \( C_F \) varies as \( Re^{-1/2} \), that is as \( V^{-1/2} \). The product therefore scales as \( V^{1.5} \), so doubling the speed multiplies the drag by \( 2^{1.5} = 2.83 \) rather than by four.
The minimum possible angle an oblique shock can make with the oncoming flow is
Your Answer : (Not Answered)
Correct Answer : C
As the deflection tends to zero the shock weakens to a Mach wave, whose angle is the Mach angle. That is the lower limit. The upper limit is ninety degrees, at which the oblique shock has become a normal shock and the deflection has fallen back to zero from the other direction.
Consider the following statements about applying thin airfoil theory to a flapped section:
1. The flap deflection is treated as a change to the mean camber line.
2. The effect of the flap can be superposed on that of the basic section.
3. The flap moves the aerodynamic centre aft of the quarter chord.
Which of the statements given above is or are correct?
Your Answer : (Not Answered)
Correct Answer : B
The first two are correct and follow from the theory's linearity, which is what makes flap analysis so straightforward. The third is false: the aerodynamic centre stays at the quarter chord, though the constant moment about it becomes considerably more nose-down as the flap is deflected.
Aerospace Structures [ Question No: 5 To 9 ] :
Which statement about plate buckling is INCORRECT?
Your Answer : (Not Answered)
Correct Answer : A
A plate has substantial post-buckling reserve, redistributing load towards its supported edges through membrane action. That reserve is what effective width design is built on, and it is the key difference between a plate and a column.
A finite element model reports reactions summing to \( 47.9 \) kN against an applied load of \( 48.0 \) kN. This indicates
Your Answer : (Not Answered)
Correct Answer : A
Agreement to about two parts in a thousand is consistent with numerical rounding and reporting precision. A discrepancy of a few per cent or more would instead point to a misapplied load, an unintended restraint or a units error.
An open channel and a closed box of the same wall material differ in torsional stiffness typically by a factor of order
Your Answer : (Not Answered)
Correct Answer : A
The open section relies on the St Venant mechanism, with its cube on the wall thickness, while the closed one develops a circulating flow round the enclosed area. Three orders of magnitude is common, which is why a slit cut along a torsion tube is so catastrophic.
The shear centre of a thin-walled angle section lies at
Your Answer : (Not Answered)
Correct Answer : A
Each leg's shear flow produces a force acting along that leg's centreline, so both resultants pass through their intersection and can generate no moment about it. The same argument applies to any section built from legs meeting at a single point, such as a tee.
An aircraft of mass \( 50\,000 \) kg touches down at \( 3 \) m/s sink rate. The kinetic energy the gear must absorb is
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: 225 kJ
\[ E = \tfrac{1}{2}mv^2 = \tfrac{1}{2} \times 50{,}000 \times 3^2 = 225{,}000\ \mathrm{J} = 225\ \mathrm{kJ}. \] The undercarriage must absorb this in a stroke of well under a metre, which is why oleo-pneumatic struts are used rather than simple springs - a spring returns the energy, whereas an oleo dissipates it.
Aerospace Vehicle Design [ Question No: 10 To 11 ] :
The thrust-to-weight ratio used on a constraint diagram is conventionally evaluated at
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: Sea level static, with per-constraint corrections
Thrust-to-weight on a constraint diagram is conventionally referred to the sea level static rating, because that is how engines are specified and selected. Each constraint is then corrected to that datum by dividing the thrust it actually requires by the lapse factor appropriate to its altitude and Mach number.
A cruise requirement of \( T/W = 0.062 \) at 11,000 m where the engine gives \( 0.28 \) of its static thrust corresponds to \( 0.062/0.28 = 0.221 \) at sea level. Without that correction, constraints evaluated at different altitudes could not be plotted on one axis.
A composite fuselage allows a cabin altitude of 6000 feet rather than the usual 8000 feet, raising the cruise pressure differential accordingly.
What is the principal structural consequence?
Your Answer : (Not Answered)
Correct Answer : C
The shell carries a greater differential, so the stresses and their once-per-flight repetition both increase. Composite structure tolerates that fatigue duty better than aluminium, which is what makes the more comfortable cabin possible.
Aircraft Instrumentation [ Question No: 12 To 14 ] :
A safety department finds that unstable approaches at one airport occur at four times the rate seen elsewhere in its network, from routine recorded data across several thousand flights.
What is the appropriate use of this finding?
Your Answer : (Not Answered)
Correct Answer : A
The programme exists to find systemic issues, and a rate four times the network average points at the procedure or the airport rather than at individuals. Using it punitively would end the crew agreement the data depends on.
Engine vibration monitoring is used principally to detect
Your Answer : (Not Answered)
Correct Answer : A
A blade shedding material or a bearing degrading changes the vibration signature before any other instrument responds. Because a rising trend matters more than an absolute value, the parameter is usually monitored over time rather than judged on one reading.
The erection system of an attitude indicator works by
Your Answer : (Not Answered)
Correct Answer : D
Pendulous vanes or an equivalent sensor detect departure from vertical and apply a torque, which precesses the axis back. Because the sensor cannot distinguish gravity from acceleration, the same mechanism is the source of the instrument's turn and acceleration errors.
Aircraft Propulsion [ Question No: 15 To 17 ] :
Match each parameter in List I with its correction in List II.
List I
A. Rotational speed
B. Mass flow
C. Thrust
D. Fuel flow
List II
1. Divided by the square root of the temperature ratio
2. Multiplied by root temperature and divided by pressure ratio
3. Divided by the pressure ratio
4. Divided by pressure ratio and root temperature ratio
Select the correct match.
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: A-1, B-2, C-3, D-4
Each correction removes exactly the dependence that matters for that quantity. Speed corrects on temperature alone, because blade Mach number depends on the speed of sound. Flow corrects on both, since it scales with density and with velocity. Thrust corrects on pressure alone, being a force proportional to pressure times area. And fuel flow, being a heat release, corrects on both.
Consider the following pairs of arrangement and its rationale:
Twin spool - Front and rear stages run at different speeds
Geared fan - Fan and low pressure turbine each run at their preferred speed
Mixed exhaust - Small gain in fuel consumption and noise
Separate exhaust - Required for low bypass ratio engines
How many of the pairs given above are correctly matched?
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: Only three
Twin spooling, the geared fan and the modest gain from mixing are all correctly described. The fourth is wrong and is in fact the reverse of practice: low bypass engines are usually mixed, because the large difference between the core and bypass velocities makes mixing worthwhile, while very high bypass engines use separate nozzles, where the velocities are close and a long bypass duct would cost more than the mixing gains.
Consider the following statements about streamtube behaviour:
1. At static conditions the streamtube is larger than the intake and contracts.
2. At high subsonic cruise it is smaller than the intake and expands.
3. Spillage drag arises when the intake captures more than the engine demands.
Which of the statements given above is or are correct?
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: 1 and 2 only
Statements 1 and 2 describe the streamtube correctly at the two extremes. Statement 3 has the sense of spillage inverted: it arises when the intake captures less than the approaching streamtube offers, so the surplus is turned aside. Air the intake actually captures is not spilled.
Aircraft Stability and Control [ Question No: 18 To 19 ] :
Two fins of \( 5 \ \mathrm{m^2} \) each replace one of \( 9 \ \mathrm{m^2} \). The change in total fin area is
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: An increase of 11 per cent
Compare the totals rather than the individual surfaces:
\[ 2 \times 5 = 10\ \mathrm{m^2} \quad \text{against} \quad 9\ \mathrm{m^2} \]
\[ \frac{10 - 9}{9} \times 100 = 11.1\% \]
So twin fins here add area rather than merely dividing it. The comparison is not the whole story, though: two fins of half the height each have a lower aspect ratio and so a shallower lift-curve slope, which is why designers do not simply halve the area when going to a twin arrangement. The gain in placing them in cleaner air often outweighs that penalty.
Consider the following pairs of effect and cause:
Nose up pitch with power on underslung engines - Thrust line below the centre of gravity
Mach tuck - Rearward shift of the aerodynamic centre
Nose down moment in the flare - Reduced downwash in ground effect
Mach tuck - Loss of elevator hinge moment
How many of the pairs given above are correctly matched?
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: Only three
The first three pair effects with their true causes: the nose-up pitch from underslung engines comes from the thrust line below the centre of gravity, Mach tuck from the rearward shift of the aerodynamic centre, and the nose-down moment in the flare from reduced downwash in ground effect.
The fourth gives Mach tuck a second and wrong cause. Hinge moments concern the force the pilot feels, not the moment about the centre of gravity, and tuck would occur on a fully powered control that transmits no hinge moment at all.
Engineering Mathematics [ Question No: 20 To 20 ] :
The mass of a solid of variable density \( \rho(x,y,z) \) is
Your Answer : (Not Answered)
Correct Answer : A
Each element carries mass \( \rho\,dV \), and summing gives
\[ m \;=\; \iiint \rho(x,y,z)\,dV. \]
Taking \( \rho \) outside the integral is valid only for a uniform solid; for a variable density it must stay inside, which is the whole reason the integral is needed rather than a product
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20