Instruction
- Total number of questions : 20
- Time allotted : 30:00 Minutes:Seconds.
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Aerospace Vehicle Design [ Question No: 1 To 20 ] :
Match each cost item in List I with its category in List II.
List I
A. Depreciation
B. Fuel
C. Advertising
D. Landing fees
List II
1. Direct variable cost
2. Direct fixed cost
3. Direct variable cost incurred per movement
4. Indirect operating cost
Select the correct match.
Fixed costs of \( 6.0 \) million dollars a year are spread over \( 3000 \) block hours. The fixed cost per block hour is
Which design change most directly reduces both production cost and operating cost?
Direct operating cost typically excludes
Three of the following follow from the design point and the design weight. Which does not?
The wing's aspect ratio
The wing area
The installed thrust
The stalling speed at a given lift coefficient
An aircraft of mass \( 52000 \) kg has a wing area of \( 105 \) m\(^2\). Its wing loading is
The same aircraft has a design thrust-to-weight ratio of \( 0.31 \). The installed thrust required is
Arrange the events following an engine failure on a twin in causal order:
1. The rudder is applied and the aircraft is held straight
2. Thrust becomes asymmetric
3. The fin and rudder are sized from the balance required
4. A yawing moment develops, augmented by windmilling drag
Select the correct sequence.
Consider the following pairs of gear parameter and what it governs:
Tip-back angle - Rotation without sitting on the tail
Overturn angle - Resistance to roll-over in a ground turn
Nose gear load fraction - Steering and braking traction
Tyre ply rating - Maximum permitted taxi speed
How many of the pairs given above are correctly matched?
A wing has \( S = 90 \) m\(^2\) and \( b = 30 \) m. The vertical tail area is \( 16 \) m\(^2\) at an arm of \( 14 \) m. The vertical tail volume coefficient is
Assertion (A): Constant-section barrels are used for as much of the fuselage as possible.
Reason (R): They make frames, panels and tooling repeatable and permit stretch by plug insertion.
Select the correct answer from the options below.
A fuselage is stretched from \( 38 \) m to \( 44 \) m at constant \( 4 \) m diameter. Its fineness ratio becomes
Assertion (A): Centre of gravity is quoted as a percentage of mean aerodynamic chord.
Reason (R): Expressed that way, positions and limits transfer between aircraft of different size.
Select the correct answer from the options below.
Assertion (A): Class II estimates commonly come out heavier than Class I estimates.
Reason (R): Summing real component groups picks up mass that a single historical fraction smooths over.
Select the correct answer from the options below.
Consider the following statements about unconventional configurations:
1. Historical regressions offer little guidance for them.
2. Physics-based estimation carries greater uncertainty than regression for conventional types.
3. Technical merit alone is sufficient to secure investment.
Which of the statements given above is or are correct?
If a sizing loop diverges, the most likely explanation is that
A digital mock-up is used to
An aircraft burns \( 25 \) t of fuel carrying \( 200 \) passengers \( 6000 \) km. Its fuel burn per passenger per thousand kilometres is
An aircraft of \( 90 \) t on a wing of \( 120 \) m\( ^2 \) has a wing loading of
If that aircraft is limited to a \( 90 \) t maximum and its tanks are enlarged to hold \( 30 \) t, the payload it can carry becomes
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Aerospace Vehicle Design [ Question No: 1 To 20 ] :
Match each cost item in List I with its category in List II.
List I
A. Depreciation
B. Fuel
C. Advertising
D. Landing fees
List II
1. Direct variable cost
2. Direct fixed cost
3. Direct variable cost incurred per movement
4. Indirect operating cost
Select the correct match.
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: A-2, B-1, C-4, D-3
The classification turns on two questions: is the cost attributable to operating the aircraft, and does it vary with flying? Depreciation is direct but fixed, accruing with time. Fuel is direct and variable with hours. Landing fees are direct and variable, but with movements rather than hours. Advertising is indirect, belonging to running the airline.
Fixed costs of \( 6.0 \) million dollars a year are spread over \( 3000 \) block hours. The fixed cost per block hour is
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: 2000 dollars
Divide the annual fixed cost by the block hours flown:
\[ \frac{6\,000\,000}{3000} = 2000\ \mathrm{dollars\ per\ block\ hour} \]
The figure falls as utilisation rises: at 4000 hours the same fixed cost would be 1500 dollars an hour. That is the whole arithmetic behind high-utilisation operating models - the aircraft's fixed charges are unaffected by how much it flies, so every additional hour dilutes them.
Which design change most directly reduces both production cost and operating cost?
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: Reducing the empty weight
Empty weight drives both halves of the equation. On the production side, engineering, tooling and manufacturing hours all scale with weight in the parametric relations, so a lighter aircraft costs less to design and build. On the operating side, less weight means less lift, less induced drag and less fuel burnt for the same mission.
The others help only one side or neither: more wing area or more engines add weight, cost and drag, and a higher cruise Mach number raises both the design difficulty and the fuel burn.
Direct operating cost typically excludes
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: Administration and marketing
Direct operating cost covers what it takes to fly the aircraft - fuel, flight and cabin crew, maintenance, depreciation, insurance and landing and navigation fees. Administration and marketing are indirect, supporting the airline as a business rather than any particular flight.
The distinction matters because direct operating cost is the figure used to compare aircraft types: it isolates what the aeroplane costs to operate from what the airline costs to run, so two carriers with very different overheads can still compare the same aircraft on a common basis.
Three of the following follow from the design point and the design weight. Which does not?
The wing's aspect ratio
The wing area
The installed thrust
The stalling speed at a given lift coefficient
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: The wing's aspect ratio
Aspect ratio does not follow from the design point - it is an input, chosen beforehand and used in constructing the cruise and climb constraints through its effect on induced drag. Given the wing area that the analysis produces, the aspect ratio then fixes the span.
The other three do follow. Wing area is the design weight divided by the wing loading, installed thrust is the weight times the thrust-to-weight ratio, and the stalling speed follows from the wing loading and the maximum lift coefficient.
An aircraft of mass \( 52000 \) kg has a wing area of \( 105 \) m\(^2\). Its wing loading is
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: 4.86 kN/m\(^2\)
Convert the mass to weight before dividing by the area:
\[ W = 52000 \times 9.81 = 510.1\ \mathrm{kN} \]
\[ \frac{W}{S} = \frac{510.1}{105} = 4.86\ \mathrm{kN/m}^2 \]
The distractor \( 495 \) divides the mass in kilograms by the area without converting to weight, giving kg/m\(^2\) - a perfectly valid unit but not the one asked for. Mixing the two conventions is the commonest error in this calculation; the factor between them is \( g \).
The same aircraft has a design thrust-to-weight ratio of \( 0.31 \). The installed thrust required is
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: 198.4 kN
The installed thrust follows from the vertical coordinate of the design point:
\[ T = W \times \frac{T}{W} = 640 \times 0.31 = 198.4\ \mathrm{kN} \]
The distractor \( 99.2 \) halves this, as if the figure applied to one engine of a twin; the diagram's \( T/W \) is always the total installed thrust, and the per-engine rating comes from dividing by the number of engines afterwards. This total is what determines which engines from the available catalogue can be considered.
Arrange the events following an engine failure on a twin in causal order:
1. The rudder is applied and the aircraft is held straight
2. Thrust becomes asymmetric
3. The fin and rudder are sized from the balance required
4. A yawing moment develops, augmented by windmilling drag
Select the correct sequence.
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: 2, 4, 1, 3
The chain runs from the failure to the design consequence. Thrust becomes asymmetric (2) the moment the engine fails. A yawing moment develops, augmented by the windmilling drag of the dead engine acting on the opposite side (4).
The rudder is applied and the aircraft held straight (1), and the fin and rudder are sized from the balance that requires (3). The last step is the design one: the surfaces exist to meet this case, so the case must be established before they can be sized.
Consider the following pairs of gear parameter and what it governs:
Tip-back angle - Rotation without sitting on the tail
Overturn angle - Resistance to roll-over in a ground turn
Nose gear load fraction - Steering and braking traction
Tyre ply rating - Maximum permitted taxi speed
How many of the pairs given above are correctly matched?
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: Only three
The first three are correct. The tip-back angle governs whether the aircraft can rotate without sitting on its tail, the overturn angle its resistance to rolling over in a ground turn, and the nose gear load fraction the traction available for steering and for braking on the mains.
The fourth is wrong. Ply rating expresses a tyre's load capacity - the strength of its carcass - and says nothing about taxi speed, which is limited separately by the tyre's speed rating.
A wing has \( S = 90 \) m\(^2\) and \( b = 30 \) m. The vertical tail area is \( 16 \) m\(^2\) at an arm of \( 14 \) m. The vertical tail volume coefficient is
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: 0.083
The vertical coefficient uses the span rather than the chord:
\[ V_V = \frac{S_V\,l_V}{S\,b} = \frac{16 \times 14}{90 \times 30} = \frac{224}{2700} = 0.083 \]
The value looks small beside a horizontal coefficient near 1.0, but the two are not comparable: the span is far larger than the mean chord, so the denominator is much bigger. Typical vertical tail volumes run from about 0.04 to 0.12, and 0.083 sits comfortably within that band.
Assertion (A): Constant-section barrels are used for as much of the fuselage as possible.
Reason (R): They make frames, panels and tooling repeatable and permit stretch by plug insertion.
Select the correct answer from the options below.
Your Answer : (Not Answered)
Correct Answer : A
Both statements are true and the second gives both reasons. Manufacturing economy and family growth potential point the same way, which is why the parallel section is extended as far fore and aft as the shaping allows.
A fuselage is stretched from \( 38 \) m to \( 44 \) m at constant \( 4 \) m diameter. Its fineness ratio becomes
Your Answer : (Not Answered)
Correct Answer : A
Dividing, \( 44/4 = 11.0 \), still within the usual range though approaching its upper end. Beyond about twelve the added wetted area and the shrinking rotation angle both start to cost more than the extra capacity is worth, which is what limits how far a family can stretch.
Assertion (A): Centre of gravity is quoted as a percentage of mean aerodynamic chord.
Reason (R): Expressed that way, positions and limits transfer between aircraft of different size.
Select the correct answer from the options below.
Your Answer : (Not Answered)
Correct 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 purpose. Expressing centre of gravity as a percentage of the mean aerodynamic chord non-dimensionalises it, so 25 per cent means the same aerodynamic thing on a regional jet as on a widebody. Absolute distances from a datum would be meaningless between types, and the certified envelope limits could not be compared at all.
Assertion (A): Class II estimates commonly come out heavier than Class I estimates.
Reason (R): Summing real component groups picks up mass that a single historical fraction smooths over.
Select the correct answer from the options below.
Your Answer : (Not Answered)
Correct Answer : A
Both statements are true and the second is the reason for the first. The regression describes aircraft as built, including their weight growth, but applied at aircraft level it hides where the mass sits and so understates awkward details.
Consider the following statements about unconventional configurations:
1. Historical regressions offer little guidance for them.
2. Physics-based estimation carries greater uncertainty than regression for conventional types.
3. Technical merit alone is sufficient to secure investment.
Which of the statements given above is or are correct?
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: 1 and 2 only
Statements 1 and 2 are correct and together describe the real difficulty of unconventional work: the statistical shortcut is unavailable, and the physics-based estimate that replaces it is less certain than a regression would have been for a conventional aircraft. Statement 3 is wrong. Investment follows commercial and risk judgements as much as technical merit, and many technically sound unconventional configurations have never been funded.
If a sizing loop diverges, the most likely explanation is that
Your Answer : (Not Answered)
Correct Answer : D
Divergence means each added kilogramme of fuel adds more than a kilogramme of weight, which happens when the mission is beyond what the assumed efficiency can deliver. Either the requirement or the technology assumption has to give.
A digital mock-up is used to
Your Answer : (Not Answered)
Correct Answer : A
Every part existing in one geometric model allows interference between pipes, wires and structure to be found in software rather than on the assembly line. Maintenance access can also be rehearsed before the first article exists.
An aircraft burns \( 25 \) t of fuel carrying \( 200 \) passengers \( 6000 \) km. Its fuel burn per passenger per thousand kilometres is
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: 20.8 kg
Divide the fuel by passengers and by thousands of kilometres:
\[ \frac{25\,000}{200 \times 6} = \frac{25\,000}{1200} \approx 20.8 \text{ kg} \]This normalised figure is how transports of different size and range are compared, and it has fallen from around 50 kg for early jets to below 20 for the most efficient current aircraft. It is also directly proportional to the carbon emitted per passenger kilometre.
An aircraft of \( 90 \) t on a wing of \( 120 \) m\( ^2 \) has a wing loading of
Your Answer : (Not Answered)
Correct Answer : B
Converting to force, \( 90\,000 \times 9.81 = 883 \) kN, and dividing by the area gives \( 883\,000/120 = 7360 \) N/m\( ^2 \). Wing loading is among the first numbers chosen in conceptual design, since it drives field length and cruise efficiency in opposite directions.
If that aircraft is limited to a \( 90 \) t maximum and its tanks are enlarged to hold \( 30 \) t, the payload it can carry becomes
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: 15 t
With the take-off weight capped, extra fuel can only come out of payload:
\[ 90 - 45 - 30 = 15 \text{ t} \]The extra 5 t of fuel has cost 5 t of payload, one for one. That exchange is exactly the sloping portion of the payload-range diagram, along which range is bought at the price of revenue load.
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20