Conceptual Design Process Questions and Answers

Answer: A

Correct answer: Diverging; the mission may be unachievable

The sequence 70, 88, 106, 130 grows by an increasing amount at each pass: every extra tonne of assumed weight demands more than a tonne of additional fuel and structure, so the loop runs away. No number of further iterations will help. The remedy is to change an input - relax the range or payload, improve the assumed aerodynamic efficiency or specific fuel consumption, or accept a technology whose risk must then be recorded.

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 fuel required depends on the aircraft’s weight, and the weight includes the fuel, so the equation is implicit in the unknown. With empty weight given as a fraction of take-off weight rather than a fixed number, there is no closed form, and the standard method is to guess a take-off weight, compute one, and repeat until the two agree.

Answer: C

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

Both are true and the reason explains the disproportion. Conceptual design spends a few per cent of the budget but commits perhaps sixty-five per cent of the lifetime cost, so the leverage on the eventual outcome is at its greatest precisely when the least has been spent. That is why the phase attracts the most experienced staff and why time spent exploring alternatives there is among the cheapest work the programme will ever do.

Answer: D

Both are true and the second explains the first. A blended wing body sits outside the sample entirely, so the correlation extrapolates into territory it says nothing about and must be replaced by physics-based estimation.

Answer: A

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 behind the assertion. In a converging loop each added kilogramme of assumed weight brings less than a kilogramme of extra fuel and structure, so the series settles. When the growth factor exceeds unity the series runs away, and no amount of further iteration recovers it. The message is that the mission, as specified, exceeds what the assumed technology can deliver, and an input must change.

Answer: B

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

Both are true and the reason accounts for the assertion. Optimising each discipline in turn produces a design that is best for none of them together: the aerodynamicist’s high aspect ratio wing is the structural engineer’s heaviest. Because the couplings between disciplines dominate the outcome, the system must be optimised as a whole, accepting a locally worse solution in one discipline where it improves the aircraft.

Answer: C

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

Both are true and the reason is why a flat optimum is welcome. If the figure of merit hardly changes across a range, the choice can be made on grounds the analysis never captured - gate span limits, commonality with an existing wing, manufacturing simplicity, certification precedent - without paying a penalty. A sharp optimum, by contrast, forces a value that may be awkward for every other reason.

Answer: D

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

Both are true and the reason is exactly why the practice matters. Each optimistic assumption is defensible on its own, and a design can accumulate several without anyone noticing that the programme now depends on all of them arriving together. Recording each with its readiness level forces that stack to be visible, counted and, where necessary, backed by a fallback.

Answer: A

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

Both are true and the reason is what drove the change. Under the sequential model a design was passed from group to group, and manufacturing or support difficulties emerged only when it reached them, by which time correcting the cause was ruinously expensive. Concurrent engineering brings manufacturing, support and cost specialists into the design team from the start, so those constraints shape the configuration rather than confronting it.

Answer: B

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

Both are true and the reason states why the model is a prerequisite. Exploring a design space means evaluating tens or hundreds of configurations, and each needs a complete geometry for the aerodynamic and weight analyses to work on. Only a parametric model can produce them automatically from a handful of driving variables; drawing each by hand would consume the schedule the exploration is meant to protect.