Design Requirements and Specifications Questions and Answers

Answer: C

Correct answer: Gradual accumulation of extra requirements

Requirements creep is the steady addition of further requirements after the specification is agreed, each defensible on its own and each carrying a little weight, cost or schedule. The difficulty is that nobody sees the total until it is large. The remedy is formal change control, in which every proposed addition is costed in weight, performance and schedule before it is accepted.

Answer: D

Explicit criteria and weightings make the reasoning visible and reviewable, which matters when a decision will be lived with for decades. The output is a recommendation with its assumptions stated, not merely a preferred answer.

Answer: A

Combining criteria into one score forces the relative importance of each to be stated openly. Its weakness is that a poorly chosen weighting can bury a decisive disadvantage inside an attractive-looking total, so sensitivity to the weights should always be checked.

Answer: B

Thousands of people cannot detail-design against a moving configuration, so at some point the shape is fixed and changes become formal and expensive. Freezing too early risks locking in a poor choice; too late wastes the design workforce.

Answer: C

Fuel burn, maintenance, crew and ownership together decide whether an aircraft earns its operator money over decades. A design that is cheaper to buy but costlier per seat-mile generally loses, which is why fuel efficiency dominates modern transport design.

Answer: D

Each level of decomposition on the descending arm has a matching level of integration and test on the ascending arm. It makes explicit that every requirement written must have a corresponding means of demonstrating compliance.

Answer: A

A design can satisfy every written requirement and still fail to serve the operator, if the requirements themselves were wrong. Keeping the two questions distinct is what stops a programme delivering exactly what was asked for and nothing that was needed.

Answer: B

Every detail design decision tends to add weight and lose performance against the optimistic early estimate. Allocating and tracking margin explicitly, rather than hoping, is how a programme avoids arriving at first flight overweight.

Answer: C

A handful of requirements usually dictate the layout while the remainder are satisfied incidentally. Identifying which they are early focuses effort where it changes the answer, and it is one of the more valuable judgements in conceptual design.

Answer: D

Shared systems, a common type rating and shared parts are worth a great deal to an operator and to the manufacturer's development budget. The cost is a compromised optimum, since the new aircraft inherits choices made for a different problem.