23-Mechatronics-B8 Product Design and Development · December 2019
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams, 16-Mex-B8, Product Design and Development — December 2019, 3 hours, open-book examination (Casio or Sharp approved calculator only). Question 1 (40 marks) is mandatory; candidates choose 4 of the remaining 6 questions (15 marks each, only the first five questions as they appear in the answer book are marked, for a total of 100%). This is an essay/design-methodology paper with no numerical calculations. All seven questions are answered below for completeness.
Reference texts: Ulrich, Eppinger & Yang, Product Design and Development, 7th ed. (generic product-development process, concept generation and selection, Design for Manufacturing and Assembly, intellectual-property strategy); Government of Canada, Canadian Intellectual Property Office (CIPO), A Guide to Patents (Patent Act novelty/ utility/non-obviousness requirements, first-to-file rule, maintenance fees); Transport Canada, Motor Vehicle Safety Act and Canada Motor Vehicle Safety Standards (CMVSS).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
A 50-year-old airframe touches structures, aerodynamics, propulsion, avionics, materials, manufacturing and certification at once, so the anchor team is chosen for breadth of judgment as much as depth. Four skill sets stand out. First, aerospace systems engineering (aerodynamics, structures and propulsion integration): the legacy airframe's loads, weight and balance and performance envelope must be re-derived before anything downstream can change, and only a systems engineer can see how a change in one subsystem (e.g. a re-engine) ripples into another (e.g. centre-of-gravity, empennage sizing). Second, airworthiness/certification expertise (Transport Canada TCCA, and cross-certification with the FAA/EASA where the aircraft is exported, plus software/hardware assurance standards such as DO-178C/DO-254 where new avionics are introduced): a 50-year-old type certificate basis predates most of today's safety rules, so certification strategy has to be set at the start, not discovered late. Third, manufacturing and cost engineering (Design for Manufacturing and Assembly, modern composite and alloy processing): new technology only helps if it can be produced at a competitive unit cost and rate, so a manufacturing engineer must sit with the design team from day one rather than review it after the fact. Fourth, program/project management with strong cross- functional communication: an update of this scope runs for years across many disciplines and suppliers, and the single biggest risk to a legacy-aircraft refresh is not a bad technical decision but a program that cannot keep its many concurrent workstreams synchronized.
(1) Fuel efficiency and reduced emissions. Operating cost is dominated by fuel burn over the aircraft's life, and both airlines and regulators (ICAO's CORSIA carbon offsetting scheme, national emissions policy) now price carbon into route economics; an aircraft that cannot show a step-change in fuel burn versus modern competitors will not sell regardless of its other merits. (2) Reduced life-cycle and maintenance cost. A modern buyer evaluates an aircraft on total cost of ownership, not just acquisition price; modern avionics, condition-based maintenance and simplified structure directly compress the largest recurring cost driver for an operator. (3) Safety and certifiability under current airworthiness standards. A design frozen 50 years ago predates fly-by-wire flight controls, modern crashworthiness rules and current avionics/human-factors standards; without closing that gap the aircraft cannot be type-certified for sale into today's market at all, which makes this the objective that gates the other two.
Taking objective B(1), fuel efficiency, three competing approaches are considered. (1) Propulsion upgrade — re-engine with a modern high-bypass turbofan (or turboprop, depending on mission), which typically delivers the single largest specific-fuel- consumption improvement of the three but carries the highest non-recurring cost (new engine mounts, nacelle, fuel system) and the longest certification path. (2) Aerodynamic refinement — wing/winglet redesign and drag clean-up (reduced parasite drag, improved lift-to-drag ratio), which is lower cost and lower certification risk than a re-engine but delivers a more modest fuel-burn gain. (3) Structural weight reduction — substituting modern composites and high-strength alloys for legacy aluminum in secondary and, where justified, primary structure, trading a moderate fuel-burn gain (weight reduction improves fuel burn roughly in proportion) against new manufacturing processes and a fatigue/damage-tolerance re-qualification effort.
A structured weighted-decision matrix (Pugh-style concept-selection matrix) is the right tool here because the three options trade off differently across several criteria that cannot be reduced to a single number by inspection. The team first agrees the criteria and their relative weight — here: fuel-burn improvement (weight 35%), non-recurring cost (25%), certification risk/ schedule (25%) and retrofit complexity onto the existing airframe (15%) — then scores each option 1–5 against each criterion against a common baseline (the unmodified legacy design) and sums the weighted scores. Propulsion upgrade scores highest on fuel-burn improvement but lowest on cost and certification risk; aerodynamic refinement scores well on cost/risk but only moderate on fuel-burn gain; structural weight reduction sits in between on every criterion. Summing the weighted scores typically favours aerodynamic refinement as the first, lowest-risk step, with propulsion upgrade reserved as a second-phase investment once the airframe's other systems have already been modernized — the matrix makes that staged conclusion traceable and defensible to management rather than a matter of opinion, which is the actual purpose of running the exercise.
The selected solution (here, aerodynamic refinement as phase one) is converted into a configuration-controlled design specification before any other subsystem team starts work on it: a written set of functional and performance requirements (target drag reduction, weight budget, interface envelope) with acceptance criteria; an interface control document defining exactly where the new wing/winglet geometry meets the existing structure, fuel system and flight-control runs; an updated weight-and-balance statement and the revised structural load cases the new geometry creates, so the structures team can begin their own analysis from a common baseline; and a requirements traceability matrix linking each specification item back to objective B(1) so that later trade studies can be checked against the original intent. This package is issued through the program's product-data-management (PDM) system under formal configuration control, and is formally reviewed and signed off at a Preliminary Design Review before the broader team (structures, avionics, certification, manufacturing) is authorized to begin detailed work against it — this gate is what prevents different subsystem teams from independently reinterpreting an informally-communicated decision.
