Paul Holbourn is an electronic engineer, (Chief Technical Officer), specialising in radar systems for aircraft. As part of Think Up’s Royal Academy of Engineering-funded research into the design strategies of engineers from different sectors of industry, I interviewed Paul about the conceptual design of electronic systems, in this case in the context of aircraft manufacture.
The questions below are loosely based around a standard set that I have been using with engineers from a range of different disciplines. The answers come from Paul’s original answers to our online questionnaire, supplemented with responses he gave in our face-to-face discussion. (To answer the questions yourself, you can do so on our online form and contribute to our research).
What is being designed?
Paul is involved in the design of airborne radar, electronic warfare and electro-optic systems for military aircraft and helicopters. As CTO he tends to get involved with design at the bid stage when the concept is being set.
Establishing the brief
In response to what need?
In general we design in response to a set of user needs supported by a systems requirement document developed by the Customer, with input from us. We also develop generic products for the export market – in this instance the design brief including user needs and systems requirement document will be developed by us, with input from our sales and marketing function.
What key information does the brief give you?
This initial brief usually provides us with a systems requirement document, which, through discussion with the customer, becomes expanded into a detailed Specification, Statement of Work and a Verification and Validation Plan.
What is the key piece of information that you look for in a brief which is likely to dominate the nature of the outcome? How does this information impact on the design outcome?
The primary things we are looking for is performance requirements, such as the detection range, functional requirements, reliability, the environmental specification, interface specifications and installation constraints, such as size, weight and power. Secondary inputs would be standards which must adhere to in terms design methodology, e.g. software, quality, etc and any information on how the equipment will be used by the end user.
What if anything is usually missing from a brief that you usually need to go and find out?
In general we start with a top-level design brief and generate very detailed design requirements with Customer involvement. Customers generally will participate in Preliminary Design Review, Critical Design Review etc which minimises surprises.
Having received a design brief, what are the first things you go and find out to enable you to do your design work?
Understanding and checking completeness and consistency of user requirements, performance specification and installation constraints.
Developing ideas
Do new ideas tend to be evolutions of previous designs, or are can they be very different?
In general, design is evolution with an empasis on re-use. A point that both Paul and Howard Matthers made (see my interview with Howard) made is that existing complex mechanical and electrical systems represent the sum of many hundreds of thousands of person hours, and so to implement a system using radically different technology is managed cautiously, with great emphasis on maturing the technology independently of any full scale product development.
When developing an initial response to a brief, what are the key systems that you usually address in your response?
The power aperture product, functionality, environment and installation – and perhaps just as importantly how will the end user will operate the equipment.
Are there are a set of ‘go-to’ answers that you regularly turn to for ideas in response to a brief. If so, what are these?
Generally we are seeking to re-use existing hardware and software modules to minimise non-recurring cost and development time. Radar is a mature product which has evolved continually over 75 years.
Can you characterise the dominant uncertainty, in other words, the key feature of any proposed idea that, once determined, tends to dictate the other aspects of the design?
The power aperture product (which determines the size), and installation constraints.
What tends to inspire the ideas you conceive of?
User requirements document, user concept of operations and talking to operators.
Developing and choosing ideas
When you developing an idea, in what format do you first express those ideas?
We use performance models, CAD models and a mock up of the human-machine interface (HMI).
What are the common sorts of models you need to develop and test an idea?
We use various models as required for stress, thermal, electromagnetic (antenna) and systems modelling. We use more detailed models for digital, analogue and microwave design, CAD models, performance modelling etc. The objective is to minimise design iteration and prototyping.
What sorts of models do you need to collaborate with others in interdisciplinary design teams?
As required by the design stage and the object being designed. We use a shared design database and tools to promote collaboration.
What models do you use for communicating ideas with others?
All of the above.
What are the most important tests that tend to determine whether or not an idea meets the brief?
Progressive verification and validation using a combination of analysis, modelling, sub-system tests, system tests, flight test and environmental tests.
When are bad decisions made in the design of electronic systems?
They come from a mixture of inexperience and loosing sight of the system specification and the user requirements. In particular a poor understanding of how the equipment will be used by the end user (pilot in a fast jet undertaking combat missions) can lead to bad design decisions.
A common error is to proceed with detailed low level h/w and s/w design before the earlier stages of Systems Definition and Systems Design is complete.
To what extent are key decisions codified?
Key design decisions are very much codified, and are captured in the formal design review process and design documentation.
What is the consequence of making a bad decision in your domain of design?
Re-design, leading to cost and schedule overrun, leading to reputational damage and unhappy customers.
When carrying out a design in your sector of engineering, what are first the three to five steps you would take?
- Understand the design brief, including how the system will be used
- Create and agree the top-level system design concept
- Identify constrains, such as installation, re-use, cost and schedule.
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