December 08 2022
In this HEMS Roundtable, the panel discuss the subject of Part21J design, the design process and why aviation Air Ambulance & HEMS design can be so expensive. The discussion covers aspects such as; ‘What is the problem we are trying to answer through design?’; ‘Is a major or minor change is required?’ and ‘What is an STC (supplemental type certificate) and do I always need one?’.
Welcome Paul and Jamie. Today we are talking about design and the design process and how it can be so expensive. So, let’s start at the beginning. Paul, what is the design process?
Paul Thanks Glenn. That is a big a question and probably one that would take the whole 20 minutes we have so perhaps I’ll just focus on some of the major considerations and then we can look at each of those in detail later on.
There are four areas that are often the most fundamental to the entire process, these being:
1 – What is the problem we are trying to answer through design?
2 – If a change is required will that be major or minor?
3 – Is there a suitable existing certified solution in the market place
4 – If major this will need the creation of a Supplemental Type Certificate (STC).
Again these are just some of the considerations but in my 30 odd years of experience these are the building blocks of a proposed change or design for those unfamiliar with commissioning design work across all aircraft types.
Jamie, perhaps I can bring you in on that first point. How do you define the problem design is being used to answer?
Jamie I think for me the first place to start is to identify who the end user of the design will be. Often within the HEMS – Air Ambulance world it’s the medical team and paramedics. They may have a requirement for the installation of a new item of equipment such as a medical cabinet or incubator. On the face of it this might not seem a difficult job, but working with the medical team we’ll need to assess what is actually required from the design in several areas:
– the ergonomic and anthropometric requirements would need to be assessed to make sure we are installing equipment in an area that suits the users work flow.
– emergency egress is another area that would need to be assessed, making sure there is enough room for an emergency evacuation should the need arise, I think we can all appreciate that the work environment inside a HEMS rotorcraft can be a bit tight.
– Assessing the modifications impact on the weight and balance of the rotorcraft is another essential area, helicopters are much more sensitive to this then their fixed wing counterparts.
Paul I’ll add an example of this Jamie, if I can come in here. The recent work we’ve been doing with COVID-19 bulkheads on the Airbus H145 has demonstrated this really well.
After discussion with the client regarding the need for the bulkhead installation we conducted an exercise with the paramedics to look at the what type of bulkhead should be introduced and how we could maintain the flow of communication through the aircraft while meeting the needs of the infectious disease control measures the barrier is designed to put in place.
This involved laser scanning the aircraft we then built a 3D model to create the design concept, sharing the concept with the clinical team, quickly adapting it with their input and then creating a 3D Computer Aided Design (CAD) model.
we used this model to generate some templates and from this built a full size concept bulkhead from hard foam. We carried out a trial installation into the helicopter and along with the whole crew complement we ran a series of tests with them in a simulated working environment wearing their full gear including helmets to assess the concept and in particular to help us agree correct position of windows. This enabled both the flight crew and the clinical team to have direct input into the design concept. From this input the CAD models have been adjusted and the parts will now go into production. We have used the CAD model to not only formulate and finalise the design but this same model transfers across into the manufacturing process for 3D printing of the various cover panels and the CNC (computer numerical control) machining of the fibrelam board for the bulkheads. This process allows for a quality accurate product to be developed and manufactured and lends itself for the product to be quickly and easily replicated or modified for future needs.
Glenn Interesting, so this sounds like the ideal opportunity to talk about the major / minor change classification. What does this mean and why is it important?
Jamie All modifications & repairs to an aircraft are classified as either minor or major. In simple terms if it is classified as a minor then the Design Organisation can approve the design under its own authority without seeking involvement from the regulator. If it is major mod then an application will need to be submitted to the authority to approve the design which brings us into the world of STC’s.
Jamie So STC stands for Supplementary Type Certificate. This is a document issued by the relevant authority such as the CAA or EASA that approves the modification for use. It’s the Design Organisations responsibility to ensure the airworthiness of the STC through its entire product lifecycle. Producing an STC can be a labour intensive task as we have to make detailed studies across various subjects including:
– configuration control
– stress analysis, particularly crash test (20G downwards)
– electrical load analysis
– RAP – resonant test (important for external helicopter modifications)
– Emergency crew egress
to name a few.
A relatively small modification requiring an STC can easily generate a 150 pages of documentation that needs to be built and then carefully checked.
This is a large part of why modifications and design changes can take a) a relatively long time, and b) cost what can be seen as a large amount of money to fit relatively simple items such as a say a medical stowage or COVID barrier bulkhead.
Glenn Ok, so reading between the lines it would appear that for those who are listening to this who aren’t in the weeds on the detail of aviation design probably need advice to work through what can be a costly exercise.
Paul In, a very simplistic way, ‘yes’.
Jamie I’d agree. It is one of those things that you can never be too early on. What seems like a simple requirement can quickly become complex and frustrating, especially if you go about them the wrong way. The worst possible situation is to have uncertainty or grey areas in what you wish to achieve as this will invariably require items to be added in later that can have a large impact.
Paul Over the last 30 years, I’ve certainly seen this but it can be easily avoided simply through early engagement with the clinical teams, the pilots, the operations team and the design team. By involving all four we have the ability to drive innovation, future proof and deliver something that works.
This is important as the role of the Air Ambulance is changing from a means of transport to a clinical environment. And as such we must be conscious of the ever changing requirements especially an awareness of population changes and something we have experience of, and addressed in one of our fixed wing air ambulance solutions. The population is getting heavier. The health survey for England 2019 estimates that 28% of the population are overweight, a trend that will no doubt sadly continue. So if people are getting heavier and larger plus more equipment is required onboard we will have to stay dynamic in our approach to producing design solutions.
Glenn It is an interesting point Paul. I know this is a complex topic and I’m sure we can spend much longer on it, but as we are close to time I wonder if we could finish on your top tips for the audience on this subject.
Jamie Top tips usually come in fives but I think I’d limit it to three from my own experience and I’ll make these non-technical.
1) If you have an inkling that you’d like to make a design change to your aircraft then call us or speak to whoever provides your 21J design services. Talk to them about what you are looking to achieve and ask them to conduct a feasibility study on the change.
2) The feasibility study should involve and be focused around the end user – the people that will actually be working in the environment and making use of the new kit. It’s so very obvious but I can’t tell you the number of times that people don’t do this, instead they focus only on a list of requirements and equipment part numbers. That is a good start but knowing how they’ll be used, what frustrations they have and what they want is fundamental to effective operations.
3) The design process is collaborative and evolves. What is first produced is rarely the final solution, prototyping (virtual and physical) irons out the wrinkles and therefore it takes time. Too often the design process is seen as something that can done quickly. Think of it as a goldilocks process – not too quick but not too long.
Glenn Thanks Jamie and Paul, we will need to end it there. Thank you to you both talking about this subject – I can see there are many more areas to cover during another roundtable. I’d like to open the floor up now for questions.