Conversations with Tee Chee Yen

Tee Chee Yen works as an aerospace engineer with Cyient Singapore, an engineering solutions company, based in Seletar – most aerospace companies in Singapore are located at Seletar Aerospace Park and Loyang. Cyient’s, main customer, Pratt and Whitney, is one of the three main engine manufacturers in the world. Cyient also has engagements with non-aerospace industries like Singapore Power.

CY: An engine is scheduled to come in for maintenance, repair and overhaul (MRO in short) every designated number of cycles or flights, and Singapore is a major maintenance hub for Pratt and Whitney engines. There are about 8 to 10 repair shops servicing Pratt and Whitney engines. So, what happens is that the engine will be sent to an engine shop for disassembly, then all the engine components will be sent to the individual repair shops. If the shop finds a problem that they cannot repair using current existing technical manuals or expertise they have, they will then approach Cyient for help to develop new repair technical information to address their problems.

Usually, a component has to be restored to its original Form, Fit and Function. But if the damage is too severe, we will have to consider it in its repaired state/condition – basically what we call something beyond its repairable limit. What we are trying to achieve is to extend the life of every engine component as long as possible. So, these repair jobs can be valued according to the severity of the damage to the engine and how it has been damaged because damages may be very different in each scenario. Basically, when the technical manual was initially done up, it was typically based on problems from previous field experiences; but out in the actual environment, when the engine goes to a flight, there will be many factors that you cannot foresee.

Whenever we develop a new repair, it has to be sufficiently substantiated due to safety and airworthiness concerns. There are various guidelines defined by the civil aviation authorities. At Cyient Singapore, my job is to perform structural analyses of the repair for the engine components. In my company, there are two engineer role: the repair design engineer who writes the repair instructions and compiles the required substantiation for approval, and the structural engineer whose job is to support the repair design engineer by providing structural substantiation in the form or an analysis report of the repair. We would have to certify whether the repair can be certified acceptable or not and whether the life of the component is still within the required number of cycles. We have to ensure that after performing the repair, the component is still within these margins.

CY: I think most people interested in aircraft would have seen the bird strike test. Whenever an engine is developed, it has to be certified by the civil aviation authorities. Since Pratt and Whitney is based in the US, the (US) Federal Aviation Administration has a list of certification criteria to fulfill a new engine. And one of the criteria is to survive a bird strike. And they do actually conduct the test with a bird, of course they don’t throw a live bird, they throw like a frozen chicken and watch the fan blades slice the bird cleanly into pieces. That’s one of the tests they conduct.

Basically, an engine is a rotating machine, and anything that rotates with thousands of revolutions per minute has a lot of kinetic energy. So, imagine one of the massive fan blade gets liberated – that is a lot of energy being released. And each fan blade is about the size of a human. So, another test is called the fan blade-out test, whereby the case (the shell) protecting the engine must be able to withstand the liberation of a fan blade. The test criteria is that the case should remain intact even after liberation of the fan blade. Also, there are other criteria like water injection, snow, hail … basically environmental testing. It’s to ensure the engine can survive harsh operating environments.

Because most of our work is dealing with structural analysis using computer simulations, I am usually deskbound. The repair will be done by the technicians at the repair shop so we don’t go down as often as you might think – only when we really need to see what really happened. Usually, photos are provided by the repair shops and we will tell them to provide relevant dimensions. So it is not as hands on as being able to handle repair tools and equipment, but still our job is definitely quite technical and challenging.

CY: Out in the aerospace industry, I think it actually does not make much of a difference whether you are from aerospace or mechanical engineering background; taking up aerospace engineering might give you more opportunities for related internships, which might perhaps be considered as relevant work experience when seeking employment with more selective aerospace companies. Otherwise, I don’t think, career-wise, for a general aerospace career that there is much difference.

From my experiences, my company does not differentiate too much between mechanical and aerospace engineers. Maybe it’s just that being from aerospace engineering might give you a slight edge, because of relevant knowledge of how the engine works. So, the time it takes to pick up the concepts may be shorter; but otherwise, from my experience in Nanyang Technological University’s aerospace engineering course, we actually learnt similar things with mechanical engineering. . It’s just that aerospace engineering has more of an aerospace application slant concerning what is taught and learnt, with some specialized modules in aerospace engineering towards the final year. I think in a course-based curriculum, you might get a bit of knowledge in everything but eventually you might not be applying knowledge from every module in your day-to-day work.

I would say that if you have an interest in planes, then you should choose aerospace over mechanical engineering. because these two courses will be geared towards their own areas of application.

For those intending to enrol in a polytechnic, there are usually two relevant courses. Aerospace electronics deals with control systems like radar, satellites and navigation systems, basically what you see on the instrument panel in the cockpit. Aeronautical engineering or technology deals with the mechanical functions of the plane: flight mechanics, aerodynamics, aircraft controls. Generally, those in aerospace electronics will go into avionics, dealing with flight electronic systems. But I think it is still quite early to make a decision at polytechnic level, and it doesn’t mean that you can’t change what you want to do later on. In fact, Singapore has licensed aircraft engineers that deal with both branches of electronics and mechanics.

If you want to cross from one side to the other, the trend is that those who are in aerospace electronics will go on to study Electrical & Electronics Engineering in university and subsequently you can choose also to specialize in aerospace topics in final year. Because if you are from electronics, and you have no mechanical background, to go into aerospace engineering will be quite a steep learning curve.

CY: I can only say that, even having been at the company for close to 4 years now, I’m not fully versed at every component of the engine (there are too many!) so there is always something new to learn and a constant need to educate yourself. Because what you see in one component may not be what you see in another, each having and performing different functions in an engine. So, there is still a need to upgrade yourself, reading up about the new technology, like 3D printing. For example, General Electric is currently using 3D printing to print some of their components; only through reading up on these and gathering new information about new technology can you keep yourself updated about your work. As for me, I am currently taking a part-time Master’s degree in Mechanical Engineering.

I’ve had some friends who’ve left the aerospace industry: some of them have gone into into banking, some of them into oil & gas – which is  somewhat of a change, but what you have learnt in engineering still applies. Some of them have moved to take on more of the operations side, as operations executives, people who do planning and project management. So, the door is open for you to move on to other pathways even if you are in an engineering degree. The sky is the limit!

CY: In my junior college days, physics was amongst my better subjects (I was in triple science), and this sort of propelled me towards engineering. I also preferred to find out how things work and try more hands-on stuff. So, aerospace engineering was quite new back then and my interest in planes helped made the decision. Some people would think that being an aerospace engineer is kind of prestigious – they usually go ‘wow’ when they hear that you are from aerospace. But for me, I think it’s just playing a small part in contributing to society and of course, helping to ensure that aviation is safe for all. I think that is what matters the most. So, if I were to say what I do, I would just say that I am an engineer.