Airplane Engines & How They’re Linked To Recent Boeing 737 Max Troubles

If you are keeping up with the news, I am sure you have heard of all the kerfuffle about the Boeing Max Jets. The entire fleet of these awfully expensive new airliners has been grounded and is now gathering dust somewhere in a desert, much to the chagrin of the airlines that own or lease them.

 You might also have read that the troubles for this new jet are due to an untried and somewhat stealthy device that Boeing has built into these planes unbeknown to many of the pilots who fly them. The device is called MCAS – which stands for Maneuvering Characteristics Augmentation System – a mouthful. There is a good engineering justification for introducing this gizmo for the first time in the upgraded version of this immensely popular and world’s most successful airplane. It had to do with its new engines!

Let me elaborate. But first a quick primer on aero engines. You will notice these engines mostly hanging under the wing although in some of the older models they are attached to the body of the airplane called fuselage. From outside they do not look all that complicated and all you mostly see are their large fans and if you are really looking, may be a cone shaped tail pipe coming out from the back of the oval metal shell that surrounds the fan. The oval shell, incidentally, is called the nacelle.

Now, the aero engines are truly an engineering marvel. Imagine if you will, the power of almost 20 diesel locomotives or 100 V8 car engines packed into the size of a living room couch. It is these engines that make the airplane fly at speeds that are 10 times faster than a car and can carry anywhere between 50 to 500 passengers on a journey that can be up to 12 hours long. And in spite of all the recent troubles reported in the media, the airplanes and the engines that power them are incredibly safe. In fact, the only reason they make news is because they are so reliable and so infrequently have problems that when they do have a problem, it becomes big news.

So, what makes these engines so powerful? It is the way in which they generate their power or more correctly thrust. The aero engines work on the principle of gas turbines which continuously swallow large quantity of air, heat that air to temperatures that could easily melt the best steel around and then jets out that superheated air through the tail pipe at velocities that approach the speed of sound. There is of course a lot more that goes on under the hood, but that briefly is the essence of an airplane engine.

Now, let us come back to what the engines have to do with the Boeing Max Jet’s troubles. It has to do with the amount of fuel the engine burns. Clearly, we want to use as little gas as possible, both for the sake of environment but more importantly to keep the cost of flying low and affordable. It turns out the bigger the fans are the more efficient the turbines are and the less fuel the engines consume. Of course, there is a limit to which the fan size can be increased before it becomes counter- productive but we have to go a long way before that limit is reached.

On the Max Jets, what limited increasing the size of the fan was the physical room available below the wings where the engines were hung. Boeing came up with an ingenious solution – move the engine a little forward on the wing where there happened to be more room. So, that is what they did. But this created another problem – the nose of the airplane began to pitch upward under some flight conditions which was not good and could cause what is known as “stall” – a real no-no for flying machines as it could completely destroy lift that keeps the planes flying.

The MCAS was meant to automatically correct that problem when it sensed the airplane nose to be pitching up beyond its safe limits and prevent it from stalling. An excellent idea and I have no doubt the engineers at Boeing would eventually make it work. Hopefully that happens sooner rather than later and when the Max’s do begin to fly again, the flying public could once again board them, confident that they would safely get to their destination on an airplane that has those powerful and much more fuel efficient engines under their wings, working in harmony with the many systems that keep a modern airliner in the air…