#3 X-Planes

3. In terms of choosing a drive train to hover above the ground, the two companies choose completely different designs. Give some pros and cons of the two approaches. If you are the chief designer, which design would you choose and why?
Boeing choice to use the more conventional and proven method in the directional exhaust system. Since this system is already in use with the Marine Corps Harrier, it is known how this system will perform and what to expect. With the use of this system, the pilots will already have knowledge of how it works and how to control it effectively. The good thing about this system is that it has a limit number of moving parts involved, in which reduces the chances of a mechanical failure. One problem that is known about this system is that it has a tendency to ingest some of the directional exhaust into the engine causing a stall, and ultimately it could cause a crash. The team of Boeing experienced a slight stall when in testing but the crash was avoided.
Lockheed Martin went out of the box on their choice of a hovering drive train. They decided to implement a lift fan in the center of the aircraft while also using the directional exhaust. This approach is rather radical in the since that it had never been tried and the possibilities of a failure is high. The interesting thing about this system is that the airplane proved to be more stable during vertical landing due to the fact that the aircraft had two columns of air for support instead of just one. The lift fan proved to be much more powerful than the method that Boeing chose to implement, thus making the aircraft more adaptable. While in testing the Lockheed team discovered that the lift fan provided a “breath of fresh air” to the situation. This means that the lift fan directs fresh air from the top of the plane towards the ground creating an invisible shield protecting the engines from ingesting any of the exhaust air and causing a stall. The one downfall to this design is the large amount of mechanical moving parts involved. It makes since to minimize the amount of moving parts in an assembly in order to reduce the possibilities of failure, but Lockheed Martin did exactly the opposite and it paid off.
If it were up to me, I would choose to use Lockheed Martins drive train. Mainly because it has a lot more power, more stable, and it reduces the chances of an engine stall. The team of Lockheed Martin showed that they are willing to take risks and be truly innovative in their design, and it is because of this that I believe they received the contract. Although this system has more mechanically moving parts, I would suggest implementing a routine inspection of the aircraft to ensure the proper function of the hover drive train.