Aerospace Blog

When people hear the acronym FOD, they think "what is that?" People in the aviation or aerospace industry know that FOD stands for Foreign Object Damage. In the field, FOD is a bad name that you don't want to be associated with. Foreign objects can be anything from a small piece of metal that broke-off one of your tools to a bird, a lost screw, or even a piece of material from your clothing – like a button, for example.

Foreign objects can get into jet engines and cause serious damage. Jet engines can have very strong intakes, so strong that people have been sucked into them before – and if a person can get sucked into an engine, it's no problem for a small piece of material to get sucked in too. FOD can happen to engines happen plain and simple. This damage is just part of the business, but it's a part that you want to minimize at all costs since some engines can cost over a million dollars.

In my personal experience in the U.S. Navy, before the jets would take-off, the whole squadron would do what is called a "FOD walk down". This is where everybody is lined up next to each other walking down the flight line, where the jets start up, or where people are doing work on the aircraft. They walk very slowly with their heads down, looking for anything that can be sucked into the intake. I've personally recovered screw tip heads, bearings, rocks, even a screw driver, amongst many other things. When doing this, you have to take it seriously since people's lives are at stake; if people are talking and not paying attention while doing the walk down, stuff can be missed.

I actually saw what happens when being careless can cause FOD. One of our jets was getting ready for a take-off on the flight line and when it was accelerating, one of the jet engines flamed-out with black smoke coming from it. The pilot almost lost control of the aircraft since he was about to take-off, but luckily didn't crash or eject. On a side-note - pilots hate to eject, so they'll stick with their aircraft through almost anything. Possibly one reason pilots hate doing this is the fact that they're sitting on a rocket launcher. When a pilot ejects, the compression is so powerful that after ejection they're a half inch shorter due to the compression.

After the pilot recovered, he came back to the hangar and shutdown the plane. We took down the engine to inspect what had happened. To those of you that don't know what an aircraft engine is composed of, it has over a hundred very thin, metal fan blades that are very closely put together among other things. After looking at it, we realized that something had gotten sucked into the intake. When the object hit the fan blades, it caused a chain reaction to the blades and they started taking each other out – almost like a domino effect. It turns out that someone's plastic button had fallen off of their uniform, and was sucked into the engines intake. So you ask yourself, "What harm could a button, that probably cost 5 cents to make, do?" Well, in this instance, it almost cost a pilot his life and it broke a million dollar engine.