Jan
15
2009

Why There Are No Screens On Jet Engines

Firstly I want to state for the record that I am NOT an aircraft engineer, nor am I a pilot. I am an aviation buff and I love aviation (including military aircraft also known as “air power”). So I do know flight engineers, pilots, aircraft designers and other members of the aviation field.

That being said, since the crash this morning I’ve had people ask why there aren’t screens on jets. Here is the answer that I have learned over the years.

The reason I asked was that in my military career and volunteering for aviation related events such as the Alaska Air Show, one of the big concerns for aviation personel is FOD (Foreign Object Debris) getting out on the flight line and endangering lives and equipment.

So here is the answer as told to me by military and civilian aviation members. There are simple reasons that it will not make any difference:

  1. The thrust would be affected by the screens (imagine a screen door after a big windstorm and all the bugs, etc. that clog it up) during regular flights
  2. The weight of the screens necessary to stop, say, a Canadian Goose would add significant weight to the engines (additional shearing stress)
  3. Icing (simply put if the jets are in a moisture rich strata at the right altitude, ice will form on the screens and cut off air to the engines)
  4. At the typical speed a bird will impact aircraft, the screen would be useless and most likely cause clogging of the intake or damage to the engine as well
  5. The chances of a bird being sucked into an engine is less than someone being struck by lightning so it’s considered a moot point

Migratory birds (like herd animals) are attracted to large open areas. Reason being is the flock can see predators at a good distance…it’s essentially a safety measure.

What needs to be done at airports is to let hunters (specifically falconers) hunt the birds. Birds naturally avoid areas where predators roam and warn others of the danger so that most areas stay empty to avoid the predator. Natural predators such as dogs and birds of prey have been more successful than horns and remote aircraft in dispersing bird populations at airports.

When the FAA did a study they stated it was too cost prohibitive to manage birds of prey and dogs at airports, however they forget that there are hunters that use birds of prey and dogs and would probably love to allow their animal companions to be able to train not hunt in the open fields at airports.

Sorry…I’m digressing. The simple answer is that it’s a rare occurrence and that the engineering needed to place some kind of screen on a plane is just not there yet.

At least not anything that is cost effective.

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