"Foreign Object Damage (FOD) is any damage attributed to a foreign object that can be expressed in physical or economic terms that may or may not degrade the product's required safety and/or performance characteristics". (National Aerospace Standard 412).
Most frequently, FOD damage is caused by bird strikes, stones, hail, ice, or bolts and metal shavings left on runways. Any of these can cause an engine to ‘throw a blade’ – to break apart in a way where parts fly off at high speed.
It is estimated that FOD costs the aerospace industry some US$4 billion per year causing:
It is physically impossible for a pebble, hailstone, ice or bolts to penetrate the vortex tubes, therefore the Centrisep EAPS offers formidable protection against engine Foreign Object Damage. In some applications, fitting mesh screens upstream or downstream of the main Centrisep EAPS may be recommended.
The Centrisep units are tested on FAR specification equipment for bird strikes, stones, hail, etc. A bird strike or large foreign objects could significantly damage the Centrisep EAPS, but the debris would not be ingested by the engine.
During the first Gulf War in 1991, the CH-47 Chinook helicopters protected by Centrisep EAPSs suffered less FOD and engine erosion damage than the CH47 helicopters operating in the same environment with no engine protection
Example: For a protected CH-47 helicopter, the average removal rate was 1.2 engines per 1000 flight hours. For the CH-47s not fitted with Centrisep EAPS, the average removal rate was 25 engines per 1000 flight hours.
