Editing Foreign object damage (section)

==Engine and airframe designs which avoid FOD==
Some military aircraft{{Citation needed|date=February 2012}} {{Which|date=May 2016}}had a unique design to prevent FOD from damaging the engine. The design included an S-shaped bend in the airflow, so that air entered the inlet, was bent back towards the front of the plane, and bent back again towards the back before entering the engine. At the back of the first bend a strong spring held a door shut. Any foreign object flying in the intake flew in, hit the door, opened it, flew through, and then exited the aircraft. Thus, only small objects swept up by the air could enter the engine. This design did indeed prevent FOD problems, but the constriction and drag induced by the bending of the airflow reduced the engine's effective power, and thus the design was not repeated.

A similar approach is used on many [[turboshaft]]-powered [[helicopter]]s, such as the [[Mil Mi-24|Mi-24]], which use a "vortex-type" or "centrifugal" intake, in which the air is forced to flow through a spiral path before entering the engine; the heavier dust and other debris are forced outwards, where it is separated from the airflow before it enters the engine inlet.

The [[Russia]]n [[Mikoyan MiG-29]] and [[Sukhoi Su-27]] fighters have a special intake design to prevent ingestion of FOD during take-off from rough airfields. The main air intakes could be closed with mesh doors and special inlets on the top of the intakes temporarily opened. This would allow enough airflow to the engine for take-off but reduced the chances of the engine sucking up objects from the ground.

Another interesting design to minimize the risk of FOD is that of the [[Antonov An-74]], which has a very high placement of the engines.

[[Boeing]] offered a [[Gravel kit|gravel runway kit]] for early [[Boeing 737|737]]s that allows the plane to be used from unimproved and gravel runways, in spite of having very low-slung engines. This kit included gravel deflectors on the landing gear; foldaway lights on the bottom of the plane; and screens that prevented gravel, which would enter the open wheelwells when the gear was extended, from hitting critical components.  The kit also included vortex dissipators, devices which would reduce the airflow into the engine from the bottom so as to reduce the likelihood of ingesting gravel.
  
[[Airbus]] engineers are investigating{{when|date=April 2023}} a novel approach to reducing FOD. By developing, in conjunction with [[Israel Aerospace Industries]], the [[Taxibot]], a tractor controlled by the pilot, aircraft will not need to use jet engines while taxiing, and therefore they will not be vulnerable to FOD on aprons or taxiways.<ref>{{cite web |title=Airbus MoU with IAI to explore eco-efficient 'engines-off' taxiing |date=17 June 2009 |url=http://www.aviationnews.eu/2009/06/17/airbus-mou-with-iai-to-explore-eco-efficient-engines-off-taxiing/ |access-date=2009-07-30}}</ref>