What is Foreign Object Debris (FOD)?

Foreign object debris (FOD) is an inanimate object in the movement area that has no operational or aeronautical function and may endanger aircraft.

Definition

ICAO Annex 14 and EASA use the same words for the definition. The object must be inanimate, it must lie in the movement area, and it must have no operational or aeronautical function.

The FAA uses wider words. AC 150/5210-24A defines FOD as any object, live or not, in an inappropriate location in the airport environment. The object must have the capacity to injure airport or air carrier personnel and damage aircraft. Under the ICAO and EASA words, a live animal is a wildlife hazard. Under the FAA words, a live animal can be FOD. The AC advises that dead wildlife are better handled in the FOD programme, and live wildlife in the wildlife hazard programme. The two programmes overlap when aircraft strike wildlife.

FOD and foreign object damage

The two terms are not the same. Foreign object debris is the object. Foreign object damage is the harm that the object does. AC 150/5210-24A defines FOD damage as any damage that a foreign object causes and that can be expressed in physical or economic terms. The AC says that the letters FOD refer only to the debris. The older AC 150/5220-24 of 2009 lists FOD as either “foreign object debris” or “foreign object damage”.

Types of FOD

FOD can be any material, any colour and any size. The EASA and FAA lists of typical FOD match, and they are not complete:

• aircraft and engine fasteners (nuts, bolts, washers, safety wire)
• aircraft parts (fuel caps, landing gear fragments, oil sticks, metal sheets, trapdoors, tyre fragments)
• mechanics’ tools
• catering supplies
• personal items (badges, pens, luggage tags, drink cans)
• apron items (paper and plastic debris from catering and freight pallets, luggage parts, debris from ramp equipment)
• runway and taxiway materials (concrete and asphalt chunks, rubber joint materials, paint chips)
• construction debris (wood, stones, fasteners, metal objects)
• plastic and polyethylene materials
• natural materials (plant fragments, dead wildlife, volcanic ash)

AC 150/5210-24A also lists contaminants from winter conditions (snow and ice). It cites a one-year airport study from a EUROCONTROL workshop in 2008. In that study, over 60 percent of the known FOD items were metal, and 18 percent were rubber. Dark items made up nearly 50 percent. AC 150/5220-24 says that common FOD can be 1 in by 1 in (3 cm by 3 cm) or smaller.

Where FOD comes from

EASA guidance lists the sources. FOD may come from personnel, aerodrome infrastructure (pavements, lights and signs), the environment (wind and heavy rain), aircraft, vehicles and other equipment. The guidance gives examples:

• Aircraft servicing and maintenance leave rivets, bolts, tools, cabin waste and small luggage parts on the apron.
• Cargo areas release cargo strapping and plastic sheeting.
• Construction brings rocks, tools and vehicle parts onto the movement area.
• Vehicles carry mud and loose stones onto pavement on their tyres.
• Mowing disturbs vegetation and soil beside the pavement.
• Grass areas, ditches and fences collect light debris that wind can blow back onto the pavement.

The FAA adds movement by jet blast and weather. Outboard engines blow loose material from the shoulders onto the runway. Wind blows sand and plastic bags onto the flight area. Rain and drainage carry mud and pebbles. The AC says that FOD is often more common when construction starts. It also says that FOD may be more common in winter, when freeze and thaw cycles crack ageing pavement.

Pavement as a source

The pavement itself can make FOD. EASA guidance says that deteriorating pavements show spalling or cracks, and that pieces of concrete can break loose. It adds that asphalt and concrete pavements may be the most common source of FOD on an aerodrome. AC 150/5210-24A says the same. It adds that tests show that pavement joints and cracks are the main sources of the foreign objects that engines ingest.

The FAA PAVER manuals rate this by distress and by severity. Raveling is the dislodging of coarse aggregate particles from the surface. The manual counts the missing particles on a representative area of 1 square yard (1 square metre) of dense mix:

Other distresses carry a FOD rating too. At high severity, alligator cracking has pieces that rock under traffic and may cause FOD. Sweeping removes the pieces that are already loose. At high severity, concrete scaling goes on producing FOD, and routine sweeping is not enough.

AC 150/5380-6C states the concern. Pavement distress can generate loose material that strikes propellers or enters jet engines. All pavement inspections should address FOD. The EASA guidance asks for special attention to the cleaning of cracks and pavement joints.

What FOD does

AC 150/5210-24A lists the types of damage. FOD can cut aircraft tyres. Engines can ingest it. It can lodge in mechanisms that affect flight operations. Jet blast can throw FOD at people at high speed and injure them. AC 150/5380-6C adds that FOD can cause damage that nobody sees, which makes an aircraft unsafe to operate. The portion of the runway where aircraft take off is where departing aircraft are most open to FOD damage.

A named event

On 25 July 2000 the Concorde F-BTSC ran over a metal strip during its take-off run at Paris Charles de Gaulle. The strip came from another aircraft. It was 435 mm long and 1.4 mm thick. The second interim report of the BEA describes how the strip cut a tyre and how tyre debris ruptured a fuel tank in the wing. A fire followed and the aircraft crashed.

How airports find FOD

Finding FOD starts with inspections. ICAO Annex 14, paragraph 10.2.1, requires the movement area surfaces to be inspected and monitored as part of a maintenance programme. The objective is to avoid and eliminate FOD. The EASA acceptable means of compliance add these steps:

• periodic inspections on foot, including areas that vehicles cannot reach, such as grass
• added inspections in construction areas, after accidents or incidents, after material spills and in extreme weather
• an inspection of each aircraft stand before the arrival and before the departure of an aircraft
• a record of the source and the location of each FOD item
• a clean-as-you-go habit for all personnel, and extra lights on vehicles at night

AC 150/5210-24A gives more detail for runways. The most effective runway inspection uses two or more passes, which reduce the width that the inspector must check. For one pass, the inspector drives, whenever practical, against the direction of landing aircraft with the beacon and headlights on. Inspectors also check the stub taxiways, because people often miss them. Some airports hold all-hands FOD walks, where staff and volunteers collect FOD by hand. The AC notes that it is not always possible to record the location and origin of the FOD that people collect on such a walk.

Detection equipment

AC 150/5220-24 sets minimum performance specifications for four types of automated FOD detection equipment. People remain the baseline. The AC treats human observation as the fundamental baseline for detection systems.

The AC is not mandatory, except for equipment bought with Airport Improvement Program or Passenger Facility Charge funds. In 2023 the FAA reported on two studies. Both found more FOD collected on runways with a detection system than on a runway that only people inspected. A noteworthy part of the detections was wildlife. The FAA also said that automated technology cannot replace the manual inspections that 14 CFR Part 139 requires. Those inspections cover many other items, such as markings, signs and the pavement surface.

Drones

The FAA began a study in 2022 of whether drones can detect FOD. Its William J. Hughes Technical Center published a proof of concept in 2024. The workflow reached a 96 percent detection rate for the FOD items that AC 150/5220-24 specifies. It did not meet all requirements. The report lists a high false positive rate, slow data processing and no detection in low light and bad weather.

How airports remove FOD

EASA guidance says that people can remove FOD by hand or with mechanical equipment. The equipment includes sweepers, vacuum systems, jet air blowers, magnetic bars and FOD sweeping carpets. AC 150/5210-24A gives detail:

• Power sweepers clear cracks and joints. Metal bristles are not recommended, because bristles can detach and become FOD. The operator checks the pavement after sweeping.
• Vacuum systems use air flow to pick up debris.
• Jet air blowers should have a collection mechanism, so that the FOD does not move to another place on the airfield.
• Magnetic bars under vehicles pick up metal. They cannot pick up titanium, aluminium alloys, some stainless steels or plastics. People must clean them regularly.
• Friction mat sweepers trail behind a vehicle and sweep FOD into capture scoops.
• Rumble strips (FOD shakers) are not a widely accepted method any more. The AC says that they remove little from tyres. The best practice is to stop a vehicle at a checkpoint, look at the tyres and remove any object by hand.

For one isolated object on a runway, the AC says that removal by hand is the most efficient. The AC sets a test for mechanical equipment. The equipment must collect 90 percent of a set of test objects on one pass at 15 mph (25 km/h). The objects lie in a 10 ft by 10 ft (3 m by 3 m) square. They include a metal cylinder, a golf ball, a chunk of asphalt or concrete and a part of a runway light fixture. They also include a wrench, a piece of tyre rubber, a fuel cap and a lug nut.

FOD containers hold the debris that people collect. EASA and the FAA ask for closed containers that wind cannot empty. The containers stand at apron entry points, hangars, maintenance areas, aircraft stands and baggage areas. People empty them often. The records of what the containers hold show where the FOD comes from.

Rules

• ICAO. Annex 14, Volume I, paragraph 10.2.1 requires the surfaces of the movement area to be inspected and monitored as part of a maintenance programme. The objective is to avoid and eliminate FOD.
• EU. Point ADR.OPS.B.016 of Regulation (EU) No 139/2014 requires the aerodrome operator to establish and implement a FOD control programme. The programme covers personnel training, prevention, detection and removal. It also covers notice to aircraft operators about aircraft parts, and analysis of FOD data. The acceptable means of compliance add inspections on foot. They also add extra inspections in construction areas, after accidents or incidents, after material spills and in extreme weather. They ask the operator to record all FOD on a grid map of the aerodrome.
• US. 14 CFR 139.305(a)(4) requires prompt removal of mud, dirt, sand, loose aggregate, debris, foreign objects, rubber deposits and other contaminants. Section 139.305(a)(3) requires pavement free of cracks and surface deterioration that produce loose aggregate. Section 139.327 requires a daily self-inspection. AC 150/5380-6C says that all pavement inspections should address FOD. AC 150/5210-24A, which replaced AC 150/5210-24 on 8 February 2024, gives guidance on FOD management. It is advisory, and it is mandatory on projects that federal grants fund.

How it matters for airfield inspection

A pavement survey does not find loose objects. It finds the distresses that make them. TarmacView maps raveling, spalling and cracks with a drone, rates their severity and gives a Pavement Condition Index. The pavement owner can then plan repairs at the places where the pavement makes FOD.