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In aviation and aerospace, foreign object debris (FOD), is any particle or substance, alien to an aircraft or system, which could potentially cause damage. External FOD hazards include bird strikes, hail, ice, sandstorms, ash-clouds or objects left on the runway. Internal FOD hazards include items left in the cockpit that interfere with flight safety by getting tangled in control cables, jam moving parts or short-out electrical connections. The term FOD is used to describe both the foreign objects themselves, and any damage attributed to them.


Jet engine design and FOD

Modern jet engines can suffer major damage from even small objects being sucked into the engine. The FAA (
Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...
) requires that all engine types pass a test which includes firing a fresh chicken (dead, but not frozen) into a running jet engine from a small cannon. The engine does not have to remain functional after the test, but it must not cause significant damage to the rest of the aircraft. Thus, if the bird strike causes it to "throw a blade" (break apart in a way where parts fly off at high speed), doing so must not cause loss of the aircraft.


Engine and airframe designs which avoid FOD

Some military aircraft 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 A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust ...
-powered
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...
s, such as the
Mi-24 The Mil Mi-24 (russian: Миль Ми-24; NATO reporting name: Hind) is a large helicopter gunship, attack helicopter and low-capacity transport helicopter, troop transport with room for eight passengers. It is produced by Mil Moscow Helicopter ...
, 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 Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
n Mikoyan MiG-29 and
Sukhoi Su-27 The Sukhoi Su-27 (russian: Сухой Су-27; NATO reporting name: Flanker) is a Soviet-origin twin-engine supermaneuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large US fourth-generation je ...
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 the Antonov An-74 which has a very high placement of the engines.
Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...
offered a gravel runway kit for early 737s 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 Airbus SE (; ; ; ) is a European multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace products worldwide and manufactures aircraft throughout the world. The company has three divisions: '' ...
engineers are investigating 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.


FOD damage examples


Vehicle tire track-in

Debris is often trapped in the treads of tires from vehicles coming onto an airfield. Types of debris trapped in a vehicle tire can include rocks, mud, stones, loose hardware (screws, washers, bolts, ect.) and many other forms of small materials. These can be crew & fuel trucks, maintenance vehicles and many others that inadvertently bring and deposit debris around a flight line. These types of FOD are very difficult to track and manage once they are introduced into the airfield. The debris can then easily be picked up by jet engine intake, engine blast and prop/rotor draft. This material, once loose around operational aircraft, can lead to serious safety concerns including personnel injury and equipment/property damage.


Runway debris

The crash of a
Concorde The Aérospatiale/BAC Concorde () is a retired Franco-British supersonic airliner jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC). Studies started in 1954, and France an ...
,
Air France Flight 4590 On 25 July 2000, Air France Flight 4590, a Concorde passenger jet on an international charter flight from Paris to New York, crashed shortly after takeoff, killing all 109 people on board and four on the ground. It was the only fatal Concorde ...
, at
Charles de Gaulle Airport Paris Charles de Gaulle Airport (french: Aéroport de Paris-Charles-de-Gaulle, ), also known as Roissy Airport or simply Paris CDG, is the principal airport serving the French capital, Paris ( and its metropolitan area), and the largest inter ...
near
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
on 25 July 2000 was caused by FOD; in this case a piece of
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion i ...
debris on the runway which had been part of a thrust reverser that had fallen from a
Continental Airlines Continental Airlines, simply known as Continental, was a major United States airline founded in 1934 and eventually headquartered in Houston, Texas. It had ownership interests and brand partnerships with several carriers. Continental started ...
McDonnell Douglas DC-10 The McDonnell Douglas DC-10 is an American trijet wide-body aircraft manufactured by McDonnell Douglas. The DC-10 was intended to succeed the DC-8 for long- range flights. It first flew on August 29, 1970; it was introduced on August 5, 19 ...
during takeoff about four minutes earlier. All 100 passengers and nine crew on board the flight, as well as four people on the ground, were killed. A Gates Learjet 36A, registration number N527PA, was taking off from Newport News/Williamsburg International Airport in
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...
on March 26, 2007, when the crew heard a loud "pop". Aborting the takeoff, the crew tried to control the "fishtailing" and activate the drogue parachute. The parachute did not work and the Learjet ran off the runway, its tires blown. Airport personnel reported seeing rocks and pieces of metal on the
runway According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt, concrete ...
after the accident. The
National Transportation Safety Board The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and inci ...
said that the accident was caused by FOD on the runway. Failure of the drogue parachute contributed to the accident.


Volcanic ash

On 24 June 1982, British Airways Flight 9 en route to
Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...
,
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, flew into a volcanic ash cloud over the Indian Ocean. The
Boeing 747-200B The Boeing 747 is a large, long-range wide-body airliner designed and manufactured by Boeing Commercial Airplanes in the United States between 1968 and 2022. After introducing the 707 in October 1958, Pan Am wanted a jet times its size, t ...
suffered engine surges in all four engines until they all failed. The passengers and crew could see a phenomenon known as St. Elmo's fire around the plane. Flight 9 dived down until it exited the cloud allowing the airborne ash to clear the engines, which were then restarted. The cockpit windshield was badly pitted by the ash particles but the aircraft landed safely. On 15 December 1989,
KLM Flight 867 On 15 December 1989, KLM Flight 867, en route from Amsterdam to Narita International Airport Tokyo, was forced to make an emergency landing at Anchorage International Airport, Alaska, when all four engines failed. The Boeing 747-400, less than ...
, en route to
Narita International Airport Narita International Airport ( ja, 成田国際空港, Narita Kokusai Kūkō) , also known as Tokyo-Narita, formerly and originally known as , is one of two international airports serving the Greater Tokyo Area, the other one being Haneda Airpo ...
,
Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, with an estimated 37.46 ...
flew through a thick cloud of volcanic ash from Mount Redoubt, which had erupted the day before. The
Boeing 747-400 The Boeing 747-400 is a large, long-range wide-body airliner produced by Boeing Commercial Airplanes, an advanced variant of the initial Boeing 747. The "Advanced Series 300" was announced at the September 1984 Farnborough Airshow, targeti ...
's four engines flamed out. After descending more than 14,000 feet, the crew restarted the engines and landed safely at Anchorage International Airport.


Item jettisoned from aircraft

An unusual case of FOD occurred on 28 September 1981 over
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...
. During flight testing of an
F/A-18 Hornet The McDonnell Douglas F/A-18 Hornet is an all-weather, twin-engine, supersonic, carrier-capable, multirole combat aircraft, designed as both a fighter and attack aircraft (hence the F/A designation). Designed by McDonnell Douglas (now pa ...
, the
Naval Air Test Center Naval Air Station Patuxent River , also known as NAS Pax River, is a United States naval air station located in St. Mary’s County, Maryland, on the Chesapeake Bay near the mouth of the Patuxent River. It is home to Headquarters, Naval Air Sys ...
of the
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
was using a
Douglas TA-4J Skyhawk The Douglas A-4 Skyhawk is a single-seat subsonic carrier-capable light attack aircraft developed for the United States Navy and United States Marine Corps in the early 1950s. The delta-winged, single turbojet engined Skyhawk was designed a ...
as a
chase plane A chase plane is an aircraft that "chases" a "subject" aircraft, spacecraft or rocket, for the purposes of making real-time observations and taking air-to-air photographs and video of the subject vehicle during flight. Background Safety can ...
to film a jettison test of a bomb rack from the Hornet. The bomb rack struck the right wing of the Skyhawk, shearing off almost half the wing. The Skyhawk caught fire within seconds of being struck; the two persons on board ejected.


Bird strikes

On 20 November 1975 a
Hawker Siddeley HS.125 The British Aerospace 125 is a twinjet mid-size business jet. Originally developed by de Havilland and initially designated as the DH.125 Jet Dragon, it entered production as the Hawker Siddeley HS.125, which was the designation used until 19 ...
taking off at
Dunsfold Aerodrome Dunsfold Aerodrome (former ICAO code EGTD) is an unlicensed airfield in Surrey, England, near the village of Cranleigh. It extends across land in the villages of Dunsfold and Alfold. It was built by the Canadian Army and civilian contracto ...
flew through a flock of
northern lapwing The northern lapwing (''Vanellus vanellus''), also known as the peewit or pewit, tuit or tew-it, green plover, or (in Ireland and Britain) pyewipe or just lapwing, is a bird in the lapwing subfamily. It is common through temperate Eurosiberia ...
s immediately after lifting off the runway and lost power in both engines. The crew landed the aircraft back on the runway but it overran the end and crossed a road. The aircraft struck a car on the road, killing its six occupants. Although the aircraft was destroyed in the ensuing fire, the nine occupants of the aircraft survived the crash. On 17 November 1980 a Hawker Siddeley Nimrod of the
Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
crashed shortly after taking off from
RAF Kinloss Royal Air Force Kinloss or RAF Kinloss is a former Royal Air Force (RAF) station located near the village of Kinloss, on the Moray Firth in the north east of Scotland. The RAF station opened on 1 April 1939 and served as a training establishme ...
. It flew through a flock of Canada geese, causing three of its four engines to fail. The pilot and copilot were killed; the pilot was subsequently
posthumously Posthumous may refer to: * Posthumous award - an award, prize or medal granted after the recipient's death * Posthumous publication Posthumous publication refers to material that is published after the author's death. This can be because the auth ...
awarded an Air Force Cross for his actions in maintaining control of the aircraft and saving the lives of the 18 crew. The remains of 77 birds were found on or near the runway. On January 15, 2009,
US Airways Flight 1549 US Airways Flight 1549 was a regularly scheduled US Airways flight from New York City (LaGuardia Airport), to Charlotte and Seattle, in the United States. On January 15, 2009, the Airbus A320 serving the flight struck a flock of birds short ...
flew into a flock of Canada geese and suffered a double engine failure. The pilot
ditch A ditch is a small to moderate divot created to channel water. A ditch can be used for drainage, to drain water from low-lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. Ditches ar ...
ed the aircraft in the Hudson River, saving the lives of all on board.


Wildlife and wetlands near airports

Significant problems occur with airports where the grounds were or have become nesting areas for birds. While fences can prevent a
moose The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult ma ...
or
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...
from wandering onto a runway, birds are more difficult to control. Often airports employ a type of
bird scarer Bird scarers is a blanket term used to describe devices designed for deterring birds by startling, confusing or otherwise repeling them, typically employed in commercial settings by farmers to dissuade birds from consuming and defecating on rece ...
that operates on propane to cause a noise loud enough to scare away any birds that might be in the vicinity. Airport managers use any means available (including trained falcons as well as robird flapping-wing falcon-like drones) to reduce bird populations. Another solution under investigation is the use of
artificial turf Artificial turf is a surface of synthetic fibers made to look like natural grass. It is most often used in arenas for sports that were originally or are normally played on grass. However, it is now being used on residential lawns and commerc ...
near runways, since it does not offer food, shelter, or water to wildlife.


Conferences

In the United States, the most prominent gathering of FOD experts has been the annual National Aerospace FOD Prevention Conference. It is hosted in a different city each year by National Aerospace FOD Prevention, Inc. (NAFPI), a nonprofit association that focuses on FOD education, awareness and prevention. Conference information, including presentations from past conferences, is available at the NAFPI Web site. However, NAFPI has come under some critique as being focused on tool control and manufacturing processes, and other members of the industry have stepped forward to fill the gaps. BAA hosted the world's first airport-led conference on the subject in November 2010.


Detection Technologies & FOD Prevention

There is some debate regarding FOD detection systems as the costs can be high and the domain of responsibility is not clear. However, one airport claims that their FOD detection system may have paid for itself in a single incident where personnel were alerted to a steel cable on the runway, before a single aircraft was put at risk. The FAA has investigated FOD detection technologies, and has set standards for the following categories: *Radar *Electro-optical (visible band imagery (standard CCTV) and low light cameras) *Hybrid * RFID on metal *Manufactured FODS Mats - Track-Out Prevention & Track-In Control
Chennault International Airport FODS Mats


Damage tolerance improvements

The negative effects from FOD can be reduced or entirely eliminated by introducing compressive residual stresses in critical fatigue areas into the part during the manufacturing process. These beneficial stresses are induced into the part through cold working the part with peening processes: shot peening, or laser peening. The deeper the compressive residual stress the more significant the fatigue life and damage tolerance improvement. Shot peening typically induces compressive stresses a few thousandths of an inch deep, laser peening typically imparts compressive residual stresses 0.040 to 0.100 inches deep. Laser peen induced compressive stresses are also more resistant to heat exposure.


Technologies, information and training materials helpful in preventing FOD

*Aerospace tool control systems *FOD prevention program manuals *Magnetic bars *Promotional and awareness materials *Tool and parts control/retrieval *Tow-behind friction sweeper *Tow-behind sweepers *Training materials *Vacuum truck sweepers *Walk-behind sweepers *FOD prevention mats


Economic impact

Internationally, FOD costs the aviation industry US$13 billion per year in direct plus indirect costs. The indirect costs are as much as ten times the direct cost value, representing delays, aircraft changes, incurred fuel costs, unscheduled maintenance, and the like. and causes expensive, significant damage to aircraft and parts and death and injury to workers, pilots and passengers. It is estimated that FOD costs major airlines in the United States $26 per flight in aircraft repairs, plus $312 in such additional indirect costs as flight delays, plane changes and fuel inefficiencies. "There are other costs that are not as easy to calculate but are equally disturbing," according to UK Royal Air Force Wing Commander and FOD researcher Richard Friend.Make It FOD Free
website
"From accidents such as the Air France Concorde, Flight AF 4590, there is the loss of life, suffering and effect on the families of those who died, the suspicion of malpractice, guilt, and blame that could last for lifetimes. This harrowing torment is incalculable but should not be forgotten, ''ever''. If everyone kept this in mind, we would remain vigilant and forever prevent foreign object debris from causing a problem. In fact, many factors combine to cause a chain of events that can lead to a failure."


Studies

There have only been two detailed studies of the economic cost of FOD for civil airline operations. The first was by Brad Bachtel of
Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...
, who published a value of $4 billion USD per year. This top-down value was for several years the standard industry figure for the cost of FOD. The second work (2007) was by Iain McCreary from the consultancy Insight SRI Ltd. This more detailed report offered a first-cut of the cost of FOD, based on a bottom-up analysis of airline maintenance log records. Here, data was broken into ''per flight direct costs'' and ''per flight indirect costs'' for the top 300 global airports, with detailed footnotes on the supporting data. The Insight SRI research was a standard reference for 2007-2009 as it was the only source presenting costs and thus was quoted by regulators, airports, and technology providers alike. However, while that 2007 Insight SRI paper remains the best free public source of data, the new analysis (2010) from Insight SRI offers new numbers. The author of the new report (not free) says "Readers are cautioned not to rely on or in the future refer to numbers from the 2007-08 Insight SRI paper ''The Economic Cost of FOD to Airlines''. This earlier effort was 'The' first document detailing the direct and indirect cost of FOD that was based on airline maintenance data (the entire document was a single page of data, followed by 8 pages of footnotes)." Per-flight direct costs of $26 are calculated by considering engine maintenance spending, tire replacements, and aircraft body damage. Per-flight indirect costs include a total of 33 individual categories: #Airport efficiency losses #Carbon / environmental issues #Change of aircraft #Close airport #Close runway #Corporate manslaughter/criminal liability #Cost of corrective action #Cost of hiring and training replacement #Cost of rental or lease of replacement equipment #Cost of restoration of order #Cost of the investigation #Delay for planes in air #Delays at gate #Fines and citations #Fuel efficiency losses #Hotels #In-air go-around #Increased insurance premiums #Increased operating costs on remaining equipment #Insurance deductibles #Legal fees resulting #Liability claims in excess of insurance #Loss of aircraft #Loss of business and damage to reputation #Loss of productivity of injured personnel #Loss of spares or specialized equipment #Lost time and overtime #Missed connections #Morale #Reaction by crews leading to disruption of schedule #Replacement flights on other carriers #Scheduled maintenance #Unscheduled maintenance The study concludes that when these indirect costs are added, then the cost of FOD increases by a multiple of up to 10 times. Eurocontrol and the FAA are both studying FOD. Eurocontrol released a preliminary assessment of FOD detection technologies in 2006, while the FAA is conducting trials of the four leading systems from Qinetiq (PVD, Providence
T. F. Green Airport Rhode Island T. F. Green International Airport is a public international airport in Warwick, Rhode Island, United States, south of the state's capital and largest city of Providence. Opened in 1931, the airport was named for former Rhode Isl ...
), Stratech (ORD, Chicago
O'Hare International Airport Chicago O'Hare International Airport , sometimes referred to as, Chicago O'Hare, or simply O'Hare, is the main international airport serving Chicago, Illinois, located on the city's Northwest Side, approximately northwest of the Loop busines ...
), Xsight Systems (BOS, Boston
Logan International Airport General Edward Lawrence Logan International Airport , also known as Boston Logan International Airport and commonly as Boston Logan, Logan Airport or simply Logan, is an international airport that is located mostly in East Boston and partial ...
), and Trex Aviation Systems (ORD, Chicago O'Hare Airport) during 2007 and 2008. Results of this study should be published in 2009.


References


External link

* {{DEFAULTSORT:Foreign Object Damage Aviation risks