Understanding Foreign Object Damage (FOD) in Aviation
Foreign Object Damage (FOD) is a critical concern in aviation, posing risks to aircraft safety, operational efficiency, and maintenance costs. FOD refers to any damage caused by foreign objects that enter an aircraft or its operating environment, leading to potential hazards.
Foreign Object Debris (FOD) is a substance, debris or object that does not belong to an aircraft or system which would potentially cause damage.
FOD is an abbreviation often used in aviation to describe both the damage done to aircraft by foreign objects, and the foreign objects themselves.
FOD can result from debris, loose tools, birds, ice, or any object that is foreign to an aircraft’s normal operation. These objects can be found on runways, taxiways, aprons, or even within an aircraft’s engine or fuselage. The consequences of FOD range from minor dents and scratches to catastrophic engine failure, endangering both crew and passengers.
When golfing, golfers teeing up a putt are not just lining up the shot but also checking for any FOD that might stand between their ball and perhaps the glory of winning the open championship. In aviation, FOD can be even more important because history has shown that it can lead to accidents that cost lives.
Notable Accidents Caused by FOD
FOD has been directly responsible for several major aviation accidents. In some cases, a small, seemingly insignificant object has triggered disastrous consequences.
One of the most well-known FOD-related accidents was the crash of Air France Flight 4590, a Concorde, on July 25, 2000. A piece of titanium debris from a previously departed aircraft lay on the runway at Charles de Gaulle Airport. As the Concorde took off, this debris punctured a tire, causing it to explode. The resulting rubber fragments struck the fuel tank, leading to a catastrophic fire and loss of control, ultimately resulting in the deaths of all 100 passengers, nine crew members, and four people on the ground.
On 7 June 2013, stabiliser trim control cable, pulley and drum damage were discovered on a Boeing 737-800 undergoing scheduled maintenance at Auckland. The Investigation found the damage to have been due to a rag which was found trapped in the forward cable drum windings and concluded that the integrity of the system which provided for stabiliser trim system manual control by pilots had been compromised over an extended period. The rag was traced to a specific Australian maintenance facility which was run by the Operator's parent company and which was the only user of the particular type of rag.
Another incident occurred on March 26, 2007, involving a Gates Learjet 36A at Newport News/Williamsburg International Airport in Virginia. During takeoff, the crew heard a loud "pop" and attempted to abort. The aircraft lost control and overran the runway due to FOD—rocks and metal debris were later found on the runway. The aircraft's drogue parachute failed to deploy properly, further exacerbating the situation. The National Transportation Safety Board determined that FOD played a significant role in the accident.
Common Sources of FOD
Runway and Ramp Debris: Loose bolts, rocks, pieces of pavement, or misplaced tools can be ingested into aircraft engines or cause tire damage.
Bird Strikes: Birds colliding with aircraft, especially near airports, can cause significant damage to engines and windshields.
Maintenance Negligence: Tools or equipment left behind after maintenance work can lead to mechanical failures.
Passenger and Crew Items: Objects like loose baggage items or misplaced belongings can contribute to FOD risks inside the aircraft.
Weather-related Debris: Ice, hail, and strong winds can introduce debris into aircraft components.
Improper Tool Control: Tools that are not properly accounted for during maintenance may be left behind, becoming a hidden hazard. That's why its a good practice to check your tools after every work performed.
FOD Prevention by Aircraft Design
Aircraft manufacturers have developed various design features to mitigate FOD risks. Many turboshaft-powered helicopters, such as the Mi-24, incorporate vortex-type or centrifugal air intakes. These force air into a spiral path before entering the engine, separating heavier debris before it can cause damage.
Fighter jets like the Mikoyan MiG-29 and Sukhoi Su-27 feature intake protection mechanisms for operations on rough airfields. Their main air intakes can be temporarily closed with mesh doors, while alternate inlets on top allow airflow for takeoff without drawing in foreign debris from the ground.
On a Cessna 208 it incorparate inertial separator which works by using the principle of inertia to separate large particles of debris from the air entering the engine essentially acting like a "slinger" that forces heavier particles to move outwards and be expelled through a bypass duct, protecting the engine from damage by foreign object debris (FOD) while still allowing clean air to flow in.
The Antonov An-74 reduces FOD risk by placing its engines high above the fuselage, far from runway debris. Similarly, Boeing offered a gravel runway kit for early 737 models, featuring gravel deflectors, retractable lights, protective screens, and vortex dissipators. These modifications allowed safe operations from unimproved airstrips by minimizing the risk of debris ingestion.
The Impact of FOD
The financial and safety implications of FOD are severe. The aviation industry incurs billions of dollars annually due to FOD-related damage, repair costs, and delays. Additionally, the risks to passenger safety make FOD prevention a top priority for airlines, airports, and maintenance teams.
Preventing FOD in Aviation
Regular Inspections: Conducting thorough runway and taxiway inspections to remove debris and hazards. Have you asked your self why on some airport after every aircraft taxiing of takeoff there is a car passing around the runway, infact this is some of the means used on some airport to inspect the runways/Taxiways for Foreign object debris.
Strict Maintenance Protocols: Ensuring all tools and equipment are accounted for after maintenance work. it's the responsibility of any crew working in aviation to be accountable for his/her tools. its a good practice to double check your tools before closing the job.
Bird Control Measures: Implementing wildlife management programs to reduce bird strikes.
Proper Training: Educating ground crews, pilots, and maintenance personnel on the dangers of FOD. Various training concerning airport safety must be conducted to improve awareness to the crews about the risk associated with the Foreign object debris.
Use of FOD Detection Technology: Employing advanced scanning and monitoring systems to detect and remove FOD before it becomes a threat.
Personal Awareness: Encouraging all aviation personnel to be vigilant and proactive in identifying and removing potential hazards.
FOD remains a significant challenge in aviation, but with strict preventive measures, continuous awareness, and technological advancements, its risks can be mitigated. By understanding the sources and impact of FOD, the aviation industry can work towards ensuring safer skies and reducing unnecessary maintenance costs.
FOD-prevention and clearance is the responsibility of all all airport users.
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