FOD: The Banal Threat

Google “the cost of FOD to airlines”and it defaults to “the cost of food for airlines.” The fact that Google doesn’t recognize the standard abbreviation for foreign object damage perhaps is not surprising as there has been only one major report done on the aggregate cost to industry and the author cannot identify specific carriers because they all want to remain anonymous.

Lack of candor is not helping to solve the problem, however. Although it is an exceedingly rare event that ends in tragedy, the direct cost of FOD, according to UK-based consulting firm Insight SRI, is $90,161 per 10,000 movements or approximately $380 million a year. Adjust for “a multiplier indirect effect” of 10 times and the actual cost becomes $3.8 billion.

These figures may somewhat understate the total impact as they take into account just the world’s 300 largest civilian airports, which collectively account for 55 million aircraft movements annually and see a disturbing 70,000 FOD incidents a year. Serious FOD strikes are put at 4 per 10,000 movements of which 3.2 are strikes to tires and 0.8 to engines, with 3.1 causing damage to the aircraft and a worrying 2.1 causing damage on the runway.

Also disturbing, according to the thesis “Effectiveness of FOD Control Measures” authored by Felice Procaccio of Embry-Riddle Aeronautical University, is that while 60% of respondents said they were aware of their airline’s or airport’s FOD control methodologies, fewer than 60% responded that they engaged in recurrent training or could identify the cost of FOD to their organization.

That apparent lack of focus is borne out by Iain McCreary, MD of Insight SRI, who says airlines treat FOD expense simply as “the cost of doing business. It is considered normal that most engines have blended blades. Tire contracts are priced to include replacements due to FOD damage. However, it is clear that if the FOD were removed, these costs would similarly disappear. FOD must therefore be considered not only a safety risk and a nuisance, but an area where airlines might start to claw back significant value from operations,” says McCreary, a former physicist from Los Alamos National Laboratory and author of “The Cost of FOD.”

The Insight report cites a large but anonymous US airline that reported 117 engine FOD events at a single airport over a 12-month period: “From those events, they replaced 65 blade pairs, blended 80 blades and made more than 57 technical inspections.” These events were found during nonroutine flight line checks, which meant that aircraft had to be removed from service, causing significant disruptions and costs.

Tire Damage 

The most famous instance of FOD damage involved a burst tire and tires are a major victim of FOD. According to Insight, the anonymous US airline “experienced 32 punctures requiring replacement and 158 tears of which 80% required replacement and 20% were within service limits; and seven gouges, all of which required replacements, at one airport” over a 12-month period.

“This is equivalent to a rate of 5.3 replacements per 10K movements at a total cost of $17,283,” says McCreary. He adds, “ATA statistics for unseen tire damage for US airlines show that 2.5% of all tires sent for retread fail due to embedded FOD.” As tires are sent every 100 flights, the net cost for tires failing retread is thus $39,000 per 10K movements. He notes that reliable civil aviation data on FOD damage to aircraft skin or airframes does not exist but this is considered only about 2% of tire cost, and “vanishingly small” compared to what is spent on engine repair.

He concedes that there are no case studies or specific examples of the indirect costs of FOD damage; “The closest parallel we can make is with apron safety events.” Citing data from Flight Safety Foundation, he says, “Indirect costs for such events are 12 to 13 times direct costs.” Insight has taken the FSF list of indirect costs and added some FOD-specific costs to come up with a list of 33 indirect costs.

For the cost of delays, McCreary’s team used a Sabre study that found a weighted average of $40 per min. per aircraft. The survey found that US airports generally do not record the amount of time a runway is shut down for FOD, but some of the larger European airports do so. “Data from two of the larger European airports indicate that their runways are shut down for an average 200-240 min. per month due to FOD and wildlife, and that in excess of 90% of that closure time is due to FOD,” he says. Pulling all the numbers together, the Insight report says FOD-caused delays cost $26,740 per 10K movements, or well over $1 million per year at large airports.

Another major indirect cost is the loss of fuel efficiency of blended blades as a result of FOD ingestion. According to GE, most aircraft in a typical fleet will have at least 30% of blades blended and up to 90% of the aircraft in a typical fleet have blended blades. Blending can drive an efficiency loss of 0.5%, according to GE and Pratt & Whitney data.

FOD Incursion 

Offering another perspective, McCreary proposes that FOD should be seen as a runway incursion: “It is relatively easy to argue that FOD is simply an invisible runway incursion. Severe FOD incidents are just as dramatic as an incursion.”

There has been only one airport-wide study of FOD, conducted by the UK CAA during 2004. It listed the dimensions and type of each item and photographed them. Not surprisingly, 55% of the items were located in the ramp area, 30% on the taxiways and 15% on the runway. Also not surprisingly, according to a Delta Air Lines forensic analysis conducted by FAST of Prescott, Ariz., the 15% of runway debris caused 50% of all FOD damage, with 40% on taxiways and only 10% on the ramp.

“Runways are the most important area to monitor for FOD from a safety perspective. Aircraft speed and engine spin rates mean that FOD ingestion during takeoff and landing is more likely to pose a serious threat,” McCreary notes. Delta also found that the largest source of FOD (45%) was aircraft parts, followed by luggage and passenger equipment (17.5%), ground vehicles and tools (15%), concrete and bitumen (11.5%) and other (11%).

A French study done on Automatic FOD Detection Systems for a Eurocontrol workshop in 2008 found that more than 60% of FOD items were made of metal followed by rubber at 18%. Dark-colored items made up nearly 50% of collected FOD and common dimensions can be 1x1-in. (3x3-cm.) or smaller.

Runway Success 

Until September 2009 when FAA published an Advisory Circular on Airport Foreign Object Damage Detection Equipment, no formal document on detection technology existed from any national safety regulator. In Europe, however, SESAR’s ATM Master Plan published in 2008 included automatic FOD detection technology in its Implementation Phase 1, with an initial operating date of 2009. In parallel, both EUROCAE and ECAC have set up FOD detection working groups to standardize equipment specifications and operational procedures.

With runways the major focus, new technology introduced by QinetiQ with Tarsier and Stratech’s iFerret is offering a dramatic improvement in locating debris. This is put into sharp focus by Colin Wood, head of airside operations at London Heathrow. “BAA does four runway inspections a day. Tarsier does a sweep every 68 seconds. There has been FOD detected by the radar which would not normally have been picked up due to the frequency of the runs we normally carry out,” he says.

Vancouver International Director-Airside Operations Brett Patterson says the airport’s Tarsier success was highlighted by a single event in its second year of operation. “During that event, Tarsier alerted us to the presence of FOD on our southern runway. The FOD picked up by Tarsier was a long steel cable from a fueling truck. We were able to dispatch someone to retrieve it before any aircraft were exposed to the risk from the cable. That one single event may have paid for Tarsier in its entirety and proved to us we made the right investment.”

Importantly, Patterson highlights that “the automation efficiencies of Tarsier have reduced average FOD retrieval times from nine minutes to five minutes, and that time saving allows runway capacity gains of between two and four slots during peak periods.”

Singapore-based Stratech’s iFerret system has a detection range of up to 300 m. per sector and can locate FOD with a 10-cm. position accuracy, scan the entire 4.4-km. runway in 2 min. and find FOD down to 10 mm. in size. Like the Tarsier system, the iFerret sensors can locate items of debris at night and in 16 mm. of rain.

FOD Sweep Up 

Another cleanup system uses Australia-based Aerosweep’s FOD Boss sweeping mats, which can cover an area almost double that of a suction sweeper in a single-mat configuration and nearly five times in a triple configuration. In a trial in Belgium, FOD Boss was used after a suction sweeper on three different occasions and picked up between 21.6 kg. and 27.9 kg. around 18 gates. In another trial, Delta found that the product cut FOD tire damage by 43%. One US Air Force base experienced zero FOD incidents for seven quarters after deploying FOD Boss.

“Things are changing, with mandated runway scanning on the agenda,” McCreary agrees, but he warns that new liability and operational issues loom. Today a twice-daily visual runway inspection may find an average of one piece of FOD every two months, whereas automatic scanning will find one piece every two days, increasing workload and runway closures, he says. “There is a liability issue every time the scanners detect an object.”

One airline experiencing minimal FOD problems is Air New Zealand, which has a robust cleanup program with the issue getting “a great deal of attention during induction and recurrence training across the business,” according to spokesperson Mark Street.

“As well as group standards, each key area of the business also has its own localized initiatives,” Street notes. “For instance, at the Auckland domestic terminal there are pre-arrival gate FOD checks, FOD sweeps performed a number of times daily, scheduled nightly mechanical FOD sweeps by the airport, monthly Health and Safety Hazard walkarounds including FOD ‘prone’ area reporting [and] monthly airport Apron Safety meetings where FOD is a discussion topic. FOD damage across the business is pretty rare.”

Such efforts notwithstanding, McCreary says the problem for many carriers is off the agenda. “There is a lot of talk but my fear is that airlines are not engaged. There is a near-term focus on profit and the problem is that much of the FOD cost is built into maintenance contracts. The dollar cost is hidden.” He argues that it is hard to get attention when the payback will not come until the renewal of the maintenance contract in 12 months’ time.