Torqued: Foreign Object Debris, Small Pieces Matter

 - September 2, 2016, 10:40 AM

I recently wrote about the importance of remembering the lessons of ValuJet so we are not doomed to repeat the same mistakes. The lessons involved ensuring that low-cost airlines have adequate infrastructure to support growth, fleet mix and oversight of outsourced maintenance. Specifically, those lessons center on complex oversight issues of airline operations and management of outside contractors. After all, determining adequate airline infrastructure to oversee growth and expansion, as well as contract maintenance providers, is not an exact science and often depends on proper auditing to spot indicators before they grow and become big problems.

While that article looked at big-picture issues that can affect the safety of flight, sometimes with devastating consequences, this month I got to thinking about how even the tiniest items can have significant safety implications. Once again, my topic is inspired by my thoughts around the anniversary of a tragic accident that occurred while I was a member of the NTSB. It also coincides with a recent Safety Alert about minimizing the opportunity for FOD (see below). So this month, my focus is on the smaller, more tangible problem of foreign object debris. Not a glamorous aviation subject, for sure. But, as we know, a deadly serious one.

The accident I’m referring to is the July 25, 2000 crash of an Air France Concorde on takeoff from Paris Charles de Gaulle Airport to JFK International in New York. According to the BEA (the French equivalent of the NTSB) accident report, during takeoff and shortly before rotation “the front tyre of the left landing gear ran over a strip of metal, which had fallen from another aircraft, and was damaged. Debris was thrown against the wing structure leading to the rupture of [one of the fuel tanks]. A major fire, fueled by the leak, broke out almost immediately under the left wing.” The aircraft took off but was unable to gain height or speed and crashed shortly thereafter into an airport hotel, killing all on board (100 passengers and nine crewmembers) and four people on the ground.

The NTSB was initially an observer on the accident investigation but was subsequently made an accredited representative as issues involving the origin of the aircraft debris—from a U.S. airliner—became prominent. According to the French report, the metal piece fell off a Continental DC-10 because the aircraft had been improperly maintained. Since the aircraft had taken off just five minutes before the Concorde, the debris could not have been reasonably found and cleared in advance, the report concluded. So while spotting and removing this debris before the Concorde began its takeoff roll was unlikely, this accident illustrates how critical the consequences of even a small piece of debris can be.

Although the debris that caused the Concorde crash would have been more difficult to prevent, the NTSB Safety Alert points to a number of recent accidents where the debris that apparently caused the crashes could have been noted and removed in advance. The NTSB highlights the problem as follows:

  • Mechanics, or others who help with aircraft maintenance, might leave items or residual debris behind after performing maintenance tasks that could become foreign object debris (FOD). Examples of FOD include tools, hardware, eyeglasses, keys, portable electronic devices (PEDs), paint chips and metal shavings.
  • If mechanics and others do not account for every item that they use in or around an aircraft and clean as they go, this FOD can be ingested into the engine or interfere with critical flight systems, leading to an accident.

Accident History

The NTSB cites five accidents it has investigated since 2010 in which FOD was involved. Two separate helicopter accident investigations found evidence of maintenance rags or towels that had been ingested. In one case material consistent with a towel was found in the inlet guide vanes and in the compressor section. The helicopter engine had been replaced on the day of the crash. In the other, the NTSB found “material consistent with rags used by maintenance personnel during installation of the air inlet barrier system ingested into the engine intake.” A third helicopter accident—an Airbus AS350—involved a wrench that had been used on the top of the main rotor head. As the aircraft was flown on the test flight after maintenance, the wrench that had apparently been left on the helicopter damaged “one main rotor blade, the tail boom and the lower vertical stabilizer.”

The last two accidents discussed by the NTSB involve airplanes: a Kitfox Series 5 and a True Flight AA-5B. In the former accident, investigators determined that a hardware clamp and a leather work glove had been left “beneath the boot and the tube seat structure and the control column bearing.” This impinged on the elevator control and resulted in the pilot losing control of the aircraft and crashing into the Atlantic Ocean. The latter accident involved the aircraft engine losing power because paint chips “obstructed the fuel filter, which led to fuel starvation.” The pilot reported to the NTSB that the aircraft had recently been painted.

It seems clear that proper maintenance practices would have prevented all five of these accidents. And while I agree with the importance of the safety alert to mechanics and other maintenance providers, I would expand the warning to include anyone working around aircraft or on the airport. I have seen vehicles of all kinds—motorized and non-motorized—lose pieces and parts on the ramp, taxiway and even runway areas. The most common debris is nuts and bolts that have come loose and fallen off. While ramp workers are supposed to be trained to look out for FOD and dispose of it appropriately, and many airports have numerous signs to this effect, I’ve seen far too many ramps where attention to FOD could use improvement. Not too long ago, a baggage handler at London Heathrow forgot a scanner on an engine cowling. The aircraft took off and the scanner was ingested into the engine, causing approximately $6 million in damage. Fortunately the pilot was able to land the aircraft safely.

Safety Alert for Minimizing FOD

The NTSB’s Safety Alert lists actions workers can take to minimize the chances of FOD being left behind to do damage:

  • Perform an inventory of tools, personal items and personal protective equipment before working on an aircraft. Take only what is necessary for the specific maintenance task. Consider placing nonessential personal items such as jewelry, coins, keys and PEDs in a secure location instead of keeping them with you during maintenance tasks.
  • Prepare the workspace on the aircraft by covering engines, pitot static ports, air inlets, and other areas with protective materials to reduce the likelihood of FOD migration (including residual debris, such as paint chips or metal shavings) to critical flight systems.
  • While working in low-visibility areas (ramp/hangar), ensure that proper lighting is used to check for FOD left behind during maintenance.
  • Keep hardware and consumables in appropriate containers to prevent them from becoming FOD. Store tools in toolboxes and bags, and organize them so that you can easily recognize if one or more is missing.
  • Distractions can cause you to forget things during maintenance tasks. Always follow the maintenance manual/task card and use a checklist. If you get distracted, go back three steps when restarting your work.
  • As you perform the maintenance task, clean as you go to reduce the likelihood of leaving any items. Keep a FOD container next to you during the maintenance task for easy FOD disposal.
  • Perform a second inventory of tools, any essential personal items, and personal protective equipment (such as safety glasses, gloves and hearing protection) after you have completed the maintenance task to ensure that items have not been left behind. Remove any aircraft protective materials so that they do not become FOD.
  • Ask another mechanic to visually inspect your work area for any items that may become FOD. A second set of eyes might see something that you missed.
  • Recognize that human factors such as complacency, fatigue, pressure, stress and a lack of situation awareness can contribute to FOD.
  • Consider conducting daily FOD walks in areas such as hangars, ramps and runways to identify and remove FOD.