For FBOs, OEMs, and other hangar keepers, the inadvertent discharge of fire foam systems is a persistent and growing problem. Nearly everyone has seen photos taken in the aftermath of one of these events—a hangar filled with a thick layer of foam that can reach 10 feet high, spilling out on to the ramp in some cases.

In a way, accidental foam discharge is like the social disease of the FBO industry. Those who have had one don’t like to talk about it with anyone outside of their insurance providers, and ditto for foam system installers and maintainers, in fear of stigma from current and prospective hangar customers.

Yet, according to a study commissioned by the National Air Transportation Association (NATA) from the University of Maryland’s Department of Fire Protection Engineering, since 2004 there have been at least 137 inadvertent hangar foam discharges—an average of one every six weeks. It’s a trend that has been increasing in frequency. Nicholas Methven, senior v-p of insurance provider Global Aerospace and the author of a white paper on the topic, stated that the average value of foam discharge claims he has seen has been $1 million. NATA estimates the overall clean up and aircraft damage costs of those events at between $64 million and $235 million.

The National Fire Protection Association (NFPA), considered the world’s foremost governing body on building fire code regulations for more than a century, addresses aircraft hangars under its 409 standard, which was last updated in 2016. While NFPA has no rulemaking authority on its own, its guidance is generally accepted as an industry standard and referenced by state and local governments when approving hangar construction.

The 409 standard was established more than seven decades ago, at a time when the hangar cost more than the aircraft it was sheltering. These days, hangars might shelter several business jets, one of which alone could be worth more than 10 times the price of the building.

As aircraft increased in size and fuel capacity, fire authorities began to worry that sprinklers would not be able to adequately reach and fight any fuel spill fires that occurred under the ever-widening wings, which at the time had an unpleasant tendency to leak fuel onto the hangar floor. As well, the organization reasoned, water alone was not effective in extinguishing large flammable liquid spill fires.

In light of this, NFPA in 1984 began to recommend the inclusion of foam fire suppression systems in large community hangars, which would rapidly cover the hangar floor in a sea of foam, smothering any aviation fuel blaze. In theory, this concept sounded good, but as most insurance companies will note, they have yet to encounter the sort of fuel spill-related fires the foam systems were meant to combat. While the University of Maryland study noted that there were 37 incidents where foam discharged in response to fire between 2004 and 2019; in the only documented case involving a pooled fuel spill fire, the foam system failed to discharge.

Industry experts also argue that advances in aircraft construction have all but eliminated leaky wing tanks, and progress in fuel refining has raised the ignition point of jet fuel, making the possibility of a fuel spill fire even more remote.

Size Matters

NFPA categorizes aircraft hangars by size, with Group I encompassing aircraft the size of an airliner with door heights exceeding 28 feet and/or a single hangar bay in excess of 40,000 sq ft, requiring the most stringent fire suppression equipment. Group II hangars are the standard business aviation hangar classification, with door heights under 28 feet, and a single hangar bay less than 40,000 sq ft.

“There was this sudden increase in the amount of fuel aircraft could hold if they had a tail height of over 28 feet,” said Michael France, NATA’s managing director for safety and training, explaining how the aircraft tail height came to be viewed as a dividing line by NFPA. “If you look at it now, and over the last 20 to 30 years, aircraft that are in service now, that doesn’t apply anymore. Aircraft with 26-some feet can hold way more fuel than even some that have 30- or 32-foot tails.”

Those hangars, which are currently advised to have foam suppression systems, are generally used by airlines, FBOs, or large flight departments, which all operate to extremely high safety standards. Typically such hangars are kept in immaculate condition, as opposed to smaller owner-operated Group III hangars, which when crowded with storage items can grow to resemble someone’s basement or garage.

The foam systems are expensive, typically adding 30 to 40 percent of the final cost of the Group II hangar, in some cases tacking on more than $1 million. The systems also require costly yearly maintenance and inspections to maintain their warranties.

“In the last 10 to 15 years, we’re seeing a lot more foam systems being installed,” said Douglas Fisher, a fire protection engineer and the principal of Fisher Engineering. Speaking in a recent Aviation Insurance Association webinar, he added, “We’ve also seen a big push to the low bid and fastest installation process and that’s what’s causing, in my opinion, an increase in the frequency of inadvertent foam system discharge.”

As part of his duties conducting forensic examinations at foam discharge scenes, Fisher noted many systems are destined for failure. From having incompatible sensors to the installation of manual release switches near the hangar doors where they could be susceptible to weather and corrosion, to being programmed with an incorrect operational sequence for the system, it's not a matter of if they will go off, but when.

Other sources of inadvertent discharge are human error and damage to the systems, perhaps due to frozen pipes that burst or other pressure-altering events. Some systems have reacted to false positives, such as smoke and heat from welding work or even an in-hangar barbeque. Improper maintenance also looms large in terms of the number of accidents, either from technicians who are not qualified to work on the systems or from outright neglect.

“Our experts indicate a cause of the inadvertent foam dumps is often poor or totally lacking maintenance of the fire suppression systems by the FBOs,” said Kerry Porter, senior v-p and director of claims for insurer USAIG.

In some cases, there were changes made to the system’s operational sequence but not documented, and when it came time to test it during an annual inspection the result was a hangar full of foam. In one reported military incident, technicians decided the quickest and easiest way to clean up a puddle of spilled solvent on the hangar floor was to ignite it and let it burn off.

Costs Hard To Calculate

It is difficult to put a price tag on each of these events, given the multiple insurers, policies, and claimants involved.

In cases involving multiple aircraft, the situation can get even more complicated. “It’s not just a matter of cleaning and wiping away the soapy foam,” said Porter. “Foam is corrosive, so if it infiltrates the avionics bay, some manufacturers of the black boxes will require replacement because of the likelihood of future failures. They believe operational failures could possibly follow as corrosion progresses.”

Porter explained that due to the corrosive nature of the foam, what would appear to have a minimal effect on aircraft could require other costly replacements. “Depending on the aircraft brand, a large corporate jet that gets only two feet of foam around it instantly costs over $1 million in mandatory replacement of wheels and brakes,” he told AIN. “If it gets foamed again a month later, which has happened, that is another million in replacement wheels and brakes.”

Some hangar contracts contain language that attempts to absolve hangar keepers from any responsibility in the aftermath of an accidental discharge. Porter added that while some FBOs and their insurers “step up to the plate” and pay for the damages caused by foam events, other cases involve operators filing first-party claims with their hull insurers, who then bring subrogation actions against the responsible parties to recoup their losses.  

Other costs resulting from one of these foam events are the clean up of the hangar and equipment, supplemental lift while affected aircraft undergo repair, and in case of the escape of the foam outside the containment area, possible environmental cleanup and remediation as well. The foams can also serve as health hazards of varying degrees.

Once all that is taken care of, simply resetting and refilling the foam system can cost as much as $50,000. According to Methven, in the aftermath of a costly foam discharge, some FBOs have learned that the contract with their fire suppression maintainer had a liability clause, which in one case placed a limit of $250 in recoverable damages.

Given the number of these occurrences, the industry has been exceptionally lucky thus far, when it comes to personal injuries associated with these events. So far there has only been one fatality during an accidental foam discharge at a military facility, but the potential for harm is great.

The span of time between the activation of the system, and being totally disoriented amid a blizzard of foam rising from the floor and dropping from the ceiling is short, and anyone caught in it will rapidly find themselves in a highly slippery, blinding, choking environment where everything can become a hazard. Tests by firefighters using infrared detectors to locate people by body heat amid the foam have proven unsuccessful.

“Some in the industry argue we are over-engineering against a non-existent threat and there is a life safety issue associated with foam fire suppression systems,” noted Methven in his white paper. “A growing chorus of industry players say the return on investment around fire suppression systems is a negative one.”

NATA Argues for Exemption

With NFPA 409 due for revision, the organization requested comments from the aviation community, which were due last November. NATA argued that Group II hangars used strictly for aircraft storage should be exempt from hangar foam requirements and has proposed the establishment of a new category of hazardous operations hangars that would be used for activities that could carry a higher risk of fire such as fuel transfer, welding, torch cutting, soldering, fuel tank repairs, and spray finishing.

NATA also requested an increase in the maximum door height for Group II hangars, from 28 to 35 feet, without the requirement for more stringent fire suppression systems. “As you know, a lot of these aircraft that are coming to market, they’re just getting bigger and a lot of our members now are having trouble fitting a G650 in a hangar,” said Megan Eisenstein, the trade association’s director of regulatory affairs, during the AIA webinar.

According to NATA, if the 409 standard were to change, it would work with its members on a local level to address the potential removal of existing foam systems on a case-by-case basis.

NFPA was slated to have a meeting to review the industry comments and recommendations in April, but like most events during the Covid-19 crisis it was canceled, possibly pushing back the 409 revision schedule until late 2021 or even 2022.

In the meantime, NATA has released several brochures explaining the different groups of hangars, their respective foam requirements, the accidental discharge problem, and its costs and hazards to educate local authorities. An accidental hangar foam discharge recovery checklist is also included. “Until changes to the NFPA 409 standard are made, this resource will serve as a guide to help educate local fire marshals and hangar developers on the safety and environmental risks, as well as the potential of aircraft damage related to accidental discharges of hangar foam suppression systems,” added Eisenstein.