Uncertainty exists over how airport fire departments will fight fires in the new composite commercial airliners, indicating that the manufacturers still have educating to do.
A top fire official at Denver International Airport, the location of the most recent airport crash and fire in the USA, believes the coming composite-based commercial airliners will require airport fire departments to change they way they fight post-impact fires. DIA is not yet served by the Airbus A380, the only commercial plane flying with more than component parts made out of composites, and the airport is not slated to be among the first served by the Boeing 787—due to enter service in early 2010.
But a platoon captain with the Los Angeles Fire Department stationed at LAX Airport, one of two US airports currently receiving service from an airliner with substantial composite construction (the A380; New York’s JFK is the other), says his airport follows substantially the same guidelines established for fighting post-impact fires of current generation airplanes.
And Boeing told the airport authorities at Everett, WA’s, Paine Field, where the 787 will perform its flight testing, that there isn’t any effective difference between a composite airplane and a traditional one.
Bill Davis, assistant fire chief of the Denver Fire Department assigned to the Denver International Airport, believes tactics have to be changed after reviewing the post-impact fire analysis of the US Air Force Northrop Grumman B-2A bomber in Guam February 23, 2008. The USAF issued its crash report in June 2008.
“This will fundamentally change everything from strategy and tactics and equipment,” Davis said. “It strikes me that we’re definitely going to have to train to and equip ourselves differently. I’ve studied fires in military composites. This (B-2A crash) is the first of an all-composite airplane; usually there are just parts that are composites.”
David Waggoner, the airport director at Paine Field, said that Boeing advised the airport fire officials to “treat the 787 like any other airplane. The fire department has been briefed by Boeing and they said not all composites act the same. The 787 composites don’t act the same as the composites in the B-2.”
In a statement to Leeham.net, Boeing had this to say:
Boeing has done extensive testing on the properties of the composite materials being used on board the 787 and its reaction in both in-flight fire and post-crash fire scenarios. Boeing has found – and by law must demonstrate to the FAA – that the 787 will be as safe, or safer than, today’s airplanes. The composites used on the 787 demonstrate performance that meets those requirements. Our testing also shows emergency responders will not need special gear, equipment or knowledge to effectively deal with a 787 event.
Among our findings in testing using FAA-approved methodologies were:
• The composite materials used for the 787 do not propagate an in-flight fire.
• The fuselage skin is an excellent fire barrier, and resists flame penetration far longer than an aluminum fuselage
• The toxic gas levels produced in a post-crash fire scenario are similar for both a composite fuselage and an aluminum fuselage
• There was no prolonged burning or re-ignition of the composite skin after tests were completed.
Capt. Rich Hanson, station commander of Platoon C at one of the four fire stations located at LAX Airport, said that every aircraft has some composite. “Quantity doesn’t make a difference, not really—you use the same fire fighting components.”
LAX uses what’s called Purple K, a dry power injected into the turrets that chemically puts out the fire and cools its.
Hanson said that Airbus and Boeing provided LAX with information “about how we can best attack a fire. Even with composites, it’s really not that much different than what we do anyway. Our first concern is the passengers, and we deal with any fire as hazmat and have a decontamination process before getting to hospital.”
At Denver International Airport, a Continental Airlines Boeing 737-500 aborted its take-off December 21, 2008, left the runway and caught fire. All on board escaped but 38 passengers were injured. The 737 was destroyed by the fire. (A Continental Connection Bombardier Q400 since then crashed into a house on approach to the Buffalo, NY, airport.)
The 737 is the standard metal fuselage that has been used on commercial airliners since the introduction of the Ford Tri-Motor in 1925. The new 787, scheduled to enter flight testing during the second quarter this year, has a composite fuselage, with approximately 50% of the airplane by weight made out of composites. The proposed Airbus A350, with a planned entry-into-service in 2013, also has a composite fuselage with 53% of the airplane by weight to be composite.
With these two airplanes gathering all the headlines, overlooked is that the A380 has already entered service. The super-jumbo’s rear fuselage, comprising 25% of the airplane’s weight, is made of composite materials.
As the 787 proceeds on its final countdown toward its flight-test program, certification and delivery, the debate over the safety, flammability and survivability of its composite fuselage continues at the Federal Aviation Administration.
Industry engineers concerned about the safety of the airplane continue to file reports and documents with the agency and whether the FAA has done—and is doing—enough to ensure the safety of passengers in the event of a crash and post-impact fire.
The high-profile 787 gets this attention because of its revolutionary all-composite fuselage, the open comment process that is part of the FAA procedures, the media obsession with anything involving commercial aviation safety and the embarrassing production difficulties that makes the 787 fodder for minutiae reporting..
Composites have been on airplanes for decades, as the two fire officials pointed out. Wing-to-body fairings, rudders and—on the Airbus A300-600 and A310—the entire tail sections are composites. Interior components contain composites.
But planes built largely of composites aren’t new, either. Furthermore, although wide-spread, some autos have been built of composites, notably some race cars. Firefighters have had to deal with blazes involving composites for decades.
Beech built the Starship personal aircraft out of composite materials and its successor, Raytheon, built the Premier business jet out of the same materials. No Starship crashed and burned and there were a few Premier accidents involving fires. New, personal jets such as the Eclipse, have composite fuselages. Airliners with composite components have crashed and burned. But with the development of the 787, and the FAA certification process, the prospect of a major accident and fire received some headlining attention. Dan Rather, the former CBS anchorman who was disgraced in a reporting scandal over ex-President George W. Bush’s military service record, went to HDNet, an obscure start-up cable network, and put together a long story on 787 composite safety. He relied upon a former Boeing engineer who, while raising legitimate questions, nonetheless was largely discounted because it was the recently embarrassed Rather who reported the story.
The focus on the current debate is the sheer volume, the entire fuselage, of composites on the 787, and whether firefighters, passengers and anyone downwind might be at risk of burn rates and toxicity associated with composites.
Another engineer, who did not participate in the Rather report, whose expertise is composites, continued to pepper the FAA with comments about the 787 well into this year. Derek Yates has a long list of correspondence with the FAA. Yates has urged the FAA to require fire testing with an entire center fuselage section to assess burn and hazmat issues. He believes the burn rate and toxicity issues with composites elevates the levels of danger to first responders and passengers alike, and cites the USAF B-2A analysis as evidence. FAA standards and Boeing tests so far have been inadequate, he believes.
Jim Helms, of the engineering consulting firm TATSCO and a former FAA Designated Airworthiness Representative, does not believe an Advanced Carbon Material airplane meets flammability airworthiness standards. He believes the danger so great that, radically, he thinks the entire 787 program should be cancelled. Helms recently published a four page analysis, Part 1 of 2, newsletter looking at the pros and cons of composites. This may be downloaded: TATSCO Composite Newsletter.
The issue of a large airplane composite fire took on new meaning with a real-life example, rather than a theoretical test, when the B-2A bomber crashed and burned on take-off at a US military base in Guam. The billion dollar aircraft stalled in an extreme nose-up attitude right after take-off and pancaked into the ground. The crew ejected safely; the airplane caught fire on impact. The entire accident was captured on a security camera. The cause of the crash was determined to be a critical instrument failure.
Boeing was a sub-contractor on the B-2 program, giving the company intimate knowledge of composites.
The B-2 accident was the first of a large composite airplane; the B-2’s empty weight is 158,000 lbs (slightly smaller than a Boeing 767-200) vs 252,000 lbs for the 787-8, 796,000 lbs for the A380 and 382,500 lbs for the A350-800.
The Air Force’s post-impact fire analysis reports that firefighters began pouring water the on the B-2 bomber less than three minutes after the accident. Within 30 minutes, every fire fighter on the base—53 of them—and all apparatus was on the scene. Four fire trucks were brought in from off base. The fire burned for 4-6 hours and, in the words of the report, the “complete combustion event did not end until day two and possibly day three.”
The base’s fire department used 83,000 gallons of water and 2,500 gallons of aqueous film-forming foam “with not much success in completely putting out the final combustion stage.”
Chief Davis, the Denver Airport fire official, said the use of 83,000 gallons of water was an astonishing amount. His firefighters used far less on the 737-500 (which at 103,000 lbs empty weight is 46% smaller than the B-2).
“We used 12,000 gallons, and that was excessive amount of water and foam” Davis said. “We did because I had the luxury of it. We could have been effective with close to half that amount.”
The large amount of water required to put out the fire on the B-2 means airports have to rethink how they provide water supplies for firefighting, said Davis.
“Water supply and agent conservation will be at a premium for fighting a composite aircraft. They went through tons of water, 83,000 gallons of water,” Davis said. “That’s a huge amount of water. Most every airport would have to have one of two things: hydrants throughout the airport or a very, very large Airport Resource Firefighting apparatus (ARF),” a truck with extremely large water capacity, and a very sophisticated shuttle operation.
The Air Force’s report concluded that “There was a change in the nature of burning as JP-8 was consumed. The aircraft structure continued to burn. The fire scenario could be explained in four distinct combustion stages: 1) 20-30 minutes for the JP-8 flaming combustion. 2) 4-6 hours for aircraft structure flaming combustion which transitioned to intermittent flare up at random locations across the aircraft. 3). 24 hours into the intitial response, cool down was taking place through-composite-thickness with indications of deep-seated smoldering and 4) 48 hours into the initial response, the final cool-down stage was reached with a hint of light smoke being released.”
By comparison, the Continental 737 fire was knocked down quickly and hot spots occurred over a much short time span, Denver’s Davis said.
The initial body of fire was very significant and it was knocked down almost immediately. “The exterior fire knocked was down within a minute by large caliber monitors 1200 GPM turrets as far as the large body of fire on the right side of the aircraft,” Davis said. “But there was still a significant fire underneath the aircraft and in the interior.”
The interior fire was knocked down within 15 minutes of response notification using 1 ¾ inch hoses and flowing A triple F foam.
The Continental accident occurred at 6:18 pm; there was a rekindling about 4am.
LAX’s Hanson didn’t draw a comparison with previous LAX accidents with the B-2A fire, but he pointed out that crashes involving conventional metal airplanes can have their own challenges. In a highly unusual accident in 1991, a US Air Boeing 737 landed on top of a SkyWest Airlines 19-seat Metro commuter plane waiting to take off on the same runway. The resulting fire took a long time to get the fire out because firefighters couldn’t get to smaller aircraft underneath the 737.
Hanson said that one of the things that emerged from this crash was the acquisition of a snozzle, a fire truck with a 50 ft articulating boom with hardened steel tip and titanium barrel that can penetrate the skin of the aircraft when the barrel is extended.
Snozzle of the Ft. Worth (TX) Fire Department. Source: Bensware.com.
Penetrating the skin of a metal or composite aircraft requires high pressure water. The two snozzles used by LAX are capable of 25,000 psi. A standard metal aircraft, such as those in service today, require 5,000 psi to penetrate the skin. Hanson says the GLARE composition used on portions of the A380 requires 6,000 psi and Boeing advised its 787 fuselage requires 8,000 psi. GLARE is a combination of aluminum and composite material.
Once the skin is penetrated, the snozzle’s barrel can be inserted into the airplane, discharging 250 gallons per minute, enough to hold the fire until firefighters can get the hand lines in.
“The biggest concern we had with composite is when you penetrate the fuselage, the direction of the fibers pushing in would grab the barrel. Boeing has done testing and found that isn’t a concern,” Hanson said.
The B-2 fire reached temperatures of 900-1,700 degrees, depending on the location, the Air Force concluded. JP-8 fireballs can reach temperatures in excess of 2,000 degrees.
The Air Force concluded that the “length of time needed to extinguish the fire and cool the aircraft was unexpected.” The report noted that the lengthy duration required trucks to leave the scene for water, “interrupting the suppression or cool-down process, allowing heat to penetrate and burn through thickness (layer-by-layer). Without having adequate water pressure or a water source near by, the structure was not continuously cooled through composite thickness….”
The Air Force explained that the nature of composite construction lay behind the lengthy fire and smoldering. The layer-by-layer manufacturing to the desire shape and thickness, made up of resin-coating fibers, causes the flames to burn through layer-by-layer. “Cooling or flame suppression occurs in the same manner.”
“During the initial response, the aircraft composite material concern is the resin, not carbon fiber,” the Air Force said.
Davis, the Denver fire chief, expressed concern about the particulates emitted in a composite fire.
“The smoke that comes off a composite fire is extremely toxic. The difference between [metal and composite fires] is you also get those fibers. When the composite is degraded by the fire, it releases physical fibers that become airborne and are extremely carcinogenic. It’s as bad or worse than asbestos,” Davis said.
LAX’s Hanson also compared composite fibers with asbestos and said LAX firefighters have to treat composites within the department’s Standard Operating Guidelines.
The Air Force also noted that “aircraft composite fires differ from metal aircraft fires because they add fuel to the fire by increasing the fuel load. In order to extinguish a composite fire, firefighters have to consider composite thickness and maintaining a continuous supply of agent.” The Air Force recommended specific composite fire fighting training.
The post-crash environmental clean-up is also a concern. Davis said DIA moved tons of dirt for environmental clean up, with a large amount of fuel soaking into the ground—the plane was fueled for take-off, as was the B-2A. DIA dug a 24 ft hole to remove dirt.
The B-2’s composite structure poses additional hazards. The Air Force conducted repeated tests of the surrounding ground and air to determine if there were any hazardous materials from the composites remaining after the fire.
Denver’s Davis also notes that new fire fighting equipment will be needed to deal with composite airplane crashes. New gear will be needed to cut, move and pry the composites, which have different properties than metal. New techniques will have to be adopted as a result of the toxicity of the composite smoke and particulates, especially the airborne fibers.
The Federal Aviation Administration imposed special conditions on the 787 testing that Boeing has to meet in order to certify the 787. Among them are conditions relating to composite burning and fire.
In response to questions for this article, the FAA said it is “aware of the B-2 accident, although as is often the case with accidents involving military aircraft, we do not know what payload or other items were carried on the airplane that may have contributed to the sustained fire.”
The FAA noted that “there is already extensive use of composite materials on commercial airplanes. On the exterior, fairings are often composite, as well as certain control surfaces. In addition, the interiors have for many years used significant amounts of composite materials. Therefore, virtually any post crash fire that threatens survivability will involve composite materials.
“The standards that the FAA has established for the 787 are intended to provide sufficient time for occupants to safely evacuate the airplane following an emergency situation. FAA research shows that the composite fuselage material significantly increases the time it takes for a post crash fire to burn through to the interior, which increases the time for occupants to evacuate before the exterior fire can endanger them.”
As for environmental and fire fighting issues, the FAA says this is beyond its scope for certification.
“The concerns raised regarding fire fighting and potential environmental ramifications of composite airframes are not airworthiness issues. Nonetheless, the FAA is working with the Air Force on future studies to assess these and other post crash fire topics that are outside the airworthiness approval process. At this point, we can’t forecast where these studies may lead.”
LAX’s Hanson said, “We feel very comfortable with our ability to deal with a fire in any of the current of upcoming aircraft. Boeing knows what our resources are and in discussion with their training people I am very comfortable we are where we need to be to deal with an incident at LAX.”
Airbus, like Boeing, was asked February 5 by Leeham.net to respond to the B-2A USAF post-impact fire analysis. We’re still waiting for a response.
The USAF post-impact fire analysis may be downloaded: B-2A Post-Impact Fire Analysis. 6 pages, PDF.