MAINTENANCE AND CERTIFICATION

MAINTENANCE AND CERTIFICATION

The Whys, Hows and Whats of the Authorities' Fire and Cabin Safety Research Activities-A Brief Overview
by Claude Lewis, Manager, Technical Projects, Aircraft Certification Standards, Standards, Civil Aviation, Transport Canada

"The CSRTG Welcomes You to the Fifth Triennial International Aircraft Fire and Cabin Safety Research Conference"

It is with these words that the fifth edition of the CSRTG's Triennial International Aircraft Fire and Cabin Safety Research Conference was opened on October29,2007, in Atlantic City, New Jersey,USA.

Airbus A340

On August2,2005, an AirbusA340, with 309passengers and crew on board, overran the runway on landing at Toronto Pearson International Airport. A post-crash fire followed. All occupants successfully evacuated the aircraft-there were no fatalities. By all accounts, this event should have been a major tragedy, but it wasn't. Why? Why didn't anybody die when similar events in the past have resulted in substantial loss of life? It wasn't a miracle as many may think! All occupants survived because of the successful research that has been conducted and that has provided the basis for improved safety regulations and standards.

This research was specifically what the CSRTG's conference was all about: the current research being conducted by aviation authorities and industry to improve fire and cabin safety on transport category aircraft.

But, what is the CSRTG?
The CSRTG stands for the "Cabin Safety Research Technical Group," an association of civil aviation authorities formed in the early90s by the United States Federal Aviation Administration(FAA), TransportCanada Civil Aviation(TCCA), the United Kingdom's Civil Aviation Authority(UKCAA) and the European Joint Aviation Authorities(JAA) to foster co-operation in research in fire and cabin safety.

The CSRTG's chief mandate is to implement research in support of rulemaking. The Group identifies and prioritizes needed research, co-operates in setting up joint, co-operative and complementary programs and projects, and co-ordinates pertinent research activities.

The prime objective of the conference was to inform the aviation community about transport category aircraft fire and cabin safety issues and pertinent recent, ongoing, and planned research activities by the participating authorities.

The conference covered both certification and operational aspects. It consisted of an opening session and four concurrent technical sessions which addressed the various aspects of fire and cabin safety: fire safety, evacuation, crashworthiness and operational issues.

Opening session
The opening session consisted of papers presenting the authorities' vision of cabin and fire safety research, as well as presentations discussing the life-saving potential of such research(TCCA project), future research challenges, the cost of safety versus the cost of accidents, and how fire and cabin safety fits into safety management systems(SMS).

Fire safety session
The fire safety session, which was by far the most expansive of all the sessions, consisted of the following segments and sub-sessions:

  1. Fire–General
  2. Materials Fire Safety
  3. Fire-Resistant Materials
  4. Engine Fire Protection
  5. Cabin and Hidden Areas Fire Protection
  6. Cargo Compartment Fire Protection
  7. Fuel Tank Fire Safety
  8. Fuselage Burnthrough

Fire–General
The papers in this introductory segment of the fire safety session provided an overview of the evolution of fire safety in recent years, of the FAA's transport category aircraft fire safety program and of the issues currently at stake, discussed the fire safety concerns and research activities by different participants, and presented a summary of the research which is currently underway and for which research is planned.

Materials Fire Safety
Materials flammability test methods formed the main focus of this sub-session.

Materials Fire Safety

The results of round robin testing for the rate of heat release(OSU) and smoke(NBS) requirements for interior materials were presented followed by a review of laboratory-scale and full-scale testing of lightweight seat cushions. Also, data regarding radiant panel testing for flame propagation on thermal and acoustic insulation(in accordance with the recently published requirements) was presented. Finally, the recently developed flammability test criteria for ducting and the certification issues of printed wiring assemblies were discussed.

Of great interest was a review of the flammability issues and ongoing research regarding the use of magnesium in aerospace applications.

Fire-Resistant Materials
This segment was the most extensive of the sessions and also the most technically complex with the presentation of some 18academic papers.

Reports were given on some of the fundamental scientific research being conducted to develop highly fire-resistant polymers designed, in the longer term, to provide the groundwork for the development of practical, cost-effective, essentially non-flammable aircraft interior materials.

Engine Fire Protection
This sub-session explored issues related to Halon-replacement fire-extinguishing agents and systems for engines and auxiliary power units(APUs).

The presentations discussed the testing of Halon-replacement options, presented work regarding the use of simulants in fire extinguishing systems testing, and reviewed research into the development of an optical fire detection system.

Cabin and Hidden Areas Fire Protection
A number of accidents in recent years, including Swissair flight111 in 1998, have raised the issue of fires in hidden areas.

Presentations given on the subject discussed the research activities being pursued to address these types of fires, including the use of nitrogen-enriched air to suppress fires in hidden areas(e.g. overhead areas) and fire ports to discharge agents in areas behind panels.

Other papers discussed the development of guidance material for Halon-replacement handheld extinguishers and the hazards associated with lithium and lithium-ion batteries onboard aircraft.

Finally, an insight was provided into the fire safety research considerations relative to design for security requirements.

Cargo Compartment Fire Protection
This segment of the fire safety session focused mainly on the current research that is being conducted to improve cargo compartment fire detection and suppression means.

The presentations firstly expanded on the work regarding various fire suppression and extinguishing agents, including water mist, and the synergistic effects of combining Halon and nitrogen in aerosol can explosion simulations. Of great significance and interest was a paper on the development of an integrated fire protection(IFP) concept-a joint TCCA/FAA/UKCAA activity. Much attention was also given on research conducted on the use of nitrogen to suppress cargo compartment fires. Other presentations dealt with various risks associated with cargo compartments, such as the carriage of lithium batteries and fuel cells. Results were also presented on the development of smoke modeling and multi-sensor technologies.

Fuel Tank Fire Safety
This portion of the session drew significant attention in light of the subject's origin-the TWA800 accident- and the associated on-going regulatory activities.

Firstly, an overview was given of the issues relevant to fuel tank inerting and its implementation on large aircraft. This overview was followed by presentations on oxygen concentration measurement and the development of fibre-optic sensing technologies.

Fuselage Burnthrough
This segment provided an overview of the basis for the fuselage burnthrough requirement and reviewed the development of the oil burner test apparatus, followed by discussion of the development of a next-generation sonic orifice oil burner aimed at achieving higher testing consistency.

Fuselage Burnthrough

Also described was research work on the development of burnthrough test method and criteria for non-metallic composite fuselages, as well as the development of toxicity tests and criteria.

Finally, data was presented on the performance of intumescent/refractory coatings to prevent burnthrough.

As well, two videos that were developed to address specific fire safety issues were presented: a crew fire fighting training video, jointly developed by the FAA, the UKCAA and TCCA in support of FAA AdvisoryCircular120-80, and a video on laptop battery fires highlighting the risks associated with lithium-based batteries.

Evacuation session
This session focused on the human element of the evacuation equation and the use of computer-based modeling to predict evacuation performance.

Evacuation session

Included were a number of presentations on the research conducted by TCCA on access to typeIII exits(in support of a harmonized rulemaking activity between EASA, the FAA and TCCA), on typeIII hatch operations and on methods used to evaluate crew fatigue.

Further, a number of papers were presented on computer-based simulation and digital human modeling of various factors on egress times and flow patterns, and on the effect of fire on evacuation.

Papers were also presented on injury mechanisms in evacuation slides and on the effect of various configurations on egress times.

Finally, there were presentations on the comprehension of symbolic exit signs-which are increasingly being proposed for installation on transport category aircraft- versus traditional exit signs, passenger safety awareness, and post-evacuation passenger assistance systems(PAS).

Crashworthiness session
The crashworthiness session examined the research efforts and programs on protection against impact injury.

Crashworthiness session

Papers were presented on the impact-injury patterns and data from past accidents and incidents, as well as on assessments of injury potential of some configurations.

This was followed by presentations which discussed impact-injury criteria, including the development of side-facing seat neck injury criteria and impact design limits.

A third area concentrated on crash dynamics analytical methods and validation metrics, as well as on anthropomorphic test device(ATD) validation testing and procedures.

Another segment included more specific discussions on inflatable restraint systems, automotive child-restraint systems and energy absorbing devices, as well as on the use of cargo compartments as passenger cabins.

Operational issues session
The operational issues session, though fairly short, nevertheless drew quite a bit of interest and discussion. It addressed two significant areas: passenger safety information and cabin environment.

The first part of the session reported on work related to the presentation of safety information to passengers, i.e. safety briefing cards. Of particular interest were the extensive studies recently conducted by the FAA regarding the comprehension of pictorials and pictograms.

The second part of the session provided an overview of research activities in cabin environment, particularly health-related and chemical and biological response issues, and cabin air quality.

Of significance to TCCA was the presentation of a number of papers regarding work under its Fire and Cabin Safety Research and Development(R&D) Project, as well as work by partner authorities in support of, and complementary to, TCCA's R&D Project.

TCCA has been conducting significant research work in fire and cabin safety in co-operation with its partner authorities: the FAA performs testing and provides data and expertise in support of TCCA's R&D Project; the UKCAA provides advice and oversees TCCA's work in the UK; industry supplies needed data; and ANAC and CASA provide technical support.

The overwhelming message conveyed during the conference was that research is the foundation of regulations, and that without solid research, there cannot be viable regulations, and without co-operative research, there cannot be unified and harmonized regulations.

The three-and-a-half-day conference, which comprised more than 125papers by over 100authors, was an unqualified success. It drew together almost 500participants from more than 20countries, representing a broad range of specialties and responsibilities.

Notwithstanding the immense quantity of information it presented, one of the conference's great benefits was that it provided a unique opportunity for those involved in fire and cabin safety research to meet and exchange on their areas of interest.

The various presentations, as well as presenters' backgrounds and bios can be found on the officialCSRTG Conference Web site at: www.fire.tc.faa.gov/2007Conference/conference.asp.

Further information regarding this conference or previous editions of this triennial event can be obtained from the author.



Landing-Gear Accident

The Twin Turbo Prop Beech King AirA100 was touching down for a landing on the asphalt runway at Buffalo Narrows, Sask., when the nose gear collapsed. The nose gear assembly on the A100, which is canted forward, collapsed forward(opposite to the normal direction of retraction), and the aircraft rolled along the runway on the nose wheel, which had become imbedded in the nose cone. Both propellers, the inside of the nose gear wheel well, and the nose cone were damaged. There were no injuries to the two crew or to the four passengers that were aboard.

The crew reported that the approach and landing were normal until the nose-gear collapse. There was no indication of a landing-gear malfunction prior to touchdown, and the gear lights showed "down and locked."

Upon initial examination, two points of failure were observed: at the upper drag brace support bracket, which had torn free from the wheel, and at the nose gear actuator shaft, which was broken.

Further investigation determined that the initiating source of the failure was traced to the left-hand upper drag brace attachment pin(P/N50-820233 or 99-820110-9) that was missing and had not been properly secured to the drag brace assembly. The missing pin caused the transfer of loads to the right upper drag brace attachment fitting, which fatigued and failed, passing the loads to the right intercostal rib. The rivets securing the intercostal rib to the wheel well began to pull from the sheet metal attachment point until failure occurred, and the landing gear collapsed.

Arrow points to where the missing left-hand upper drag brace attachment pin should have been
Arrow points to where the missing left-hand upper drag brace attachment pin should have been

The aircraft had been imported from the U.S. and issued a Certificate of Airworthiness(C of A) for type-certificated aircraft into Canada. The aircraft had not yet undergone its first-phase inspection. The landing gear was last overhauled and installed on the aircraft eightyears earlier(February25,2000),2 051 cycles prior to the failure.



Update–Canadian Aviation Regulation(CAR) 703.25–Carriage of External Loads

The data collected from May11,2006, to December31,2007, reported 506flights, most of which were carrying single or multiple canoes(measuring up to 20ft), aluminum boats(measuring between 14ft to 16ft), kayaks, plywood and/or lumber. This data was collected from eight companies located in Ontario,BritishColumbia, the Yukon and the NorthwestTerritories.

Commercial operators operating under CAR703 are now exempted from CAR605.03(1)(b) and CAR703.25 until December31,2008. However, all other operators who are not operating under CAR703.25(commercial and private) can only carry external loads with an approved configuration change. Carrying an external load on an aircraft changes flight characteristics, which affects airworthiness, and therefore represents a change to the aircraft configuration for which an approval is required.

As of January1,2009, CAR703.25 will become redundant and will be repealed through the Canadian Aviation Regulatory Advisory Council(CARAC) process. No other changes are required as CAR605.03(1)(b) adequately addresses changes in configuration.

Reporting is still required for operations until December31,2008. We ask that operators who take advantage of the exemption tell us about their operations, as this will help develop relevant guidance material.

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