Julian Moxon/NOORDWIJKERHOUT
To a travelling public that sees the occasionally horrific television images of the aftermath of a major air disaster, the idea that they might one day fly on an aircraft capable of carrying up to 1,000 passengers is likely to bring the inevitable thought - what if it crashes?
While in a rational world there is little difference between a very large transport aircraft (VLTA)crash and one involving a fully loaded Boeing 747-400, the emotional effect of such an accident on the public perception of air transport safety is undoubted.
The initiative to hold the Noordwijkerhout conference came from a European organisation, the Joint Aviation Authorities - not least because the first such all-new aircraft, Airbus Industrie's proposed A3XX family of 480-660 seaters - will be looking to the authority for initial certification. Meanwhile Boeing continues to study stretched derivatives of its 400-seat 747-400, with seating increases to up to 500 passengers. Airbus has already filed its application for an A3XX type certificate with the JAA to enable it to begin detailed discussions regarding certification issues before it begins final definition of its new giant.
The conference, co-hosted by the the International Civil Aviation Organisation, the US Federal Aviation Administration and Eurocontrol, was the first to address safety considerations of a new generation of aircraft before certification, and was welcomed as such. The organisers also drew praise for having invited not only representatives of the manufacturers and regulatory bodies, but also from cabin crew and pilot organisations, which, despite their fundamental role in accident prevention, are often forgotten in debates about safety.
The introduction of the Boeing 747 and other widebodied aircraft in the early 1970s attracted a raft of new certification rules aimed mainly at the aerodynamic and structural considerations related to the weight and size of such aircraft. Whether the same will be true of VLTAs is uncertain.
PUBLIC PERCEPTION
In her opening speech, Netherlands transport minister Tineke Netelenbos pointed out that the size effect of VLTAs "-should not be exaggerated". She noted that the step from the Boeing 707 to the 747 took passenger numbers from 150 to 375 - an increase of more than 100%, while from a high density 747-400 to the A3XX represents an increase of just 50%. She added, however, that "-public perception of one large accident has more impact on awareness than numerous small accidents with the same overall number of fatalities". While VLTAs themselves would not be inherently less safe, she received some support for her view that their introduction "-is a good reason for a fresh look at our safety regulations".
Although aerodynamic and structural considerations were discussed at the conference, it became clear early on that human factors safety issues are potentially the least understood. These include the vexed question of emergency evacuation from the full-length upper deck, problems linked with the spaciousness of the cabin areas and how to manage passengers during emergencies or in turbulence.
Some safety issues are specific to VLTAs, while others, although applicable to such aircraft, should also be considered as applying to all passenger transports. General safety problems such as controlled flight into terrain, although a major safety concern, were therefore not considered at the conference.
On the need for a whole new set of certification requirements, Airbus and Boeing share essentially the same view - that the existing standards will be adequate for approving VLTAs. Airbus, which hopes to achieve A3XX certification in September 2004, contended that there are likely to be fewer certification issues with this aircraft than there were for its fly-by-wire A320. It also pointed out that design faults in the aircraft themselves are less and less responsible for accidents, 95% of which are caused by human failure, and that new design features are already contributing to overall safety in accident prevention and survivability.
Airbus vice-president for product integrity Wolfgang Didszuhn insisted there was "-no justification to develop new regulations for a specific VLTA safety level", while Boeing's vice-president of engineering and technical operations - Europe, Jerry Mack, said a complete set of VLTA-unique certification rules is "-not needed-current regulations for transport category airplanes are relevant for the VLTA". He added, however, the clear proviso that new rules will be needed "-if the VLTA is proven to expose the public to greater safety risks in certain areas", while insisting that the fact that such aircraft will carry more passengers than any previous flying machine does not in itself warrant change.
"We have to define what is our safety objective for VLTAs," said FAA associate administrator for regulation and certification Thomas McSweeney. The US organisation has already set a goal of reducing accidents by a factor of five over the next 10 years, which, it says, "-means that our past way of doing business will have to change". He stressed that, while the rate itself must clearly be lowered, major emphasis must be on improving methods of finding out exactly what happened during the events leading up to an accident.
This has become all the more imperative in recent months following the failure of flight data and cockpit voice recorders in several accidents, including the recent disaster in which a Swissair Boeing MD-11 crashed into the sea off Canada after what appears to have been a total electronics failure following an on-board fire. So, while asking the question: "Should our goal be to virtually eliminate accidents in this category of airplanes?" McSweeney believes that the aim must also be that any accident that does happen "-cannot go unsolved, no matter what the force of the impact, or where the aircraft crashes and what happened on the flightdeck before it crashed". He suggested, therefore, that questions such as "-do we need multiple flight data and cockpit voice recorders-dedicated power supplies for sensors and recorders-digital video cameras or acoustic sensors-should we telemeter the data and have no onboard recorders-should there be a different media for storage of the data-" must all be addressed as fundamental to the steps necessary to introduce VLTAs.
HUMAN FACTORS
The full-length, two-deck twin-aisle passenger cabin planned for the A3XX, and which any near term VLTA doubtless will use, raises new safety issues for the occupants. Shane Enright, assistant secretary of the International Transport Workers Federation (ITF), said that while "-we have no ideological preoccupation with the concept of large passenger aircraft", a straw pole of cabin crew organisations would reveal a "general disquiet" about the development of such aircraft.
Gertie Sommerstad, of the JAA's cabin safety study group, said: "The importance of solving cabin crew issues is especially important [sic] when designing an aircraft with a passenger capacity of between 600 and 1,000 people." The UK CAA's Nicholas Butcher pointed out that the novel cabin designs associated with twin independent decks, "-each of which can accommodate more passengers than an existing medium range airliner", raise major questions about turbulence related injuries, which have been on the increase in recent years. He worries that new features likely to appear on VLTAs, such as duty-free shopping areas, executive-style offices, children's play areas, casinos and so on will encourage passengers to leave their seats, raising the potential for serious injury as passengers move between decks. "It is therefore possible that some of the JAR-OPS 1 [European Joint Aviation Requirements - Operations] and FAR Part 121 certification requirements may need to be reviewed," says Butcher.
There was general support for the idea of having a senior cabin crewmember (CCM)on each deck, who would "-have overall responsibility for all standard operational safety related duties", and be the primary source of cabin related safety information for the flightcrew. The CCM would also ensure, for example, that a minimum crew complement was maintained on each deck in the event of an emergency.
The addition of a third cockpit crewmember was suggested by the International Federation of Flight Engineers (IFEO) and, predictably, it raised strong views. The organisation said: "There have been many instances where the two-man crew of a large high technology aircraft have been stretched to and beyond their limits when faced with high workload or abnormal conditions." It added that "-safety margins can be eroded in the less relaxed atmosphere when pilots find they are struggling to meet departure schedules without the assistance of an extra crewmember".
Airbus (which pioneered two-crew cockpits on widebodied aircraft) and Boeing replied that long-range flights today carry at least one extra pilot to take over during rest periods, adding that the safety of two-pilot operations has been confirmed in numerous reports, not least by the US Government. Airbus said: "We see no need to change the system. It would be a mistake, since there is no evidence whatsoever that three-man cockpits are safer than two."
The IFEO replied that a third crewmember will be needed for VLTAs, to perform such tasks as outside checking of the aircraft, freeing the pilots to concentrate on flight preparation and to carry out cabin maintenance during the flight.
EMEREGENCY EVACUATION
Controversy also attends the cabin emergency evacuation issue - with argument over the best way to test whether the existing 90s rule is adequate. The ITF's Shane Enright insists that the organisation will be satisfied with "nothing less than a full-up, rigorous, full scale evacuation demonstration", showing compliance with today's regulations. "We also believe that such demonstrations need to more closely mirror the likely conditions in real emergencies, including restricted visibility, obstructed pathways, or what we euphemistically refer to as 'competitive behaviour'."
Some point out, however, that such full scale demonstrations not only cost a lot of money - typically $2 million - but risk lives (there has been at least one death during an evacuation trial) and are unrepresentative, since they cannot include the infirm, the disabled, or the mentally unstable.
One solution, from the University of Greenwich Fire Safety Engineering Group, led by Ed Galea, is to simulate aircraft evacuation using models. Its air EXODUS model, developed with the UKCAA, has been tested on the A3XXdesign, and on the Boeing 767-300ER, with the 767 trials predicting evacuation times to within 2.1% of those observed in real-life tests. Galea pointed out that repeated simulations can be carried out in conditions that would be impossible for humans, including the effects of fire spreading from any part of the aircraft, different smoke scenarios, varying combinations of passengers in the seats and different exit arrangements.
Development continues, using more explicit modelling of passengers and crewmembers, and with a virtual-reality processor under development. Galea said that such modelling "-has the potential not only to replace current certification practice, but to enhance current 90s practice". He added, however, that the aviation community should take responsibility for validating evacuation models and to determine, for example, what actually needs to be examined for certification purposes.
The design of evacuation slides and life rafts also received attention, with the University of Newcastle presenting two designs (one shaped like a spiral) aimed at preventing the bending of the long slides that VLTAs would use in upper-deck evacuations.
The issue of fire prevention and detection in VLTAs was addressed by the JAA's Cliff Barrow, who pointed out that such aircraft will have potentially more sources of fire through the greater number of internal stowage areas and additional features provided for entertaining (one speaker from the cabin attendant community said that, on current widebodied aircraft, there can be up to 15 video recorders stacked in a small area, which often became "extremely hot"). Improved fire-resistant materials, and better management of cabin smoke, were also among the suggestions.
VLTA aerodynamics and structures issues considered raised few matters of concern, although it is clear that changes may be necessary to certification requirements in areas such as manoeuvre load, where the JAA says "-current JAR requirements may not necessarily be adequate" - and the effects of gust and turbulence - "-the validity of the simplifying assumptions [of the current approach to defining them] needs to be reviewed".
PASSENGER DISTRIBUTION
The effect of the raised vertical centre of gravity resulting from the double deck design was thought likely to affect the calculation of static and dynamic stability (and hence handling), and could affect take-off performance through the changed longitudinal trim. Passenger redistribution between the decks during the flight should also be considered, said Graham Weightman of the JAA's flight group.
Current certification regulations covering crashworthiness and ditching "-do not make a realistic allowance for variations in aircraft geometry, seating location or aircraft size", said Vic Card, chairman of the JAA's structures group. He said that issues such as the definition of what is a "minor crash landing" when applied to a VLTA need clarifying, as well as asking what consideration should be given to the protection of the lower deck occupants because of the presence of the upper deck.
The advent of the VLTA will "-bring further unknowns with respect to the typical operating conditions that will be encountered on the ground", said Card. Landing gear and ground loading criteria "-will need to be reviewed very carefully", while "-some of the basic assumptions on which ground loads requirements are based may be called into question". Landing gear design must take special account of fatigue failure, he added, saying: "A major problem in this area will be the establishment of a realistic load spectrum, given that no operating experience exists for this class of aeroplane."
The workshops produced a full set of recommendations, covering occupant safety (emergency evacuation, fire protection, turbulence and human factors), policy (VLTA definition, level of safety, human factors, recorders, minimum crew, bomb hardening and vertical centre of gravity), structures (crashworthiness, ditching, flight and ground loads, proof of structure) and operating environment (impact on airport operations, airport rescue and firefighting, critical-incident response, de-icing, air traffic control, wake vortex, fuel dumping, noise and the concealment of dangerous articles).
JAA secretary general Klaus Koplin said of the meeting that "-even if we failed to define the VLTA, it was the start of a good discussion on the safety aspects". The problem, he added, is to answer the question: "Does the VLTA require a new level of safety? There is certainly a consensus that we must achieve the highest possible level, but I don't believe we can require a new level as such, because we would then have to justify not applying it to existing aircraft." He went on: "We all know we cannot avoid accidents, but the problem is how to deal with the public perception of VLTAs after an accident. We have to think about that."
Copies of the conference recommendations can be obtained from: Inge Steenberg, PO Box 3000, 2130 Hoofddorp, Netherlands; tel: +31 235679712; fax: +31 23 5621 714.
Source: Flight International
