Subordinate Concepts

Subordinate concepts are those concepts that could be considered for application within each subsystem of the air transport system (aircraft, ATM, airports) without the necessity of widespread introduction. Some examples are given in the table below.

1. Standard cockpits/avionics

The number of airliners is set to rise considerably. There will also be many replacements so the number of new aircraft will be very great. Some estimates put this as high as 24,000 new airliners in the next twenty or so years.
An argument has been put forward that a major contribution to overall safety and costs would be achieved by standardisation of cockpits and avionic interfaces. The literature has many instances of pilots losing their grasp of what their instruments are telling them and this can lead to total loss of situational awareness. Inevitably in such situations, wrong decisions are made with tragic results. The differences between cockpits are more at the detail level than in the macro provision – all modern airliners have more or less similar equipment levels. It is in these details that problems very often arise; visual, audible and numerical signals that are supposed to help the pilots to interpret the situation of the aircraft. Where pilots fly the same type of aircraft for much of their career they can and do become extremely familiar with its layout. This can be a two-edged sword; greater familiarity can also make changing types more of a hurdle.With over 30,000 airliners in the world the number of pilots changing type is set to increase, perhaps substantially. Airbus have had a major programme of making the cockpits of their range very similar and easily absorbed by pilots transferring between Airbus types.
Standardising cockpit and avionic interfaces would make changing types much less dramatic and would eliminate many of the detailed but serious risks that signals will be misinterpreted in times of crisis. There would also be substantial savings in airline pilot training and training courses could be standardised to give world-wide compatibility.
Making the interfaces standard – the gauges, input controls, read-outs and so on – must not however become a barrier to progress or to change. Making progress on this front will required sophisticated architectures that allow systems to be changed and improved without inflicting additional changes on pilot response. Considerable study will be required to ascertain how much of the cockpit should become standardised and what the standard should be.What must be avoided is the appearance of standardisation, similar looking layouts that do not respond as expected.
A particular extension of this idea is that of the "zero-training" cockpit. This idea surfaced with special relation to PTS but is generally adaptable. It envisages a cockpit with many of the checks and pilot skill inputs being replaced by electronic systems. It is not an "automatic" cockpit because the pilot could still dictate heading, altitude and speed subject to him not calling up unsafe combinations. For example, it would not be possible to fly into buildings because their airspace would be designated as excluded areas. Likewise, zones set-aside for commercial traffic and restricted areas would also be excluded.Take-off and landing settings would be linked to speed and altitude sensors so that coming into land with improper settings would be impossible. The cockpit would be programmed to default to a safe heading, speed and altitude in case of any conflict between the sensed position of the aircraft and the pilot’s commands.
The electronic sophistication of such a cockpit would be considerable but with electronics moving forward as they are it is perfectly feasible to see such a cockpit becoming viable.

2. MEMS

MEMS are nano-scale devices that can be controlled by microelectronic signals to command the state changes for which the device is designed. The changes of state may be very variable. They are sometimes known as "systems-on-a-chip" and they may have pervasive applications in every aspect of our lives.
One of the areas being actively researched is the use of MEMS in aerodynamic applications, particularly in flow separation control. This is seen to have the potential for raising lift performance by 10-15%, without corresponding increases in drag. Several research programmes exist with broadly related objectives and this application of MEMS technology can be regarded as very well adopted already.
Other applications, either established or in research, include those for gyro sensors, sensor and control packages, optical switches and pressure sensors. Their application to miniature flying objects is also being studied although this seems to have little apparent application in the air transport system, at least for the present.
More innovative concepts include massive MEMS arrays capable of changing the flow characteristics of complete airfoils, whether these are flying surfaces or air intakes. Arrays of MEMS on mirror or radar reflective surfaces might allow these to be tuned, directed or focused.

3. Wireless aircraft

One of the impressive features of modern aircraft during their build phase is the mass of wiring that connects the various systems. Kilometres of wire threads its way around the structures to make these systems work together.
Much of the wiring is standard to all members of the fleet but many variations have to be worked into the wiring scheme to serve specific customers. The complexity of the wiring is such that its management can become an issue of importance at the highest programme level. The concept is to dispense with this wiring and to move to a wireless aircraft.
We are familiar with wireless technologies in the domestic and office arenas and extending these to aircraft services has many attractions. How feasible is it? What are the issues to be overcome?
The basic idea of radio frequency (RF) signals being used for communication of data is not new nor, today, especially difficult. However, if we imagine a wireless aircraft dependent on the same number of signals that control all of its systems passing through the ether of the aircraft we must also take into account all other RF sources. These may include computers, games and the accessories of modern life. It is believed that only a very small number of aircraft accidents may have been caused by interference by these devices. Nevertheless, it is also believed that incidents involving them might be numbered in the range 15-25 annually. Therefore, the possibility of interference is clearly an issue.
Many of the wires running around an aircraft are not for communications and data processing but for delivering electrical power. The transfer of substantial power is not possible by means of RF transmission within an occupied aircraft. How then are we to reduce these demands for wiring? One partial answer might be to disperse power generation to more generators allowing power to be directed only to nearby consumers and to rely on wireless transmission of the control signals that would control them. Such power generators might be air-powered devices or have separately powered generators. Alternatively because the power distribution system is relatively simple compared to the data transmission links a hierarchical electrical distribution bus could be installed which, if they were the only wires, would still dramatically reduce the challenge of aircraft wiring plans.
Such concepts are being actively address in research laboratories, with regulators and in determining new standards.

4. Baggage handling ideas

The transportation, control, transfer, storage, security and identification of baggage is a major headache for the air transport system today. Although many millions of baggage items are successfully moved the small percentage of items lost represents a considerable problem to its owners. New ideas for addressing this issue formed the topic of a number of ideas.
Perhaps the most radical was the "Zero Baggage" concept whereby the passenger would be barred from taking baggage onto a flight. The choices for the passenger would be to send personal items beyond the carry-on limit by freight service or to hire or purchase items of clothing etc at destination. The design challenges to this idea are relatively easy to manage. Passenger aircraft would simply not have to assign hold space to baggage purposes but might have to assign somewhat more volume to passenger cabins to allow a reasonable carry-on limit. More severe would be the cultural and acclimatisation problems. It would take people some time to come to terms with the concept of not taking so much baggage and that excess would be refused passage at the airport. The savings in the ATS would be substantial since hauling the tons of baggage that people wish to take today costs a significant amount of fuel and imposes a consequent climate impact.

5. Optimal fuel mixtures

Aviation has moved on from petrol to kerosene and more recently to particular varieties of kerosene with antiflame properties. The question posed was whether there is an even more efficient fuel that could be used and how might this optimal mix be formulated.

One of the considerations would be what more efficient means in a world becoming very concerned about global sensitivities to hydrocarbon pollution. It might mean using fewer gallons per passenger mile, or using less weight per r.p.k.. Or it could mean producing less hydrocarbons per r.p.k. or in total. Or it might mean a more sustainable fuel, or a safer fuel. So the question is not an idle one.
Kerosene has many admirable qualities. It is relatively hard to ignite which makes it safer at low temperatures. It has high energy density, about 45 MJ/Kg. Which makes it efficient as an aviation fuel. But it is a hydrocarbon and produces CO2 and NOx pollutants when burnt.
Hydrogen and methane could be used if cryogenically stored in the aircraft as a liquid. Their energy densities are much lower than kerosene at about 25% and 65% respectively so aircraft would need larger fuselages10. (The cooled gas would need to be stored in the fuselage because heat transfer problems in the wings makes this preferable).
The lighter fuel weight of hydrogen would produce about 20% energy saving on a 10,000-Km stage length even accounting for losses. However, for medium stage lengths of 3,000 – 5,000 Km there would be a net penalty of about 20-40%.
Assessing relative impact on the climate is more difficult but research indicates that relative to kerosene at unity whilst fuel hydrogen produces zero CO2 methane produces about 0.8.Total greenhouse effects at 12 Km altitude are, in relative measures, kerosene 340 and hydrogen 180.
Unless hydrogen could be produced in an economical and climatically acceptable manner kerosene types are likely to remain the favoured fuel for aviation. Nuclear powered hydrogen production could meet most of these aims but would carry with its acceptance tremendous infrastructure costs.
An interestingly different idea was to use water as the fuel, to carry out the conversion process from water to oxygen and hydrogen on-board, and to burn the two gases in the engine. Theoretically, it is possible to gain more energy from burning the gases than is necessary for the dissociation process. In practice the efficiencies of all processes are far from ideal and this presently prevents us from benefiting from this apparently free energy source. The University of Valencia has claimed to have discovered a process that produces a net energy output but this has not yet been substantiated.
The subject is being very thoroughly researched around the world.

6. Ornithopters

Ornithopters are aircraft that more closely mimic birds and insects than fixed wing aircraft in that they achieve both thrust and lift by flapping their wings. Since the days of the ancients, these machines have attracted man’s attention and this has produced some strange machines. The advent of computers has enabled researchers to study and simulate the mechanisms by which birds and insects achieve flight. These mechanisms are now much
better understood enabling the contribution made by each movement of the wing to be related to the flight needs of the creature.
Recent efforts have been concentrated upon small ornithopters where the power to move the structures of the wing is more manageable. At larger scale the movement of very large wings will increase the power needed faster than the installed power will be increased. A feature of birds and especially insects is the low weight of their flight surfaces. We have become accustomed to using wings to carry fuel and undercarriages and it would require a radical review of the aircraft concept to revert to the lightest possible wing structure.
Control of the flapping wing is also a great challenge. Its motion is not a simple sinusoidal movement but has components of motion that twist the wing and vary the speed during the cycle. Flight control in nature is achieved by the relative motion of the two wings, in an airliner these control issues would need to be resolved so that pilot control and automatic control were possible. Evidently, the human pilot would suffer from both a lack of directly linked brain commands, and probably, from a lack of experience in their use.

7. Weather control

One of the ideas with the largest vision of both aviation and our own abilities was to control the weather at a very large scale. We already know that weather can be controlled at relatively small scale. This idea suggests that we might be able to control the direction and force of jet stream winds upon which airliners could ride with enormous savings in fuel.
Jet streams occur at heights of 30,000 to 45,000 ft and create wind speeds sometimes over 120 knots. They are caused by two contra rotating masses of air, one cool and the other hot which create between them a wide flat mass of high speed air some 10 Km deep and perhaps 100 Km wide. The jet stream travels from west to east in an irregular pattern with wind directions varying from just east of south to just east of north.
It is impossible currently to control such massive weather systems although our knowledge enables us to make use of them. It is arguable whether we would want to control even if we had the means.We know, for example, that jet streams effect local weather conditions quite extensively and have an essential role to play in the formation of super cells and tornadoes. The economic and social consequence of controlling these effects is unpredictable at present.

8. Teleportation

With the literature full of sayings by people declaring things to be impossible, one is hesitant to declare any idea to be beyond our reach. Teleportation is perhaps the most common, least understood and most difficult of the common "innovations" that is put forward.
Certainly it attracts research effort and this is occasionally marked with some success. However, a look at some of the challenges might convince us that if teleportation is to be a feature of the future ATS that future is a long way ahead. The American National Institute of Health calculated that to describe a human being to a resolution of 1 mm would take 10 Gb (or 1011 bits) of data. Samuel L. Braunstein has calculated that to extend this to describing
a human to a resolution of the atomic wavelength would take 1032 bits of data. If we imagine 10Gb being, say one hundredth of the largest hard disk in present use (1,000 Gb or 1 Tb) we are then talking about 1018 Tb of data! If present rates of progress are continued teleportation may be possible this century – but may not be.

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