IELTS Academic Reading Practice Test 183

A jet engine produces thrust not by turning a propeller but by throwing hot gas backwards at high speed. Air is drawn in, squeezed by a rotating compressor, mixed with fuel and burned, and the resulting gases expand through a turbine and leave through a nozzle at the rear. The gas departs at great speed, so the aircraft is pushed forward, a direct application of Newton's third law. The principle is far older than the aeroplane: around the first century AD, Hero of Alexandria wrote of a hollow ball, mounted on pivots, that rotated as steam rushed out of curved pipes, though it remained a novelty and never did useful work. A gas turbine was patented in England by John Barber in 1791, and in 1913 the French engineer René Lorin proposed driving an aircraft by reaction to a jet of air, but no practical engine followed.

The person who made the idea workable was Frank Whittle, a young officer in the Royal Air Force. In the late 1920s, while training as a pilot, he became convinced that aircraft would soon need to fly higher and faster than propellers would allow, and he set out his reasoning in a thesis written at the RAF College at Cranwell. In 1930 he applied for a patent for a turbojet engine, but the Air Ministry showed little interest in the idea. Officials regarded the scheme as impractical, and Whittle was sent to Cambridge to study engineering rather than to build an engine.

His patent lapsed in 1935 because a renewal fee had not been paid, and it was only through private support that the work continued. In 1936 Whittle and a group of investors founded Power Jets Ltd, and with backing from the engineering firm British Thomson-Houston an experimental engine was built. It ran for the first time on 12 April 1937 in a factory in Rugby and, although it was far from airworthy, it demonstrated that the cycle worked. The engine used a single-stage centrifugal compressor, in which air is flung outwards by a spinning disc, a design that was simpler and more robust than the axial compressors used in modern engines.

In Germany, meanwhile, a young physicist named Hans von Ohain had reached a similar conclusion by a different route. Von Ohain, who had studied at Göttingen, developed his engine independently and appears to have been unaware of Whittle's patent when he began work in 1935. He was supported by the aircraft manufacturer Ernst Heinkel, who saw the commercial value of high speed. Von Ohain's engine also used a centrifugal compressor, and on 27 August 1939 it powered the Heinkel He 178, a small experimental aircraft, on the world's first flight by a jet-powered aeroplane.

Britain followed nearly two years later. Whittle's W.1 engine was installed in the Gloster E.28/39, a compact experimental aircraft, which took off from RAF Cranwell on 15 May 1941 with the test pilot Gerry Sayer at the controls. Development of production engines passed to Rolls-Royce, and the twin-engined Gloster Meteor entered service with the RAF in 1944. Germany's Messerschmitt Me 262, a swept-wing fighter, had flown in 1942 and was used in combat from 1944, but shortages of suitable metals meant that its engines had to be rebuilt after a very short period of use.

In 1941 one of Whittle's engines and a set of drawings were flown to the United States, where the information was passed to the General Electric company, which built a version of the design. This powered the Bell XP-59A Airacomet, the first American jet aircraft, which flew in October 1942. Relations between Whittle and the British establishment were never easy; he was exhausted and unwell for much of the war, and he resigned from Power Jets in 1946.

The early engines were difficult to live with. They consumed fuel at a prodigious rate, produced a deafening noise, and their turbines ran at temperatures close to the limits of the metals available, so components had to be replaced after only a few hours of running. Early jet aircraft were also slow to accelerate at low speed and needed long runways. In spite of these problems the advantage was obvious: a jet could fly far faster than any propeller-driven machine, and at altitudes where a piston engine would struggle for lack of air.

After the war the axial compressor, in which air flows straight through rows of blades, replaced Whittle's centrifugal design in most large engines because it was more efficient. The next step was the turbofan, in which a large fan driven by the turbine pushes a mass of cool air around the hot core. The Rolls-Royce Conway, which entered service in 1960, was the first turbofan in airline use, and modern airliners fly with engines of high bypass ratio, meaning that most of the air they move passes outside the combustion chamber. This is why today's engines are quieter and far more economical than those of the 1950s.

Whittle was knighted in 1948 and later moved to the United States, where he died in 1996. The basic principle of his engine has not changed: air is compressed, fuel is burned and gas is expelled at high speed. What has changed is the engineering, in materials, in combustion and in the control of airflow, and the result is an industry that carries billions of passengers each year. Few inventions have altered the world so quickly.

A biometric passport looks much like any other: a small book with a photograph on the data page. What distinguishes it is a microchip, usually set into the back cover, and the symbol printed on the front, a circle inside a rectangle, which tells officials that the document can be read by machine. The chip holds the same details as the printed page, together with a digital image of the holder's face. Passports of this kind, often called electronic or e-passports, are now issued by well over a hundred countries, and most air travellers carry one without giving it much thought.

Chip passports were first issued in the late 1990s, but they spread quickly for a political reason. After the attacks of 11 September 2001, the United States decided that visitors arriving without a visa should carry documents that were harder to forge. Countries whose citizens could enter the United States without a visa were told that their passports must contain a chip and a machine-readable data page by October 2006, or their citizens would need visas. Governments that had shown little interest in the technology suddenly had a strong incentive to adopt it, and most did so within a few years.

The technical rules are set not by any single government but by the International Civil Aviation Organization, a United Nations agency whose document 9303 specifies almost every detail of the passport, from the layout of the data page to the radio protocol used by the chip. The chip is passive: it has no battery and draws the small amount of power it needs from the radio field produced by the reader. At the end of each record the issuing country adds a digital signature, which allows another country to check that the data have not been altered.

As a minimum, the chip holds the information printed on the data page and a digitised photograph. Countries may add fingerprints and images of the iris, and a growing number do so, but the specification permits these without requiring them. The same chip can carry separate sections for visas, so that a visa issued by one country can be stored electronically inside a passport issued by another. Because a camera can compare a photograph with a live face, facial recognition has become the dominant technology at borders, while fingerprints are used mainly at automated gates in the countries that collect them.

Reading the chip is deliberately made difficult. Before any data can be released, the reader must supply a key derived from the two lines of machine-readable characters at the bottom of the data page, a protection known as Basic Access Control. Because the key depends on the printed page, the chip cannot be read by anyone who has not opened the passport, an important safeguard against skimming by hidden readers. Fingerprint records are protected further by Extended Access Control, which requires a certificate issued to the receiving country. Certificates for checking the signature are distributed through a directory, so that a border post in one country can verify a passport issued in another.

At an automated gate, the traveller places the passport on a reader and looks at a camera. The machine reads the printed characters, unlocks the chip and compares the stored photograph with the image it has just captured. If the two match closely enough, and the signature on the chip is valid, the gate opens. A border officer watches over a row of gates and intervenes when the software is uncertain, so that a single officer may supervise a dozen machines. This is where much of the cost saving of the technology comes from.

Face recognition is not perfect. Accuracy depends on the quality of the stored photograph, the lighting at the gate and the age of the traveller, since a child's face changes shape quickly and a passport may be valid for five or ten years. Identical twins have caused difficulty, and a photograph taken years earlier may resemble the holder only loosely. Even so, the algorithms have improved enormously. Independent evaluations by the American government's standards laboratory have documented sharp reductions in error rates since 2010, and the best systems now make fewer mistakes than human inspectors.

Privacy groups point out that a passport is not the only copy of the data. Images held in national databases can be kept for years, and the spread of facial recognition in public places makes the link between a face and a name more valuable than it once was. Research is moving towards documents that never leave the traveller's pocket. In recent years the same international organisation has been drafting a standard for a digital travel credential, a virtual version of the passport that could be held on a phone and sent to the destination country in advance, with the chip in the physical passport used to confirm that the two belong together.

Since July 2022, every new type of car sold in the European Union has had to be fitted with intelligent speed assistance, or ISA, and since July 2024 the requirement has covered every new car registered. Similar rules are being introduced in Britain and in other markets, and the device is now fitted as standard to most new cars sold in Europe. It is not, in most models, a limiter in the sense that a lorry's governor is, because it does not usually prevent the car from exceeding the limit. It reads the limit from a camera that recognises signs and from digital mapping, displays the figure on the dashboard and, when the driver presses the accelerator beyond it, resists gently, by increasing the pressure needed or vibrating the pedal, until the driver pushes firmly through.

The case for the rule rests on a familiar piece of physics. The energy a moving car carries rises with the square of its speed, so a car travelling at 50 km/h has more than twice the energy it has at 30. In a collision that energy has to go somewhere, and the severity of injury rises steeply with it, especially for people on foot or on bicycles. Analyses of crash data from many countries have found that a small reduction in average speed produces a much larger proportional fall in deaths, a relationship robust enough that transport agencies now use it to predict the effect of new limits.

Trials of the technology began long before the law. In the 2000s several European countries equipped fleets of cars with early versions and recorded how drivers behaved. The results were consistent: those with an advisory system spent less time above the limit than a control group, and the effect was largest among drivers who had previously been the worst offenders. The trials were small and short, so their results cannot be extrapolated with confidence, but the direction of the effect has been repeated often enough to be convincing.

The practical weaknesses are real. A camera cannot always tell which sign applies to which lane, and it may read a sign on a side road, a sign intended for heavy goods vehicles, or one left behind after roadworks. Digital maps are better but are not always current: a road that was a 60 km/h limit last year may be a 30 km/h zone now. When the system is wrong, the driver may be slowed unexpectedly on a fast road or, worse, may come to distrust the display and ignore it when it is right.

Psychologists warn of a subtler problem. When part of a task is automated, people tend to give it less attention. Drivers who rely on the car to tell them the limit may stop reading signs themselves, and may drive faster on the many roads where no reliable figure is available. This is a form of behavioural adaptation, the same phenomenon that blunted some of the expected benefits of antilock brakes and seat belts. The effect is hard to measure, and in my reading of the evidence it is likely to be modest, but it is not zero.

Then there is the question of control. A system that physically prevented a car from exceeding the limit would be unacceptable to most drivers, and rightly so, because a driver may need to accelerate briefly to overtake a lorry, to escape a hazard or to join a motorway. The regulations recognise this by allowing the driver to override the system simply by pressing harder. But the moment the driver can override it, the device becomes an adviser rather than a governor, and its effect on the determined speeder is close to nil. The law's value lies elsewhere: it changes the default, making the legal speed the path of least resistance for the ordinary driver.

There are questions about data too. ISA needs to know where the car is, which means satellite positioning, and the cameras record what the car sees. New cars in Europe must now carry an event data recorder that stores information from the seconds before a crash for use in investigations. Privacy campaigners argue that the same data could be used for commercial purposes, and that the boundary between safety and surveillance is being crossed without much public discussion. Insurers have shown interest in pricing policies according to how people drive.

Public opinion, so far as it can be measured, is cautiously favourable. Surveys in several European countries have found that a majority of drivers support a system that warns them of the limit, and that support falls sharply if the car takes control away. Complaints reaching motoring organisations are mostly about false warnings, and about the feel of the pedal rather than the principle.

On balance, the case for compulsory ISA is strong, provided it remains an assistant. The evidence that speed kills is overwhelming, the hardware is cheap, and the alternative of more cameras and larger penalties is both more intrusive and less effective. What I would resist is the drift towards a hard limit, presented as a natural next step now that the hardware sits in every car. A system that tells drivers the limit and makes obedience easy is a reasonable use of public power; one that overrides the driver's judgement is not.