LNAT Practice Passage 12: The Making of Flight
Read the passage below and answer the three LNAT-style multiple-choice questions. Full answers and explanations follow.
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The Making of Flight
For centuries, proposed flying machines followed the most obvious example available: birds. Their wings flapped, so artificial wings ought to flap too. The machines were ingenious and useless, because mere imitation of movement supplied no adequate account of lift, stability or control. Aviation advanced when experimenters ceased treating flight as one marvellous faculty and began separating its mechanical problems.
In 1799, English engineer Sir George Cayley sketched an aircraft with fixed wings for lift and a separate mechanism for propulsion. He later measured aerofoils with a whirling arm and flew an unmanned glider in 1804. Cayley had not built an aeroplane, but he had removed a conceptual obstruction: an aircraft need not beat the air like a bird. Otto Lilienthal carried the enquiry into the air. Between 1891 and 1896, the German experimenter made roughly 2,000 glides, shifting his body to steer and recording what curved wings actually did.
Lilienthal's death following a glider crash in 1896 did not make his work fruitless. Wilbur and Orville Wright studied it, then discovered that accepted tables of lift did not agree with their gliders. A wind tunnel in their Dayton bicycle shop allowed them to test wing shapes and revise the figures. Power was only the conspicuous part of the answer. Their more important achievement was three-axis control: the pilot could govern pitch, roll and yaw rather than merely endure them. On 17 December 1903 at Kitty Hawk, Orville remained airborne for 12 seconds and travelled 120 feet. The fourth flight lasted 59 seconds. Short flights, certainly; controlled ones, decisively.
Speed soon transformed the problem again. Piston engines drove military and civil aviation through two world wars, but on 27 August 1939 the Heinkel He 178, powered by Hans von Ohain's turbojet, flew in Germany. The engine produced thrust by accelerating a stream of gas. Aircraft no longer depended upon propellers biting the air.
When the de Havilland Comet began passenger service in May 1952, its pressurised cabin and jet engines appeared to have settled the future of travel. Then Comets broke apart in flight. Earlier certification tests had used the same prototype for high-pressure proof and later fatigue trials; the overload had altered the metal and made that specimen misleadingly durable. During the accident inquiry, a service fuselage was repeatedly pressurised in a water tank until it failed at an angular opening, where stress had concentrated. Recovered wreckage likewise disclosed fatigue around a window aperture. Catastrophe revealed a mechanism which confidence had concealed.
Modern flight therefore rests on a mixed inheritance: Cayley's distinction, Lilienthal's experience, the Wrights' measurements and controls, jet propulsion, and structural lessons extracted from failure. The familiar list of first flights records only the moments when this slower accumulation became visible.
Questions
Question 1
What did the investigation of the Comet accidents establish?
- ARepeated pressurisation could cause fatigue around angular openings.
- BTurbojets overheated aluminium fuselages whenever aircraft remained at cruising altitude for too long.
- CThe original prototype had failed its pressure tests.
- DEvery fracture began at a passenger window.
Question 2
Which of these best expresses the writer's account of aviation's development?
- AIt was chiefly the work of inventors who replaced mistaken theories with successful machines.
- BIt accelerated once designers reproduced the flapping movement of birds mechanically.
- CIt advanced by separating, testing and revising distinct problems of flight.
- DIt depended less on experimental evidence than on technical imagination.
Question 3
What does the writer identify as the Wright brothers' more important achievement?
- ABuilding the first engine light enough to carry both an aircraft and pilot.
- BCombining revised aerodynamic data with effective three-axis control.
- CDemonstrating that pilots could steer by shifting body weight.
- DSeparating the production of lift from propulsion.
Answers & explanations
Question 1: show answer and explanation
Correct answer: A.
Repeated pressurisation could cause fatigue around angular openings.
Repeated pressurisation caused fatigue to develop where stress was concentrated around angular openings in the fuselage. Trap: Option D resembles the familiar simplified account of the Comet disasters, but "every" and "passenger window" make it narrower and more absolute than the passage.
- A Repeated pressurisation caused fatigue to develop where stress was concentrated around angular openings in the fuselage.
- B The passage does not attribute the accidents to heat from the turbojets or to the length of the flights.
- C The earlier prototype appeared misleadingly durable. Its high-pressure proof test had altered the metal before the subsequent fatigue trials.
- D The passage refers to different angular openings, including a window aperture. It does not claim that every fracture began at a passenger window.
Question 2: show answer and explanation
Correct answer: C.
It advanced by separating, testing and revising distinct problems of flight.
Cayley separated lift from propulsion, the Wrights tested aerodynamic data and control, and the Comet inquiry revealed structural fatigue. Each advance isolates and revises a particular problem. Trap: Option A is tempting because the passage contains several famous inventors and machines. It loses because it mistakes the visible landmarks for the writer's underlying explanation of progress.
- A The word "successful" is too broad as each invention listed had faults. Additionally, individual inventors are important, but the passage resists treating aviation as merely a succession of heroic inventions. Failed machines, revised measurements and accident investigations all contribute.
- B The earliest attempts imitated the flapping of birds and were generally unsuccessful. Progress began when flight was divided into separate mechanical problems.
- C Cayley separated lift from propulsion, the Wrights tested aerodynamic data and control, and the Comet inquiry revealed structural fatigue. Each advance isolates and revises a particular problem.
- D Wind-tunnel measurements, gliding experiments and pressure testing all demonstrate the importance of experimental evidence.
Question 3: show answer and explanation
Correct answer: B.
Combining revised aerodynamic data with effective three-axis control.
The Wrights revised accepted lift data through wind-tunnel experiments and developed control over pitch, roll and yaw. Trap: Option A exploits the popular assumption that powered flight was principally an engine problem. The passage expressly corrects that assumption.
- A The writer calls power the "conspicuous" part of the answer, but explicitly gives greater importance to control.
- B The Wrights revised accepted lift data through wind-tunnel experiments and developed control over pitch, roll and yaw.
- C Steering by shifting body weight was Lilienthal's method. The Wrights developed a more comprehensive control system.
- D Cayley, not the Wright brothers, is credited with separating lift from propulsion.