The Jet

A military secret that is becoming too big a cat to be kept in the bag, got partly out last week. WPB announced that production of jet-propelled planes, the latest and most revolutionary thing in aviation, is being sharply stepped up; by next year the jets may be the biggest single item in the U.S. plane-building program. Recent performances by new types have been so sensational that most plane designers now believe the propeller-driven airplane is obsolete, may be largely displaced in the final drive against Japan.

The Bell P-59, only U.S. jet plane yet given a name and public showing, already far surpasses in range and general performance the two known German types (Me-262 and Me-163). U.S. air officers undisturbed by such skeptical armchair critics as the New York Times's Hanson W. Baldwin, are biding their time, expect to show the enemy some jet surprises before long.*

Peace Design. But plane designers have found the jet plane's peacetime possibilities more exciting than its potential military uses. The jet plane gives an amazingly smooth, comfortable ride, with no vibration, little noise. Passengers would hear only the rush of air over the plane's wings; groundlings do not hear the plane at all until it is overhead, when it whooshes past like the blast of a giant blowtorch. Equipped with a pressurized cabin, the plane is expected to cruise at well over 400 m.p.h., and to fly at altitudes above the prewar U.S. record (43,166 ft). Once a pilot gets used to it, it is easier to fly than a fast propeller-driven plane. It is also safer and easier to keep in repair, can use such cheap fuels as kerosene (engineers say it will fly on "anything from coal oil to Napoleon brandy").

The great advantage of the jet engine is its simplicity. In contrast to the conventional reciprocating engine, the Bell P-59 motor has only four basic parts: 1) compressor, 2) combustion chamber, 3) turbine, 4) the cone-shaped jet through which the expanding gases that drive the plane are expelled. Because its operation, like a gun's recoil, is based on Newton's third law of motion (every action has an equal and opposite reaction), engineers prefer to call it the "reaction engine, "/-

Engine Design. Since it has only one moving gear (the compressor and turbine, mounted on the same shaft), the jet en gine needs little oil. The plane needs no warmup, is ready to fly 30 seconds after the motor starts. The pilot, relieved of worries about oil pressure, fuel mixture, propeller pitch, etc., has only three controls to operate: the stick, the throttle and rudder pedals. Test pilots have found the P-59 more maneuverable in the air than a conventional plane. Taxiing on the ground is tricky. Because there is no propeller to blow wind against the tail and rudder control surfaces for steering, pilots steer with the wheel brakes.

On the ground, the P-59, needing no clearance for a propeller, presents an odd, squat profile with an upswept rear end (to keep out of the way of the hot blast from the jets). Ground crewmen give the plane a wide berth at its takeoff; anyone within 20 feet of the jets would be burned to a crisp. But in the air, the fuel is burned so completely in the combustion chamber that the jets show no flame, even at night. The openings in front of the plane through which air is sucked into the motor posed a problem: they also sucked in birds. Engineers have partly solved the problem by screening the intakes.

Human Design. The U.S. pioneers in jet-plane research, which began before Pearl Harbor and has been based on the design by British Inventor Frank Whittle, have been General Electric (the motor) and Bell Aircraft (the frame). But today almost every major U.S. planemaker is up to his ears in jet plans.

The two big problems in jet-plane design are 1) its high fuel consumption, 2) its approach to supersonic (i.e., faster than sound) speeds. (The Navy announced last week that it was building a 750-m:.p.h. wind tunnel to test jet planes.) At high speeds, the jet engine is more efficient than a conventional engine; it uses little more fuel at 500 m.p.h. than at 400. But because the jet engine usually must operate at maximum capacity from the start, it has been relatively inefficient at low speeds. Moreover, to cut air resistance, the P-59 has extremely thin wings which have no room for fuel tanks. Nonetheless, U.S. engineers are reported to be approaching a solution to this problem.

For the other major problem, the plane's great speed, engineers see no easy solution. Even at the jet-plane's present cruising speed, 400 m.p.h., a pilot has almost all he can do to stay conscious during maneuvers ; a slight turn may make him black out. Some jet-plane enthusiasts are beginning to observe, only half-jokingly, that it may soon be necessary to redesign the human body.

* Their reasons for withholding jet planes from combat so far: 1) the U.S. fighters and bombers already in action are good enough to control the enemy air; 2) air officers think it unwise to let any jet planes fall into enemy hands before they are ready to strike in force,

/- Not to be confused with the turbocompressor engine which drives the P-59 is the pure rocket type used in the German Me-163, which is theoretically capable of flying beyond the atmosphere because it carries its own oxygen for combustion.

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