Jets Are Different

At the Cleveland Air Races, 60,000 spectators snapped their heads from side to side as jet-propelled P-80s, hissing hoarsely, swooped past at nearly 600 miles an hour.* Many wondered how it felt to ride in their hurtling cockpits. Non-jet pilots wondered too, and envied. Handling a P-80, they agreed, was about the most exciting experience a flying man could know.

Speed makes the difference--a higher order of speed. Many military planes can plunge in a power dive, faster & faster until the needle of the airspeed indicator creeps close to the dread red mark of "compressibility." At this critical speed, the airstream, accelerated by crowding over the curved surfaces, reaches at certain spots the speed of sound./- Then a standing sound wave may form on the wing or tail, roaring and hammering, perhaps chewing holes in the plane's skin or freezing the controls.

P-80s, at high altitudes, can reach compressibility in ordinary level flight. The pilot opens the throttle. The speed picks up as the magic jet engine shoves harder. It is as smooth as oil, so nearly vibrationless that sometimes a special gadget is installed to tap on the instrument board and keep the plane's instruments from sticking.

Warning Buzz. The first sign of trouble is a tiny buzz in an aileron, which means that a small standing sound wave is forming. Most pilots ease back when they feel it. But some are tempted. Said one: "You feel a surge of excitement and mischievous satisfaction as a gentle nibbling disturbs the controls. Some unreasonable devilment urges you to start the compressibility processes which in a few seconds can wrench all control away from you and plunge the ship into wild, tremendous vibrations."

Then the plane may flip in a violent roll, or snap into a dive as the wing loses its lift. Racked by enormous forces, the plane may suddenly disintegrate in midair,

At normal jet cruising speed, which is well above 300 m.p.h., every air effect is sharply exaggerated. "A patch of rough air," said an Army pilot, "which would be slightly jostling to another plane, suddenly slams you against your belts. You thank your crash helmet for absorbing the shock when the canopy smacks downward."

G-Suits & Coolers. The jet plane's controls, helped by hydraulic boosters against the powerful airstream, are devilishly sensitive. "The slightest movement hurls you over miles of the earth's surface as the ground blurs beneath you." Jet pilots normally wear "G-suits" to protect them from loss of consciousness. These operate automatically on the turns, keeping the pilots' blood from leaving their brains and concentrating in the lower parts of their bodies. "When you do a sudden steep turn, you are punched severely in the belly as the abdominal bladder inflates and the laces tighten around your legs. The centrifugal forces of a 500-mile-an-hour turn increase your weight seven to ten times. You contract your stomach, breathe in gasps."

At top speed, heat from the engine and the friction of the airstream zipping over the canopy raises the inside temperature from 40 to 60 degrees. When the outside temperature is already high, this increase is enough to prostrate the pilot. Some ships have elaborate refrigeration systems to cool the cockpits.

But in spite of these dangers and torments, pilots love their jets. "In a moment of vertical flight, you gain two miles of altitude. Your ears are popping, and the gas belches out of your throat. At 40,000 feet you feel small and high. Mountains are wrinkles in green-and-brown cloth, and cities are patches of ragged wire screen. The upper altitudes are silent except for the slight singing hum of the whirling rotor behind you."

* Jet plane record established in Britain: 616 m.p.h. /- 770 m.p.h. near sea level; about 650 m.p.h. at 40,000 ft.

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