The New Industry - Radio - Modern Airliners - DC-3 - Pressurized Cabins - 1938 Civil Aeronautics Act - World War II - Jet Engine - Radar
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The New Industry

By 1935, the US had four major airlines: American, Eastern, Transcontinental, Western Air (now TWA), and United. Other notable, but smaller airlines, were: Delta, Northwest, and Braniff. Pan American World Airways served as the United States primary international airline with flights to Latin America. European governments on the other hand were still forming governmanet airlines, such as Air France and Ala Littoria (Italy).
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Radio

Another development of enormous importance to aviation was radio. Aviation and radio developed almost in lock step. Marconi sent his first message across the Atlantic on the airways just two years before the Wright Brothers' first flight at Kitty Hawk. By World War I, some pilots were taking radios up in the air with them so they could communicate with people on the ground. The airlines followed suit after the war, using radio to transmit weather information from the ground to their pilots so they could avoid storms.

Perhaps an even bigger development, however, was the realization that radio could be used as an aid to navigation when visibility was poor and visual navigation aids such as beacons were useless. Once technical bugs were worked out, the Department of Commerce constructed 83 radio beacons across the country. They became fully operational in 1932, automatically transmitting directional beams, or tracks, that pilots could follow to their destination. Marker beacons came next, allowing pilots to locate airports in poor visibility. The first air traffic control tower was established in 1935 at Newark International Airport in New Jersey.
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Modern Airliners

Boeing built what generally is considered the first modern passenger airliner, the Boeing 247. It was unveiled in 1933, and United Air Lines promptly bought sixty of them, tying up Boeing production lines for two years. Based on a low-wing, twin-engine bomber with retractable landing gear, the 247 accommodated 10 passengers and cruised at 155 miles per hour. Its cabin was insulated to reduce engine noise levels inside the plane, and it featured such things as upholstered seats and a hot water heater to make flying more comfortable to passengers. Eventually, Boeing also gave the 247 variable pitch propellers that reduced takeoff distances, increased the rate of climb, and boosted cruising speeds.

Not to be ouTDone by United, TWA went searching for an alternative to the 247 and eventually found what it wanted from the Douglas Aircraft Company. Its DC-1 copied Boeing's innovations and improved upon many of them. The DC-1 had a more powerful engine and accommodations for two more passengers than did the 247. More importantly, the airframe was designed so that the skin of the aircraft bore most of the stress on the plane during flight. There was no interior skeleton of metal spars, thus giving passengers more room than they had in the 247.

The DC-1 also was easier to fly. It was equipped with the first automatic pilot and the first efficient wing flaps for added lift during takeoff. However, for all its advancements, only one DC-1 was ever built. Douglas decided almost immediately to alter its design, adding 18 inches to its length so it could accommodate two more passengers. The new, longer version was called the DC-2, and it was a big success, but the best was still to come.
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The DC-3

Called the plane that changed the world, the DC-3 was the first aircraft to enable airlines to make money carrying passengers. As a result, it quickly became the dominant aircraft in the United States following its debut in 1936 with American Airlines (which played a key role in its design).

The DC-3 had 50% greater passenger capacity than the DC-2 (21 seats versus 14), yet cost only 10% more to operate. It also was considered a safer plane, built of an aluminum alloy 25% stronger than materials previously used in aircraft construction. It has more powerful engines (1,000 horsepower versus 710 horsepower for the DC-2), and it could travel coast to coast in 16 hours -- a fast trip for that time.

Another important improvement was the use of a hydraulic pump to lower and raise the landing gear. This freed pilots from having to crank the gear up and down during takeoffs and landings. For greater passenger comfort, the DC-3 had a noise-deadening plastic insulation, and seats set in rubber to minimize vibrations. It was a fantastically popular airplane, and it helped attract many new travelers to flying.
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Pressurized Cabins

Although planes such as the Boeing 247 and the DC-3 represented significant advances in aircraft design, they had a major drawback. They could fly no higher than 10,000 feet because people became dizzy and even fainted due to the reduced levels of oxygen at higher altitudes.

The airlines wanted to fly higher to get above the air turbulence and storms common at lower altitudes. Motion sickness was a problem for many airline passengers, and an inhibiting factor to the industry's growth.

The breakthrough came at Boeing with the Stratoliner, a derivation of the B-17 bomber introduced in 1940 and first flown by TWA. It was the first pressurized aircraft, meaning that air was pumped into the aircraft as it gained altitude to maintain an atmosphere inside the cabin similar to the atmosphere that occurs naturally at lower altitudes. With its regulated air compressor, the 33-seat Stratoliner could fly as high as 20,000 feet and reach speeds of 200 miles per hour.
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The 1938 Civil Aeronautics Act

By 1938, over 3.5 million passengers were flying on airlines, over a million of them Americans. This extreme growth promted new government policies. Government decisions continued to prove as important to aviation's future as technological breakthroughs, and one of the most important aviation bills ever enacted by Congress was the 1938 Civil Aeronautics Act. Until that time, numerous government agencies and departments had a hand in aviation policy. Airlines sometimes were pushed and pulled in several directions, and there was no central agency working for the long term interests and stability of the industry. All the airlines had been losing money since the postal reforms in 1934 significantly reduced the amount they were paid for carrying the mail, and all were at risk of losing postal routes (still key to staying in business) to a low competing bid at the next Post Office auction.

The airlines desperately wanted greater government regulation through an independent agency they could call their own, and the Civil Aeronautics Act gave them what they wanted. It created the Civil Aeronautics Authority (CAA), and gave the new agency power to regulate airline tariffs, airmail rates, interline agreements, mergers, and airline routes. Its mission was to preserve order in the industry, holding rates to reasonable levels while at the same time nurturing the still financially-shaky airline industry by protecting carriers from unbridled competition.

Congress created a separate agency -- the Air Safety Board -- to regulate the carriers on matters of safety. In 1940, however, President Roosevelt convinced Congress to transfer the safety regulatory function to the CAA, which was then renamed the Civil Aeronautics Board (CAB). These moves, coupled with the tremendous progress made on the technological side, put the industry firmly on the road to success.
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World War II

Aviation had an enormous impact on the course of World War II and the war had just as big of an impact on aviation. There were fewer than 300 air transports in the United States when Hitler marched into Poland in 1938. By the end of the war, over 40 U.S. aircraft manufacturers were producing 50,000 planes a year. By the end of the war the US had built more than 300,000 aircraft. During the war aircraft production had become the world's leading manufacturing industry.

Most of the planes, of course, were fighters and bombers, but the importance of air transports to the war effort quickly became apparent as well. Throughout the war, the airlines provided much needed airlift to keep people and supplies moving to the front and throughout the production chain back home. For the first time in their history, the airlines had far more business -- for passengers as well as freight -- than they could handle. Many of them also had opportunities to pioneer new routes, gaining an exposure that would give them a decidedly broader outlook at war's end.

While there were numerous advances in U.S. aircraft design during the war that enabled planes to go faster, higher, and further than ever before, mass production was the chief goal of the United States. The major innovations of the wartime period -- radar and jet engines -- occurred in Europe.
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The Jet Engine

Isaac Newton was the first to theorize (in the 18th century) that a rearward-channeled explosion could propel a machine forward at a great rate of speed (Newton's 3rd Law). However, no one found a practical application for the theory until Frank Whittle, a British pilot, designed the first jet engine in 1930. Even then, widespread skepticism about the commercial viability of a jet prevented Whittle's design from being tested for several years.

The cold war between the Soviet Union and the United States following World War II helped secure the funding needed to solve such problems and advance the jet's development. Most of the breakthroughs related to military aircraft that later were applied to the commercial sector. For example, Boeing employed a swept-back wing design for its B-47 and B-52 bombers to reduce drag and increase speed. Later, the design was incorporated into commercial jets, making them faster and thus more attractive to passengers. The best example of military-civilian technology transfer was the jet tanker Boeing designed for the Air Force to refuel bombers in flight, thus extending their range. The tanker, called the KC- 135, was a huge success as a military plane but even more successful when revamped and introduced in 1958 as the first U.S. passenger jet, the Boeing 707. With a length of 125 feet and four engines with 17,000 pounds of thrust, the 707 could carry up to 181 passengers and travel at speeds as high as 550 miles per hour. Its engines proved more reliable than piston driven engines, and they produced less vibration, putting less stress on the plane's airframe and reducing maintenance expenses. They also burned kerosene, which cost half as much as the high octane gasoline used in more traditional planes. With the 707, first ordered and operated by Pan Am, all questions about the commercial feasibility of jets were answered. The jet age had arrived, and other airlines soon were lining up to buy the new aircraft.
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