The inventions, institutions, gadgets, and lucky breaks that have shaped the story of the airplane.
- By Roger Bilstein
- Air & Space magazine, March 2003
(Page 3 of 3)
Ironically, the rocket-propelled Bell XS-1, which in 1947 became the first airplane to break the sound barrier, had straight wings. Because its configuration evolved before theories of swept wings had become well known, designers carefully gave the wings a thin cross-section, using thicker wing skins to provide needed load-bearing qualities at supersonic speed. The overall shape of the XS-1, including its rather blunt nose, reflected what was known about the aerodynamic qualities of a .50-caliber bullet; the airplane’s job was to fill in massive gaps of information about the dynamics of aircraft cleaving the air beyond the speed of a gunshot. America’s nimble shift to swept wings relied in part on key contributions from a Russian immigrant and a maverick aerodynamicist at the NACA’s Langley center. A man named Jones At work for Republic Aviation (founded by fellow Russian immigrant Alexander de Seversky), Michael Gluhareff concluded that a triangular, or delta, wing had great potential at sonic speed. World War II diverted his attention, but a wind tunnel model wound up on the desk of the NACA’s Richard Jones. A college dropout, Jones had flown with a barnstorming troupe and eventually wound up in a New Deal-era work program at Langley, where he blossomed into a highly regarded engineer. Examining the Gluhareff model and test documents, Jones realized that recent mathematical formulas and tunnel data sustained the postulates that swept wings are better performers at sonic speeds. When the German work on swept wings came to light during Operation Paperclip, the NACA and the Air Force adroitly exploited the convergence of these lines of investigation. The Boeing B-47 bomber and the North American F-86 fighter, both flown in 1947, acquired swept wings and a configuration that set the pattern for a host of postwar bomber, transport, and fighter designs. The swept-wing North American F-100 Super Sabre, which first flew in 1953, became the first U.S. fighter to crack the sound barrier in level flight. During the 1960s, swept wings and speeds around Mach 2 became the norm.
Military programs like the Convair F-102 interceptor and B-58 supersonic bomber also relied heavily on newfangled management approaches. Exceedingly complex, such aircraft were designed from scratch with aerodynamic framework, avionics, engines, armament, payload, and maintenance all considered as part of an organic whole—in other words, a weapon system. Systems management required new levels of documentation and bureaucratic expertise. In the cold war era, such aerial weapons usually evolved in the context of what was considered a national emergency—catching up to or gaining an advantage over the Soviets. It took years for the protracted design-build-test-accept sequence to produce an airplane. “Concurrency” became the watchword, with construction of production facilities, tooling, and other fabrication requirements running in parallel with design and test of the airplane itself.
As high-speed aerodynamics evolved, designers wrestled with problems involving the performance of Mach 2 fighters; aerodynamic forces on ailerons, rudders, and elevators were too great for the pilot. Mechanical and hydraulic systems solved some problems, but they added weight and complexity to airframes and were vulnerable to hostile fire. Moreover, modern aircraft, like sensitive racehorses, had a certain degree of inherent instability; this enhanced their agility in combat and reduced the size and weight of their control surfaces. To manage control dilemmas, designers sought a solution using computers and electronic systems: “Fly-by-wire” technology replaced mechanical cables and linkages to control surfaces with slim electrical cables carrying signals to actuators that moved ailerons, rudders, and elevators. The pilot's joystick was no longer directly connected to the surfaces it controlled—except by electrical impulses. During the 1970s, a series of NASA test programs involving a converted Vought F-8 Crusader supersonic fighter led the way to the first successful fly-by-wire control systems. In the case of the Lockheed F-117A Nighthawk fighter and Northrop’s B-2 Spirit bomber, stealth technology dictated designs for completely unstable aircraft. Without the computerized flyby-wire systems, these aircraft would have been unflyable.
A new class of aircraft, unmanned aerial vehicles, or UAVs, completed the evolutionby ushering in a total reliance on computers and fly-by-wire technology. The genre began as drones during World War I—like torpedoes with a biplane’s wings and tail—and by the time of the Vietnam War, remotely piloted vehicles, or RPVs, had jet engines and carried electronic surveillance gear. The subsequent generation of UAVs included quiet, propeller-driven designs like the General Atomics Predator and jet-powered, long-endurance types like the Northrop Grumman Global Hawk, which operates at high altitudes and carries an impressive array of video cameras and ultrasensitive electronics. Some UAVs toted missiles, while others took on such challenges as trans-Pacific journeys from the U.S. West Coast to Australia.
For sophisticated, supersonic combat aircraft developed from the late 1950s on, fabrication procedures presented challenges so new that in many such programs, the Air Force had to become a partner with commercial manufacturers. Aluminum forgings of unprecedented size required Alcoa to adopt innovative methods; Wyman-Gordan, which made machinery to produce specialized components, had to develop new types of presses and machine tools. MIT ran one intensive four-year research program that cost upward of $180 million to develop numerically controlled machine tools that were directed not by hand but by electronic code and allowed for quicker, more precise manipulation of material. Such efforts led to a new generation of machine tools delivered by companies like Cincinnati, Kearney and Trecker, Giddings & Lewis, Onsrud, and others. To turn out components from heat-resistant, high-strength metal alloys while reducing the number of stiffeners (the weight problem again) used in constructing wings for supersonic fighters, a whole new process evolved. This revolutionary fabrication method, called electrical discharge machining (EDM), used electrical currents to carve out sections of metal, leaving integral stiffeners. The F-100 became the first fighter to feature these one-piece, integrally stiffened skins.
Additional unique tooling appeared to fabricate components made of composite materials (derived from plastic, carbon fibers, and other untraditional substances) coupled with metal alloy skins to form a resilient but lightweight “sandwich” panel. The search for lighter components contributed to the creation of an industry for the production of titanium, geared to a previously unheard-of output of up to 600 tons per month. The F-100 used six times as much titanium as early models of the F-86D.
Within the first century of flight, an uninterrupted expansion of technology transformed the structure and performance of the Wrights’ invention. Along the way, an electronic revolution led to new compact radars and avionics mounted in light airplanes, giant airliners, and Mach-plus fighters. When Boeing developed its 777 airliner in the early 1990s, electronics permeated all aspects of its design, which relied entirely on automation and personal computers and introduced the concept of the “paperless airplane.” Lockheed’s new F-35 Joint Strike Fighter, which incorporates all these aspects of computer electronics, also required a whole new approach to program management in order to accommodate three U.S. armed services—the Air Force, Navy, and Marines—and the Royal Air Force, all of which will be using the fighter. Moreover, follow-on propulsion systems will be added to the same basic airframe to produce a short-takeoff/verticallanding variant. (What would the Wright brothers have thought of a STOVL supersonic jet fighter armed with rockets, laser targeting, helmet sight, head-up display, radar, and night combat capability?) Components will be manufactured worldwide and the airplane itself will be assembled in the United States and Europe.
And now for the next hundred years…