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Erik M. Conway, Blind Landings: Low-visibility Operations in American Aviation, 1918-1958.

Erik M. Conway, Blind Landings: Low-visibility Operations in American Aviation, 1918-1958, Johns Hopkins University Press, Baltimore MD (2006), 256 pp., $45.00.

A veteran of flying the 'Hump' in the Second World War finds work in South America as a pilot for a fledgling airline. This entails flying to remote locations, landing on unimproved strips and, of course, flying in areas without navigation aids. He recounts an approach to his destination that finds the area completely socked in by clouds. His destination sits at the base of a range of mountains. Recognising the circumstances, he mutters to his co-pilot, 'This has the makings of a bad accident.'

Erik Conway's new book is a history of the efforts to make the aforementioned pilot's macabre remark unnecessary. It is a story that begins almost with the dawn of practical flight: flying without being able to see the ground. In the United States the problem became a major issue with the advent of airmail service. Unlike a ship at sea, there is no safe haven for an aircraft but the ground, although weather at a destination may preclude a landing with any cues at all. The problem that Conway chronicles is a mixture of human, technological and political issues.

The first hurdle was human failings--stubbornness. Until pilots were convinced that instruments were more accurate and more reliable than they themselves were, accidents continued, for pilots, trained to see their way from A to B, were reluctant to set aside their physiological instincts when they couldn't see. Enter the turn-and-bank indicator, the artificial horizon, the gyroscope, the liquid compass: all pre-dated the end of the First World War in one form or another but were little used, yet, when combined, they enabled a pilot to maintain co-ordinated turns without outside reference. Despite this, reliance on these instruments was rare.

The introduction of new flight instruments by Sperry Corporation, creator of the automatic pilot, and the requirement among American airlines to have instrument-rated pilots, helped pave the way for change. But it took the failure of the Army Air Corps, while flying the mail in 1934, to underscore the importance of being able to fly blind. Despite their best efforts, military pilots died in droves trying to deliver the mail by air. This led to, among other things, the purchase of Link trainers to teach pilots how to fly on instruments, while at the same time driving home their own human failure to stay upright without visual cues.

But flying blind is only half the story: being able to land blind is the other half, and that was the next--the more difficult--step. Various approaches emerged, each using radio beams to guide pilots to a specific point. One option used multiple beams to try and align the pilot correctly, allowing him to descend at a specified rate to the runway. But odd things cropped up to make these systems largely unusable. Radio beams bent in a curve; beams raised or lowered themselves because of climatic changes, often too high or low to accomplish a landing; geological interference gave multiple paths to follow, something participants in the experiments dubbed 'uniformly recurrent multiple course phenomena'. The latter were notable in mountainous terrain, a region precisely where the system was needed most.

Two developments tried to address the problems. First were radio beacons rather than beams, meant to allow the pilot to locate himself accurately in airspace. Second, and more interesting in some ways, were arguments that the objective itself had to change to match the reality of the technology of the moment: if blind landings were not going to be possible, the solution was to redefine the objective. This the airlines did (led by United), switching from blind landings to 'instrument approaches'. It seems a subtle distinction, but it is one of significance that Conway writes about in detail.

Efforts to develop a microwave landing systems seemed to hold promise yet led nowhere initially because the two primary customers, the military and the airlines, preferred different and incompatible systems. Cost meant only one could be chosen, and the military, with nearly ten times more large aircraft than the airlines (courtesy of its new heavy bombers), won the contest.

While the exigencies of the Second World War led the Army Air Forces to pick a system and go with it, that system was itself a mixture of several competing instrument landing methods. In spite of this, and the varied successes the system enjoyed during the war, neither that which the AAF selected nor that which the airlines wanted emerged the winner in the end. This was in no small part because of the British invention of the resonant cavity magnetron, or radar, which changed the method of aircraft control in blind landing configurations. Up to then equipment on the ground sent information to the aircraft, which the pilot used to fly the plane to a desired spot. Control of the landing was firmly in the cockpit. Radar shifted that control to the ground, to an entirely different landing method. The system on which the new approach method was based was in fact a gun radar designed to track aircraft so a gun could fire anti-aircraft shells at it. It was only a small step to a radar that could tell a ground controller the position of an aircraft, allowing that controller to talk the pilot down. The new method meant that a landing was controlled not by the pilot but by someone on the ground. The pilots now followed instructions from the ground, ceding fundamental control of the plane.

The organisation that introduced the winning system, MIT's Radiation Lab, was an outsider to the decades-old contest for a blind landing system, notes Conway, and this is significant, for the new organisation felt unconstrained by pre-existing customs or assumptions. This was a key factor in the fundamental shift of control from the cockpit to a ground controller.

Two profound advantages lay in the ground-controlled radar approach. First, it required no bulky, heavy or drag generating equipment to be carried on the aircraft. All equipment was on the ground and the controller directed the pilot to the landing. This meant the system could work for pursuit aircraft as easily as for heavy bombers. And, second, it required no pilot training beyond the ability to fly on instruments. The real work was done by the ground controller, who passed instructions on to the pilot via radio, meaning that the intense training for a blind landing was restricted to a few ground controllers, freeing the pilots to follow their own work without any additional burden.

In one sense Conway casts the play as between the skilled and the unskilled, a frequent scenario in histories of technology--the skilled workers losing control of the job to unskilled managers. But he also points to the democratisation of a technology, and that, too, is a regular feature in histories of technology. In this case the airlines and professional pilots are pitted against the small plane owner and private pilot when it comes to flying in bad weather. This is because the version of blind landing preferred by the airlines and professional pilots kept control of the landing--of the aircraft--in the cockpit, while the ground-controlled approach placed the skill for that job largely on the ground. The second option also removed the cost of blind landing equipment from the airplane, making it more uniformly accessible.

It was never planned this way, of course. The entire system was a technological development driven by political and professional forces that cared little if at all about democratising aviation, which is what historians of technology have been arguing for several decades now. In the end, Conway's book is both technical in nature and important, for it is a key piece in the patchwork of the history of aviation.

Christian Gelzer, NASA Dryden Flight Research Center, California
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Author:Gelzer, Christian
Publication:The Journal of Transport History
Article Type:Book review
Date:Sep 1, 2007
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