Wednesday, 23 January 2002

Engleski valjda razumijete? Malo zanimljivosti.The author is a former member of the Society of Licenced Aeronautical Engineers & Technologist, London
In the mid-seventies America faced a new and escalating crisis, with US commercial jets being hijacked for geopolitical
purposes. Determined to gain the upper hand in this new form of aerial warfare, two American multinationals collaborated
with the Defense Advanced Projects Agency (DARPA) on a project designed to facilitate the remote recovery of hijacked
American aircraft. Brilliant both in concept and operation, “Home Run” [not its real code name] allowed specialist ground
controllers to listen in to cockpit conversations on the target aircraft, then take absolute control of its computerized flight
control system by remote means.
From that point onwards, regardless of the wishes of the hijackers or flight deck crew, the hijacked aircraft could be
recovered and landed automatically at an airport of choice, with no more difficulty than flying a radio-controlled model plane.
The engineers had no idea that almost thirty years after its initial design, Home Run’s top secret computer codes would be
broken, and the system used to facilitate direct ground control of the four aircraft used in the high-profile attacks on New
York and Washington on 11th September 2001.
Before moving on to the New York and Washington attacks, we first need to look at the ways in which an aircraft is
normally controlled by its pilot, because without this basic knowledge, Home Run would make no sense. In order to control
an aircraft in three-dimensional space, the pilot uses the control yoke (joystick) in front of him, rudder pedals under his feet,
and a bank of engine throttles located at his side. Without engine thrust the aircraft would not fly at all, so the throttles are
largely self explanatory: For more speed or altitude increase throttle, for less speed or altitude decrease throttle.
In order to raise or lower the nose of the aircraft, the pilot pulls or pushes on the control yoke, which in turn raises or lowers
the elevators on the horizontal tailplane. To bank the aircraft left or right, the pilot moves the control yoke to the left or right,
which in turn operates the ailerons on the outer wings. Lastly, to turn left or right at low speed or “balance” turns at high
speed, the pilot presses the left or right rudder pedals as required, which in turn move the rudder on the vertical stabilizer.
Back in the early days of flight, the control yoke and rudder pedals were connected to the various flight control surfaces by
thin cables, meaning the pilot had direct physical control over every movement the aircraft made.

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