|Flying High at Zero Altitude
By BEN PREECE
Special thanks to Charles at
providing the original scans!
THE PILOT and copilot of the Douglas DC-8 Jetliner
couldn’t see anything through the windshield. It was totally dark outside.
The altimeter was winding down as the giant plane dropped through the
overcast. The crew chief watched his instrument panel.
“We’ll be out in a minute,” the pilot said, referring to the cloud bank
he’d been in since take-off. Then the lights of the field appeared below.
“There it is,” the copilot gestured. A bright, double row of lights,
outlining the runway, could be seen ahead and below. The DC-8 Jetliner
dropped slowly until it was over the runway. The pilot pulled the nose up,
there was a slight bump, then a squeal of tires as the brakes were
applied, and the ship had landed.
The pilot, copilot and crew chief had just experienced a coast-to-coast
flight. However, their greatest altitude had been under ten feet, the
greatest speed zero miles an hour. Yet, except for the gravitational
forces, this crew had experienced every sensation of being in an airplane
flying five hundred miles per hour at 35,000 feet. They had just completed
a “ride” in the DC-8 flight simulator!
Electronic Flight. The DC-8 simulator works electronically to produce all
the sensations of flying, including correct instrument readings, climb and
bank altitudes, everything. It even has a closed-circuit television system
which shows you an airfield, just as you would see it in the real DC-8.
Such simulators train pilots to fly planes that haven’t rolled off the
Swift, new planes like the Douglas DC-8, the Boeing 707 and the Lockheed
Electra will be “old hat” to airline pilots when they go into service.
A DC-8 simulator is as realistic as the actual airplane. It consists of a
cockpit section, a scale model airport, a closed-circuit television
system, and a computer system and servomechanisms to control the position
of the cockpit section.
Realism in Training. The cockpit has all the dials, levers and gauges of
the DC-8 itself. When the pilot “flys” the simulator, he experiences all
the motions he would feel in real flight, except the g-loads. There are
air pockets, sudden wind gusts, the sound of the jet engines, even the two
quick jars the real DC-8 feels when it slips into a bank at high altitude
and the wings lose their lift.
The crew of the simulator consists of the pilot, copilot, crew chief and
instructor. Additional personnel outside operate the radio signal system
and the closed-circuit television. The instructor can simulate any
emergency a pilot will find in flight. The crew in the radio control room
can duplicate the signal of any radio station in the world, and send six
signals at once. Thus, the pilot may receive every radio indication that
he is flying over Chicago, New York, Los Angeles or London. The radio crew
can even vary the compass reading to allow for the magnetic variation
typical in any part of the world.
In short, once the pilot and his crew take their seats, they are in a real
airplane. When the jet engines are running, the cockpit may buck against
the brakes, depending upon the throttle setting. When the brakes are
released … off they go! The runway lights whirl by on either side. Looking
straight ahead, the crew has the illusion of motion as the lights go by.
In the air, the instructor throws the book at the pilot. Engine failure
may “occur,” hydraulic failure, cooling system failure, a change in the
plane’s center of gravity, or any other trouble. More than one pilot has
been saved by his simulator training. It teaches him to think fast and to
do the right thing in a split second.
The DC-8 simulator does everything but fly. “It’s really an electronic
brain,” one engineer said. “It must handle as many as forty variables at
one time, including the six differential equations of motion. Then it must
solve the problem and translate the answer into airplane motion,
instrument readings and a visual television picture for the pilot.”
Among those forty variables are engine thrust, fuel pressure, Mach number,
altitude, rate of climb or descent, and many others.
Simulator Design. D.C. circuits are used throughout for several reasons.
Direct current provides a higher degree of accuracy, eliminates the
possibility of phase shift, harmonic distortion, erratic instrument motion
and noise pickup. The circuits are simpler and therefore easier to
maintain. Direct current also eliminates the fluctuations and variations
inherent in most of the alternating current supplies.
The DC-8 simulator uses printed-circuit boards and utilizes various
electronic systems. For example: the characteristics of the engines are
carried electronically on one circuit board. If another engine with an
extra 500 horsepower is to be inserted, the old engine circuit board is
removed and the new one plugged in. This way “engines” can be switched in
only half an hour.
A room behind the cockpit section is lined with tall, gray cabinets. On
the left are racks holding various amplifiers and other electronic gear.
On the right are small circuit boards and motors with spinning dials.
Under each unit is a label: Fuel Flow, Bank, Altitude, etc. The computer
essentially takes a rate of change, integrates it, and tells the crew
through cockpit motion or instrument readings just what is happening.
Televised Airport. In the TV room there is a model airport made to scale
mounted on a long wall. A television camera is mounted on two tracks which
run the length of the model airport. The model is built to a
three-hundred-to-one scale, and represents an area 21,000 feet by 3000
feet. The TV camera is connected to the computer system. If the pilot
dives, the camera tilts down. If he climbs, the camera tilts up. It
follows every motion of the airplane, so it sees what the pilot would see.
The picture is then flashed on the screen in front of the pilot.
A television projector is located on top of the DC-8 simulator cockpit.
And the televised picture from the map room is projected onto a motion
picture screen which covers the visible area viewed by the pilots in
The DC-8 simulator gives to the public a well-trained, proficient crew.
This flying team practices and “polishes” on the ground. When the
Jetliners are put into operation, the passengers can be sure that the
pilot and his crew have many hours of simulated and actual flying time
under their belts. The simulator offers safety through practice.