[Table of Contents]
Wax nostalgic about and learn from the history of early
mechanics and electronics. See articles from
published continuously sine 1902. All copyrights hereby acknowledged.
RF technology has been
a large part of new and upgraded aircraft development not just for studies of radio
and radar performance, but also for remote control (R/C) of small- and full-scale
prototype models. R/C began life as bulky vacuum tube systems with transmitters
that needed to sit on the ground with a hand-held command box. Airborne systems
carried lead-acid batteries for power*.
Frequencies in the U.S. were in the 27 MHz
citizens band, and then moved into 53 MHz (Ham band), 72 MHz (airborne
only), and 75 MHz (ground only) bands. All modern R/C systems operate in the
2.4 GHz ISM band using spread spectrum modulation (FHSS and DSSS). Having been
a builder and flyer of R/C models since the 1970s, I have read many articles about
the role played by modelers over the years in modeling magazines and more general
purpose magazines like this one in a 1974 issue of Popular Mechanics. Prior
to the availability of super-powerful computers and sophisticated fluid dynamics
simulation programs, model construction and testing in wind tunnels and in the air
was the only way to test theories and actual performance. It is nearly the year
2020 and aircraft designers still build and test fly physical models in the research
and development process. Scaled Composites,
Burt Rutan's* famous futuristic, bleeding edge aircraft outfit
that gave us SpaceShipOne, the
Voyager round-the-world flyer, the VariEze and
Long EZ homebuilts, and many other out-of-the-box designs
familiar to aerospace enthusiasts, still uses R/C models today for proving design
concepts prior to committing to full-scale construction. The company encourages
employees to build and fly radio controlled model aircraft at home and during break
times at work in order to engender a feel for what is required to make an airplane
* Often, if a model survived a bad landing (aka crash), the battery case would
break and leaking acid would destroy the balsa wood framework.
** I want to be like Burt Rutan when I grow up ;-)
Burt was an avid aircraft modeler as
a youngster, having won many contests, per this Academy of Model Aeronautics (AMA)
Plane at 20,000 - Pilot at Altitude Zero
NASA and the Air Force are flying unmanned
aircraft by remote control from ground-based cockpits. Airborne TV helps the swivel-chair
pilot to guide the plane.
by Frank A. Tinker
The layout around me was deceptively simple. The display of flight and engine
instruments was standard, the controls the same as those of a light plane or basic
simulator. But this was neither simulator nor aircraft.
I sat in a remote-control cockpit in NASA's control center at Edwards Air Force
Base, California, aware that the instruments and controls before me had actually
guided distant aircraft in test flights.
These planes are unmanned RPVs - Remotely Piloted Vehicles - and the science
of flying them is advancing so rapidly that some military men predict completely
pilotless air combat in possible future wars. The technology could have civil applications
Prior to flight, the scale-model F-15 undergoes static tests
atop platform at Edwards Air Force Base. Model is under 24 feet long, weighs less
than a ton.
Actually, the "ghost flying" of airplanes goes back some decades. A remotely
piloted Curtiss-Robin was flown in 1928. In recent years, the radio control of elaborate
model aircraft has become common.
A military ancestor of today's RPVs is the buzz bomb that Germany flew against
Britain during World War II. But this pilot-less craft was a drone and not remotely
controlled. It flew a preset course until a time switch cut off the fuel, causing
it to dive.
Much more advanced drones are part of today's American arsenal. A target version
of the Teledyne-Ryan Firebee has been used for years by our Air Defense Command.
The Firebee is used in simulated attacks from the sea. As it sweeps toward our shores,
manned fighters try to intercept it and destroy it.
Another Firebee carries a bomb and is guided by an operator located a safe distance
away in a Hercules C-130 "mother ship." The drone is guided to the target initially
by radar and on-board TV, then is "locked onto" the target, continuing the rest
of the way automatically.
The use of drones for reconnaissance and radar-jamming is one of the less-discussed
developments of Vietnam and the surveillance contest we engage in with communist
countries. Red China, for example, has exhibited a number of U.S. drones claimed
to have been downed over her territory.
In Vietnam, reconnaissance drones were widely used. They followed a pre-programmed
route over the region to be scanned photographically or electronically. They also
dropped propaganda leaflets (hence the nickname, Litterbug) and, in all probability,
electronic snoopers. Returning to secure territory, they were recovered by helicopter,
usually with an air grab, and made ready for another mission.
Unlike the drones, which are equipped with an automatic pilot and follow, at
least partially, a preprogrammed flight, the true RPV is completely controlled by
a ground-based pilot.
NASA is a leader in RPV development, starting a research program at Edwards AFB
in 1969. Two years later, a twin-engine Comanche was equipped for remote control.
Although a flesh-and-blood pilot has been aboard during test flights, he functions
simply as a backup.
The NASA remote pilot system uses telemetry to relay control commands to the
plane and flight information back to the ground-based pilot. He uses the instruments
as if he were flying blind, navigating mainly by radar and referring to a TV screen
mounted over the instrument panel when he needs outside visual contact. The TV picture
is relayed from a camera in the cockpit or the nose of the plane aloft.
The test vehicle hangs below the big wing of a B-52, which will
carry it up to launch altitude.
Engineers check out F-15 model: a smaller, cheaper stand-in for
a $57-million fighter plane.
NASA research has already been put to practical use in the testing of the new
F-15 superfighter. The full-scale fighter weighs some 40 tons and costs a reported
$57 million. By contrast, the three-eighths-scale RPVs, identical replicas of the
F-15, cost about $250,000 each and weigh less than a ton. Made of fiberglass strung
over an aluminum frame, they have a wingspan of only 16 feet and are slightly over
23 feet long. The control surfaces are activated by a receiver that obtains its
commands from the remote ground pilot. A battery-operated hydraulic system furnishes
In October, 1973, the first such model, complete with remote-control package,
was air-dropped from a B-52 at 45,000 feet and maneuvered down to "pick up" altitude
by remote test pilot Einar K. Enevoldson, who has been with the program since it
began. Even on this first unpowered flight, the model was put through high angle
of attack flight maneuvers. Then, at 15,000 feet, its 79-foot-diameter chutes were
deployed and an air grab made by a waiting helicopter.
Airline traffic is already controlled from the ground
Actual landings are planned in the future, with the RPV powered by some type
of rocket engine. A special TV system may also be installed to give the test pilot
complete visual coverage. Right now, the RPV's assignment is to demonstrate the
spin characteristics of the F-15, a risky maneuver for supersonic aircraft that
results in one plane loss for every 60 such spin tests.
In March, 1974, while NASA personnel kept their fingers crossed, Enevoldson pulled
the RPV up into a stall, then kicked it into a violent spin.
"It spun around too fast to count," reported one observer.
But when the test pilot applied corrective controls, the small plane came out
of the spin in the standard way.
Although these flights are intended only to supplement tests with the full-scale
F-15, the data obtained are of real value to the aircraft engineers involved. The
tests also serve to point up other advantages of the RPV. The RPV's performance
is not hindered by the physical limitations of a human pilot. You can forget about
G-stress in turns and sudden pullouts.
The absence of an on-board pilot also eliminates the need for a cockpit, oxygen
systems, ejection seat and other safety devices, resulting in a lighter, simpler,
cheaper plane. Small wonder that the Air Force is holding competitions for RPV contracts,
has a full-time Drone-RPV office, and is now working on mini-RPVs that may be produced
for as little as $20,000. It's estimated that even larger RPVs, capable of carrying
considerable weaponry, need cost but a few hundred thousand dollars, or about one-tenth
the going price of a cheap manned fighter.
The Air Force is using Edwards AFB for its own tests of a reconnaissance RPV
called the "Compass Cope." One prototype crashed after several successful flights
during the summer of '73. No explanation for the accident was given.
Two new prototypes built by Teledyne Ryan Aeronautical - not the maker of the
crashed plane - were delivered to Edwards last spring and one of them was flown
Chopper is on hand to catch experimental model on its descent
by chute from altitude of 15,000 feet.
This RPV is the "Compass Cope," a surveillance plane. Maiden
flight to 25,500 feet was a success.
Guided entirely by ground control, NASA's Piper Comanche cruises
over California desert.
Air Force and Teledyne officials were more than happy about the maiden flight,
the results of which were announced as this issue of Popular Mechanics was ready
to go to press.
The plane stayed aloft for 1 hour and 50 minutes, "demonstrating takeoff, primary
flight maneuvers and landing capabilities while under remote flight control of a
ground operator," according to officials. "It flew at speeds up to 200 mph and at
altitudes up to 25,500 feet... "
Designed for high-altitude, long-endurance flight, the Compass Cope has an 81-foot
wingspan, a fuselage 37 feet long, and is powered by a single turbofan jet engine
with a rated thrust of 4050 pounds.
Despite the earlier Compass crash, RPV research has gone forward smoothly. Still,
officials are concerned about the possibility that an RPV will somehow break loose
from its radio tether and take off for the wild blue yonder. A human pilot who could
take over the controls was aboard NASA's Piper Comanche, but military testers use
other safeguards. Chase planes follow the RPV, ready to take over control with their
own radio units or to send a signal triggering the RPV's chutes.
Though it has obvious military applications, is there also a role for the RPV
in civil aviation? Proponents say the RPV would be ideal for hazardous types of
flying-the testing of new planes, crop dusting and fighting forest fires.
The work already accomplished with the F-15 scale model demonstrates that flight-testing
would be a logical application. But crop dusting? Here the tolerances may be too
small since the job frequently requires pilots to drag the landing gear" through
the tops of foliage and fly by "instinct" more than by sight or instrument. On-board
TV cameras would provide little help.
Similarly, aerial forest-firefighting depends largely on the pilot's ability
to "feel" his way through severe turbulence, with the plane often poised on the
brink of a stall. Another factor is that there would not be any money saved in replacing
a human pilot with a complex radio-control system.
A much better case can be made for the application of RPV technology to the flying
of commercial airliners. Though the average passenger's faith in gadgetry would
be sorely tested by the knowledge that there was no human hand in the cockpit to
bring him down safely, the fact remains that in recent years the control of all
airline traffic has passed from the cockpit to the ground.
This F-106 is almost a drone. Electronic black boxes can guide
it to target and fire its missiles.
The United or Pan Am pilot, for example, flies his jet in accordance with company
rules and under the direction of a ground controller. His altitude is assigned and
his route narrowly laid out between navigation points. The only time his skill really
is needed is on takeoff, landing and during an emergency.
During most of the flight the pilot does not physically control the plane. This
is routinely done by an autopilot, which flies a much straighter, more level course
than any human could.
The autopilot can be coupled to the ground navigational system so that it steers
unerringly along the desired course. Auto-pilots can even be tied in with the instrument
landing system. Thus the plane is brought down the glide slope without a hand touching
the controls, the power automatically reduced at flare-out and then completely chopped
off at touchdown.
If the pilot has become little more than an airborne monitor of a plane's systems,
why does he even need to be aloft? It can be argued that it's safer to use a ground-control
pilot who's a specialist in landings, someone who does nothing but bring down plane
after plane during his duty shift. Would he not be superior at the job because of
his constant practice? He would also have the advantage of working in a stable,
comfortable environment instead of a cramped cockpit. A backup pilot could ride
in the plane, ready to take over if the link between ground and plane should break
If all this seems far-fetched, keep in mind that overseas there already are trains
that are run in just this fashion.
How far the automation of aircraft may go is anybody's guess right now, but the
techniques and hardware are already with us.
Now: Dogfights Without Planes
Two F-15 fighters realistically projected on 360° wall screen
inside an air combat simulator, as seen by pilot occupying cockpit centered in the
40-foot spherical chamber.
Pilots in smaller simulators "fly" other planes, carryon dogfights.
Simulator, in McDonnell Douglas Corp. St. Louis plant, is at left.
Though the Air Force's new F-15 fighter is still being tested, pilots have already
"flown" the bird in hundreds of dogfights against a variety of opponents.
This trick is made possible through the use of an elaborate simulator - reportedly
the only one of its kind in the world - at a McDonnell Douglas facility in St. Louis.
McDonnell Douglas makes the F-15.
The F-15 pilot sits in a cockpit that's a replica of the real thing. His assignment:
to "maneuver" his aircraft so its guns are brought to bear on two opposing planes.
The cockpit is situated in the center of a 40-foot spherical chamber, the wall
of which forms a 360° screen for the projected images of the two opposing aircraft.
These planes are being "flown" by pilots in smaller but similar simulators. They,
in turn, see the F-15 projected on the walls of their chambers.
When the F-15 pilot sees his "enemies," their size is directly related to range.
They grow as they come closer, shrink as they fly farther away. As the pilots "fly"
their aircraft, their stick, rudder pedal and throttle movements are translated
into action that moves the images correspondingly. Performance characteristics of
the aircraft involved are also taken into account.
To further enhance the realistic quality of the experience, the pilots hear flight
noises and the firing of their own missiles and guns. As they fly through tight
turns, their bodies feel the pressure through specially designee G-suits. If a pilot
pulls too many Gs, the lights grow dim to simulate a gradual blackout.
Keeping track of all the variables in the three-aircraft dogfight is a computer
with the capability of executing some 2,500,000 instructions per second. It's the
hard-working computer that keeps the action going.
The images are obtained from models of the full-sized planes. They are shot with
a TV camera - at a variety of attitudes - to yield realistic projections of dives,
loops and other maneuvers.
The complex simulator system is currently used as an engineering design aid in
fighter research and development. A future possibility, according to McDonnell Douglas
officials, is to use the simulator to train pilots in air-to-air combat maneuvering.
Members of the McDonnell Douglas simulation department recall a remark made by
Irv Burrows, the company's chief test pilot, after he had piloted the F-15 on its
first actual flight: "It flew just like the simulator."
That's the kind of talk the simulation experts like to hear.
Posted December 9, 2019