January 1947 Radio News
[Table of Contents]
Wax nostalgic about and learn from the history of early
electronics. See articles from
Radio & Television News, published 1919-1959. All copyrights hereby
Even though the U.S. Army Air
Force and other research agencies around the world were at the forefront of experimenting
with remote control airplanes, helicopters, tanks, trucks, cars, boats, and rockets,
hobbyists were forging their own paths in the electronic art. I did not know until
reading this article that drones were flown through the radiation field at the Bikini
Atoll atom bomb test site for data collection. In fact amateur radio operators have
long had the privilege of broadcasting for the purpose of remotely controlling a
vehicle - the only scenario of Earth-based† transmission whereby the "control
operator" is not required to identify his/her call sign at an interval prescribed
by the FCC (currently at least once every 10 minutes and at the end of the broadcast).
Vintage modeling magazines have articles on
early radio controlled (R/C) airplane experimentation. Target
drones subject to remote control were not just small models, but also full-size
aircraft that were deemed not airworthy enough to carry a human crew. All manner
of planes were outfitted with R/C gear, even including the big 4-engined B-17
Flying Fortress, which among other uses was sent to attack German targets deep
within the country.
A Radio Controlled
Radio Controlled Flight
For peace or war, the radio control of airplanes and rockets marks a new era
in aviation history.
Editor's Note: Since the recent appearance in Radio News of several articles
on the atom bomb test and drone planes, we have received many letters requesting
more detailed information on the electronic equipment used to control the drone
The PQ-14, radio controlled AAF plane which provides realistic
target for anti-aircraft gunners.
In view of this fact, Radio News brings to its readers in this article much of
this information. The material contained herein is as detailed as possible under
present security regulations.
American Army Air Force, technically superior in all phases of air defense or
warfare, is a tired world's surest guarantee against the terror of war. Rockets
and missiles, controlled by radio, traveling at supersonic speeds and equipped with
atomic warheads, shrivel the imagination.
But in August the Army Air Forces revealed that two B-17 Flying Fortresses had
flown the Pacific without pilots aboard. Though the news received but slight attention,
it pointed the road to future military and civilian aerial activity.
The flight from Hawaii, known as Operation Remote, took to the air at Hile and
flew 2600 rugged overwater miles before coming down at Muroc Army Air Field, California.
The drones were accompanied by mother planes which directed all their flight operations
by radio. Throughout the 14 hours and 55 minutes of the record-breaking journey,
the mother planes maintained contact with their crewless charges at distances varying
from 200 feet to three miles.
Radio jeeps, near runway, control take-off and landing of the
drone planes. One works the elevators and throttles of the drone while other controls
Block diagram illustrates stage-by-stage operation of T-61/AXT-2
transmitter installed in drone airplane.
The control box which relays "commands" from the "mother" plane
to the drone. Above the control box is shown the television scope which allows the
pilot to view the instrument panel in the drone being controlled or alternately,
permits him to see the area directly in front of the drone plane. This equipment
should find wide application in the testing, of experimental models of aircraft,
thus eliminating the necessity for endangering a test pilot's life.
Full view of the cockpit of the modified Boeing B-17 radio controlled
drone aircraft designed for use on the Crossroads Project atomic bomb test. Pilots
are excess baggage in B-17 drone. Controls are activated by radio signals emanating
from the "mother" plane or the ground control station.
Functional block diagram of the R-68/AXR-1 television receiver
used in "mother" plane.
"Mother" plane hovers near her drone. In foreground a jeep control
station is about to "take over" the operation of landing the drone.
Closeup of jeep control station showing the control box in the
Before landing at Muroc, one of the drones dropped a practice smoke bomb off
Santa Rosa Island. This involved opening the bomb bays, releasing the bomb and closing
the bomb bays, all by remote control.
The two drones which spanned the Pacific were veterans of the Bikini atom bomb
blast. Together with a number of other AAF drones at Bikini, they gathered invaluable
data which will enormously increase scientific understanding of atomic phenomena.
The current drone research program is being pushed with high intensity by Headquarters
Army Air Forces through its technical branch, the Air Materiel Command, located
at Wright Field, Dayton, Ohio. However, the present activity is just one facet of
the total investigation into the application of radio control to flight. It is an
integral part of the research program which began with the development of target
planes and is currently concerned with guided missiles and completely automatic
The latest model in the target plane category is the PQ-14. Controlled by radio
and maneuvering much as an enemy combat plane would under field conditions, the
PQ-14 is a lifelike target which eager marksmen actually can shoot down.
In operation, the PQ-14 is trailed at a safe distance by a mother plane, much
as in the Operation Remote set-up. A pilot sitting in the co-pilot's seat of the
mother ship holds a small control box on his lap. Flipping a lever on the upper
left hand corner of the box gives the pilot the function he wants. Small lights
indicate the number of functions the drone will perform and give the pilot a check
on the operation desired.
On the lower right hand side of the control box a small metal "stick," similar
to an airplane control stick, is moved to give the horizontal and vertical movements
demanded of the PQ-14. Another switch is available on the control box for auxiliary
A frequency-modulated, ten-channel radio receiver relays the "commands" of the
mother plane to a gyro-stabilized, remote flight control unit which actuates hydraulic
servo motors. This unit corrects the three functions of roll, pitch and yaw, and,
in addition, applies the brakes. Through its use, the PQ-14 is enabled to perform
maneuvers including 70-degree banks and dives.
Such auxiliary operations as throttle control, retracting and extending of the
landing gear, and raising and lowering of the flaps, are accomplished by radio activation
of small electric motors which are installed as standard equipment in the target
plane. Coordination between the control plane and the target plane is instantaneous.
Drones were in operational use during the recent war. War weary B-17s, which
had flown full quotas of missions against German installations, were used as guided
missiles in a project known as Operation Castor. The planes were not outfitted to
take off by remote control. A minimum crew took them up and, after the mother plane
assumed radio control, parachuted to earth.
The first Flying Fortress flown in this operation was directed at the submarine
pens at Helgoland, Germany, on September 11, 1944. Unfortunately, it was shot down
by anti-aircraft fire 1000 feet short of its goal. Another, guided to these same
high-priority objectives in October, destroyed 2 1/2 acres of buildings in the target
In current usage, such as the trans-Pacific flight, the drone is equipped with
a high-powered v.h.f. radio receiver which can filter out a single channel, or any
of the ten audio-frequencies. The v.h.f. transmitter may be located either in a
ground installation or a mother aircraft, or, in some installations, both.
Each of the ten audio-frequencies or tones, when filtered, actuates a relay which,
in turn, accomplishes a distinct flight function. The drone's mission determines
the variety and choice of functions which can be accomplished by radio in any particular
A control box installed in a jeep, or other ground station, supervises the takeoff
of the drone until an airborne mother plane takes over. Either the ground station
or the mother plane can control the drone up to a distance of 75 miles. However,
effective control varies with the quality of radio reception.
In addition to its radio receiving set, the drone carries two television transmitters.
One is trained on the instrument panel and the other on the outside atmosphere.
The control pilot can, by flicking a switch, place himself in the position of a
pilot in the drone. He can view the area in front of the drone from the "pilot's"
seat, or examine the control panel when blind flying is necessary.
The television units in the drone contain an infinity-focus optical system and
television camera pickup tube, plus the necessary sweep and electrical circuits
for transforming the light waves from the viewed scene into equivalent video signals
which modulate the transmitter. A conversion unit generates signals which synchronize
the scanning of the mosaic screen with the sweeps of the reproducer tube at the
The drone's radio receiver actuates the relay mechanism which operates the camera
lens stop and optical filter, to prevent "burning" the mosaic, and the optical heating
system which prevents fogging.
The transmitter in the drone may be adjusted to operate on anyone of the ten
separate frequency channels between 264 and 372 mc. This permits the simultaneous
operation of ten separate sets within the general area without interference. However,
a different antenna unit is required for each of the ten operating frequencies.
The FM radio control receiving equipment on the drone permits ground-to-air or
air-to-air control up to a normal range of 18 miles. However, by the use of an r.f.
amplifier unit the effective range may be stepped up to 75 miles. The receiver-selector
incorporates an eight channel audio filter selector circuit for discrimination between
the various tones received. A relay unit passes control voltages to the automatic
pilot from the receiver output.
Normally, the altitude of the drone is automatically controlled by altimeter
equipment installed for that purpose. However, the altimeter setting may be overridden,
when necessary, by a special relay box.
The television receiving and reproducing system employed in the mother aircraft
is a superheterodyne type receiver which amplifies the received signal and removes
the video component from the carrier. It impresses this video signal on the grid
of the picture reproducing tube, which in turn reproduces the scene viewed by the
drone camera equipment.
This unit also generates the necessary horizontal and vertical deflection voltages
for the cathode-ray picture reproducer tube. The scanning of the picture pickup
mosaic screen on the drone, and the generating of sweep circuits for the picture
reproducer tube on the mother plane, are synchronized by special pulses generated
by the drone transmitter.
Ten different antenna units are supplied with each receiving set. They operate
at spot frequencies within the frequency bank of 264 to 372 mc., and are located
approximately 12 mc, apart. The antenna is gyro stabilized within the aircraft.
Operational and tactical use of the drone and other guided missiles is being
subjected to a thorough evaluation by a group of highly-qualified specialists under
the direction of Colonel Harvey T. Alness, commanding officer of the Army Air Forces
1st Experimental Guided Missiles Group at Eglin Field, Florida. It is his duty to
subject to punishing tests new projects in the remote control field development
of AAF engineers.
The following radio control and television equipment was used in the flight from
Hawaii to the United States in Operation Remote:
a. Installed in drone aircraft:
(1) AN/ARW-1 Radio Control Receiver
(2) AN/AXT-3 Television Transmitter
b. Installed in mother aircraft:
(1) AN/ARW-18 Radio Control Transmitter
(2) AN/AXR-1 Television Receiver
The AN/AXT-3 differs from AN/AXT-2 in that it contains an additional optical
system and conversion unit for televising flight panel data. All AN/AXT-3 sets were
created through modification of AN/AXT-2 sets.
* This article was prepared by the Information and Public Relations Division,
Headquarters Army Air Forces, New York, New York.
† An amateur operator from a space station is not required to transmit
a periodic ID.
Posted May 26, 2023
(updated from original
post on 8/26/2016)