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History of Communications-Electronics in the United States Navy, Captain Linwood S. Howeth, USN (Retired), 1963, pages 267-281:
Development of Aircraft Radio Equipment
A study of various articles, statements, and requisitions for equipment leads the writer to believe that the operational use of aircraft radio equipment during World War I has been overly glamourized and distorted. However, it was a period of intensified research and development of equipment for that purpose. Had the war continued longer, it is most probable that operational use of aircraft radio would have increased rapidly.
Following the Maddox experiments1 there is no record of further action to provide radio equipment for aircraft until about April 1915 when four Foot-Pierson, battery powered, spark transmitters were purchased for fitting into aircraft for controlling the fall of shot. With their limited range of 5 miles, they proved unsatisfactory for that purpose.2
When Hooper became the Head of the Radio Division, one of his first acts was an endeavor to interest the Aeronautical Division, then a part of the Bureau of Steam Engineering, in equipping aircraft with radio. He was not very successful in this. Our early naval aviators were rugged individuals, flying underpowered aircraft difficult to maintain in a safe altitude even without the added weight of radio equipment. The additional tasks of mastering the telegraphic code and operating the equipment while flying the plane did not appeal to many of them. However, Hooper rightfully believed that the value of scouting planes was lessened unless they could report enemy contacts by radio and remain on station to provide continuing information. Likewise, spotting planes would be of little value unless they could continuously radio corrections in range and deflection.
Hooper's next action was to direct the Naval Radio Research Laboratory to prepare a study of the probable range of an aircraft radio transmitter of a weight not exceeding 100 pounds. On 13 May 1916 Austin submitted the following report:
- Antenna wires on wings of plane, 7 feet apart. Weight of set, 300 pounds; distance, 10 miles.
- Trailing wire 50 feet long, plane as counterpoise. Weight of set, 100 pounds; distance, 15-30 miles.
- Trailing wire 400 feet long, plane as counterpoise. Weight of set, 100 pounds; distance 75-100 miles.
2. PRE-WAR EQUIPMENT
On the same day Hooper forwarded this information to the Aeronautical Division. After waiting a reasonable time, and having received no reply, he discussed the problem with the Chief of the Bureau of Steam Engineering, Rear Adm. R. S. Griffin, USN. Griffin was sympathetic and directed him to procure the necessary equipment.
Lt. E. H. Loftin, USN, whose brilliant work in radio engineering had brought him to prominence, was ordered to the Radio Division to assist in the preparation of the necessary specifications. When completed, they listed the following requirements:
Weight not to exceed 100 pounds;
The initial requisition, dated 25 July 1916, was for 75 sets. This number was chosen because it was believed that the development work would be so costly that manufacturers would not be interested unless sufficient incentive was provided.3 It was expected that 2 or 3 companies might be interested but, to the surprise of all concerned, 13 submitted bids, and of these seven submitted models. A memorandum from Loftin to Clark stated:
Fit into an aircraft space of dimensions which were provided;
Antenna to be of trailing wire type, 200 feet long and provided with reel, brake, weight, and other necessary appurtenances;
Transmitter to provide for telegraphic operation but could include radio telephone capability;
Transmitter range to be 100 miles or more; and
A working model to be submitted prior to contract award.
The De Forest Company and the Western Electric Company offered sets for code and voice; the Marconi Company, E. J. Simon, F. Lowenstein and the Wireless Specialty Apparatus Company made provision for code only. The successful bidders were the Marconi Wireless Company of America, the De Forest Radio Telephone and Telegraph Company, the Western Electric Company, and the Sperry Gyroscope Company.4
Hooper in his memoirs stated:
The award was made to four bidders, the bids split evenly and then I purchased two or three of the other samples which had novel features but which were not by the lowest bidders. I don't recall exactly who got the awards,--as I recall it was E. J. Simon and Company, Marconi Company of America, Lowenstein and one or two others. I cut the number of sets down from 75 to 50 when I found we didn't have 75 airplanes.5
In a paper presented before the New York Chapter, Institute of Radio Engineers, on June 1919, T. Johnson, Jr., Expert Radio Aid, Navy Department, stated that the sets purchased at that time were the Marconi spark set, CM 295; the Sperry vibrator arc set, CS 350, designed by Dubilier; and the De Forest vacuum tube set, CF 118. He further stated that the latter apparatus was the first radiotelephone equipment installed in aircraft.6 The contract records of the Navy Department and the assignment of type numbers by the Bureau indicate the following purchases of aircraft radio sets at this time:
|De Forest|| ||16|| ||CF 118,7 CF 5498|
|American Marconi|| ||15|| ||CM 2959|
|Sperry Gyroscope Company|| ||15|| ||CS 35010|
|E. J. Simon|| ||15|| ||CE 61511|
The context of Hooper's statement indicates that he was speaking from memory. The contract for purchases are most probably correct, although they could have been modified after being awarded.
The Simon set, designed by Israel,12 was the only one of these prewar purchases that showed promise. It was powered by a wind-driven generator, mounted on a wing of the aircraft, that could be braked when not required. A completely insulated antenna reel permitted the tuning of the antenna circuit while the 500-watt transmitter was in operation by varying the length of the trailing antenna. The receiver used one three-element vacuum tube and a regenerative circuit. Installed, the entire equipment weighed approximately 100 pounds. During the tests of this equipment signals were transmitted over 150 miles.13 Early in 1918 an additional 100 sets were purchased from Simon.14
Most of the sets manufactured by De Forest were transferred to the Army Signal Corps for use in developing equipment for the Army Air Corps, which desired to use voice equipment.15 Later, when we became an ally of the British, some of the Marconi and Sperry equipments were delivered to them.16
3. ESTABLISHMENT OF NAVAL AIRCRAFT RADIO LABORATORY
After these contracts were awarded, Loftin was transferred to New Orleans, La., as District Communication Officer to supervise the work of the Aircraft Radio Laboratory, established in the summer of 1916, at the Naval Air Station, Pensacola, Fla. This Laboratory, under the direction of Expert Radio Aid B. F. Meissner, was charged with the testing of the equipment procured under these contracts. In addition to this function, Meissner was directed to study and devise methods for providing intercommunication between crewmembers, reduction of ignition and other noises caused by a plane in flight, and the adaptation of the radio direction finder to fit aircraft requirements.17
4. DEVELOPMENTS OF NAVAL AIRCRAFT RADIO LABORATORY
Communication between crewmembers of early aircraft by the normal means of conversing was prevented by the noises of the motors and wind rush. The Pensacola Laboratory first developed equipment of the voice-tube type with suitable helmet and appurtenances. This was clumsy and after the development of satisfactory radiotelephone equipment it was supplanted by an intraplane telephone system which also allowed the pilot telephonic communication with other planes.18
The elimination of ignition and other electrically redundant generated noises from the receivers presented a problem not easily solved. The best solution, that of shielding the entire ignition system, was unacceptable to the aviators because it reduced its efficiency. The next best method was the use of suppressors in the sparkplug leads. This was also unacceptable to the aviators because it reduced the intensity of the ignition spark. Under these limitations, the only thing which could be done was to bond and ground all parts of the plane structure which formed closed loops, and to accept the ignition noises. In his memoirs Dr. Taylor stated in 1947: "The conquest of ignition disturbances in planes is not completed, even at this time."19
In adapting the radiocompass to aircraft, ignition noises prevented the use of the minima method of obtaining bearings. Dr. James Robinson, of Andover, England, devised a method of utilizing two loops on the same rotating frame, the planes of which made an angle of approximately 60° with each other.20 By first connecting one loop and then the other to the receiver, by means of a manually operated switch, maximum signal could be obtained in either loop by rotating the frame. The bearing was obtained by rotating the loops so that the strength of the received signal was the same regardless of the position of the switch.21
A trailing-wire antenna system had been designed and patented by Maj. Harry Mack Horton, Army of the United States, prior to his entry into the service. The Laboratory at Pensacola had adapted this to flying boats by improving the braking, the dielectric quality of the reel, and by adopting a type of antenna wire sufficiently brittle to snap upon entanglement with buildings, masts, or other objects before interfering with the stability of the plane. The latter was a necessary improvement, but it often resulted in the streamlined weight at the trailing end of the wire snapping off and falling to earth. Once one plummeted through three floors of a house and imbedded itself in the concrete floor of the basement. Another time one barely missed a policeman and flattened itself on the pavement at his feet. Lt. C. B. Mirick, USNR, later devised a hollow shell weighted with fine shot. If this became detached from the antenna, the shell would open, spilling the shot which would fall with less chance of causing serious damage or loss of life.22 Horton was later granted $75,000 for the infringement of his basic patent by the Government.
The spark transmitters of the flying boats had to be fitted within the hull in the same space that held the gasoline tanks. In order to prevent the spark from igniting the ever-present fumes, Meissner designed an enclosed spark gap which eliminated the danger.
5. WARTIME REQUIREMENTS
Shortly after our entry into the war, a decision was reached to strengthen the naval air arm. Requirements called for longrange aircraft for antisubmarine, patrol, and convoy duties, and shorter range ones for scouting and spotting fall of shot. Communication equipment of different types were necessary for the long- and short-range planes. It was necessary that this equipment be operated by aviators with a minimum of training. Fortunately, they were required to have an operating proficiency of 18 words per minute prior to the completion of their flight training.
The Navy program was based upon the use of a single-engine flying boat for the short-range purposes and a twin-engine flying boat and dirigibles for the longer range duties. Both planes were to utilize Liberty engines. Altogether, 1,185 single-engine and 864 twin-engine craft were contracted for, and it was necessary that they be equipped with radio as they came off the production lines during 1918.23 Spark transmitters were considered essential to provide the ranges desired for dirigibles and the flying boats, while tube transmitters would suffice for the single-engine craft.
The development of satisfactory standardized radio equipment and its production in large quantities in a short time, presented the Bureau with one of its most difficult wartime tasks. It was essential to combine compactness, light weight, and simplicity of manufacture with ease of control, water-tightness, and ruggedness. Moreover, the configuration of the craft was a controlling factor in the final encasement of the apparatus. Development was slowed by lack of aircraft for radio test purposes. Early in the development work it was discovered that it was necessary to employ pilots who were sympathetic with radio investigations and who could visualize the extended uses of aircraft fitted with reliable communications.
Faced with the necessity for providing equipment and fitting it into the aircraft under contract, the Bureau requested all possible manufacturers to submit aircraft sets for test. Spark transmitters were submitted by the E. J. Simon Co., the National Electric Supply Co., the International Radio Telegraph Co., and Cutting & Washington. The General Electric Co., the Western Electric Co., the Marconi Wireless Telegraph Co. of America, the General Radio Co., and the De Forest Radio Telegraph Co. submitted vacuum tube transmitters.
6. WARTIME DEVELOPMENT OF AIRCRAFT EQUIPMENTS24
On 1 January 1918 the Naval Aircraft Radio Laboratory was moved to the Naval Air Station, Hampton Roads, Va., where flying boats of the two standardized types were available. Standardized antenna systems were designed and developed for both types and the measurements of their constants accomplished. Experiments directed toward standardized installations were made. The equipments submitted by the manufacturers were tested and those described hereafter were approved for service use as standard equipment.
The CQ 1115, 200-watt, and the CQ 1111, 500-watt, spark transmitters were designed, developed, and manufactured by the International Radio Telegraph Co. They were powered by a wind-driven generator which, with the main element of a rotary gap transmitter, was contained in a streamlined case mounted on a wing of the plane. A tuning variometer was located in the cockpit. The 200-watt transmitter weighed 65 pounds and had a range of 100 miles. The 500-watt unit weighed only 20 pounds more and had a range of almost 1,500 miles when received by a shore radio station and 500 miles when received by a ship. These were the most satisfactory spark transmitters developed for use in aircraft. The CQ 1115 was also supplied to the Army Signal Corps. The complete transmitting equipments installed in the boats and utilizing these basic elements were designated SE 1300 and SE 1310, respectively.
The CP 1110 (later modified and designated CP 1110A) transmitter was designed, developed, and manufactured by Cutting & Washington. This impact excitation type transmitter was designed for transmission on the single frequency of 800 kc. Installed, it weighed 77 pounds and was capable of transmitting to shore stations for a distance of 200 miles. It was powered by a Crocker-Wheeler, wind-driven, alternating current generator mounted on one of the wings of the aircraft. It was used with other components to provide a complete aircraft transmitting system, designated SE 1320.25
The CN 1105 spark transmitter, powered by a wind-driven, inductor-type alternator, was developed and manufactured by the National Electric Supply Co.26
The CW 1058 was a low-powered radiotelephone transceiver manufactured by the Western Electric Co. It was a modification of similar equipment that had been accepted by the Army and included intraboat telephone equipment. One hundred and two sets were contracted for on 4 December 1918, at a cost of $66,000.
The Marconi Co. manufactured the first large order of tube transmitters. Their initial bid for the manufacture of 350 SE 1100, Navy-designed, 200-watt transmitters was rejected because it was considered to be exorbitant. They were then directed to manufacture them on a cost-plus-10-percent basis.27 The "History of the Bureau of Engineering During the World War" states that this was a Marconi-designed transmitter.28 Clark describes it as Marconi developed.29 It was similar to CG 1130. Taylor states: "This set was able to work continuous-wave telegraph, with a theoretical range of 150 miles, and voice communication with a range of 60 miles. . . This set gave us lots of trouble and was never particularly reliable, although when in first-class condition, it would operate and the range obtained was very good."30 Installed, including all components and a receiver, this equipment weighed approximately 210 pounds. The transmitter used two large General Electric Plyotron tubes, one as an oscillator, the other as a modulator. It was powered by a battery and a dynamotor, but it was difficult to keep the batteries charged. Tone-modulated telegraph transmission could be used. By erecting a small telescope mast, normally stored in the tail of the plane, battery-powered transmissions could be made while on the water.
CG 1104, a 50-watt vacuum tube transmitter, powered by a wind-driven generator and dry batteries; CG 1104A, which was the same as CG 1104 except the dry batteries were eliminated; and CG 1130, a 250-watt transmitter, similar to the SE 1100, were designed and manufactured by the General Electric Co. The CG 1104A weighed 50 pounds. It had a range of 30 miles and was used primarily for spotting the fall of shot. The CG 1104 was used in the single-engine flying boats and as an auxiliary transmitter in the larger flying boats. It had a range of 100 miles. The CG 1130 had a telephone range of 200 miles and a telegraph range of approximately twice that distance. It was used in large flying boats and dirigibles. One hundred CG 1104A, 100 CG 1104, and 10 CG 1130 transmitters were purchased.31 When combined with other components to provide complete aircraft radio transmitting systems, the CG 1104A was designated SE 1340, and the CG 1134 the SE 1380.
Clark mistakenly lists these transmitters as the SE 1340 for single-engine aircraft and SE 1370 and SE 1390 for larger flying boats and dirigibles.32 The contract for these Navy adaptations of General Electric equipment was dated 9 October 1918 and amended in 1921. It was designed to secure improved equipment resulting from the increased capabilities of manufacturers in providing higher quality vacuum tubes with more constant operating characteristics. Before these equipments were completely developed, better equipment had been designed and developed by naval personnel and only a small number was purchased.
In the summer of 1918 Comdr. H. P. LeClair,33 USN, who had relieved Hooper as Head of the Radio Division, became concerned about the slow progress being made at the Laboratory at Hampton Roads. In an endeavor to bolster the program, Taylor, now a lieutenant commander, was detached from duty as Transatlantic Communication Officer and ordered to head the Laboratory. In a further endeavor to strengthen the Laboratory, plans were made to move it to the Naval Air Station, Anacostia, D.C. This was accomplished in the fall of 1918.34
Prior to moving from Hampton Roads the Laboratory was service-testing the CG 4050, a component of the SE 1390. The General Electric Co. sent their representative, Mr. E. M. Kinney, to assist in these tests being made in one of the large flying boats. One day the weather was bad and the boat was forced down in rough seas by engine trouble about 10 miles offshore. Upon landing, a hole was torn in the bottom and the hull filled rapidly, sinking to the lower wing. The crew and the testing personnel, except Kinney, scrambled up on the wing. He finally emerged from about 6 feet of water struggling with the transmitter which, being the only model, he was determined to save. Again he dived into the hull and disconnected and salvaged the dynamotor. The plane crew had been unable to transmit an emergency message; therefore, no one at Hampton Roads was aware of their plight. Shortly thereafter the lower wing became waterlogged and went under. The luckless people scrambled to the upper wing with the salvaged equipment. Things looked pretty black; no one was in sight; the weather was worsening and becoming colder. At this point Kinney, cold, shivering, and with chattering teeth, remarked:
Well boys, this looks like the finish, but if I have to go, I am glad I am going in such darned good company.
Half an hour later a fisherman hove into sight. Frantically they signaled him and finally attracted his attention. He took them ashore where they could telephone the station for a boat. Arriving after dark, Kinney remembered that he had left the dynamotor on the other side of the river. He could not be persuaded from immediately returning to procure it. The transmitter later passed the tests and became a component of the SE 1390.35
After the laboratory was moved to Anacostia, its staff was increased by several radio engineers and it was assigned the additional functions of design and development of complete aircraft radio systems. Two transmitters, the SE 1375 and SE 1385, which later became the backbone of naval airborne communications, were designed and developed. Both of these produced a clear 500-cycle note and neither was voice modulated. The SE 1375, 20 watts, which used four three-element tubes and operated on frequencies between 570 and 750 kc., was designed by Mr. F. B. Monar for use in small aircraft. The SE 1385, 500 watts, which used two 50-watt three-element tubes and covered the frequency range, 300-600 kc., was designed by Mr. L. A. Gebhard for use in large flying boats. One of the first radioteletype transmissions from aircraft to ground was made utilizing the SE 1385. It also became the transmitting component of the first aircraft radio transmitting system given a model designation, the GA.
It was difficult to procure receivers of commercial design and development rugged enough or shielded adequately enough for use in aircraft. Since Eaton and his assistants at the Washington Navy Yard were producing excellent designs of receivers for other purposes, the Bureau directed the yard to design receivers for aircraft.
In less than 2 weeks after receipt of the directive, the SE 950 receiver was designed, the model built, minor changes made, and then tested. It was so good that, for many years, it was the best aircraft radio receiver in the naval service.36 It consisted of an inductively coupled three-element vacuum tube receiver, covering the frequency range 125-1,000 kc., provided with static tube coupling for regeneration and oscillation, and two stages of audiofrequency amplification. It is of interest that this was the first receiver ever designed with the amplifying circuits as an integral part. It was also equipped with the proper switching and compensating inductances to permit it to be used as a component of their aircraft direction-finder equipment.37 It was manufactured by the National Electric Supply Co.38 and the Washington Navy Yard.39
After completion of the development of the SE 950, Eaton and his group designed the SE 1414. It consisted of a conductively coupled receiver, covering the frequency range 300-1,500 kc., with inductive tube coupling to produce regeneration and oscillation. The individual tubes were not provided with shock mountings but the entire receiver was mounted in a rubber suspension. It was manufactured by the Westinghouse Electric & Manufacturing Co. and the Washington Navy Yard.
The need for greater amplification of signals received in aircraft led to the Washington Navy Yard design and development of the SE 1405 amplifier with three stages of radiofrequency amplification, a detecting circuit, and two stages of audiofrequency amplification. This was followed by the development of an entire family of such devices covering the usable frequency range. The best of these developed for use with aircraft direction-finder equipment was the SE 1605B, an improved version of the SE 1405. It was manufactured in large quantities by the General Electric Co.40
In early types of aircraft the severe acoustic disturbances caused by the combination of wind rush and motor and vibration noises necessitated that all crewmembers wear a helmet containing a headset for intercommunication. Several helmets had been designed, all of which produced pressures upon the wearer's head, resulting in violent headaches from prolonged use. The first adopted as standard by the Navy, the CW 1113, was designed and manufactured by the Western Electric Co. This was very unsatisfactory and was supplanted by a Western Electric redesign, temporarily accepted by the Army, and fairly satisfactory for flights of short duration. Meissner, while at Pensacola, redesigned this helmet by replacing the Western Electric ear cups with solid rubber ones. This was designated the SE 1981 helmet, but it also proved unsatisfactory for prolonged use. Meanwhile, Western Electric redesigned the helmet a second time and produced the Army-type HS-2 which was also found unsatisfactory by Navy tests. The Aircraft Laboratory was immediately directed to design a helmet that could be worn indefinitely without pain. This action occurred almost simultaneously with the adoption of the SE 1981 as the temporary standard as evidenced by the designation, SE 2000, included in the directive. However, it was not until after the Laboratory was moved to Hampton Roads and placed under Taylor that a design meeting the requirements was submitted. It was produced by the combined efforts of Taylor, Lt. (jg) W. R. Davis USNR, and Ens. C. D. Palmer, USNR.41
This helmet was made of soft leather lined with flannel, with the central rear seam left unsewed in manufacture to permit individual fitting. The earpieces were enclosed in deep, soft rubber cups of less depth at the back of the ear, where continued pressure is unbearable. The cups were held tightly against the head by a strap running around the head and back of the neck instead of by the previously used uncomfortable chinstrap. The chinstrap was utilized only to bring the forward edges of the helmet close to the face and to tighten the lower portion of the helmet. A flannel-lined cape at the bottom of the helmet, when buttoned within the flying clothes, prevented entry of wind and noise at that point. It proved extremely satisfactory under service conditions and was worn continuously by the crew of the dirigible C-5 during its 36-hour flight to St. Johns, Newfoundland.42
During the early tests of the De Forest radiotelephone equipment, it was found necessary to develop a microphone which would balance out the terrific noises generated under flying conditions. While at Pensacola, Meissner conceived the idea of mounting the diaphragm so that both sides would be exposed to the vibrations from extraneous noises, but only one side would be affected by the directional vibrations set up by speaking into it. He failed to make a satisfactory design. Several companies experimented with his idea and in 1918 the Magnavox Co., assisted by the Aircraft Radio Laboratory, succeeded in the construction of a satisfactory device, the SE 4005.43
7. AIR STATION RADIO EQUIPMENT DEVELOPMENT
The improvement in aircraft radio equipment, with consequent longer ranges, produced a requirement for air station continuous-wave transmitting equipment usable for either radiotelephony or telegraphy. The contract for the development of this equipment was given to the General Electric Co. Just after the termination of hostilities a model was submitted for service testing. All elements of this unit, except the modulating amplifier and the motor generator, were in one encasement. All meters and essential controls, including a switch for instantaneous shifting to any of five frequencies, 135, 190, 320, 350, and 500 kc., were installed on the front panel. Six vacuum tubes were used, three as oscillators and three as modulators. During tests it delivered 750 watts to the antenna and gave a reliable radiotelephone range from shore to aircraft of over 200 miles. Provisions were made for remotely controlling the transmitter so that the air station commanders, using regular telephone lines, could utilize the equipment from their desks. On 12 March 1920 Secretary Daniels, seated in his Office, conversed with Lt. Harry Sadenwater, USNR, in a flying boat 70 miles away. Regular telephone lines connected the Secretary's telephone with the transmitter at the Washington Navy Yard. Reception of the aircraft radiotelephone transmission was received at the same place, then amplified by two audio stages and carried over the telephone wires to the Secretary's Office.44 This was a very satisfactory transmitter and proved to be the prototype of the broadcast transmitter of the "twenties." With some minor modifications, it became a component of the model TD shore-station transmitting equipment.
8. RADIO AND THE TRANSATLANTIC FLIGHT
During the war a decision was reached to design, develop, and construct a flying boat capable of crossing the Atlantic via Newfoundland and the Azores. While this project was not completed prior to the termination of hostilities, the excellent progress which had been made indicated it could be satisfactorily completed. Therefore, the project was continued and four type NC planes were constructed and satisfactorily tested. At 1000, 8 May 1919, three of these, the NC-1, NC-3, and NC-4, with Comdr. J. H. Towers, USN, commanding the NC-3 and the flight, took off from Rockaway Beach, Long Island, on their historic effort to fly across the Atlantic. Towers had originally decided to eliminate all radio equipment to decrease weight during this flight. Hooper was able to convince him that this would be an error.45 Tower's radio officer was Lt. Comdr. R. A. Lavender, USN, Head of the Aircraft and Radio Compass Sections of the Radio Division. Lt. Comdr. P. N. L. Bellinger, USN, commanded NC-1, with Sadenwater as radio officer. The NC-4 was commanded by Lt. Comdr. A. C. Reed, USN, and his radio officer was Ensign H. C. Rodd, USNR.
Aircraft radio equipment developed during the war was installed in these planes. The main transmitter was the 500-watt SE 1310, mounted on the outside of the hull. The auxiliary was the 50-watt CG 1104, fitted within the hull. The receiver was the SE 950, modified by removal of the radio direction-finder elements and the two stages of audiofrequency amplification. Radio direction-finder equipment consisted of the standard revolving coils installed in the afterpart of the hull and a control board. The six-stage audio radiofrequency amplifier SE 1605B was provided for signal amplification for both traffic and direction finding. Skid-fin and trailing-wire antennas were installed for both transmission and reception.46
Considerable difficulty was experienced in installing the equipment because it could not be placed in the planes until all other apparatus had been installed and tested. The only place the direction-finder coils could be installed was in the after compartment, where it was surrounded by lighting cables, the brace wires of the hull, and the control wires to the tail. These tended to act as a shield and a refractor and also radiated the ignition disturbances, thereby increasing the signal-to-noise ratio, During preliminary tests the direction finder in the NC-2 gave accurate bearings up to distances of 50 miles. Just prior to the beginning of the flight, changes to the auxiliary ignition systems reduced this range to 15 miles. Immediately after this, the planes were tested for full load conditions and thereafter there were no opportunities to flight-test the radio equipment or to calibrate the direction-finder equipment.47
On the first leg of the flight, Rockaway Beach to Halifax, the NC-3 had a forced landing 40 miles short of its destination. Using the auxiliary transmitter, communication was established with the tender U.S.S. Baltimore within 50 seconds. Information giving the location of the plane, the trouble encountered and that no assistance was required was transmitted.48
It is possible that time would have been made available for the proper readying of the radio equipment had this first crossing of the Atlantic by aircraft not developed into a race between the United States and England. Three teams of British aviators were already at St. Johns, Newfoundland, preparing for transatlantic flights.49
A statement made by Reed at this time gives an insight as to the general view of the enterprise:
If the flight were successful, not only would an immense amount of valuable . . . information be obtained concerning long-distance overseas flying, but Naval Aviation, the Navy Department, and the whole country would receive the plaudits of the entire world for accomplishing a notable feat in the progress of science; the mass of the people would be made to realize the importance of aviation as a valuable arm of the naval service and the way would be blazed for others to follow and thus act to promote commercial trans-Atlantic service.50
At Trepassey Bay, Newfoundland, the end of the second leg, weather conditions prevented departure of the American planes for the Azores. Load conditions for this, the longest leg, prompted Towers to order the removal of the auxiliary transmitter to reduce the weight by 26 pounds.
To provide rescue and navigational assistance, 68 destroyers were stationed, at intervals of 50 miles, along the route from Newfoundland to the Azores and then on to Lisbon. These were augmented at 400-mile intervals by five battleships which functioned as weather stations. Since the greater part of the leg between Trepassey Bay and the Azores was flown during darkness, the picture presented must have been one of a gigantic traveling Fourth-of-July celebration. The searchlights of the ships were directed skyward as the planes approached. As they passed over each station the ships fired star shells until each plane acknowledged by radio.
Communications with the planes in flight were excellent. They were heard by the radio station at Bar Harbor, Maine, when 1,450 miles distant. Communications were maintained between the planes and shore for 700 miles and between planes and destroyers for 500 miles. Signals emanating from the U.S.S. George Washington, distant 1,800 miles, were copied by one of the planes. The radio direction finder was used constantly for homing on each succeeding station vessel.51
Dense fog was encountered as the planes approached the Azores. The NC-1 was forced down about 100 miles from Flores, but was promptly contacted by the station vessel which unsuccessfully attempted to tow her to port. Forty-five miles from the same port, the flagship NC-3 was forced to land in rough water prior to transmitting her position to the station vessels. Since the auxiliary transmitters had been removed, there was no transmitting equipment which could be used because the motors could not be run without danger of damaging the plane's hull. The plans for search could be heard on the plane's receiver. Ultimately, the NC-3 managed to drift and sail into Ponta Delgada Harbor. Luckily, the NC-4 spotted a hole in the fog and landed at Horta at 0925, 17 May.
The NC-3 was severely damaged and could not proceed. On 20 May the NC-4 joined Towers at Ponta Delgada. From there it departed for Lisbon, Portugal, at 1818, 26 May. Shortly after departure the auxiliary ignition system became defective and was cut out. The radio direction finder again had an operable range of at least 50 miles. At the same time a casualty affected her magnetic compass and caused her to drift 40 miles from her prescribed tracks. Utilizing the transmissions of the closet station vessel, which was determinedly transmitting in an endeavor to gain contact, the plane was homed to the proper location and proceeded to Lisbon, homing thereafter on each successive vessel. She landed at 1602, 27 May, and later proceeded to Plymouth, England.52
The intense interest in this flight and the acknowledged role played in its successful conclusion did much to convince aviators of the necessity for aircraft communications and navigational aids. This interest has continued through the years until today the navigation of planes is almost totally electronic.
Considering, under normal conditions, years as the accepted period of time between the conception of an idea and the operational use of new equipment, one cannot help but be amazed at the miraculous developments of a short period of months. Both the Western Electric Co. and the General Electric Co. were engaged in research in radio equipment for England and France prior to our entrance into the war. When we became a combatant this research, intensified by the patriotism of the management and workers, produced results of which all Americans should be proud. The work of the naval radio engineers and their accomplishments cannot be overly praised. In commenting upon the presentation of the paper "Naval Aircraft Radio" by T. Johnson, Jr., before the Institute of Radio Engineers, New York, on 4 June 1919, Mr. John V. L. Hogan, then president of that noted body, stated:
I wish particularly to express my appreciation of the assistance which the Aircraft Radio Division of the Bureau of Steam Engineering . . . . has given toward the advance in radio for aeronautic use. From details of design, apparently minor in importance but so often of tremendous consequence in service, right through to such basic topics as the effective capacity, inductance and resistance of flying antennas, Mr. Johnson has led us in a most helpful and constructive way. The success of commercial aircraft will depend largely upon the success of aircraft radio, and so large a contribution to progress as has been given to us by Mr. Johnson deserves the fullest measure of recognition.
1 Supra, ch. XIV.
2 "Radioana," Massachusetts Institute of Technology, Cambridge, Mass., G. H. Clark, "Radio in War and Peace," p. 194.
3 Ibid., p. 197.
5 S. C. Hooper, "History of Naval Radio, Radar, and Sonar," Office of Naval History, Washington, D.C., recording 21R51.
6 Proceedings, Institute of Radio Engineers (vol. VIII, No. 2, February 1920), pp. 6-7, T. Johnson, Jr., "Naval Aircraft Radio."
7 Contract NPO 918, 16 Feb. 1917.
8 Contract 28308 NSA, 21 Dec. 1916.
9 Contract 28309 NSA, 21 Dec. 1916.
10 Contract 28310 NSA, 21 Dec. 1916.
11 Contract 28386 NSA, 1917.
12 Israel was a naval expert radio aid during World War I.
13 "History of the Bureau of Engineering, Navy Department, During the World War," Washington, Government Printing Office, 1922, p. 120.
14 U.S. Navy contract 35258, dated 22 Jan. 1918.
15 "Radioana," op. cit., Clark, "Radio in War and Peace," During World War I there was no Army requirement for long-range planes; therefore, they could accept the short-ranges resulting from the use of voice modulation.
16 Hooper, op. cit., recording 21R52.
17 "Radioana," op. cit., Clark, "Radio in War and Peace," p. 200.
18 Johnson, op. cit., pp. 7, 127.
19 A. Hoyt Taylor, "Radio Reminiscences: A Half Century," U.S. Naval Research Laboratory report, p. 113.
20 U.S. Patent No. 1,435,941, dated 21 Nov. 1922.
21 Taylor, op. cit., p. 106.
22 Taylor, op. cit., p. 112.
23 "History of the Bureau of Engineering, Navy Department, During the World War," op. cit., p. 138.
24 These equipments and their normal usages are listed in app. M.
25 U.S. Navy contract 33596 and NSA requisition 757 dated 7 Dec. 1917 to Cutting & Washington for 20 ½-kw. commercial-type sets with receivers, antenna, and Chafee gap, $30,000.
26 U.S. Navy contract 33258 dated Dec. 1917 to National Electric Supply Co. for 50 aeroplane sets.
27 U.S. Navy contract 2916-18; June 13, 1918; Marconi Wireless Telegraph Co. of America; 350 200-watt flying boat transmitters, SE 1100.
28 "History of the Bureau of Engineering, Navy Department, During the World War," op. cit., p. 122.
29 "Radioana," op. cit., Clark, "Radio in War and Peace," p. 314.
30 Taylor, op. cit., p. 114.
31 U.S. Navy contracts 39850 and 40836, dated June 28, 1918.
32 "Radioana," op. cit., Clark, "Radio in War and Peace."
33 LeClair was born in and appointed a midshipman from Wisconsin. He graduated from the Naval Academy in 1909. He relieved Hooper as head of the Radio Division for about 9 months in 1918. He retired as a commander on 30 June 1937. During World War II he returned to active duty and was promoted to captain.
34 Taylor, op. cit., pp. 101, 120.
35 Ibid., pp. 116-117.
36 "History of the Bureau of Engineering, Navy Department, During World War," op. cit., p. 122.
37 Ibid., p. 125.
38 U.S. Navy contract 25659, 26 Jan. 1918, to National Electric Supply Co., for 321 SE 950, $99,510.
39 Job order 12-Z-2252, 7 Feb. 1918, for 25 SE 950, $9,530.33.
40 U.S. Navy contract N-5068, 9 Oct. 1918, to General Electric Co. for 275 SE 1605B aircraft amplifiers.
41 "History of the Bureau of Engineering, During the World War," op. cit., p. 221; Johnson, op. cit., pp. 109-110, 139.
43 Johnson, op. cit., p. 48.
44 Johnson, op. cit., pp. 129-135.
45 Hooper, op. cit., recording 24R60.
46 "History of the Bureau of Engineering, Navy Department, During the World War," op. cit., p. 124.
47 U.S. Naval Institute Proceedings, vol. VIII, 1920, R. A. Lavender, "Radio Equipment on NC Seaplanes," p. 1604.
48 Ibid., p. 1607.
49 It was not until 14 June, a fortnight after the NC-4 arrived at Plymouth, England, that Alcock and Brown completed their nonstop flight from Newfoundland to England.
50 Archibald D. Turnbull & Clifford Lord, "History of United States Naval Aviation" (Yale University Press, New Haven, Conn., 1949), p. 166.
51 "History of the Bureau of Engineering, Navy Department, During the World War," op. cit., p. 124; Lavender, op. cit., p. 1605.
52 Ibid., p. 151.
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