Monthly Archives: April, 2016
We continue with noted Pan American Airlines radio officer Almon Gray’s analysis of the radio problems that Amelia Earhart encountered during her final flight. Before we proceed, a word from the late Art Kennedy, an aircraft technician for the Pacific Airmotive Company in Burbank, Calif., during the 1930s, who directed the repairs of the Electra when it was shipped back to the Lockheed facility following the “ground-loop” at Luke Field, might be instructive. In Kennedy’s 1992 autobiography, High Times, Keeping ’em Flying, he was quite frank in his appraisal of Amelia’s radio skills, or lack of same.
Kennedy believed that Earhart’s cavalier attitude toward radios led to her undoing. “In her unique fashion Earhart was quite a lady, although it is well known that she punctuated her airport conversation with a spectacular lexicon of aviation vulgarities,” Kennedy wrote. “This was especially the case when she had trouble contacting the tower, because she was notoriously lazy about learning how to use the radio properly. She would get so frustrated that her language became unprintable and Burbank tower operators often found it necessary to reprimand her. That failure to learn radio procedures may be significant in light of the apparently frantic transmissions before she disappeared. I remember Paul Mantz telling her that she must be up to speed on frequencies for daylight and night transmissions, but she flippantly replied that if she couldn’t get what she wanted she’d just keep trying until she got a response.”
“AMELIA EARHART AND RADIO,” By Almon A. Gray
Part II of III
ANATOMY OF A GOOF
While we shall never have a positive and complete answer to the above questions, it is possible to deduce a great deal. Therefore there follows a hypothetical scenario which, it is believed, reflects quite accurately what actually transpired. It is emphasized that some parts are conjecture.
1. Earhart was at Bandung having maintenance done on the plane when the query came in from Itasca as to what radio frequencies she wished Itasca, Ontario and Swan to use in supporting her flight from Lae to Howland. Time was running out and she had to provide the answers right away. It had been pounded into her head time and time again that-she needed low frequency radio beacons for homing purposes. She knew that was what she wanted from the ships but she did not know what particular frequencies to specify. She therefore sought advise from the best local source available and arranged for herself and Noonan to meet with the top KLM airline communications man.
2. The KLM man did not speak English very well and was accustomed to talking in terms of wavelength and meters rather than frequency and kilocycles. From his service in the British Navy, Noonan was familiar with the wavelength/meters system so he and the KLM man did most of the talking. Earhart scribbled notes. Among them they developed the following plan:
(a) Ontario and Itasca would both use the same frequency but transmit at different times. This would allow Earhart to receive signals from both ships without the necessity of re-tuning her receiver. To avoid any uncertainty as to which ship’s signals were being received, Ontario would transmit the Morse code character for the letter “A” rather than the customary Morse “M O” as its homing signal. Itasca would transmit the Morse character for the letter “N” as its homing signal. These same characters (A and N) were used it identify the quadrants of the four-course radio ranges in the United States and Earhart could readily recognize them.
Apparently it was envisaged that there would be an overlap of signal coverage over a good part of the leg, and that Earhart would be able to take bearings alternately on the two stations and thus keep on course. The frequency chosen for Ontario and Itasca was 400 kilocycles, which is equivalent to a wavelength of 750 meters. It was a frequency assigned worldwide for aeronautical radionavigation and was an excellent choice. It probably was chosen over equally good frequencies in the same band because it was easy to remember and easy to find on the receiver tuning dial.
(b) Swan used the frequency of 333 kilocycles which is equivalent to a wavelength of 900 meters. Use it for voice communication with the plane if possible, but in any event be prepared to send homing signals on it. 333 kc was in the band allocated worldwide for aeronautical radio navigation and air-ground communications. It was widely used in Europe, the Commonwealth nations and other countries having close ties with Europe, as a calling frequency and for ground-air communications. Earhart had probably received on it during earlier legs of her flight but called it “nine hundred meters.” It was an excellent direction-finding frequency.
3. Noonan left the meeting satisfied that the radio navigational plans were adequate, or at least as good as could be developed.
4. Earhart went back to the hotel and drafted and dispatched her message of June 27 to Itasca (Black). She did not show the message to Noonan.
5. It had been difficult for Earhart to understand the adviser’s English, and she had experienced great difficulty in following the discussion as it shifted rapidly back and forth among “frequency,” “wavelength,” “megacycle,” “meter,” kilocycle,” etc. Perhaps too she was suffering from dysentery and was actually ill. Whatever the reason, the message she drafted suggested frequencies for the Swan and Itasca vastly different from those settled on in the meeting. Specifically:
(a) The frequency for Swan was changed from an intended 333 kilocycles (900 meters) to 900 kilocycles. One can readily deduce that the wavelength in meters was used but was labeled as frequency in kilocycles.
(b) The frequency for Itasca was changed from an intended 400 kilocycles (750 meters) to 7.50 megacycles. Again it appears that the figures for the wavelength in meters were used but labeled as a frequency.
Had normal air-ground communications existed between Itasca and the plane, the homing problem could almost certainly have been solved quickly. All that was needed was for Itasca to tell Earhart to home on 500 kHz, which frequency was already being transmitted (in addition to 7.50 MHz) by Itasca. She should have been able to get bearings on that frequency that would have taken her right in to the ship. Unfortunately she was unable to hear signals from Itasca on 3105 kHz, although the ship was hearing her well. It thus was impossible for Itasca and Earhart to coordinate their actions.
THE AIR/GROUND COMMUNICATION PROBLEM
Why could Earhart not hear Itasca‘s transmissions on 3105 kHz? Here again we probably shall never know for sure, but from the information which is available it is possible to hypothesize an answer which is reasonable and probably reflects quite accurately the actual situation. Following are some of the things that are known which are germane to the question:
1. There was but one radio receiver aboard the plane and it was used for both communication and radio direction finding purposes. There were two antennas aboard, a conventional fixed antenna and a rotatable shielded loop. Either of these, but not both simultaneously, could be connected to the input of the receiver by means of an antenna selector switch on the receiver. Radio signals could be received on either antenna but usually were stronger when using the fixed antenna, therefore it was the one generally used for communications. Direction finding could be done only when using the loop antenna.
2. The fixed antenna was used for both receiving and transmitting purposes. There was a so-called “send-receive” relay in the transmitter which switched the antenna back and forth between the units. Normally the antenna was connected to the receiver, but when the relay was energized by pushing the “push to talk” button on the microphone, the antenna was switched over to the to the transmitter and remained that way until the microphone button was released.
3. Energy from the loop antenna went directly to the antenna selector switch of the receiver. Energy from the fixed antenna passed through the “send-receive” relay mentioned above before reaching the antenna selector switch of the receiver.
4. The receiver had six frequency bands; however, the vacuum tubes, voltage determining resistors, bypass capacitors etc., were for the most part, common to all band, and it was rare that a single band would fail. It usually was none or all.
5. The radio equipment aboard the plane was checked at Lae by Harry Balfour, the Guinea Airways wireless operator, and was found satisfactory. The only unusual thing noted was a roughness of the transmitted signal on 6216 kHz, which made Earhart’s speech difficult to understand. Two-way communication was maintained during a 30-minute test hop at Lae.
6. After takeoff from Lae to Howland it appears that two-way communication with Lae was maintained until about 0720 Greenwich Mean Time (GMT) (6 p.m. Lae time) July 2, at which time Earhart shifted to her “night” frequency (3105 kHz). Several times after that, throughout the night, she was heard by Nauru and Itasca broadcasting at the pre-arranged times, but little of what she said was intelligible. Nauru, and later Itasca, called her numerous times but there is no indication she heard any of the calls. At 1744 GMT (seven hours, 44 minutes into the flight), she asked Itasca for a bearing on 3105 kHz and made a signal upon which the bearing was to be taken. Itasca made a response but Earhart did not acknowledge receiving it. The same thing happened at 1815 GMT. At 1912 GMT (0742 Howland Island Time), Earhart said the following to Itasca:
“WE MUST BE ON YOU NOW BUT CANNOT SEE YOU. RUNNING OUT OF GAS. ONLY ONE-HALF HOUR LEFT (there is controversy about that phrase). BEEN UNABLE TO REACH YOU BY RADIO. WE ARE FLYING AT ONE THOUSAND FEET.”
At this time the signals from the plane were very strong. It is known that the Itasca was putting out strong signals and was on the correct frequency. (They were heard in San Francisco.) Therefore the statement “BEEN UNABLE TO REACH YOU BY RADIO” clearly indicated that a failure had occurred in her radio receiving system, and that it probably had occurred early in the flight. Inasmuch as she could still transmit it was obvious that the fixed antenna was intact; beyond that there was no clue as to the nature of the failure. That clue was given very shortly however. AT 1925 GCT Earhart asked Itasca to transmit signals “on 7500,” meaning 7.50 MHz. This indicated that she intended to take radio bearings on Itasca with the plane’s direction finder.
Itasca complied immediately and sent the desired homing signals. The transmitter had no radiotelephone capability so it was impossible to also talk with the plane by voice on that frequency. Earhart responded immediately saying, “WE RECEIVED YOUR SIGNALS ON SEVENTY FIVE HUNDRED BUT UNABLE TO GET A MINIMUM. PLEASE TAKE BEARING ON US AND ANSWER THREE FIVE NAUGHT FIVE (3105 intended) WITH VOICE.” This was followed by a series of long dashed on 3105 kHz on which bearings were expected to be taken by Itasca/Howland. This was the first (and only) time Earhart acknowledged hearing signals from Itasca. From the fact that Earhart asked for the homing signals it is clear that she intended to take a bearing, which could be done only with the loop antenna. From her report of hearing the homing signal but being unable to get a minimum on it, it is obvious that she, in fact, shifted the receiver to the loop antenna, and that the homing signals were received on the loop antenna.
Why could she receive 7500 kHz signals on the loop but not 3105 kHz on the fixed antenna? At the distances and time of day involved, propagation would not account for it, so something must have changed in the receiving system. Actually two changes had been made: (a) The receiver had been shifted from band IV which included 3105 kHz to Band V or VI, both of which included 7500 kHz and (b) The receiver had been shifted from the fixed antenna to the loop antenna.
It is possible that some component peculiar to band IV had failed making reception on that band impossible, whereas reception on other bands would be normal. However, as mentioned previously, the probability of that happening was small, therefore it is unlikely that shifting bands, per se, made the difference between not receiving and receiving signals. Shifting antennas however was a horse of a very different color. With the antenna selector switch in the “DF” position incoming signals picked up by the loop antenna went directly to the input of the receiver. With the switch in that position Earhart heard signals from Itasca.
With the antenna selector switch in the “FA” (Fixed Antenna) position, signals picked up by the fixed antenna did not go directly to the input of the receiver; instead they passed through contacts on the “send/receive” relay in the transmitter. With the switch in the “FA” position Earhart did not hear signals from Itasca. This indicates very strongly that signals from the fixed antenna were not reaching the receiver and that the receiver, in effect, had no antenna.
The feed line from the fixed antenna was in two sections. One was between the antenna and the “send/receive” relay in the transmitter. This section was used both for receiving and for transmitting. Earhart’s transmissions were being heard, therefore this section, including the “send” part of the relay, was functioning. The other section was between the receiver input and the “send/receive” relay, including the “receive” part of the relay. There appears to have been an open circuit or a complete “ground” in this section, either of which would have prevented the receiver from picking up signals.
It is possible that the wire in that section of the feed line broke or came loose from a binding post; however, that possibility is very small. It is much more likely that the trouble was in the “send/receive” relay. Those devices were subject to damage from several sources. Lightening or heavy static discharge sometimes burned the contacts completely off or welded them together. Contacts on the “receive” part of the relay were particularly subject to this type of damage. Mistuning of the transmitter or antenna sometimes caused arcing and subsequent pitting and sticking of contacts. And sometimes contacts would stick, or not make good contact, for no apparent reason.
It should not be implied from this that the relays were inherently unreliable; they were not. Most went hundreds of hours between routine replacement with no trouble, but occasionally one would fail. This appears to have been one of those times. In this writer’s judgment the odds are about 95 to 5 that Earhart was unable to hear Itasca on 3105 kHz because she was switched to the fixed antenna and the “send/receive” relay was defective on the receive side.
Had she shifted to the loop antenna she no doubt would have heard Itasca very well on 3105 kHz or whatever frequency the ship might be using and she was tuned to. It probably never occurred to her to do that, however. Earhart knew very little about the technical aspects of radio and consequently operated the gear by rote. Obviously she had been taught to turn the antenna selector switch to “FA” if she wanted to talk, and to “DF” if she wanted to take a bearing — and that is precisely what she did. (End of Part II of Almon Gray’s “Amelia Earhart and Radio.”)
For the pilots and other technically astute readers among you, Almon Gray’s analysis might be easily understood, even if you disagree with some or all of his ideas. But for the lay person, which includes this writer, it’s not so easy to follow Gray’s narrative with clear comprehension. Just when I thought Gray was attributing Earhart’s radio failures to a misunderstanding about the meters and wavelengths that the “KLM man” was advising Earhart and Noonan to use during their meeting at Bandung, he launched into completely different set of reasons to explain the communications nightmare that was the final flight. I must admit that I don’t fully grasp the totality of Gray’s narrative thus far, and may never. Still, I think it’s important to present the important and unique work of experts like Almon Gray, regardless of how much I fail to understand.
In the final segment of “Amelia Earhart and Radio,” Gray will examine some of the possible “post-flight signals” that have long been sources of controversy and contention among researchers, take a closer look at Fred Noonan’s role in the proceedings, and present his well-informed conclusions. Please stay tuned.
Almon Andrew Gray was a pioneer in aeronautical communications. After graduating from the George Stevens Academy in 1928 and the Massachusetts Radio Telegraph School in 1930, he enlisted in the Navy, where he was a radioman and gunner aboard cruiser based aircraft. He also learned to fly.
Upon expiration of his enlistment he signed on with Pan American Airways, and in 1935 helped build the bases to support the first trans-Pacific air service and was first officer-in-charge of the PAA radio station on Wake Island. After the San Francisco-Hong Kong air route was opened in late 1935, he was a radio officer in the China Clipper and her sister flying boats. Later he was assistant superintendent of communications for PAA’s Pacific Division. Gray was also a Navy Reserve captain, flew with Fred Noonan in the 1930s and was an important figure in the development of the Marshall Islands landing scenario. He died at 84 on Sept. 26, 1994 at Blue Hill Maine. In coming weeks and months, some of Gray’s writings will be featured on this blog.
More than anyone in Earhart research history, with the possible exception of Paul Rafford Jr., Almon Gray was qualified to discuss Amelia Earhart’s radio arrangements and behavior. “Amelia Earhart and Radio” first appeared in the June 1993 issue of Bill Prymak’s Amelia Earhart Society Newsletters.
From the outset, readers should understand that in this analysis, Gray assumes that Earhart was actually trying to reach Howland island, and that she was attempting to establish two-way communication with Itasca, which never happened. In his piece, Gray also doesn’t try to explain why she was never on the air for more than 10 seconds, something that has led many to speculate that Earhart didn’t want her position to be known and that something else was afoot besides her official flight plan.
“AMELIA EARHART AND RADIO,” By Almon A. Gray
Part I of III
Most of that written about the disappearance of Amelia Earhart while on an around-the-world flight in 1937 attributes her failure to reach Howland Island to unstated deficiencies related to radio. It appears however that very little has been written about the nature of those deficiencies, or how they came about. What follows will attempt to fill that gap and show what errors in planning and execution were made in respect to radio; what failure or malfunctioning of radio equipment occurred and the probable reason for it; and will point out the single item or event deemed most directly responsible for the failure of the plane to reach Howland Island.
Since 1937 the unit of measurement for radio frequencies had been changed from “cycles” to “hertz” (Hz), consequently kilocycles (Kc) and kilohertz (kHz) will be used interchangeably, as will megacycles (Mc) and megahertz (MHz). It is assumed that the reader already is familiar with the general history of the flight.
In early 1937, several weeks before her Oakland-Honolulu flight, and while she still intended to circumnavigate the world in a westerly direction, Miss Earhart met at Alameda, Calif., with George Angus, the superintendent of communications for the Pacific Division of Pan American Airways. Angus was responsible for the radio communication and radio direction finding networks which supported the PAA clippers on their trans-Pacific crossings, and Miss Earhart wished to arrange for help from those facilities during her planned flight. She was particularly interested in obtaining radio bearings to augment her celestial navigation. At that time PAA had specially designed versions of the Adcock radio direction finding system in service at Alameda; Mokapu Point, Hawaii; Midway Island; Wake Island; Guam; and Manila, Philippines to support Clipper operations.
These systems were capable of taking radio bearings on frequencies much higher than could be utilized successfully by conventional loop-type direction finders, hence were effective over much greater distances. They were commonly referred to as “high frequency DFs,” and were the only ones of that type in the United States and its territories. Angus agreed to help Earhart while she was within radio range of PAA stations, and details for so doing were worked out.
This was somewhat complicated inasmuch as PAA was not equipped to transmit on either of Earhart’s communication frequencies (3105 kHz and 6210 kHz.) and could not transmit voice on any frequency. The solution agreed upon was that the plane would request a bearing by voice on the frequency in use, (usually 3105 kHz at night, 6210 kHz during the day) and follow the request with a series of long dashes lasting in the aggregate a couple of minutes. The PAA DF station would take a bearing and transmit it to the plane on a previously agreed upon PAA frequency, using “CW” (telegraphy) sent at such a slow speed that the individual dots and dashes of the numbers could be copied on paper and later translated into numbers. This arrangement was tested on the flight from Oakland to Honolulu with the bearings being taken by PAA on 3105 kHz and sent to the plane on 2986 kHz It worked out very well.
The Oakland-Honolulu flight was uneventful, and from the standpoint of radio was handled much the same as a Clipper flight. Captain Harry Manning, an experienced radio operator, handled the Electra’s radio and DF gear while the ground radio facilities were operated by the regular PAA professional radio operators. Radio bearings were furnished the plane at frequent intervals, first from Alameda and later from Mokapu Point. They checked well with the positions Noonan determined by celestial navigation. As the plane neared Oahu, Manning set up the plane’s direction finder to home on the Marine Radio Beacon (290 kHz.) at Mokapu Point (near Diamond Head) and Earhart homed in on it to a successful landfall.
During an attempted takeoff for Howland Island from Luke Field, near Honolulu, on March 20, 1937 the Electra ground-looped and was damaged to the extent that it was shipped back to the Lockheed plant in California for repairs. There had been no major damage to the radio gear, and the main thing done to the radio system while at Lockheed was to replace the Western Electric Model 20B radio receiver and its remote control apparatus with a Bendix Type RA-1B Aircraft Radio Receiver and its accessories,which included means for complete remote control from the cockpit. This work was done by Lockheed contract technician Joe Gurr.
THE NEW RECEIVER
The RA-1B was a brand new Bendix product and was reputed to be pushing the state of the art in aircraft receiver design. It was a super heterodyne, which had the frequency range .150-1.50 and 1.80-15.0 Megahertz, which was divided into six bands: I: .150 – .315; II: .315 – .680; III: .680- 1.50; IV: 1.80 – 3.70; V – 3.70 – 7.50; VI: 7.50 – 15.0.
The gap between 1.50 and 1.80 MHz was to accommodate the intermediate frequency. It could receive voice or “CW” signals, and there was a three-position antenna selector switch which permitted three choices of antenna. With the switch in the “DF” position, the receiver was connected to the Bendix type MN-20 rotatable loop mounted atop the fuselage over the cockpit, and the combination comprised a radio direction finder. With the switch in the “TA” position the receiver was connected to the trailing antenna, and when in the “FA” position it was connected to the fixed antenna. It should be noted that signals from the loop antenna went directly from the loop, through the antenna switch, to the input of the receiver, whereas signals from the fixed or trailing antenna passed through the “send-receive” relay in the transmitter before going through the antenna switch to the receiver input.
It also should be noted that on this model receiver any radio signal within its overall frequency range could be received on the loop antenna. Because of this, some people had the impression that radio bearings could be obtained on any frequency within the receiver’s frequency range, and the unit was sometimes spoken of as a “high frequency direction finder.” The unit of course had no such high frequency direction finding capability, and in later models circuitry was introduced to limit reception on the loop antenna to only frequencies in that part of the overall range deemed suitable for radio direction finding with a loop antenna, i.e. below about 1.80 MHz.
THE RADIO SYSTEM
When the plane left the Lockheed plant after being repaired the radio system was comprised of the following elements:
(1) Bendix Type RA-1B Aircraft Radio Receiver. Mounted in the cabin but having remote controls in the cockpit.
(1) Western Electric Model 13-C 50-watt Aircraft Transmitter. It had three crystal-controlled channels, 500, 3105 and 6210 kHz and could be used for voice or “CW” (radiotelegraph) transmissions. It was mounted in the cabin but there were remote controls in the cockpit.
(1) Bendix Type MN-20 rotatable shielded loop antenna. It was mounted on the top of the fuselage over the cockpit, with the knob which rotated it located on the overhead of the cockpit, between the pilots. It was used primarily for taking radio bearings but was useful as a receiving antenna under conditions of heavy precipitation static noise.
Provision for plugging in a microphone, headphones, and a telegraph key at each side of the cockpit.
A telegraph key and provision for plugging in headphones at the navigator’s table.
A 250-foot flexible wire trailing antenna on an electrically operated, remote-controlled reel, located at the rear of the plane. The wire passed to the outside through an insulated bushing and had a lead weight, or “fish,” at the end to keep it from whipping when deployed. There was a variable loading coil used in conjunction with this antenna to permit its use on 500 kHz. This antenna was long enough to give excellent radiation efficiency on all three of the transmitting frequencies.
A fixed antenna which was a wire “Vee” with its apex at a stub mast mounted on the top of the fuselage, about over the center section of the wing, and the two legs extending back to the two vertical fins. This antenna was so short that its radiation efficiency was extremely low. It was not intended to be used on 500 kHz and probably the radiated power on the other two frequencies was very low. It was meant to be used mainly for local communications around an airport when it was not possible to have the trailing antenna deployed. According to some accounts there was a second “V” antenna mounted on the underside of the fuselage and connected in parallel with the top “V” antenna. If so, it was removed or disconnected before the plane left Miami.
THE SECOND MISTAKE
Earhart flew the plane to Miami in the latter part of May 1937, and there made her second major error of judgment in respect to communications. (The first was in deciding on rely completely on radiotelephone for her air-ground communications.)
One of the first things she did after arriving in Miami was to have the trailing antenna and associated gear completely removed. John Ray, an Eastern Airlines technician, who had his own radio shop as a sideline, did the work.
This had a devastating impact both on her ability to communicate and on her ability to use radio navigation. With only the very short fixed antenna remaining, virtually no energy could be radiated on 500 kHz. This not only precluded her contacting ships and marine shore stations, but more importantly, it prevented ships (including the ITASCA) and marine shore direction finding stations from taking radio bearings on the plane, inasmuch as 500 kHz was the only one of her frequencies within the frequency range of the marine direction finders. Thus any radio aid in locating Howland Island would have to be in the form of radio bearings taken by the plane on radio signals from the U.S. Coast Guard Cutter Itasca.
The shortness of the antenna also drastically reduced the power radiated on the two high frequencies. Paul Rafford Jr., an expert in this field, estimated that the radiated power on 3105 kHz was about one-half watt. This obviously was a tremendous handicap in the high static level of the tropics.
The fixed antenna also may have been responsible for the distortion in Earhart’s transmitted signals reported by the operators at Lae, Howland and Nauru as seriously affecting the intelligibility of her voice transmissions. (A mismatch between the antenna and the final amplifier of a WE-13C transmitter could cause the transmitter to over-modulate and thus introduce distortion.)
Despite the shortcomings of her radio system, Miss Earhart got as far as the Dutch East Indies without major incident. There however, through lack of understanding, she made an error which ultimately lead to her failure to reach Howland Island.
THE THIRD MISTAKE
Three ships had been assigned to assist Earhart on the South Pacific over-water flights. Itasca was at Howland Island, Ontario about half way between New Guinea and Howland, and Swan between Howland and Hawaii. One function of these vessels was to transmit radio signals upon which Earhart could take bearings with her radio direction finder and thus be helped with her navigation. Suitable homing signals from Itasca were extremely important, in fact vital. Should Noonan’s celestial navigation not hit Howland right on the nose, homing in on Itasca‘s signals with her DF was the only way Earhart could be sure of finding Howland before her fuel was exhausted.
In a message dated June 23, 1937 addressed to Earhart at Darwin or Bandung, Mr. Richard Black, aboard Itasca, advised her of the radio frequencies available aboard the Ontario, Swan and Itasca, and asked her to designate the frequency she wished each ship to use to provide homing signals for her. The same day the Commanding Officer of Itasca requested that he be advised twelve hours prior to her departure from New Guinea of her desires in matter of radio, and warned her of the slowness of communication via Port Darwin.
Miss Earhart received these messages while she was at Bandung, Java, having work done on the plane. On June 27, the day before she took off from Bandung for Koepang and Darwin, she sent the following response:
From: Earhart via RCA Manila & N-PM Navy Radio Honolulu
To: ITASCA (Black) June 27, 1937 (Java date: June 26, Howland)
SUGGEST ONTARIO STANDBY ON 400 KILOCYCLES TO TRANSMIT LETTER N FIVE MINUTES ON REQUEST WITH STATION CALL REPEATED TWICE END OFEVERY MINUTE STOP SWAN TRANSMIT VOICE NINE MEGACYCLES OR IF I UNABLE RECEIVE READY ON 900 KILOCYCLES STOP ITASCA TRANSMIT LETTER A POSITION OWN-CALL LETTERS AS ABOVE ON HALF HOUR 7.5 MEGACYCLES STOP POSITION SHIPS AND OUR LEAVING WILL DETERMINE BROADCASTING SPECIFICALLY STOP IF FREQUENCIES MENTIONED UNSUITABLE NIGHT WORK INFORM ME LAE STOP I WILL GIVE LONG CALL BY VOICE THREE ONE NAUGHT FIVE KCS QUARTER AFTER HOUR POSSIBLY QUARTER TO (signed) EARHART
A person experienced in radio direction finding would find that message very strange. Why would Swan be asked to transmit homing signals on 900 kc, a frequency in the broadcast band, when a lower frequency in the aeronautical radio navigation band would be much better? And why would Itasca be asked to send homing signals on 7.5 Mc when that frequency was so high that the possibility of getting useful bearings on it with the plane’s direction finder was nil? Perhaps some of the personnel in Itasca had those questions but took the attitude “She is in the Flying Laboratory. Who knows what hush-hush gear she has aboard? If she wants 7.5 Mc, that is what she is going to get.”
No one questioned the message and Itasca tuned up its transmitter to send homing signals on 7.5 Mc. What happened after that has been well covered in the media and in numerous books. When the plane arrived at what Earhart believed to be the vicinity of Howland, no land could be found despite considerable visual searching, whereupon Earhart asked Itasca to send homing signals on 7.5 Mc, Itasca complied. Earhart heard the signals but reported to Itasca that she was “unable to get a minimum” on them. This meant she could not get a bearing on that frequency. She then asked Itasca to take bearings on her 3105 kHz. transmissions, apparently believing that the direction finder ashore on Holland Island could take bearings on that frequency just as the PAA Adcock systems had done on the earlier flight from Oakland to Honolulu. When she heard no response from Itasca (the reason she did not hear any response will be addressed elsewhere) she transmitted her line of position, said they were running north and south and that she was shifting to 6210 kHz. She was not heard again by Itasca. Apparently she commenced execution of her Emergency Plan at about that point.
Because the unsuitability of the homing frequency used by Itasca had such an adverse impact upon the flight it seems appropriate to digress a bit here to try to find out:
(a) How was the plan for the use of radio homing beacons aboard the three ships developed?
(b) What was the plan?
(c) Did the message of June 27 from Earhart to Itasca (Black) accurately reflect the plan which had been developed? If not, what were the differences and why had they been introduced? (End of Part I.)
In Part II of “Amelia Earhart and Radio,” Almon Gray will continue to analyze Amelia Earhart’s radio communications during her doomed last flight. He will also attempt to explain how and why Amelia’s transmissions were so completely ineffective, or at least appeared to be.