Almon Gray’s “Amelia Didn’t Know Radio,” Part II

We continue with Part II of Almon Gray’s comprehensive analysis of Amelia Earhart’s radio communications and lack of same during her final flight.  Bill Prymak, Amelia Earhart Society founder and president, has called Gray’s analysis of Earhart’s radio problems during her last flight “one of the finest pieces of work ever presented on this subject.”

 “Amelia Didn’t Know Radio,” Part II
by Almon Gray

Precisely what happened next remains unknown, but it appears that Earhart conferred with a local aeronautical communication specialist to get information she could use to base a reply to [Richard] Black.  A plan was developed that fulfilled her requirements with a minimum of receiver tuning on her part.  The Ontario and the Itasca were to transmit on the same frequency but at different times, and each would transmit a distinctive Morse identification signal.  The Ontario’s identifier was “N” and the Itasca’s was “A.” 

(These were the characters used to identify the quadrants at the four-course radio ranges, then the principal navigation aid in the United States.  Hence, Earhart was familiar with them.)

In 1937 it was still common to describe radio emissions in wavelengths expressed in meters, rather than in frequencies expressed in cycles per second.  It seems apparent that the specialist did this during his discussions with Earhart and that he suggested that the ships transmit beacon signals on wavelengths as follows:

– Ontario 750 meters (400 kcs)
– Swan 900 meters (333 kcs)
– Itasca 750 meters (400 kcs)

On Howland Island Adm. Richard Black supervised construction of the air strip for Amelia Earhart’s scheduled refueling stop, and later arranged for a special high frequency direction finder to be set up on Howland.  Black was in the radio room of the USCG Itasca as he listened to Earhart’s last known radio transmission indicating that she was low on fuel and was searching for Howland.

These were excellent choices.  All were allocated internationally for aeronautical radio navigation and were ideal for use with the direction finder in the Earhart plane.

Unfortunately, Earhart did not understand the relationship between wavelength and frequency nor how to convert from one to the other.  Consequently, when she replied to Black on 27 June, she confused the figures and unwittingly specified incorrect frequencies for the Swan and the Itasca; she was correct with the Ontario.

In the case of the Swan, she apparently confused the wavelength and frequency figures, and specified that the Swan transmit on 900 kcs (rather than 333 kcs).  This was a bad error in that 900 kcs was in the broadcast band and not available for aeronautical use.  It also was inferior to the intended frequency of 333 kcs for DF purposes.  It was not necessarily devastating, however, and fair bearings probably could have been taken on it with the aircraft DF.

In the Itasca’s case, however, it was to have grave consequences when she again apparently reversed the numbers and told Black to use 7.50 mcs (rather than 400 kcs) on the Itasca.  The 7.50 mcs frequency was so high that there was practically no possibility of obtaining usable radio bearings on it with the aircraft DF.

Following is the text of Earhart’s reply to Black, sent the day before she left Bandoeng for Koepang and Darwin:

From: Earhart via RCA Manila & NPM Navy Radio Honolulu
To: Itasca (Black) June 27, 1937 [Java Date; it was 26 June on Howland east of the International Date Line]

SUGGEST ONTARIO STANDBY ON 400 KILOCYCLES TO TRANSMIT LETTER N FIVE MINUTES ON REQUEST WITH STATION CALL REPEATED TWICE END OF EVERY 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

Had normal air-to-surface communications existed with the Itasca as Earhart approached Howland, the homing problem could almost certainly have been solved quickly.  The ship could have told her to home on 500 kcs, the frequency already being transmitted (in addition to 7.50 mcs), and she should have been able to get bearings that would have led her to the ship. Unfortunately, she was unable to hear signals from the Itasca on 3105 kcs, although the ship was hearing her well.  It was thus impossible for the Itasca and Earhart to coordinate their actions.

The Coast Guard Cutter Itasca was anchored off Howland Island on July 2, 1937 to help Amelia Earhart find the island and land safely at the airstrip that had been prepared there for her Lockheed Electra 10E.

THE AIR-TO-SURFACE COMMUNICATION PROBLEM: A report by Guinea Airways Ltd. shows that Earhart’s radio gear was checked at Lae by one of its wireless operators, H.J. Balfour, and found satisfactory.  Good two-way communication was maintained during a 30-minute test hop at Lae, although a roughness in the transmitted voice signal made Earhart difficult to understand.  Balfour told her that her speech might be more intelligible if she spoke in a higher pitch while transmitting.

After the flight left Lae for Howland, two-way communication with Lae was maintained until about 0720 2 July Greenwich Mean Time (GMT) [now Universal Coordinated Time], when she shifted to her 3105 kcs night frequency.  Several times throughout the night she was heard broadcasting at the prearranged times by stations on Nauru Island and the Itasca, but little of her transmissions were intelligible.  Nauru, and later the Itasca, called her numerous nines, but there is no indication that she heard any of the calls.  At 1515 GMT, the Itasca picked up Earhart calling to say she would listen on 3105 kcs on the hour and half-hour.  At 1744 GMT she asked the Itasca for a bearing, to be taken then and given to her on the hour.  She then whistled into the microphone on 3105 kcs to create a signal on which the bearing could be taken.  The DF operator on Howland heard this signal but was unable to get a bearing.  He remarked that the signal had very little carrier and seemed over-modulated.  The plane made no response to numerous calls from the Itasca at this time.

At 1815 GMT Earhart again asked the Itasca for a bearing.  She wanted it taken then and reported to her in a half hour (at 1845 GMT), and she whistled into the microphone to provide a signal; she said they were about 100 miles out.  Again the Howland DF heard her signal but was unable to get a hearing, and again Earhart made no response to numerous calls from the Itasca.  At 1912 GMT, Earhart transmitted the following to the Itasca on voice radio:

WE MUST BE ON YOU NOW BUT CANNOT SEE YOU.  RUNNING OUT OF GAS. ONLY ONE HALF HOUR LEFT. BEEN UNABLE TO REACH YOU BY RADIO.  WE ARE FLYING AT ONE THOUSAND FEET.

The Itasca was on the correct frequency and putting out strong signals at the time — even San Francisco picked them up.  In turn, the aircraft’s signals were very strong when the Itasca picked up her transmission; it was obvious that the aircraft’s fixed antenna and its feeder to the transmitter were still intact.  Thus Earhart’s transmission “BEEN UNABLE TO REACH YOU BY RADIO” clearly indicates that her receiving system had failed, probably early in the flight.  Beyond that there was no clue as to the nature of the failure — but the clue was not long in coming.

View of group posed in front of Amelia Earhart’s Lockheed Model 10-E Electra (NR 16020) at Lae, New Guinea, July 1937.  Second and fourth from left are identified as Mr. and Mrs. Joubert (manager of Bulolo Gold Dredging (BGD) and his wife), while Mrs. Chater (wife of the Manager of Guinea Airways) is seen third from left.  Amelia Earhart is third from right, and Fred Noonan is at far right.

After twice failing to obtain a bearing from the Howland DF on 3105 kcs, Earhart tried to home on the Itasca radio beacon using the aircraft’s direction finder.  At 1925 GMT she broadcast to the Itasca:

WE ARE CIRCLING BUT CANNOT HEAR YOU.  GO AHEAD ON 7500 NOW OR ON THE SCHEDULE TIME ON HALF HOUR.

By “7500” she was referring to 7500 kcs, the radio beacon frequency she had specified for the Itasca.  The ship complied immediately and transmitted the specified beacon signal — Morse “A” on 7500 kcs.  The transmitter had no voice capability, so it was impossible to talk to the plane on that frequency.  Earhart responded at once on 3105 kcs, saying:

WE RECEIVED YOUR SIGNALS ON SEVENTY FIVE BUT UNABLE TO GET A MINIMUM.  PLEASE TAKE BEARINGS ON US AND ANSWER THREE FIVE NAUGHT FIVE (3105 intended) WITH VOICE.

This was followed by a series of long dashes.  No bearing was taken and there was no reply to the Itasca’s subsequent transmission.

Earhart obviously picked up the Itasca’s 7500 kcs beacon signals on the aircraft’s loop antenna, because she reported being “Unable to get a minimum,” (the indication of a bearing) and she would not have expected to get a minimum except with a loop antenna.  That she heard the signal indicates her receiver was functioning on at least one band.  It was uncommon for only a single band to fail; usually, if one failed, they all failed, and so it is quite likely that the receiver was also functioning on the frequency band containing 3105 kcs.  Under existing conditions, Earhart should have been able to hear both signals on the loop and on the fixed antenna.  She did hear 7500 kcs on the loop, where signals went directly from loop to receiver, but she did not hear 3105 kcs on the fixed antenna, where the incoming signals had to pass through the send-receive relay before reaching the receiver.  It is probable, therefore, that the relay had been damaged by lightning or static discharge so that the contacts were not closing properly on the receive side, thus leaving the receiver without an antenna.

No more requests for a bearing were heard.  At 2013 G.MT Earhart came up on 3105 kcs, gave a line of position, and said she was shifting to 6210 kcs; that was the last time the Itasca heard signals from the plane.

Had Earhart been more familiar with her radio gear and manipulated the antenna selector switch on the receiver to transmit on the fixed antenna, but receive on the loop, she probably would have established two-way communication with Itasca.  She apparently did not attempt it.

End of Part II.