The Amelia Earhart mystery continues, and Ray Robinson and Jeff White bring hobbyists the radio side of the story.
Jeff: It’s almost 90 years now since Amelia Earhart disappeared in July 1937 while on her ill-fated attempt to fly around the world. The unsuccessful use of radio technology, hinging on something as basic as a lack of understanding of the relationship between wavelength and frequency, was a critical factor in the tragedy, which has been in the news again recently. So, here with the remarkable story is Ray Robinson in Los Angeles.
Ray: Thanks, Jeff. The reason the disappearance of Amelia Earhart has been in the news again recently is because researchers from Purdue University in West Lafayette, Indiana proposed that an anomaly visible in satellite images of the remote Nikamuroro Atoll, could in fact be the wreckage of her plane, a Lockheed Electra 10-E. Nikamuroro, formerly known as Gardner Island, is an atoll in the Kiribati group about 420 nautical miles SSE of Amelia’s intended destination of Howland Island. The anomaly, which arguably could look like the fuselage and wings of a plane in shallow water just off the beach, was first noticed in 2020. But, after the researchers mounted a very expensive expedition to get to the island, it turned out the satellite imagery was simply of a cluster of fallen tree trunks, most of which had been washed away by the time the expedition arrived.
So who was Amelia Earhart? Well, she was an American born in Atchison, Kansas on July 24, 1897. She was fascinated by early air flight, and in 1932, made a record-breaking eastward-bound solo flight across the Atlantic, taking 15 hours to cross from Newfoundland to Ireland. Five years later, in March 1937, she set out from Oakland, California on an attempt to fly around the world in a westerly direction, but she only got as far as Honolulu, Hawaii. While she was taxiing there for take-off on the second leg, the plane swerved and crashed. It sustained quite a lot of damage, and had to be shipped back to California for repair.
Two months later, the 39-year-old Earhart set out again on a second attempt to fly around the world, this time in an easterly direction. A former PanAm navigator, 44-year-old Fred Noonan, flew with her. And it has come to light that Amelia’s lack of understanding of how radio worked led to her making some fundamental mistakes that ultimately cost the pair their lives.
They left Oakland, California, this time without publicity, on May 21, 1937, arriving in Miami, Florida with two intermediate overnight stops on the way. It was while they were in Miami that it was first disclosed publicly that they intended to fly completely around the globe, and a blaze of publicity then began following them.
They continued from Miami on June 1, 1937, making one stopover in the Caribbean, four in South America, eight in Africa, nine in Asia, and one in Australia, at Darwin, before arriving in Lae, New Guinea almost a complete month later on June 29. While en route at Bandoeng in Java, Indonesia, they had the long-distance flight instruments repaired, and in Darwin, the radio direction finder was also repaired.
After a two-day stay at Lae in New Guinea, they flew out mid-morning on July 2, never to be seen again.
The airplane that Amelia Earhart was flying was a Lockheed Electra, model 10E, with registration number NR16020. This model was designed for civilian use, with two crew and could accommodate ten passengers. It was the first all-metal airplane manufactured by Lockheed at their factory in Burbank, California.
The plane duly took them out over the western Pacific, but soon after take-off, they had to maneuver around the south of a rough weather pattern. 4 hours and 18 minutes into the flight, Lae aviation radio, PAE, received a message from Amelia Earhart, KHAQQ, on 6210 kHz, her daytime channel, stating all was well. One hour later, a similar message was received. Nauru Radio, VKT, also heard several similar transmissions from the aircraft on the same channel, 6210 kHz.
At 07:18 GMT, with late afternoon darkness coming on, Amelia switched to the night time channel, 3105 kHz, and a number of weak and hard to decipher messages were heard by the U.S. Coast Guard Cutter ‘Itasca’, NRUI, stationed at Howland Island. A few other ships and other island-based radio communication stations in the area also heard these garbled messages.
On only one occasion, was there a two-way transmission between the ‘Itasca’ at Howland Island and Amelia’s airplane. At 1930 GMT, soon after local sunrise the next morning and now 19½ hours into the expected 18 hour flight, Amelia acknowledged that she had heard a transmission from the ship ‘Itasca’. The final confirmed radio message from the Electra was received by the ‘Itasca’ at 2044 GMT, when Amelia stated that they could neither see the ‘Itasca’, nor Howland Island. She stated that their fuel was low, and they were flying along a line 157-337 degrees, i.e. SSE-NNW, although she didn’t say in which direction. Her radio signal had become stronger, indicating she must have been somewhere in the area, but no one at Howland saw or heard the plane. Using the loop antenna, Amelia did hear the Itasca using Morse Code on the requested beacon frequency of 7500 kHz, but unsurprisingly she was unable to obtain a minimum (a null). Significantly, though, Amelia could not hear the Itasca’s voice transmission on 3105 kHz, where the incoming signals had to pass through the relay switch before reaching the receiver. It is probable 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.
Had Earhart been more familiar with her radio gear and manipulated the antenna selector switch to transmit on the V doublet and receive on the loop, she probably could have established two-way communication with the ‘Itasca’. But apparently that did not occur to her, and she did not attempt it.
When the plane failed to arrive at Howland Island, rescue procedures were quickly implemented, just one hour later. For over a month, government and private search parties hunted all over the area, mainly to the north of Howland, utilizing a dozen ships, more than 100 planes, and more than 3,000 men, but no evidence of a downed airplane was ever found.
It is now thought that due to the avoidance of the weather pattern east of Lae, Amelia Earhart and Fred Noonan had actually been flying south of their planned flightpath, and that they had overestimated their position. According to one of the messages Amelia sent, she descended to 1,000 feet when she thought they were close to Howland Island, although in reality they were probably still several hundred miles to the southwest.
Consequently, when the flying pair travelled along the NNW-SSE line that they announced over the radio, instead of flying closer to Howland Island, they were actually flying away from it. With even the reserve fuel running low, when they spotted another small island, they apparently landed on it. That was long suspected to have been Gardner Island, now known as Nikumaroro Atoll, some 420 nautical miles SSE of Howland. However, no trace of wreckage has ever been found there.
In the days immediately following the disappearance of the Electra, there was a lot of radio activity on 3105 and 6210 kHz, its first harmonic. Some were direct transmissions to the downed plane from search parties on boats, planes and islands, on the plane’s fixed channels. Importantly, though, it is now believed that a small number of these so-called post-landing radio transmissions were actually from the Electra, although not fully recognized as such at the time.
On July 3rd, 1937, some 12 hours after the ‘Itasca’ had last heard from the Electra, a professional wireless operator at Nauru station VKT sent a wire note to RCA station KPH in San Francisco saying he had heard a voice at 0843 and 0854 GMT with fair signal strength, S3, on 6210 kHz, with bad modulation, but with no hum from the plane in the background.
On the following day, July 4th, from 1523-1530 GMT, a signal on 3106 kHz was heard by the Mokapu Point station on Oahu. Bearings were attempted and were given as approximately 213-215 degrees.
At 0638 GMT on July 5th, a man’s voice signal was heard on 3105 kHz at Midway Island, from an approximate bearing of 201 degrees. But the signal strength varied rapidly (consistent with overmodulation), and the signal was unintelligible.
Three hours later at 0948 GMT on the 5th, a signal with the same characteristics on 3105 kHz was heard at the Wake Island station for several minutes, from an approximate bearing of 144 degrees.
None of the transmissions were heard well at any location, and none were correctly understood at the time. But it seems from the available evidence:
• that the plane had been landed somewhat safely,
• that the right-hand motor was running at times in order to generate electricity for the batteries that powered the radio equipment, and
• that both Earhart and Noonan had survived and were alive for at least a few days after the crash landing.
Their radio signals seemed to be coming from the eastern or southeastern part of the Marshall Islands, a few hundred miles west of Howland.
And so the mystery continues, but it’s certain to inspire even more searches in the future, as technology provides new tools.
Back to you, Jeff.
(wavescan/Ray Robinson, Jeff White)
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