TIGHAR
Amelia Earhart Search Forum => General discussion => Topic started by: Ric Gillespie on February 20, 2020, 09:18:22 AM
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In the Google docs timeline (https://docs.google.com/document/d/1EWWg4KlVwc0s07Fv6MLoiWORRe-pAJI1ZPBpQ_raux0/edit#) for May 24-29, 1937, cited newspaper clippings describe PanAm technicians installing a radio direction finder in Earhart’s Electra "similar to those used in South American and Pacific flights.” I don’t think that’s right.
I don’t know about South American flights but the only photos I can find of a Pacific Division aircraft with an external RDF antenna are of the Sikorsky S-42B "Hong Kong Clipper," formerly "Pan American Clipper II" and later again renamed "Samoan Clipper." A "football" antenna was added in April 1937 when the aircraft was overhauled in Hawaii following the first survey flight to New Zealand (March 17 - April 9) as "Pan American Clipper II." On April 18, the ship was ferried to Manila and renamed "Hong Kong Clipper" to serve the newly-approved route from Manila to Hong Kong. The aircraft flew that route until December 1937 when it was returned to Hawaii for the first airmail flight to New Zealand as "Samoan Clipper." It was on the next New Zealand flight in January 1938 that the ship and its crew were lost in an inflight fire/explosion near Tutuila, American Samoa.
There was certainly no externally visible change to the RDF antenna on Earhart's Electra while she was in Miami. Pan Am radio technician Michelfelder and others did try to sort out the airplane's radio communications and auto-pilot problems but there is no mention of installing a new RDF receiver - and yet, something prompted those press reports.
Back in early March, in the final preparations for the first world flight attempt, the Hooven Radio Compass installed the previous October (photo below) was removed and a "new Navy type" Bendix direction finder (photo below) was installed. According to an article in the August 1937 issue of Aero Digest, Bendix direction finders were coupled to a Bendix Type RA1 receiver but would also work with "any standard radio receiver covering the desired frequency range". My suspicion is that she removed the Bendix RA1 in Miami to save weight and had the loop and loop coupler connected to her standard WE 20B receiver.
I have a recollection of correspondence or a transcribed interview with, I think, AE's favorite reporter C.B. Allen describing just such a thing, but I don't seem to have a record of it. It might have been posted here on the Forum. This is kind of important so any help finding it would be appreciated. Thanks.
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Ric, you posted this on January 12, 2016. Did this collection include the article you are searching for?
This just in:
"This is on file in the NASM Archives and is known as:
Amelia Earhart Collection [Allen], Acc. XXXX-0520
Dates: 1932-1971
Description: Carl B. Allen learned to fly during World War I. He was active in aviation events and as an aviation writer. Allen was the first airmail passenger to make a continuous flight across the continent in 1927 and he made an air tour of South America in 1933. He won the Sportsman Pilots' cup at the National Air Races in 1930. Allen was the aviation editor of several newspapers, including the New York Herald-Tribune, and he wrote several aviation books, including 'ghosting' Clarence Chamberlin's 'Record Flights.' He was also a flight advisor to Amelia Earhart.
This collection consists of correspondence and writings of Mr. C. B. Allen on the disappearance of Amelia Earhart."
Somehow we missed this source. I'll be making a pilgrimage to Udvar-Hazy Center NASM Archives to review the collection for any new nuggets.
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Thanks Karen. Your tip led me to the files I was looking for. As it turned out, it was Art Rypinski who went to Udvar-Hazy and looked at the C.B.Allen files. From what he found and from what we know from other sources it is possible to reconstruct what happened. We actually had it figured out in 2016 but it got lost in the shuffle.
I'll put it together and post it here. It will also be an important part of the Electra book which is, I'm happy to say, "back in the shop" for completion this year (Lord willin' and the creek don't rise).
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There was no RDF change in Miami. Here's a Reader's Digest version of what happened:
In February, 1937 Earhart flew the Electra to New York to announce the world flight. At that time the aircraft had a Western Electric 13C transmitter with crystals for 3105 and 6210 kcs. While the aircraft was at Newark Airport (at that time the only airport in the New York metropolitan area), W.C. Tinus of Bell Laboratories (half-owned by Western Electric) convinced Earhart and Putnam the airplane needed the capability to communicate with ships at sea using 500 kcs, the international calling and distress frequency monitored by all ships. A 500 kcs crystal was added to the transmitter so that navigator/radio operator Harry Manning, using the trailing wire antenna, could send morse code messages to ships on that frequency.
Earhart's WE receiver was not able to receive signals on 500 kcs so she agreed to swap out the Hooven Radio Compass installed the previous October, for a Bendix Navy RDF-1 system that used a loop antenna coupled to a Bendix RA1 receiver which included 500 kcs so Manning would be able to receive and take bearings on that frequency. On February 14, AE sent a telegram to Paul Mantz (below) advising him of the change.
In Burbank, on or about March 7, 1937 as NR16020 was being prepared for a planned March 15 departure from Oakland, the Hooven Radio Compass was removed and replaced with the Bendix system. The new receiver was installed on top of the fuel tanks behind the cockpit bulkhead behind the copilot - the same location where the Hooven receiver had been situated.
Manning used the Bendix system during the approach to Honolulu on March 18 but left the team after the accident on March 20. With Manning gone and neither AE nor Noonan able to use morse code, there was no longer any point in having 500 kcs capability so, to save weight, when the airplane was repaired the RA1 receiver and trailing wire were not reinstalled. The Bendix loop and loop coupler would work with any standard receiver so they were connected to the Western Electric 20B.
When Earhart got to Miami her friend, journalist C.B. Allen, noticed the changed and asked AE about it. He described the conversation in the draft of a story that was never published (excerpt below).
All of this will be covered in greater detail with sources cited in the forthcoming Electra book.
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At the beginning of this thread I wrote, "I don’t know about South American flights but the only photos I can find of a Pacific Division aircraft with an external RDF antenna are of the Sikorsky S-42B "Hong Kong Clipper," .."
That's still true, but a history of Pan Am operations in the University of Miami archive says:
"Radio equipment for the M-130s was specially designed by Pan American and had been service-tested in the Atlantic and the Pacific on the tests and survey flights of the S-42. This equipment consisted of two direct ground receivers with plug-in coils; two 50-watt single frequency master oscillator power amplifier transmitters with plug-in coils; a Belloni-Tosi (sic - should be Bellini Tosi) direction-finder and vacuum tube amplifier.
While meteorological and oommunications aspects of transpacific operations were boing studied, specialists in navigation were likewise absorbed in the new problems confronting them. Although the long distance direction-finder
system had been brought to a high state of perfection, it was apparent that this radio device, mountod ashore, could give only single lines of position and did not permit a determination of distance f'rom tho station. Additional means of determining definite position were necessary. Small direction-finders were installed aboard the S-42 and M-130s.
Experience already gained in the Caribbean operations made it clear that the type of celestial navigation employed on surface craft could not be applied to aircraft because of the time factor involved in surface methods. Nor were instruments available at that time which were well fitted for the type of celestial navigation which the Company's specialists [led by Noonan?] found to be necessary. Those specialists, organized in a Navigation Section of the Operations Department at Miami after the decision to establish over-ocean service was reached, succeeded in developing.a dependable system of aircraft navigation combining the direction-finder and celestial methods with dead reckoning.
Celestial octants were ordered to supplant the bubble sextants then in common use. Specifications for an adequate aircraft Polorus (sic) were drawn. A specially designed drift indicator was obtained.
To aid in navigation at night, a drift flare suitable for aircraft use was found. Lengthy experiments were conducted with "paint bombs" to facilitate determination of drift over smooth water in daylight hours. In these experiments, glass containers were filled with various substances which would leave a slick" on the water as a reference mark for obtaining drift indications. After the S-42 aircraft had been ferried to the Pacific coast, the navigation methods were subjected to new tests. Before the survey flight to Honolulu was attempted, navigators were required to take the S-42 into stormy conditions hundreds of miles off the California coast on several flights."
This is quite revealing. The Bellini-Tosi DF is described in this 1933 Bureau of Standards Research Paper (https://nvlpubs.nist.gov/nistpubs/jres/11/jresv11n6p733_A2b.pdf)
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So, despite the lack of photos showing Pan Am Clippers with loop antennas, at least some Pacific Division ships were equipped with Bellini-Tosi DFs. As mentioned at the beginning of this thread, in the Google docs timeline for May 24-29, 1937, cited newspaper clippings describe PanAm technicians installing a radio direction finder in Earhart’s Electra "similar to those used in South American and Pacific flights.” Did Pan Am, in fact, install a Bellini-Tosi DF in NR16020? I don't think so. Discussions about doing so might have prompted the newspaper articles, but there was no visible change to the loop antenna on the aircraft. It's clearly a Bendix Mn-5 rotatable loop and the Bellini-Tosi DF is a fixed-loop system.
Incidentally, in researching this I stumbled upon an error in Finding Amelia. On page 74, in describing Earhart's radio tests in Lae, I wrote:
"It is not clear whether Balfour’s previous ground test of the receiver
included taking a bearing using the direction finder, but it is known that he
carried out his test on a signal of 500 kilocycles, a frequency well within the
loop antenna’s 200 to 1500 kilocycle capability."
It is NOT known that he carried out the ground test on 500 kilocycles. That comes from Elgen Long in his book "Amelia Earhart - the Mystery Solved" page 183. Long cites the Chater letter (https://www.tighar.org/Projects/Earhart/Archives/Documents/Chater_Report.html) but Chater makes no mention of the frequency used. In fact, a test on 500 kcs would be impossible because the Western Electric 20B receiver could not be tuned to that frequency (which was the reason for the whole abortive installation of a Bendix RA-1 receiver).
This is another example of Long stating his own assumptions as fact. My bad for falling for it.
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Regarding "clearly a Bendix Mn-5", what was the primary documentation for that? There are a lot of images of Mn-20 on the internet but I haven't found an Mn-5. This was the subject of a forum thread a few years ago.
Dan Brown, #2408
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Regarding "clearly a Bendix Mn-5", what was the primary documentation for that? There are a lot of images of Mn-20 on the internet but I haven't found an Mn-5. This was the subject of a forum thread a few years ago.
August 1937 Aero Digest article (pdf below).
"In Type MN-1, the loop is mounted directly on the coupling unit, with manual rotation control and lock at its base. Type MN-3 provides for external mounting of the loop directly above the coupling unit on an extension shaft. Also manually controlled, the loop of Type MN-5 can be mounted at a point not immediately above the coupling unit, with the rotational controls on the loop shaft at the cabin roof. In Type MN-7 the loop is remotely controlled by a hand wheel operating a hydraulic pressure system which provides a smooth and positive means of rotation and control over distances of 25 ft."
The loop on NR16020 was manually controlled by a hand wheel on the loop shaft on the cockpit roof. We don't know where the coupling unit was located but it wasn't directly under the loop.
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Thanks. It's regrettable that the article states these are available as versions Mn1, Mn3, Mn5 or Mn7 but the figure legend refers to Mn2. Still haven't found an image of an Mn5 elsewhere.
Dan Brown, #2408
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. . .Those specialists, organized in a Navigation Section of the Operations Department at Miami after the decision to establish over-ocean service was reached, succeeded in developing a dependable system of aircraft navigation combining the direction-finder and celestial methods with dead reckoning.
If you will permit a closely related piece of trivia, Smithsonian Air & Space Museum's online "Time and Navigation" exhibit (https://timeandnavigation.si.edu/navigating-air/early-air-navigators/charles-lindbergh/air-navigation-community (https://timeandnavigation.si.edu/navigating-air/early-air-navigators/charles-lindbergh/air-navigation-community)) has a photo of Fred Noonan at the Sikorsky S-42 navigation table that appears to be from this exact period. You can see Fred working on a map of the Caribbean with Cuba clearly visible, and to his left what appears to be a bubble octant.
BTW the "Time and Navigation" exhibit is quite interesting in general.
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"Noonan had been flying for Pan American for many years and it was all in his day's work to hit smaller islands than Howland square on the nose." - P. V. H. Weems, After Noonan disappeared en route to Howland Island with Amelia Earhart in 1937.
. . .Those specialists, organized in a Navigation Section of the Operations Department at Miami after the decision to establish over-ocean service was reached, succeeded in developing a dependable system of aircraft navigation combining the direction-finder and celestial methods with dead reckoning.
If you will permit a closely related piece of trivia, Smithsonian Air & Space Museum's online "Time and Navigation" exhibit (https://timeandnavigation.si.edu/navigating-air/early-air-navigators/charles-lindbergh/air-navigation-community (https://timeandnavigation.si.edu/navigating-air/early-air-navigators/charles-lindbergh/air-navigation-community)) has a photo of Fred Noonan at the Sikorsky S-42 navigation table that appears to be from this exact period. You can see Fred working on a map of the Caribbean with Cuba clearly visible, and to his left what appears to be a bubble octant.
BTW the "Time and Navigation" exhibit is quite interesting in general.
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Also manually controlled, the loop of Type MN-5 can be mounted at a point not immediately above the coupling unit, with the rotational controls on the loop shaft at the cabin roof.
In several photos (e.g. timeline 3/16/37 of AE and Mantz in cockpit) there is a taught cable extending aft from the loop crank housing to a pulley (?) attached to the cabin roof in front of the cabin door. Do we know enough about that cable to understand its function? It might help in dating certain photos.
Dan Brown, #2408
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In several photos (e.g. timeline 3/16/37 of AE and Mantz in cockpit) there is a taught cable extending aft from the loop crank housing to a pulley (?) attached to the cabin roof in front of the cabin door. Do we know enough about that cable to understand its function? It might help in dating certain photos.
That's not the loop crank housing. It's the aileron trim. The loop was rotated with a wheel, not a crank.
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Incidentally, in researching this I stumbled upon an error in Finding Amelia. On page 74, in describing Earhart's radio tests in Lae, I wrote:
"It is not clear whether Balfour’s previous ground test of the receiver
included taking a bearing using the direction finder, but it is known that he
carried out his test on a signal of 500 kilocycles, a frequency well within the
loop antenna’s 200 to 1500 kilocycle capability."
It is NOT known that he carried out the ground test on 500 kilocycles. That comes from Elgen Long in his book "Amelia Earhart - the Mystery Solved" page 183. Long cites the Chater letter (https://www.tighar.org/Projects/Earhart/Archives/Documents/Chater_Report.html) but Chater makes no mention of the frequency used. In fact, a test on 500 kcs would be impossible because the Western Electric 20B receiver could not be tuned to that frequency (which was the reason for the whole abortive installation of a Bendix RA-1 receiver).
This is another example of Long stating his own assumptions as fact. My bad for falling for it.
I was wrong. Chater did specifically say, "At noon on June 30th Miss Earhart, in conjunction with our Operator, tested out the long wave receiver on the Lockheed machine while work was being carried out in the hangar. This was tested at noon on a land station working on 600 metres.”
600 meters is 500 kHz
Thank you to Les Kinney for pointing out this error.
So how did Harry Balfour test the WE 20B receiver on 500 kHz? Bob Brandenburg recalls:
"Mike Everette's analysis of Earhart's radio equipment says, of the 20B receiver: "As the requirement for 500 KHz operation existed in Earhart’s case, the Band 2 tuning range was factory modified to 485-1200 KHz, covering the lower frequencies at the expense of the upper part of the broadcast band. A 1939 source lists a Model 20BA receiver, with Band 2 covering 485-1200 KHz. Earhart’s equipment may have been the prototype for this off-the-shelf model. "
And by the way, I was also wrong about the reason for installing the Bendix RA-1 receiver. Bill Davenport pointed out that the Hooven Radio Compass, which operated on the low frequency radio (LFR) beacon range -- roughly 190 to 530 kHz --- could receive on 500 kHz. So why did Earhart swap out the Hooven Radio compass for the Bendix system?
According to Elgen Long (page 59), in November 1936, on her way to the New York to have radio work done by Western Electric, AE visited Vince Bendix in South Bend, IN. Putnam had been after Bendix for sponsorship. He agreed to donate $5,000 “and some new Bendix aircraft radio equipment.” Unfortunately, Long provides no citation but there is no doubt Earhart did stop in South Bend. Long says the Bendix receiver installed in early March was a prototype of the RA-1 being developed for the Navy.
So it appears the replacement of the Hooven system with the Bendix loop and receiver was motivated by money.
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Apparently there was change made to the WE 20B receiver when Earhart was in New Jersey in Feb. 1937.
Photos taken at that time show Earhart with Western Electric technicians E. Jay Quimby and William Tinus holding a 27A Remote for the WE 20B. It's clear from the photo with Tinus that a new remote is being installed. The airplane already had a 27A Remote. There would be no need to install a new one unless there had been a change.
(Helpful photo dating hint: Any photo showing AE wearing the wool scarf was taken during the February trip to NY and NJ.)
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If I am following this correctly it had been established that:
A. The RA1 receiver was removed after the accident on March 20 to save weight, along with the trailing wire antenna. That leaves us with the WE receiver.
B. Chater's report confirms the ability to receive 500 kHz, establishing that the WE receiver tuned a range of 485-1200 kHz (as noted by Brandenburg)
Now I am scratching my head, my question is: how would it be possible to receive KGMB at a frequency of 1320 kHz? History of Broadcasting in Hawaii (https://www.qsl.net/ah6rh/am-radio/hawaii/history.html) I sense I missed something. KGU broadcasting at 760 is, of course still within the receivers tuning range.
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B. Chater's report confirms the ability to receive 500 kHz, establishing that the WE receiver tuned a range of 485-1200 kHz (as noted by Brandenburg)
Now I am scratching my head, my question is: how would it be possible to receive KGMB at a frequency of 1320 kHz?
We know she could receive on 3105 and 6210, so the receiver did not top out at 1200. Hearing KGMB on 1320 would not be a problem.
Going back to Mike Everette's radio analysis (https://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#12) The standard 20B had four bands:
200 - 400
550 - 1500
1500-4000
4000-10,000
Mike was referring to changes in Band 2.
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Thanks Ric.
I should have been a little more specific. Band 2 on the modified WE receiver now ends at 1200 kHz. Band 3 is listed as starting at 1500 kHz. So the modifications applied to the broadcast band (making it possible to receive 500 kHz) seems to have created a "hole" between 1200 kHz and 1500 kHz. Which is where 1320 kHz lies. Hence the head scratching.
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I should have been a little more specific.
I should have been a little less dense.
Band 2 on the modified WE receiver now ends at 1200 kHz. Band 3 is listed as starting at 1500 kHz. So the modifications applied to the broadcast band (making it possible to receive 500 kHz) seems to have created a "hole" between 1200 kHz and 1500 kHz. Which is where 1320 kHz lies. Hence the head scratching.
Of course, we don't know for sure exactly what changes, if any, were made to the receiver. However, we do have a new historical document courtesy of Earhart researcher Les Kinney (see below). It appears to be a Western Electric press release dated February 17, 1937 written by E. J. Quimby of the Western Electric Information Department, describing the work done on Earhart's Electra during her visit. Quimby is the guy in the photo attached to my earlier post standing beside AE sitting on a step ladder. AE is holding a 20B remote. The reverse side of that photo (courtesy of TIGHAR member Larry Inman's "Remember Amelia" collection) is attached below. The photo probably accompanied the press release.
I find several things about the press release interesting.
• It's important to note that Quimby is a PR man, not a technician, which may account for some of the ambiguity in the wording.
• Quimby begins by saying, "When Amelia Earhart left Newark Airport shortly before 3 o'clock this afternoon, her Lockheed Electra plane carried a complete installation of the latest radio aids to aerial navigation." I find it interesting
he says "latest aids to aerial navigation," not "communication." When AE left Newark, the plane still had the Hooven Radio Compass. Western Electric had nothing to do with the Hooven installation, so why the puff about navigation? Three days earlier, as the telegram she sent to Mantz from New York confirms, she had decided to swap out the Hooven Radio Compass for a Bendix system. Was Western Electric aware of the impending change?
• Quimby says, " Her standard Western Electric type 13 transmitting equipment has been specially modified for the round-the-world flight so that she can communicate with ships at sea and shore marine stations on a crystal controlled frequency of 500 kilocycles." This is entirely in agreement with Tinus' later description of changes made to the transmitter. Does Quimby's word "communicate with ships at sea" imply two-way communication?
• Quimby "The type 20 [notice he does not say 20B] radio receiver may be employed for either telegraphy or telephony and covers the frequencies necessary to receive beacon signals, commercial broadcast stations, aircraft and police radio stations, amateurs, and various frequencies employed by foreign radio stations." That sounds like a standard 20B.
• Quimby then describes the "diminutive remote control unit mounted directly on the instrument panel." That's the 27A Remote AE is holding in the photo. I'm quite sure (but I'll double check) the plane has had a 27A Remote since shortly after it was delivered in 1936. If there has been no change to the receiver, why are they installing a new remote?
Getting back to the original question, if Earhart's receiver cannot tune to KGMB, how does that change our assessment of the post-loss radio signals?
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Yep, the 27A Remote was included in the original (May 21, 1936) specs for the airplane. It was, supposed to be installed in the control box lid. I'm not sure where the "control box lid" was. All photos show it in the instrument panel "shelf" on the right side of the cockpit.
The 20B receiver was originally supposed to be installed on top of the fuel tanks in the cabin but they ended up putting it under the copilot's seat.
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"Getting back to the original question, if Earhart's receiver cannot tune to KGMB, how does that change our assessment of the post-loss radio signals?"
It would seem to be a question worthy of discussion. I've tried to think of a way that the receiver might still be able to tune beyond the frequency specifications but I can't quite get there. Maybe someone else has some thoughts on this.
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Bob Brandenburg and I have been reviewing the question. It's clear that Earhart was hearing KGMB.
Below are a few references to the Post-Loss Signals Catalog (https://www.tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/signalcatalog.html). Earhart was sending dashes long before KGMB began asking her to:
Message 16 Itasca asks Earhart to send long dashes
Message 17 long dashes heard by Achilles on 3105
Message 18 dashes heard by New Zealand Star on 3105
Message 19 “generator start and stop” herd by Itasca on 3105
Message 26 long dashes on 3105 heard by Ft. Shafter
Message 27 long dashes and weak voice heard by COMHAWSEC on 6210
Message 41 long dashes on 3105 heard by COMHAWSEC
Message 54 KGU asks Earhart to transmit
Message 55 PAA Mokapu hears unintelligible voice on 3105
Message 63 PAA Mokapu hears two long dashes in apparent response to first KGMB broadcast
Message 66 COMHAWSEC hears carrier and voice on 3105 at end of KGMB broadcast
Message 100 PAA Mokapu heard KGMB request Earhart to send four dashes, and heard 4 dashes on 3105 immediately following the broadcast. Mokapu then asked KGMB to repeat the broadcast, to verify the response, and KGMB did so. Mokapu heard two dashes immediately following the second broadcast. Mokapu said that KGMB repeated the broadcast message to Earhart at half hour intervals “during the evening.” Mokapu obtained a radio direction finder bearing of approximately 215° on the source of the dashes.
Message 101 COMHAWSEC heard “carrier broken” – i.e. dashes – signals responding to the 0630Z KGMB broadcast
Message 103 Navy Radio Tutuila hears series of 4 dashes in response to KGMB broadcast
Message 104 Ditto 10 minutes later
The bearing Mokapu took (Message 100) pretty much proves she was hearing KGMB.
Bob points out that the logical way to modify the 20B receiver to cover 500 kHz would be to extend the upper end on Band 1 to 500 or 550, rather than alter the broadcast band coverage of Band 2.
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Agreed. As a long time amateur radio op the Post Loss signals analysis are mostly what brought me to TIGHAR. I've always thought the KGMB data were very persuasive. But if that data impeaches Michael Everette's analysis of the Electra radio coverage then shouldn't that information be revisited? As it is the website presents conflicting data that would seem to be consequential.
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But if that data impeaches Michael Everette's analysis of the Electra radio coverage then shouldn't that information be revisited? As it is the website presents conflicting data that would seem to be consequential.
As a matter of policy we don't "correct" research bulletins. They are a snapshot in time and many are now obsolete, but they are valuable as an historical record of our investigation.
I can't change Mike Everette's analysis. His analysis is generally excellent but he should not have said, "As the requirement for 500 KHz operation existed in Earhart’s case, the Band 2 tuning range was factory modified to 485-1200 KHz, covering the lower frequencies at the expense of the upper part of the broadcast band." That was an opinion, not a fact. Our current opinion is different but we still don't know for sure how her receiver was set up.
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Thanks Ric. That does clarify the matter.