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Author Topic: Research needed - RDF change in Miami?  (Read 2878 times)

Ric Gillespie

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Research needed - RDF change in Miami?
« on: February 20, 2020, 09:18:22 AM »

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.” 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.

« Last Edit: February 20, 2020, 09:20:40 AM by Ric Gillespie »
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Karen Hoy

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Re: Research needed - RDF change in Miami?
« Reply #1 on: February 20, 2020, 10:28:56 AM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #2 on: February 20, 2020, 11:11:40 AM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #3 on: February 21, 2020, 09:47:16 AM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #4 on: February 23, 2020, 08:41:46 AM »

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)
« Last Edit: February 23, 2020, 08:44:28 AM by Ric Gillespie »
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #5 on: February 24, 2020, 09:34:22 AM »

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 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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Daniel R. Brown

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Re: Research needed - RDF change in Miami?
« Reply #6 on: March 24, 2020, 12:57:21 PM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #7 on: March 24, 2020, 01:33:33 PM »

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.
« Last Edit: March 24, 2020, 01:35:54 PM by Ric Gillespie »
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Daniel R. Brown

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Re: Research needed - RDF change in Miami?
« Reply #8 on: March 24, 2020, 02:34:39 PM »

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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John Balderston

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Re: Research needed - RDF change in Miami?
« Reply #9 on: March 24, 2020, 03:31:22 PM »


. . .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) 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.
John Balderston TIGHAR #3451R
 
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Christian Stock

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Re: Research needed - RDF change in Miami?
« Reply #10 on: March 26, 2020, 01:14:56 PM »

"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) 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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Daniel R. Brown

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Re: Research needed - RDF change in Miami?
« Reply #11 on: March 26, 2020, 02:14:26 PM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #12 on: March 28, 2020, 10:10:34 AM »

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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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #13 on: March 28, 2020, 10:30:22 AM »

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 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.
 
« Last Edit: March 28, 2020, 10:34:37 AM by Ric Gillespie »
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #14 on: March 28, 2020, 12:41:08 PM »

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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