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Author Topic: Another mystery solved  (Read 16108 times)

Ric Gillespie

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Another mystery solved
« on: March 27, 2016, 09:46:54 AM »

Dan Brown recently found this reference to the frequency range of Earhart's direction finder:

 Charleston (WV) Gazette (AP) 12/20/36 “Radio Call Stirs Hope For Plane” re Western Air Express plane missing in Utah since 12/15/36. Calls were heard in Kingman AZ and Las Vegas NV on WAE’s daytime frequency 5692 kc. Paragraph headed “Amelia Earhart Can’t Aid”: “Amelia Earhart has a directional finding set in her flying laboratory but it is set to the army (frequency) band - and there were tears in her eyes when she regretfully said she could not help.” Second source: 12/20/36 Cedar Rapids (IA) Gazette (AP)

The direction finder aboard the Electra at that time was the Bendix/Hooven Radio Compass, but what was "the army band" (presumably not three trumpets, two trombones and a snare drum) and why would Earhart's radio be set to military frequencies?  Bob Brandenburg quickly provided the answer.:

"The 'army frequency band' is a reference to the low frequency radio (LFR) beacon range  -- roughly 190 to 530 kHz.  In the 1930s the  Army signal corps managed a system of LFR beacons across the country, used for point-to-point navigation by aircraft.  A perfect fit for the Hooven design."

Of course, the issue was not how Earhart's direction finder was "set".  The faint distress calls from the missing airliner were being heard on 5692 kc.  In 1936 no airborne homing device could DF on a frequency that high.
« Last Edit: March 27, 2016, 09:54:37 AM by Ric Gillespie »
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Matt Revington

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Re: Another mystery solved
« Reply #1 on: March 27, 2016, 06:48:12 PM »

So this shows that the Bendix/Hooven radio compass was still in the Electra on December 20, and worked in the "army band".  Would the Bendix unit that replaced it and that was used during the world flight have worked in the same range?
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Ric Gillespie

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Re: Another mystery solved
« Reply #2 on: March 27, 2016, 07:27:03 PM »

So this shows that the Bendix/Hooven radio compass was still in the Electra on December 20, and worked in the "army band".  Would the Bendix unit that replaced it and that was used during the world flight have worked in the same range?

Yes. All aircraft DF systems intended for commercial use in the U.S. worked in the "army band".  The Bendix/Hooven unit wasn't swapped out until March.
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Harbert William Davenport

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Re: Another mystery solved
« Reply #3 on: March 27, 2016, 08:17:18 PM »

Concerning the RDF unit that was in the Electra when it left Miami on the second attempt:
  Is that still an open question, given that news report that Pan Am technicians in Miami had installed yet a third DF unit in the plane, 'similar to ones used on Pan Am's South American and Pacific routes'? 
   Are we supposed to be researching the question, what sort of DF units were being used in Pan Am planes at that time?  Or may I relax a bit, in expectation that you, Ric, and your crack team are already well underway in finding all the answers...??
H. Wm. (Bill) Davenport
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Ric Gillespie

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Re: Another mystery solved
« Reply #4 on: March 27, 2016, 08:25:06 PM »

Bill, if there is a crack team you're an important member of it.  The news report about Pan Am installing another DF doesn't make any sense. It is dated the day she arrived in Miami.
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Friend Weller

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Re: Another mystery solved
« Reply #5 on: March 27, 2016, 09:56:19 PM »

Charleston (WV) Gazette (AP) 12/20/36 “Radio Call Stirs Hope For Plane” re Western Air Express plane missing in Utah since 12/15/36.

The faint distress calls from the missing airliner were being heard on 5692 kc.  In 1936 no airborne homing device could DF on a frequency that high.

I know what I have to say here an aside to what this thread is all about but as I read an account of this (http://www3.gendisasters.com/utah/15297/salt-lake-city-ut-25-miles-sw-plane-crash-dec-1936) I found other online references which explained that while there were indications the aircraft had almost cleared the ridgeline,  the aircraft and it's occupants were found far down in the Hogum Basin on the other side (http://www.skytamer.com/Boeing_247D.html).  My question is:  with the searcher's descriptions including where they had seen the engine oil splashed on the rocks below the ridgeline and the wreckage and bodies being found far down on the other side, what radio distress calls were actually heard?

It is very interesting that AE and PM were briefly part of the search effort; especially that Amelia probably intersected the 157/337 LOP about the same distance south of Howland as she expressed she felt the WAE ship might be found north of where it actually crashed.  Also interesting is that the same issue of the Salt Lake Tribune which carried the news of the first of the WAE victims being discovered in the Hogum Basin also included the news of an overdue AE and FN.
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Matt Revington

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Re: Another mystery solved
« Reply #6 on: March 28, 2016, 07:06:20 AM »

What is curious to me here is that we have AE telling the press in December 1936 that her "directional finding set" was limited to the army band (so she had some idea of its limitations) but in lead up to the Lae-Howland leg of the flight she told to the coast guard to transmit at 7500 kcs for her to get a bearing.  Was she misinformed about the frequency of the replacement  Bendix unit?
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Ric Gillespie

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Re: Another mystery solved
« Reply #7 on: March 28, 2016, 08:19:41 AM »

Was she misinformed about the frequency of the replacement  Bendix unit?

That does seem to be the case.  That bad information may have come from Joe Gurr, a United Airlines technician that AE used as a radio consultant.  In a 1982 letter Fred Goerner asked Gurr:
"According to the ITASCA (Coast Guard vessel) radio log, Earhart asked for homing signals to be sent to her on 7500. Did her DF have that range? Could she have taken a bearing on that frequency?"
Gurr replied:
"Yes - that Navy receiver had 200-400 & up to 22 MC [megacycles].  The DF loop on the airplane was designed for low frequencies - 200-400KC. It would be much less efficient on 7500, & then the signal would have to be quite strong to overcome the greatly detuned from resonance) condition."

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Ric Gillespie

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Re: Another mystery solved
« Reply #8 on: March 28, 2016, 09:13:26 AM »

Concerning the RDF unit that was in the Electra when it left Miami on the second attempt:
  Is that still an open question, given that news report that Pan Am technicians in Miami had installed yet a third DF unit in the plane, 'similar to ones used on Pan Am's South American and Pacific routes'?

The source is:
"5/23/37 Miami FL: “EARHART IN MIAMI ON TEST FLIGHT: Radio Direction Finder Installed in Plane”. “Pan-American Airways loaned her two technicians to install in her plane a radio direction finder similar to those used in South American and Pacific flights.” With GP, FJN and Bo. Source: 5/24/37 Atlanta Constitution (AP)"

This is really strange. 5/23/37 was the day AE, FN, GP, and Bo arrived in Miami.  It is true that Pan Am loaned AE two technicians to work on problems she was having with the transmitter and the auto pilot.  Nothing about the DF.  "...similar to those used in South American and Pacific flights."  The loop antenna on NR16020 did not change while the airplane was in Miami and, looking at photos of Pan Am Sikorskys, I don't see any loop antennas at all. The Pacific Division used a ground-based system.  Sometimes a reporter simply gets it wrong.
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Ric Gillespie

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Re: Another mystery solved
« Reply #9 on: March 28, 2016, 09:42:31 AM »

Here's the complete article courtesy of Dan Brown. The dateline is Miami so an AP reporter must have talked to AE (or GP, or FN, or Bo) after they arrived.  Everything about the story (just a test flight, fine-tuning the airplane, expects to stay two or three days, not sure where she’ll go next, help from two Pan Am technicians) is correct, but the installing a DF part cannot be right.
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Andrew M McKenna

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Re: Another mystery solved
« Reply #10 on: March 28, 2016, 01:50:26 PM »

Smokescreen to divert attention from the Patch installation?

amck
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Ric Gillespie

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Re: Another mystery solved
« Reply #11 on: March 28, 2016, 04:39:37 PM »

Smokescreen to divert attention from the Patch installation?

Did AE intentionally put out false information?  It wouldn't be the first time, or the last - but I don't see a need to lie about a new DF.  The patch installation didn't happen for another week.  None of the other press accounts of her stay in Miami mention a new DF except a repeat of this story by the NY Times on May 30.
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Randy Conrad

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Re: Another mystery solved
« Reply #12 on: May 14, 2016, 09:44:01 AM »

Ric...do we know exactly where these directional finders were placed in the cockpit? Help me out on this, but is it possible that data and readings can be messed up with radio interference or poor voltage input. I'm led to believe that Amelia not only had lack of navigational skills with the radio, but might not have had the capablility of knowing how to detect issues that might arise from faulty equipment or battery failure. As an employee of a battery manufacturing company, I have seen things over the years that makes me wonder if this didnt really happen. I don't know how corrosion or salt water effected aircraft batteries during Amelia or Linbergh days...most likely these were the old gel type of batteries...but corrosion is corrosion....and causes poor performance. Also, did any of the Lockheed planes or Pan Am planes during the 30's have any gauge indicating a charged or uncharged battery? Very curious! Thanks!
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