TIGHAR
Amelia Earhart Search Forum => General discussion => Topic started by: Daniel R. Brown on October 27, 2016, 12:41:02 PM
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GP said that a new Bendix DF would be installed by the end of the first week of March 1937 (sources: Associated Press reports), and the installation that week was confirmed by later independent reports (Atlanta Constitution and Christian Science Monitor). Newspaper accounts describe the loop in detail.
Manning arrived in Oakland toward the end of that week (source: Atlanta Constitution and others). Getty Images has a photo dated 3/13/37 of Manning and AE in the cockpit but no loop or control box. So, that photo date seems suspect.
Purdue has photo b10f7i25 dated 3/15/37 showing AE in the cockpit but no loop or control box. So, that photo date seems suspect too.
The unattributed photo attached here is dated 3/12/37 on the "fansinaflashbulb" website. An interesting aspect is the control box below the instrument light, which I recall was thought to have been associated only with the Hooven DF and both removed at the same time. Is this photo just a "missing link" taken at an instant when the loop had been installed but the control box not yet removed?
Dan Brown, #2408
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The unattributed photo attached here is dated 3/12/37 on the "fansinaflashbulb" website. An interesting aspect is the control box below the instrument light, which I recall was thought to have been associated only with the Hooven DF and both removed at the same time. Is this photo just a "missing link" taken at an instant when the loop had been installed but the control box not yet removed?
In 2009 I wrote a research bulletin called The "Miami" Cockpit Photo (https://tighar.org/Projects/Earhart/Archives/Research/Bulletins/53_MiamiPhoto/53_MiamiPhoto.htm) in which I argued that the photos showing the box in question could not have been taken in Miami as alleged by Elgen Long. I still think that's true but, from what we've learned since then, I no longer think the box was associated with the Hooven Radio Compass. I think it was associated with the Bendix receiver that was installed at the same time the Bendix loop replaced the Hooven unit (early March 1937). As we have learned, that Bendix receiver (and logically the control box), were removed from the airplane before Earhart left for Miami to begin the second world flight attempt.
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Ric, Did the removal of the Bendix receiver necessitate the removal of the Bendix control box?
As I understand it, what we are calling the control box included a readout that gives the compass heading when a null is found on a homing signal. When the Bendix receiver was removed, the overhead open loop via its coupler was then connected to the original WE receiver under the co-pilot's seat. And the control box could likewise be connected to the WE receiver, without necessarily being moved or removed? And the control box would remain connected directly to the overhead loop, because it has to know what compass direction the loop is facing, as it is being turned?
If the Bendix control box were to be removed, what device would then provide that crucial compass heading?
This is getting into the nitty-gritty of the DF apparatus and procedure on the second attempt, but I keep wondering, I guess we all do, whether there was something about the apparatus itself that could have misled AE into thinking that she could home in on a high-frequency signal. She requested 7500 kcs from Itasca, and then misdiagnosed the problem when she could not get a null on Lae's high frequency signal on July 1.
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If the Bendix control box were to be removed, what device would then provide that crucial compass heading?
Not a compass heading per se but a PDI (Pilot Direction Indicator) to show what direction to go. See instrument #2 from the Harney Drawings. The question I need to answer is - "Where did we get that information?"
I believe it is the case that, although the box is visible in some photos taken before and during the fist world flight attempt, it does not seem to be present in photos taken during the second world flight attempt. I guess we need to find a second attempt photo that definitely shows the presence or absence of the box.
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Although there were / are certainly more complex Radio Direction Finders that do the calculations for you, all you need is a simple compass and relative bearing to the transmitter to quickly calculate a true bearing to / from a station. A basic task on a navigation exam would be to confirm which of the two 'Null's is towards the station and calculate "time" to the station by a timed observation of the change in relative bearing as you track across it.
I'm aware the above does not answer question of what equipment was actually installed at the time, but rather what was actually needed to locate the Itasca.
The obvious and tragic "would'a-could'a-should'a" that we know didn't happen was had she voiced her "misdiagnose" at Lae, she would have been told the difference in "Null" capabilities from high-frequency radio signals. But then this great mystery would not exist.
It's difficult for me to see beyond what 'should' (so simple) have occurred to discover exactly what actually did happen. This group has certainly discovered a lot from so few clues to work with.
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Here are three photos in which the box is clearly present and one photo where the box seems to be absent. All seem to have been taken on different days. None of the photos are reliably dated. In all of the photos there is a white string attached to the Sperry Gyropilot. I have no idea what it's purpose may be unless there is a pencil tied to the end.