Aviate, Navigate, Communicate
-- in that order.
July 2, 1937 at 0000 GCT, the Lockheed Electra Model 10E began its take-off
role at Lae, New Guinea. It was the beginning of a tragic flight
and the biggest aviation mystery in history. The over-water
flight of 2,556 miles along the Equator to Howland Island would place extreme
demands on all navigation resources and skills of that time. The
navigator for the round-the-world
adventure was arguably the best in the world, Fred Noonan. Nevertheless,
the successful conclusion of the flight could be assured only by RDF
-- Radio Direction Finding (see Live Reckoning)
performed by the Pilot-in-Command, Amelia Earhart.
Aviating, Navigating, Communicating
Piloting requires multitasking
aloft. Each task has its own primacy; each is a sine
qua non for the successful completion of every flight. Contrary
to the simplistic mandate
cited above, priorities must change with the various phases of flight.
Thus, during take-off and early stages of climb-out,
the pilot will be focused most intensely on Aviating
Nightmare). Same during the final stages of approach and landing
(see Sloping in the Dark).
Still, are there occasions when Communicating
must take center stage? Indeed yes, when radio operations become
essential for Navigating. Nota
bene, the principles of RDF have not changed over the decades, only
the radio technologies. There are two modes...
In between, often for hours-on-end, Navigating
takes first priority, as satirized in one definition,
"Latitude is where we are lost, and Longitude is how long
we have been lost there."
So it would seem that Communicating
belong as the lowest priority.
"Never drop the plane to fly the microphone," goes an old saying.
RDF ~~~ To establish a course
directly toward Howland Island, Amelia Earhart would need to operate an
RDF antenna, which is the loop being displayed on the right and visible
as it was mounted atop the Electra in the photograph above. With an appropriately
tuned radio receiver, she would be able to rotate the loop to "get a minimum"
signal and thereby determine the direction from which a radio signal is
being transmitted. Using that bearing
angle, the Electra would be turned to take up a heading
directly toward the source. In this mode, airborne RDF equipment
operates "receive-only" -- simplex
in radio parlance. However...
In 1937, no permanent radio
was installed on Howland. Such a facility would be transmitting an
identification signal continuously on a dedicated frequency identified
by Morse Code. Instead, the US Coast
Guard cutter Itasca had been positioned at anchor offshore Howland
to support RDF for the Earhart flight. A qualified radio operator
on board Itasca was supposed to broadcast an improvised
signal in compliance with a time-of-day schedule on an assigned
with station identification to be recognizable by Amelia Earhart
-- all by protocols coordinated in advance of the inbound flight.
RDF ~~~ For guidance from the ground ('DF
steer'), two-way communications had to be established with USCG Atasca,
which is shown on the right. Communications were to take place by
voice or by Morse Code on assigned frequencies. Amelia Earhart would
then be requested over the radio to transmit a steady signal long enough
for the Itasca radio operator to ascertain the direction of the
source in the sky using a loop antenna on the ship. Having obtained
the bearing to the
Electra relative to the ship's heading, the operator must compute the appropriate
compass direction for the Electra to fly and transmit that information
to Amelia Earhart as a heading
by voice or Morse code. All of that takes time, of course, and all
the while, the Electra would be flying at over a hundred miles per hour
on an uncorrected heading.
In concept, Duplex RDF
operates as a reciprocating, two-way, simplex system -- half-duplex
in radio parlance. By the way, wireless telephony, which we take
for granted today, supports what is called full
duplex communications, with transmitting and receiving going on in
both directions simultaneously. Full duplex is a feature still not
found in radio equipment installed on even the most complex airliners of
the Twenty-First Century.
As readily seen in the descriptions above, for RDF to
be successful in either mode, equipment and people on the ground and in
the sky must all be in good working order and coordinated.
Last Words of Amelia Earhart
The figure below is based on transcriptions from the radio
room aboard the USCG Itasca standing by Howland Island on July 2,
1937. These are the last six radio messages received from Amelia
Earhart over a period of two and a half hours on that fateful day.
The pre-arranged 'radio schedule' comprises 'time-slots'
during which Earhart was supposed to transmit
simplex at quarter-to
and quarter-passed each hour In between, Itasca was
supposed to transmit simplex on the hour and the half-hour.
have taken special notice of the potential for confusion resulting from
two time-zones: Earhart and Noonan operated on Greenwich Civil Time (GCT)
while the Itasca clocks were all set on local time at Howland ("IST"
for 'Itasca Standard Time'), such that IST
= GCT minus 11:30. A source
of confusion for sure, but if everybody stuck to the script, those time-slot
assignments ought to have worked just fine in half-duplex.
Sophisticated solvers will immediatly observe the following
For the many technical issues and facts beyond those appropriated
for Simplexity Aloft, there can be no doubt
that the most comprehensive reference in all of Amelianna
is the fascinating e-book entitled Amelia
Earhart’s Radio: Why She Disappeared by Paul Rafford, Jr.
Three different radio frequencies being called out by Amelia
Earhart: 3105, 6210, and 7500 Kcps (thousands of cycles per second, "Hz"
in today's terminology).
Three different forms of modulation: "noise," "voice," "whistling"
-- but not "code" (neither Amelia Earhart nor Fred Noonan understood
Complexity trumped simplicity for
Amelia Earhart and Fred Noonan that day, hence the appropriation of "simplexity"
in the title of this puzzle. As the Electra approached the end of its final
flight, a lot could go wrong. And apparently did.
How many critical issues
can you identify by parsing the last words of Amelia Earhart?
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