Copyright ©2010 by Paul Niquette. All rights reserved.
would be difficult to name a more qualified navigator
for Amelia Earhart's round-the-world adventure than
Frederick Joseph "Fred" Noonan, 44, an American sea
captain and aviation pioneer who charted the first
commercial airline routes across the Pacific Ocean
during the 1930s. Figure 1 below is based on
contemporaneous information and depicts Noonan's plan
for the ill-fated flight on July 2, 1937.
In retrospect, we recognize three navigational phases:
That report curiously agreed exactly with the revised forecast by radiosonde (23 kts = 26.5 mph). Earhart and Noonan were 'making good' only 130.3 mph instead of the planned 142.8 mph. The Electra's groundspeed implied a total of more than 19.5 hours to reach Howland Island."0718 GCT 4.33 SOUTH, 159.7 EAST, EIGHT THOUSAND, CUMULUS,
long flight, fuel exhaustion would ordinarily be the
main concern; however, the Electra took off with 22
hours of fuel on board for an 18-hour
flight. Solvers of Here Comes the Sun puzzle
have addressed a different deadline: Noonan's
main concern was the time available for taking his Last Celestial Fix before
Figure 2a below depicts the estimated arrival situation for the planned flight. Figure 2b shows the actual situation, as Fred Noonan was forced to complete his Last Celestial Fix more than 435 miles away from Howland Island-- hundreds of miles too far from Itasca for homing. Cut off from Live Reckoning by the rising sun, he had no choice but to rely again on compass and clock. More dead reckoning, folks.
Figure 3 below depicts a gathering range for RDF as a circle reaching out a hundred miles or so in all directions from Itasca at Howland Island. That estimate may not be especially conservative, given the limitations in wireless technologies back in the '30s. A handful of available frequencies were crowded with maritime broadcasts. Low power transmitters, confusing protocols, some in Morse code others by 'radiophone' -- all these realities resulted in uncoordinated transmissions and blocked signals for the Earhart Flight. Accordingly, as the sun began lighting up the sky obliterating celestial objects, Fred Noonan necessarily commenced a second interval of dead reckoning. Over a distance 300 miles or more from the Last Celestial Fix, there would be nothing to do but hold a magnetic heading in the windy sky and wait for an assigned time-slot on a negotiated frequency, trying repeatedly to establish RDF with Itasca -- the beginning of Phase 3.
One day before the flight, Amelia Earhart took the Electra aloft for a brief test of the engines and instruments, which included exercising the on-board RDF equipment. Using the Electra's loop antenna, she was unable to obtain a relative bearing from a ground station at Lae. She speculated that the signal was simply too strong for a "null."Her speculation was apparently wrong, for we shall see in Which way, Amelia? that the on-board RDF equipment must have been defective and Simplex RDF was not available for completing the flight.
Figure 1 above shows the USS Ontario 1,200 miles into the flight, about half-way to Howland. The U.S. Navy made the ocean-going tug available as an RDF fix in Phase 2. If either mode of RDF succeeded, however, no evidence is recorded in the form of a position report by Amelia Earhart. Moreover, according to the ship's logs, two-way communications were never established with the Electra, which ruled out Half-Duplex RDF at Ontario and thereby put in doubt any expectations for Simplex RDF using a radio transmitter on Itasca as a homing beacon.
With one exception, there are no records throughout Amelia Earhart's last flight that any radio transmissions were received on board the Electra. In effect, she made her transmissions 'in the blind'. Here is that exception...
"KHAQQ CALLING ITASCA WE RECEIVED YOUR SIGNALS BUT UNABLE TO GET A MINIMUM PLEASE TAKE BEARING ON US AND ANSWER 3105 WITH VOICE."...which depicts an admission by Amelia Earhart that Simplex RDF had failed and that she was changing to Half-Duplex RDF. Solvers of Which Way Amelia? will have some idea about the reasons why neither RDF mode could be made to work. Given the failed two-way communications with Ontario, Earhart and Noonan must have concluded long before sunrise that Phase 3 was in serious jeopardy -- that for the approach to Howland there would be no Live Reckoning -- no homing by radio, that is (see Shoot the Moon)..