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Path C - Initial Discussion

Considered the most likely path flown

Path C is a likely path. Although it deviates south of other, more direct paths, this deviation is supported by two weather forecast reports. One report was delivered to AE in Lae on July 1, from Navy headquarters in Hawaii.14 AE received this report in hard copy. The second forecast arrived in Lae on July 2 during AE’s takeoff from Lae.15 This report was broadcast to AE on the hourly schedules arranged with Lae, and throughout a period of approximately 7 hours. Both pre-launch forecasts were for strong and dangerous thunderstorms east of Lae, on the direct path to Howland. The second report expanded the area of thunderstorms from 250 to 300 miles east of Lae, and provided an updated estimate of en route winds. While the first report contained wind estimates less than what AE reported at 0718 GMT, the second forecasted en route winds at “…east southeast about twenty five knots to Ontario, then east to east northeast about twenty knots to Howland….”

These winds estimates were surprisingly accurate, corroborated by AE’s 0718 GMT in-flight position report that included winds, at 23 knots, and from wind reports from Nauru Island, and surface vessels. Second-half mission winds were very likely at reduced velocity and from slightly left of the track from Lae to Howland.

These wind profiles were modeled by out team in the Jeppesen FliteStar software and in sensitivity analyses resulting in establishing the search grid.

AE was well aware of the existence of hazardous weather, between Lae and Howland. In fact, weather forecasts from Hawaii contained admonition to avoid flying through these dangerous thunderstorms. AE previously experienced heavy weather, from Natal to Dakar, and likely heeded Hawaii’s warnings.

Fred writes, in a letter to his friend, movie actor Eugene Pallette, “…The flight from Natal, Brazil to Africa produced the worst weather we have experienced - heavy rain and dense cloud formations necessitated flying blind for ten of the thirteen hours we were in flight.”16

AE also felt compelled to comment on the rain, “…the heaviest rain I ever saw. The heavens fairly opened. Tons of water descended, a buffeting weight bearing so heavily on the ship I could almost feel it.”17

Midday cumulous buildups over landmasses, such as the island of New Britain, may have also presented hazardous weather on the direct route to Howland Island that could be avoided with a relatively minor deviation southeast, across very good landmarks.

From their Atlantic crossing segment, Natal to Dakar, AE and FN possibly, and intentionally, planned a southerly deviation around New Guinea area weather, one with few penalties and several advantages.

Path C passes over Choiseul Island, the first island south of Bougainville Island. Both Bougainville and Choiseul are prominent visual landmarks. Bougainville’s mountains exceed 8,000 feet in the northern half of the island, but are easily avoided. Choiseul’s highest terrain is approximately 2,000 feet.

This deviation on Path C added only 42nm to the overall mission distance. The path also facilitated an afternoon setting-sun celestial fix, from the left side of the aircraft, inbound to the 0718 GMT reporting point near Nukumanu Island.

Figure 2.jpg

Figure 2 - Path depictions and supporting Factors for Path C.

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Figure 3 - Pilot-eye view approaching the 0718 GMT position on Path C.

Only on Path C do all initial position reports in time coincide reasonably and closely with AE reported positions in space, and they agree in time within 5%. From the Oakland to Honolulu navigation logs, position reports were often made at some time after passing the reported position, and with the aircraft not co-located with the reported position. The lag between position passage, and reporting, is understandable in that it was AE’s first real navigation challenge working with Fred Noonan and Paul Mantz, and there were no landmarks corresponding to reported positions and times.

AE and FN may have sought to be more precise on the Lae to Howland segment, to more closely report positions and times. The data supports such an intention.

A more detailed analysis of Path C is contained in Part IV.

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