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Flight Data - AE Natal to Dakar

The longest over-water flight segment of the World Flight

This flight segment was the longest over-water portion of the World Flight, and among the two segments with the longest duration, prior to the planned Lae-Howland segment. AE crossed the Atlantic at night, just as the planned Lae to Howland flight would be executed.

Position and Time
In AE’s flight notes62, this flight segment offers the most comprehensive detail of flight conditions, speeds, outside air temperature, aircraft location (by calculation), possible sun position, and factual data of any World Flight segment. It’s worth studying carefully, and it relates directly to the Lae to Howland segment.

These notes are recorded in a logbook fashion, at “6:50.”63

Takeoff from Natal was at “…0315 in the morning…”

We assessed this as local time.

The notation “6:50″ could be the mission elapsed time since takeoff.

The notes include “crossing the equator” which was approximately 513sm from Natal, and would have corresponded to approximately 3 hours 30 minutes flying time, crossing the equator at approximately 0645 AM local Natal time.

“6:50″ is then the Natal local time of this logbook entry, and the local time of the equator crossing.

With this entry is “sun brilliant” which may refer to sunrise, which in Natal on the morning of June 7, 1937 was at 0636 local time.

Later in these same notes, AE records an entry titled “9:41 Natal time.” In this entry AE notes 147 mph for 8 hours [since takeoff] covering 1176 statute miles.

This 147 mph is a ground speed, multiplied by time and resulting in a distance covered.

“9:41 Natal time” is 6 hours 26 minutes elapsed mission time, approximately the mid-point of the Atlantic crossing. Natal to Dakar is a 3-hour time zone change. AE notes their time airborne as 8 hours since takeoff. This may simply be an error, or the entry “9:41 Natal time” could simply be unrelated to the notes about speed, time and distance.

At “9:41″ Natal time, on June 7, 1937, the sun azimuth from true north was 050.35 degrees, and its elevation above the horizon was +40.81 degrees. AE writes that “…they can hardly believe the sun is north of them….” Their true course to Dakar was approximately 038 degrees. The sun would have been slightly to the right of their heading, south of their course, if they were on course. If they were heading in a more easterly direction, the sun would indeed appear north of them.

From AE’s logs we know that AE was north of course at some point in the crossing. It is possible that these observations of the “…sun…north of them…” were made after a heading correction to rejoin their original track to Dakar. This heading correction would place the sun to their left, possibly appearing as if it was “north” of them.

These observations are tremendous insights into flight parameters, mission timing, how AE recorded information, and the accuracy of their navigation.

All of these are central to the Lae-Howland recalculation.

En route Weather - Overcast or Undercast
In AE’s notes from Natal to Dakar,64 at approximately the halfway point, she writes, “High overcast now. Good visibility except now and then showers. Fred takes sight. Says we’re north of course a little.”

The importance of this entry is significant for the Lae-Howland segment. The insight here is that with a high overcast, Fred could not take a sight, unless the “overcast” was actually an “undercast.”

Even today, pilots observing a cloud deck below them in cruise flight sometimes refer to the condition as an overcast sky. The term “undercast” is not widely used, or common in the “pilot-vernacular” of aviation today, and in 1937 aviation, it likely wasn’t yet conceived.

In several AE Lae to Howland in-flight position reports, references to “overcast” conditions are made.

At 1415 GMT, AE reported “cloudy and overcast.”

At 1515 GMT, AE reported “overcast.”

At 1627 GMT AE reported “partly cloudy.”

Traditionally, researchers have concluded, in reference to these reports, that the sky above AE was indeed as reported, “overcast.” However, it is possible that we have misinterpreted flight conditions, from semantic or contextual differences between today, and 1937.

If AE was in fact reporting an “undercast,” which we believe is likely, it means that FN had good celestial navigation targets (as AE stated), could take good position fixes, and assure that they were on their planned track from Lae to Howland.

This conclusion has a significant effect on the end-of-navigation position. It essentially allows that AE had a good opportunity to be on course to the end-of-navigation fix. It could further allow that AE descended at the perceived descent point, slightly early, and while on track.

The end-of-navigation fix would then be quite accurate.

The Lae to Howland implications from studying these World Flight segments preclude wildly off-track navigation positions, gross timing and navigation errors, poor en route weather conditions, or excessive fuel use due to large un-forecast headwinds, or in greatly varying distances flown on various profiles proposed in some previous works.

This understanding increases confidence in the end-of-navigation and fuel consumption calculations.

Aircraft Fuel Load
AE writes of refueling the aircraft at Natal, and with some concern for adequate fuel quantity, for using the “secondary” grass runway at Natal, and for departing that runway, “…in the dark with such a heavy load….”

She had a backup plan, as she frequently detailed throughout her flying experiences, which called for delaying that takeoff until more suitable conditions existed. Her backup plans for fuel generally included a safety margin.

AE and FN examined that grass runway by walking its length with flashlights, and ultimately departed as planned, “…we got into the air easily.” This is the 1937 equivalent of today’s safety risk management process.

In Natal, the Electra was likely refueled to approximately 80% of the fuel loaded at Lae. The Natal-Dakar segment of approximately 1900 statute miles was 656 statute miles less than the planned distance from Lae-Howland, or approximately 74% of the Lae-Howland distance At AE’s baseline 150 mph still-air ground speed, the 4.4 hour difference in mission time, at nominally 50 gallons per hour, would mean 218 less gallons of fuel were required at Natal, and a takeoff fuel load from Natal was approximately 862 gallons. This provided more than 4 hours endurance at destination.

AE stated on the OAK-HNL flight segment that she considered 4 hours reserve fuel an adequate safety margin, “Incidentally, we arrived at Hawaii with more than four hours’[sic] supply of gasoline remaining, which would have given us over 600 miles of additional flying, a satisfactory safety margin.”65

It is important to note in that passage, that AE’s baseline speed is 150 mph ground speed as recommended, and apparently 50 GPH as a general fuel consumption rate.

Here, Natal to Dakar, we have the second incidence of knowing that AE planned for a 4-hour fuel reserve.

This has implications for the Lae to Howland segment, in terms of how much fuel AE planned upon arrival at Howland Island. While perhaps not 4 hours, AE may have planned at least 3 hours fuel remaining at Howland Island, 120-150 gallons of fuel, again providing us with a valuable insight to what went wrong on the Lae to Howland segment.

AE’s details of the Natal to Dakar flight parameters after 6 hours 50 minutes can be compared with her in-flight position reports from Lae, made at 0718 GMT, as a quality assurance process.
In-Flight Speed and Performance

Following, the two segments, Natal-Dakar (St. Louis) and Lae-Howland, are compared and evaluated.

AE writes at 6:50 elapsed mission time:

Indicated Air Speed 140 (likely in mph since her airspeed indicator was calibrated in mph)

Altitude 5,780 feet

Manifold pressure 26.5 inches

RPM 1700

Outside Air Temperature 60 (likely indicated air temperature in degrees Fahrenheit)

These conditions equate to approximately a power setting of 250 Brake Horsepower (BHP), burning approximately 46-49 gallons per hour in cruise flight. Accounting for an estimated 70 gallons for climb in the first hour, 25 gallons for a 30-minute descent, and a cruise portion of 11.8 hours at an average 47.5 gallons per hour, the Natal-St. Louis segment should have consumed 655 gallons. From an initial fuel load of 862 gallons, at least 4 hours fuel remained at arrival in Dakar (St. Louis).

AE likely adhered as much as possible to these parameters during the Lae-Howland segment.

Comparing Natal-Dakar (St. Louis) and Lae-Howland
We can make some comparative assessments. For example, if we use the same Natal-Dakar climb and descent numbers for fuel and time, it leaves a Lae-Howland 17.7-hour cruise segment at 47.5 gallons per hour, consuming 841 gallons. Adding the climb and descent, the Lae-Howland mission fuel consumption would have been 936 gallons.

Our Lae to Howland specific fuel consumption analysis resulted in a segment fuel consumption of 957 gallons, leaving 123 gallons of fuel remaining at Howland.

We have two different mission segments, two very different computational methods and processes, one generalized and one very specific, and two conclusions for segment fuel consumption, that differ by just 2.2%. The confidence in these solutions, the Lae to Howland analysis, the End-of-Navigation point, and the possible location of the Electra, increases with each MSI corroboration.

Reproducing Table 1 and including data from AE’s Natal-St. Louis flight segment provides analytical corroboration, and again reflects AE’s consistent, disciplined adherence to specified flight parameters.

Table 3 - Table 1 with added detail for Natal to Dakar mission segment.

(Footnote 67 is in bottom right cell of Table 3)

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