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Detailed Flight Analysis

Reviews previous documented flight characteristics to apply them to the final flight

Validated Statistical Data
Direct evidence includes AE’s flight performance on earlier World Flight segments, in which weather, winds and navigation challenges were similar to the final flight segment. Terrain was a factor in some mission segments, however, on the final flight segment, only Bougainville Island presented a terrain consideration with mountains reaching approximately 8,000 feet.

Wherever first-hand factual evidence was available from AE’s flight logs and accounts, that data was used to establish AE’s historical flight patterns. Analysis of an audit of World Flight mission segments provides important understanding for mission performance.

This data is also important when considering alternative flight profiles and mission outcomes, offered by various authors. When alleged mission flight parameters fall outside an established pattern of historical performance, the associated theory and conclusions demand careful scrutiny. The business analogy is that if a performance factor were well outside statistical Quality Assurance ranges, such as Six-Sigma, or Control Chart limits, it would exist as an abnormal data point, one requiring additional validation.

Some alternative theories about the World Flight, for example, require aircraft and mission performance that exceeds capabilities or that falls well outside historical patterns.

Winds
There are 7 weather reports relevant to this mission segment.

Reported wind speeds from weather observations are in mph. Only AE’s position report of wind speed was in knots at 0718 GMT.

Two reports are from Hawaii Headquarters, one issued 1 July and handed to AE, and one issued 2 July and broadcast from Lae to AE.31

Both ship-based and shore-based weather reports of upper winds are not extremely accurate in 1937. A meteorograph instrument was sent aloft under a tethered balloon or kite, where it recorded a few parameters for examination following retrieval. Upper winds may also have been established from an observation made by a qualified weather person.

Two reports are from Itasca, both at noon local time. One, on June 30, 1937 reported winds at 5000 feet from the east (090 deg) at 22 mph. The other, on July 1, 1937 reported winds at 7000 feet ENE (060 deg) at 30 mph and at 9000 feet ENE (060 deg) at 31 mph.32

One report is from AE at 0718 GMT (1718 local time) on July 2, 1937, as an in-flight position report, in which a reference to “winds 23 knots” is made. No direction was specified.33

One report is from the USS Ontario, July 2, 1937 bridge logs, that reported surface wind ENE (060 degrees) at force 3-4 (up to 16 knots) but it is only a surface report of sea state and winds.34

One report is from Nauru Island, on July 2, 1937 at 0800 local time GMT, approximately 3 hours prior to AE’s departure from Lae, and nearly 10-12 hours prior to AE’s arrival in the vicinity of Nauru Island, en route to Howland. In this report, upper wind values were reported at 4000 feet from 090 deg at 12 mph and at 7500 feet from 090 deg at 24 mph.35

This is evidence that at the mid-point of the Lae to Howland Island segment, upper winds were very close to those used by Long (26.5 mph) and our own baseline analysis.

Long36 assumed a constant headwind of 26.5 mph (23 knots) throughout his analysis. In arriving at this value, Long likely considered the AE in-flight position report at 0718 GMT reported wind value, and a single Nauru Island weather observation with wind direction and values linearly extrapolated to assess winds at AE mission altitudes of 8,000 and 10,000 feet.

While wind profiles are often not linear, over small altitude differences, a linear interpolation is sufficiently accurate for this analysis. Evidence exists that wind velocity was reduced, and direction shifted slightly, in the second-half of the mission.

For this research, the authors used upper winds from 070 deg magnetic at 23 knots, or 26.5 mph. On course to Howland Island, this was a headwind component of 23 knots, or 26.5 mph. Sensitivity analyses for second-half wind changes were completed, with resulting aircraft positions contained in the search grid.

Speeds - Aircraft and AE Performance
There are seven principal sources of historical and statistical in-flight performance data. These include L487; Kelly Johnson Telegrams; Electra capabilities in terms of power, speed, and fuel consumption, from operating manuals and Pratt-Whitney engine data; AE’s first-hand reports during her World Flight performance37; research by Long; and research by Swenson and Culick38 with aerodynamic and engine performance research.

Definition of speed is important in understanding a Lae-Howland specific segment analysis.

Below is a table compiled from two reference sources, Long39 and Finch.40 The data was crosschecked with notes reported by AE41, providing a single source for historic mission segment examination.
The data show that in 30 World Flight legs, excluding 3 test flights of short duration (less than 2.5 hours) the average ground speed is 142.1 mph.

This is useful in assessing various AE reported speeds, that often omitted units (statute or nautical miles per hour), or what type of speed was being used (indicated, true or ground speed). AE frequently omitted other details, such as altitude, outside air temperature, and winds, from her in-flight reports.

Statistical data combined with report times and positions, helps to assess the reasonableness of aircraft performance and to corroborate other data.

A report of speed in knots likely resulted from FN calculations, handed to AE for reporting, since FN likely worked in nautical miles from navigation charts, and AE’s airspeed indicator was calibrated in statute miles per hour. AE, simply due to the state of aviation in 1937, most likely did not possess the tools to convert statute miles per hour to knots, or to work between indicated, true, and ground speed, from the cockpit and without reference to published tables or graphs.

AE’s Lae to Howland performance is defined from corroborating power settings, Brake Horsepower, Cambridge Fuel Analyzer indications, L487 and Kelly Johnson recommendations, and statistically validated to calculated and historical values. These values can be used to determine flight path data, with reasonable assurance that a re-calculated flight path represents an accurate calculation.

Table 1 - Segment Speed Performance

FROM TO

DATE

TIME

DIST NM

FLIGHT TIME

AVG GS KTS

AVG GS MPH

OAKLAND BURBANK

20-May-37

1550

283

2.25

125.78

144.75

BURBANK TUCSAN

21-May-37

1425

393

3.33

118.02

135.82

TUCSON NEW ORLEANS

22-May-37

730

1070

8.67

123.41

142.02

NEW ORLEANS MIAMI

23-May-37

910

586

5

117.20

134.87

MIAMI SAN JUAN

1-Jun-37

556

908

7.56

120.11

138.22

SAN JUAN CARIPITO

2-Jun-37

650

492

4.53

108.61

124.99

CARIPITO PARAMARIBO

3-Jun-37

848

610

4.83

126.29

145.34

PARAMARIBO FORTALEZA

4-Jun-37

710

1142

9.33

122.40

140.86

FORTALEZA NATAL

6-Jun-37

650

235

2.08

112.98

130.02

NATAL SAINT-LOUIS

7-Jun-37

313

1727

13.37

129.17

148.65

SAINT-LOUIS DAKAR

8-Jun-37

905

100

0.87

114.94

132.28

DAKAR GAO

10-Jun-37

651

1016

7.92

128.28

147.63

GAO FORT LAMY

11-Jun-37

610

910

6.63

137.25

157.95

FORT LAMY EL FASHER

12-Jun-37

1224

610

4.1

148.78

171.22

EL FASHER KHARTOUM

13-Jun-27

610

437

3.25

134.46

154.74

KHARTOUM MASSAWA

13-Jun-27

1050

400

2.83

141.34

162.66

MASSAWA ASSAB

14-Jun-37

730

241

2.43

99.18

114.13

ASSAB KARACHI

15-Jun-37

313

1627

13.37

121.69

140.04

KARACHI CALCUTTA

17-Jun-37

725

1178

8.33

141.42

162.74

CALCUTTA AKYAB

18-Jun-37

705

291

2.45

118.78

136.69

AKYAB RANGOON

19-Jun-37

842

268

2.5

107.20

123.37

RANGOON BANGKOK

20-Jun-37

630

315

2.72

115.81

133.27

BANGKOK SINGAPORE

20-Jun-37

1027

780

6.47

120.56

138.74

SINGAPORE BANDOENG

21-Jun-37

617

541

4.33

124.94

143.78

BANDOENG SURABYA

24-Jun-37

1400

310

2.58

120.16

138.27

SURABAYA BANDOENG

25-Jun-37

600

310

2.5

124.00

142.70

BANDOENG SURABAYA

26-Jun-37

1154

310

2.6

119.23

137.21

SURABAYA KOEPANG

27-Jun-37

630

668

5.5

121.45

139.77

KOEPANG DARWIN

28-Jun-37

630

445

3.43

129.74

149.30

DARWIN LAE

29-Jun-37

649

1012

7.72

131.09

150.86

AVG

119.49

142.10

SDEV

12.14

This graph below of average speeds flown on each World Flight mission segment, illustrates two important conclusions.

AE typically operated at parameters specified by experts, especially for longer duration flights.

AE’s performance consistently adheres to a reasonably small range of speeds.

The data shows a larger variance in speed for shorter segment lengths. As the segment length increases, the speed variance decreases, approaching speeds recommended by the L487 Report42 and Kelly Johnson.43

This process increases confidence in the preflight planning, flight parameter specifications, and, for the few longer segments flown by AE, a sense that these values were typical.

The final mission segment is not included in this data, since a definite completion time was not established.

Figure 5.jpg

Figure 5 - Average World Flight Ground Speed

This graph below depicts flight segment times, providing an interesting perspective of some of the human factors involved in this flight.
The 30 World Flight times in the graph average 5.1 hours per flight segment. For comparison, the Lae to Howland segment was planned for approximately 18 hours, and lasted in excess of 20 hours.

The maximum flight time prior to Lae, was 13.37 hours, recorded for two mission segments.

No other mission segment was more than 10 hours.

AE had completed flights of durations approaching the length of the Lae-Howland segment.

On May 20-21, 1932, AE completed a solo transatlantic crossing in 14 hours 56 minutes.

On August 24-25, 1932 AE completed a solo non-stop transcontinental crossing in 19 hours 5 minutes.

On July 7-8, 1933, AE completed a transcontinental crossing in 17 hours 7 min.

On January 11, 1935 AE completed a solo flight from Honolulu to Oakland in 18 hours.

On May 8, 1935, AE completed a Mexico City to Newark flight in 14 hours 19 minutes.

AE was no stranger to long flights, yet all were completed 2-5 years earlier, none were to islands, and none required a need for maximum range performance and fuel management to the level required from Lae to Howland Island.

This data provides insight into not only the challenge undertaken by AE and FN, but the complexity of this operation relative to their previous experience.

Figure 6.jpg

Figure 6 - Average Segment Length

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Flight Modeling - Lae to Howland Island

Key factors involved in re-navigating this flight

For this research, prior to AE’s 0718 GMT in-flight position report, climb speeds were determined from L487 and Kelly Johnson power setting recommendations, engine operating limitations, climb speed specifications, with consideration of climb rate as reported by Pellegreno.

From AE’s 0718 GMT in-flight position report, to Howland Island, the re-calculated true airspeed was determined by setting power in accordance with L48744 and Kelly Johnson recommendations45, with reference to direct evidence from previous flight profiles, statistical reference, and behavior where AE included specifics about power setting and speed, in flight notes. Lockheed and Pratt-Whitney data were also considered.

This technique produced en route speeds after 0718 GMT, of 138 knots true air speed, or 158.8 mph.

Applying the 23 knots, or 26.5 mph, headwind component, produced 116 knots ground speed, or 132.3 mph ground speed, after the 0718 GMT position, which was held until the perceived descent point to Howland Island at approximately 80 statute miles per Kelly Johnson, Paul Mantz (OAK-HNL) and Fred Noonan recommendations.

Our result of 132.3 mph ground speed, from the 0718 GMT position to Howland Island, is only 1.7 mph (1.2%) less than Long’s overall mission average ground speed. Our result of 158.8 mph true air speed is also 1.7 mph (1.1%) less than Long’s overall average true air speed.

These are considered valid performance numbers, and when combined in a discrete and stepwise analysis, the modeling technique provides a more accurate profile.

Despite flying a Lockheed Model 10A aircraft with smaller engines, less weight and likely a lower drag profile, Pellegreno46 routinely observed ground speeds of 133-135 mph during a Commemoration Flight, indicating that computed speeds are in the range of reasonable performance.

Pellegreno’s aircraft has effectively the same horsepower-to-weight ratio as AE’s Electra 10E.

Long assumed a constant overall true air speed of 160.5 mph47, in the presence of a constant headwind component of 26.5 mph, producing an overall mission average ground speed of 134 mph.

Long’s approach of averaging distance and time was updated in our research using a discrete approach, a stepwise analysis at each waypoint, facilitated by software.

Using flight planning and analysis software to model the climb, cruise, descent performance and wind effects, can produce a more accurate overall mission analysis. The software enabled modeling three flight paths, sensitivity analyses from headwind speed and direction modifications, and examination of route timing and the terminal EON position.

Further corroboration of these results is found in L487 48 that recommended flying at 155 mph indicated air speed at 2,000 feet, 145 mph indicated air speed at 4,000 feet, and 135 mph indicated air speed at 8,000 feet. This profile was apparently not flown, as it was pre-empted by later Kelly Johnson profile recommendations, which appear to have been executed and adhered to on many World Flight segments, including the Lae to Howland Island segment. The 8,000 feet speed specification is very near what AE likely flew.

The later Kelly Johnson recommendations specified flying at 8,000 feet, and under conditions that likely existed during AE’s flight, are equivalent to 155.4 mph true air speed. Kelly Johnson Telegrams49 indicated power settings and speeds, showing that after 0718 GMT, a target speed would be 133-158 mph true air speed.

This data and resultant recommendations were based on analytic aerodynamic calculations including wind tunnel testing, and actual flight test data from AE’s aircraft.

L48750 provided values for flight at sea level, with no altitude adjustments, and recommended flying 150 mph true air speed in still air, and with a 20 mph headwind, flying 154 mph true air speed.

Table 2, from 0718 GMT to approximately 1830 GMT, compares cruise performance in statute miles per hour (MPH), for this specific cruise segment.

Table 2 - Comparative Speed CalculationsAE adhered remarkably close to these recommendations. These speeds are highly corroborated. (Footnote 51 next to Long Research in table 2)

The MSI and modeling process forms a corroborating body of evidence of the likely mission flight performance actually achieved on the Lae to Howland Island mission segment, in terms of speed, fuel consumption, position and time. MSI incorporated a broader range of corroborated data sources:

All AE in-flight reports

AE historical performance data

The Nauru Island weather observation of upper altitude winds

Data used by Long

The L487 report aerodynamic data

Kelly Johnson recommendations

Swenson and Culick’s analysis

Our independent analysis for validation of previous work

Lockheed Electra Operating Manuals

Pratt-Whitney engine operating data specific to AE’s engines

Using this MSI blending process we calculate performance used in our aircraft modeling and flight planning process, as follows:

Indicated Air Speed within 2.3% of L487 and 0.8% of Long

True Air Speed within 2.2% of L487 and 1.1% of Long

Ground Speed within 1.2% of L487 and 1.3% of Long

This methodology directly affects speed, time, fuel consumption, and most important, final position. Except for lateral navigation track errors or deviations from a planned path, speed and fuel consumption are the most fundamental parameters in locating the Electra, and worthy of close scrutiny.

Improved Accuracy
Modern methods yielding 2% improvements in a solution represent approximately 50nm in a final EON point on a Lae to Howland Island segment.

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Performance Specification Challenges

Factors complicating the analysis

Among sources of Lockheed Electra 10E aircraft performance specifications, Lockheed and Kelly Johnson provide reference data. Lockheed Electra Operating Manuals provide good information. AE provides data in nine citations of some aspect of en route aircraft performance52. Pellegreno provides two climb airspeed citations and two en route ground speed citations under normal wind and weather conditions that are useful.53

Lockheed Report 487 54 contains extensive aerodynamic and performance analyses of the Lockheed Electra Model 10E.

Completed 13 months in advance of the actual World Flight attempt, this report detailed a recommended flight profile, flight parameter recommendations, and supporting aerodynamic data.
Among these, are useful information on engine power settings for Brake Horsepower (BHP), Manifold Pressure (MP), propeller RPM (RPM), fuel flow in gallons per hour (GPH), flight speed, range, fuel consumption, and Cambridge Fuel Analyzer settings.

Conversion factors used in this analysis55 are shown below.

1 nautical mile per hour = 1.1508 statute miles per hour

1 nautical mile = 1852 meters = 1.1508 statute miles = 6076.1 feet.

These conversions are important. Charts, tables, AE in-flight position reports of speed and distance, Fred Noonan’s notes to AE and radio logs of communications, contain either no definitions for the metrics being reported, or when a unit of measure is defined, it sometimes conflicts with other reports, historical accounts, or engineering data.

Within L487,56 and in most every resource, flight speed is frequently not defined in terms of the units, nautical miles per hour (knots) or statute miles per hour (MPH). In some cases in the same report, speed units are mixed in different charts or tabular data, and flight speed is sometimes defined in one graph, and not defined in other graphs or tables.

In every case, these precise units of measure require definition to enable meaningful analysis.

This complicates all analyses.

Flight speed is an important metric. There are three flight speed measures of interest, and in this research the authors have been required to calculate, and identify the measure being used in a majority of historical references.

AE’s airspeed indicator was calibrated in statute miles per hour, or MPH. AE flew her airplane with reference to MPH. This is Indicated Air Speed (IAS) in MPH.

When Indicated Air Speed in MPH is corrected for altitude (pressure and temperature) the result is an associated True Air Speed (TAS) in MPH. This is “over the earth” speed in a no wind condition.

When TAS in MPH is corrected for headwinds and tailwinds, the result is Ground Speed. This is the aircraft’s actual speed over the ground, in the air mass existing at the time of flight.

For distances measured in nautical miles, the associated speeds are defined as knots, or nautical miles per hour.

While AE’s IAS registered in MPH, many charts such as aeronautical and marine charts are presented in nautical miles. Fred Noonan’s chart navigation was likely in nautical miles, requiring a conversion from nautical miles (or NM per hour which is defined as Knots) to statute miles (or statute MPH).
“Speed 140 knots…”

As an example of this complexity and the importance of precise specifications, AE provides, according to Chater, an in-flight position report at 0418 GMT including a report of “140 knots.”

Chater 57 reports this as 140 knots.

Collopy 58 reports this as 150 knots.

The type of speed is not specified. It could be 140 knots True Airspeed, Indicated Airspeed, or Ground Speed. The implications of each are very important.

Referring to L487,59 for ambient meteorological conditions likely at 0418, area weather reports indicate outside air temperature at sea level of approximately 83 degrees F. Using the standard adiabatic temperature lapse rate of -3.5 degrees F per 1000 fee to find the ambient temperature at AE’s cruise altitude, we find that if “140 knots” were an indicated air speed, it would imply the aircraft was flying at a true air speed beyond the Electra’s performance capability at its gross weight at 0418 GMT.

Similarly, if “140 knots” were a ground speed, with an assumed 23-knot headwind component (26.5 mph headwind defined by Long), the true airspeed required is again, beyond the Electra’s performance capability at its gross weight at 0418 GMT.

If “140 knots” were a true air speed (equivalent to 161.1 mph true air speed), it would place AE’s indicated airspeed in miles per hour (143 mph IAS), in the range of historical performance and Electra capabilities, and near the speeds prescribed in L487 and Kelly Johnson,60 and Paul Mantz recommendations.

If the reported speed was 150 knots, and a true air speed, this would be uncharacteristically high for the Electra’s gross weight and mission time, atypical of AE’s performance, and beyond statistical norms.

At 140 knot, and 161.1 mph true air speed with the assumed 26.5 mph headwind (Long), AE’s ground speed would have been 134.6 mph, which is within 7 mph (5.6%) of AE’s statistical range of historical World Flight performance, within the Electra’s capabilities at that gross weight, closely aligned with flight recommendations, and typical for the mission time en route.

The conclusion is that AE’s report of “140 knots” is a true air speed. Fred Noonan likely handed AE the data to make this report (in knots), and AE was flying very close to recommended or prescribed parameters. This precise and consistent performance is typical for AE throughout the World Flight, and vitally important to understanding the Lae to Howland Island mission segment.

Further, Chater’s61 report is considered more accurate regarding this reference to speed.

Fred likely worked in knots and nautical miles, making conversions from AE’s indicated airspeed and meteorological data such as outside air temperature. There would be no instrument indication presenting “knots” to AE in the cockpit, and AE would likely not have made conversions from mph to knots with Fred aboard, and possibly, not at all. The charts and process for these calculations were largely unavailable for most flying in 1937. The conversions were not easily performed, and no handy calculators existed to make the job easier or more reliable.

In 1937 aviation, flying was referenced to “miles per hour,” which is statute miles per hour.

The ubiquitous handheld calculator, the E-6B flight computer, made it possible for pilots to easily and rapidly compute speeds, winds, conversions, and other flight performance data. Unfortunately, it was effectively not yet invented in July 1937, and did not gain widespread use until mid-WWII.

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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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