Read the…

Experience the thrills and defeats of an authentic deep sea adventure as you immerse yourself in the CATALYST 2 Mission Log. More>>

Waitt Institute

The Waitt Institute is a non-profit research organization that serves as an exploration catalyst, enabling scientific pioneers to transform the ways in which discoveries are made. More »

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.

Back To Top