The Earhart Search In PNG Project
Contains two distinct sides:
1. The Factual side
2. The Hypothesis of the flight
For interest: Content of the Robert Gross Letter to G.P. Putnam 5th March 1936
This is what was written to George Putnam before the Electra was purchased....
"Dear Mr. Putnam,
As promised in our wire of yesterday’s date, we hand you herewith, certain performance guarantees on the “special flight” airplane under discussion. For reasons stated below, we are making the guarantees with two different fuel capacities. Provided the airplane is built substantially in accordance with our previous letter to you dated J]February 21, we will guarantee that:-
A. With 1,050 Gallons of Fuel
The range will be – 4,000 miles
The maximum speed at 6,000 feet will be – 190 m.p.h.
The cruising speed at 4,000 feet for best range – 145 m.p.h.
The gross weight, depending in equipment, about – 15,500 lbs.
B. With 1,200 Gallons of Fuel
The range will be 4,500 miles
The maximum speed at 6,000 feet will be – 189 miles [sic: mph]
The cruising speed at 4,000 feet for best range – 145 m.p.h.
The gross weight, depending in equipment will be about 16,500 lbs.
We will not guarantee the takeoff distance because so much depends upon the condition of the runway, wind velocity, and the human element always resent in piloting. We believe, however, that the takeoff run with 1,050 gallons of fuel will, under favorable conditions, be about 3,000 feet and will [with] 1,200 gallons under the same conditions about 3,500 feet. We further believe that with a favorable runway and air conditions that are not too rough the structure of the airplane will satisfactorily carry the loads above mentioned. All takeoffs are contemplated with 100 Octane and full throttle setting.
When you were here before, we gave you our informal assurances that a range of 4,500 miles was possible with 1,050 gallons of gasoline. We still believe it is possible, but in order to achieve this range, the conditions would have to be perfect and the mixture control operation during the flight would demand the utmost care and attention. For our own protection, therefore, we feel it advisable to submit our guarantees on the basis of the extra fuel as well as the 1,050 gallons if the 4,500 miles range is essential.
Yours very truly
LOCKHEED AIRCRAFT CORPORATION
Robert B. Gross
President"
The document I have is a copy produced by Author Richard (Dick) Strippel dated Jan 14, 1974 and Notarised by M. Sohayda, of New Jersey.
The Excel Plot
The Excel plot is by no means finished but reflects Horsepower required to keep the Electra in the air over a long distance with data taken from Page 30 of LR487 when that data has been corrected for typos and then checked using performance formulae some of which is in the report itself. However the typos continue... Page 24 has a typo in the formula for Drag for example, the report obviously was not proof read by anyone from the Performance Dept.. .. An expanded Excel file of the "refreshed" data can be used to show H.P. required for any speed, Pressure altitude or altitude corrected for Density and for any gross weight . It matches the distance and the timings of what we do know.
In the old days they used slide rules, we can now use Excel.
When I have finished I will post the final results. It takes a long time to get these things done and to reflect credible results. I am using full fuel and a gross weight of 15,000 pounds. This is essentially where Excel comes into the fore because the expanded tables for any speed, weight or altitude show what is required and all the values.
One thing I will, say is that "Commercial" operations of aircraft is to get the passengers and freight to the destination as fast as possible, using lots of power and speed. The Earhart Long Range flights were not conducted with that maxim in mind, we are talking chalk and cheese. I repeat, METO or Max. Continiuous does not "fit" anywhere an any of the plots I have done, too much speed and too much gasoline used. Try thinking the other way around . "Best Lift./Drag" also does not feature totally in this latest plot, it (the plot) meets the time and distance constraints using far less power than you could think of in a "Commercial" operation.
Regard,
David
Last edited by David Billings; 6th May 2018 at 04:16.