Gary, I might as well take a shot: isn't the specific fuel consumption chart a little backwards? shouldn't the pounds per hp increase from left to right instead of right to left?
I retract my wag, after I played with the figures a little, it started to make sense. so I am going to keep looking for the "glaring error". This sure beats working the crossword puzzles.
Randy
You should have quit while you were ahead, you got it right in you previous post. The Mantaro report on page 12 states they are extrapolating by "keeping efficiency constant above 350 BHP" and this is shown on their graph on page 13 by extrapolating the BSFC straight up. Anybody who has ever flown an airplane knows that this is wrong! Above 65% power on P&W round engines (above 400 BHP on Earhart's 600 BHP engines) requires a "full rich" mixture to prevent damage to the engines. Using "full rich" causes the BSFC to increase greatly. This calls into question the rest of the Mantaro report.
The Pratt and Whitney power setting table for Earhart's P&W S3H1 engines is attached.
According to Pratt and Whitney this engine burns 65 gallons per hour at full 600 hp power output making the BSFC .65, 130 gallons per hour total for two engines. Running the engines at full power would have used up the 1100 gallons on board in 8:28.
Running the engines at 550 hp burns 55 gallons per hour making the BSFC .60 and
burning all the 1100 gallons in 10:00
Contrary to Lockheed report 487 and other documents that state the BSFC of .42, the best BSFC obtained according to this Pratt and Whitney table (the people who manufactured the engines) is .48 and this was at 300 and 350 hp. Cruising with 350 hp per engine burns 28 gallons per hour per engine which would have used 1100 gallons in 19:38. Cruising with 300 hp per engine uses the 1100 gallons in 22:56.
The lowest fuel flow stated is 21 gallons per hour per engine for 250 BHP (BSFC of .50) so it appears that Earhart's statement on the Hawaii flight that they were burning 20 gallons per hour was referring to the fuel flow to each engine making the total fuel flow about 40 gallons per hour. At 21 gallons per hour per engine the 1100 gallons would have produced an endurance 26:11. (But higher power settings had to be used early in the flight.)
So Mantaro's extrapolation is completely wrong and the graph, instead of going straight up, should bend sharply to the left.
I have also attached page 33 from report 487 and you can see that these BSFC values are optimistic compared to the P&W document.
gl