Originally Posted by
propertee64
Mr Billings , Lockheeds Kelly Johnson did figures that showed the Electra, albeit he used 1200 gallons- not her actual 1150 gallons, had a range of 4,500 miles. If her return leg involved stronger tailwinds than the outgoing leg would you expect this range calculation Kelly Johnson did to be valid in this case?
C.L. Johnson and W.C. Nelson wrote Lockheed Report 487 in June 1936 specifically for the two Long Range versions of the Model 10E, C/N 1055 (Earhart's) and C/N 1065 (The "Daily Express") and most of the 'extreme' range graphs are based on 1200 USG and starting with an AUW of 16,500 lbs.
The "Daily Express" retained the 1200 USG capacity while C/N1055 had the last aft tank of 49USG removed possibly because of "aft C.G." limitations" with Noonan's NAV position in the back by the RHS Rear window..
In LR487 we see various altitudes using stepped climbs and various power settings but what we see in actuality is Earhart climbing straight through to 10,000 feet (SFO-Hawaii March 1937) and not following the C.L. Johnson laid down regime on this "Last Flight" either, viz: the altitude of 10,000 feet to avoid cloud between LAE and CHOISEUL Island way before the 10 hour point (if accepted that she flew by way of Choiseul ...as I explain in detail).
The only way to tackle the fuel consumption (as I see it) is to do the flight at a desk using aerodynamic formulae and power equations in an "hour by hour" method in MS Excel subtracting the fuel used each half-hour and adjusting the AUW and moving the plot forward as you go. This is what I did for the HYPOTHESIS side of the website and it takes time.
That method takes time because of the varying ALT's used and the introduction of wind, climbs and descents until finally establishing a Cruise altitude from the run after the climb at NUKUMANU up until the time of 1912 GMT and the famous "Must be on you" call.
All of any calculations made must also be wound up in the Radio calls and the
PR's and what Groundspeeds we can use which have credibility and any average G/S's used must have a "Start speed value" and an "End speed value" which is also credible.
I can't argue against Clarence Johnson's calculations at all. I can only say that Earhart did not follow the regime he laid down on the last LR flight so the fuel figures become a totally different ball game and have to be worked out as described above.
One thing I did yesterday was to plot the Electra Polar of Lift/Drag against Velocity of the three weights in LR 487 and the surprising thing about the result is that the tangent line hitting the Polar curve at best Lift Drag and the same line hitting the curve for Headwind and Tailwind shows that the speed variance for a 25mph HW or TW is only a few mph difference to either side of the Best L/D Speed. This indicates that Range speed and Best L/D speed have little variance only two or three mph. LR487 says that speed should be increased "about 4mph for a 20 mph headwind" and this is borne out in the Polar Plot that I did yesterday.