There were two "Obviously" bad things about the original Propeller Efficiency Graph:
The first issue was that the efficiency curve for 15 degrees was very strangely shaped,
(That was not difficult to correct, but the assumption is that we will need to re visit to fine tune later.
The second issue and the main reason for wanting to edit the Propeller Tables to begin with was that even for very shallow pitch angles, the efficiency did not drop to Zero fast enough with increasing Advance Ratio.
Both issues were "Addressed".
At this point (and probably earlier) it made sense to gather a few numbers to figure out how these Propeller Tables fit in with the Aircraft's speed ranges.
(I used data from the FW 190A when I could not find specific data for the BV 141B.)
Propeller Diameter 3.30 Meters
Reduction Gear 24:13
Pitch Range 23-65 Degrees
Maximum RPM 2700 for Take-Off
Normal Maximum RPM 2550 which was used for speed testing.
Advance Ratio 1.0 = 170 MPH.
When I found the Propeller Pitch Range, it became obvious that the 15 degree graphs in the Propeller Tables served no purpose at all other than as a distraction.
The entire level speed range at 2550 RPM is between Advance Ratio 1.2 and Advance Ratio 1.6.
It also became obvious that just changing the Propeller Efficiency Graph (Table 511) would not work because the current Power Coefficient Graph (Table 512) currently selects a propeller pitch somewhere between 27 degrees and 34 degrees depending on altitude.
27 degrees at 227 MPH would be hitting the very steep drop as propeller efficiency dropped off.
34 degrees at 280 MPH would actually be fairly reasonable though.
Next step will be to try adjusting the Power Coefficient Graph in an attempt run slightly higher pitch at each Advance Ratio.
- Ivan.
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