Why still no dive acceleration difference?

[BlackBerry]

http://digital.library.unt.edu/ark:/...dc62616/m1/19/
P47D tested with a Hamilton Standard 6507A-2 3-blade airfoil(NACA-16)

Cp=P/(r*n^3*D^5)

r=air density

We can see when dive to low altitude @0.7 Mach, prop efficiency will be as low as 63%. Fw190A8's 3.3m propeller advance ratio is quite bigger than P47's, so its efficiency should be quite less than 63% if the VDM prop. shares the same airfoil with 6507A-2.

But don't forget Hamilton Standard 6507A-2 has a NACA-16 airfoil. see here

http://digital.library.unt.edu/ark:/...adc63942/m1/3/


Allied also tested Hamilton Standard 6507A-2 with both 3-blade and 4-blade configuration at 0.4 Mach, also here

http://digital.library.unt.edu/ark:/...dc63942/m1/40/

http://digital.library.unt.edu/ark:/...dc63942/m1/43/


Fig 16 and Fig 18

Appearently, 4-blade NACA-16 airfoil shows around 5%-10%+ efficiency advantage over 3-blade cousin even at medium speed. That's one of the reasons p47D picked up 4-blade airscrew.

It's probably that when dive to high-speed fw190a8's 3-blade Gottingen prop. efficiency is much inferior than P47's 3-blade NACA-16 airfoil. But I know Crumpp will argue that Gottingen(WWI standard) outperforms NACA16 at high speed. I'll remind you that NACA-16 airfoil was widely used after WWII until 1970s when computer calculating method helped people designed better airfoils. To sum up, in high speed diving:

1)P47 has less advance ratio than fw190a8.
2)P47 has NACA-16 lower drag airfoil than fw190a8.
3)P47 has 4-blade prop rather than fw190a8's 3-blade.

In future, if someone finds the proof or calculates out that fw190A8 Gottingen 3-blade prop only has 30% efficiency in high speed diving while P47 has 75% with 4-blade NACA-16 airfoil, don't be surprised because that will perfectly explain why Fw190G was badly outdived by P47D at 65 degree in Italy 1943 summer.


How about 0.7 Mach comparation of 3-blade vs 4-blade efficiency? That's more interesting. But I guess the truth will change il2's diving FM.