Why still no dive acceleration difference?

[BlackBerry]

Originally Posted by RegRag1977

Thanks again for this interesting topic.

I just want to remind that 4-blade propeller fighter aircraft were used before WW2, so perhaps it is not really something as revolutionary as we may think?

Some german design (not produced in great series or prototypes) using 4 blade prop in the 30ies are for instance DO C1 nightfighter (1931) , or Arado 64 experimental (1931).

The oldest fighter design i know using a 4-blade propeller is the german WW1 fighter Siemens Schuckert SSW DIII series (1917-1918 ), that was considered as a very capable fighter at the time, once its cooling problem solved.

The key is airfoil. IMO, at high speed above Vmax:

3-blade Gottingen=3-blade RAF=3-blade ClarkY=3-blade NACA16=4-blade Gottingen/RAF/ClarkY


However, 4-blade NACA16 is an exception. NACA16 was developed after 1939. There are three disadvantages of German propeller edficiency in late WWII AT HIGH SPEED ABOVE Vmax,ie 0.7Mach.

1)smaller diameter with same rpm as allied, so bigger advance ratio, less efficiency(maybe 10-15%). This is confirmed easily.

2) late period wide chord airfoil gives better performance within Vmax, but worse above Vmax(maybe 10%). This is also comformed.

3)allied 4-blade Naca16 outperforms 3-blade naca16 above Vmax. This has NOT been confirmed yet, but probably. maybe 7-10% efficiency improvement.


The third issue is very important, if it is confirmed, allied may have 30% efficiency advantage over German/Russia when above Vmax. If not, or 4-blade naca16 even worse than 3-blade naca16 at high speed. The allied advantage will not be profound.

30% efficiency advantage is around 500-600 HP in late WWII, hugh difference, key role in high speed dive/flight, vital for P47P51 high speed tactics.