three prop mustang

fly boy · Mar 2, 2009

would it have made any diffrance?

Colin1 · Mar 2, 2009

fly boy said:
would it have made any difference?

The P-51F was to be fitted with a 3-bladed prop
I'm playing football now so more later if I can dig it up

drgondog · Mar 2, 2009

The Brits experimented with three bladed props on Mk III reporting no significant performance results,

As Colin noted the 3rd XP-51F had a three blade Aeroprop prop and the Xp-51G had the 5 blade Rotol prop. The XP-51G did 495mph but more likely because the then experimental Rolls 14 S.M. engine which had more than 325 hp than the F's 1650-3's.

antoni · Mar 2, 2009

The XP-51F was a lightweight version using plastic and other light materials. The Aeroproducts prop had hollow-steel blades and was probably a weight saving feature as well. The Allison Mustangs had three blade props but in general more power requires more blades to cope with it.

Colin1 · Mar 2, 2009

antoni said:
The XP-51F was a lightweight version using plastic and other light materials. The Aeroproducts prop had hollow-steel blades and was probably a weight saving feature as well. The Allison Mustangs had three blade props but in general more power requires more blades to cope with it.

It was
and combined with all the other weight-saving measures, the gross weight of the P-51F was reduced by about 1 ton over the P-51D to 9,060lbs, empty weight to 5,635lbs to the P-51D's 7,125lbs.

I know at least one of the hollow-blade screws tried by NAA on the P-51 had horrible vibration problems but I can't remember which one.

I'm curious as to the efficacy of more blades for more power, the Germans didn't seem to think this was the case; the Bf109K had a 4-bladed screw but that seemed to be the exception rather than the rule. Can anyone expand on that?

KrazyKraut · Mar 2, 2009

Only the K-14 that never entered production was designed for the 4 blade prop. All production K-4s had a 3 blade propeller. Instead of increasing the number of blades, Germans increased chord (e.g. late Fw 190 Ds or Ta 152). AFAIK this is the easier yet less aerodynamically efficient option. In that speed or engine power region the difference is small.

drgondog · Mar 2, 2009

Colin1 said:
I know at least one of the hollow-blade screws tried by NAA on the P-51 had horrible vibration problems but I can't remember which one.

The 51K used the Aeroproducts hollow prop and at one time it had a 19% rejection rate before they solved the problem.

It was lighter, and had a self contained oil resevoir and was able to make more rapid blade pitch changes.

drgondog · Mar 2, 2009

KrazyKraut said:
Only the K-14 that never entered production was designed for the 4 blade prop. All production K-4s had a 3 blade propeller. Instead of increasing the number of blades, Germans increased chord (e.g. late Fw 190 Ds or Ta 152). AFAIK this is the easier yet less aerodynamically efficient option. In that speed or engine power region the difference is small.

I would like to see the design studies on those blades. In comparison to US props the German designs were smaller diameter, lower rpm and broader chord (as you stated).

This would have the effect of always keeping the tip speed well below supersonic with the attendant reduction in compressibility effects in drag on the prop airfoil.

The 3 Blade Aeroprop prop that RAF experimented with on P-51B were also smaller diameter than the 11'+ Hamilton Standard, more similar in shape to 109/190 props, but operated at same rpm with no significant change in performance.

three prop mustang

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