enginehistory.org

[jjuutinen]

Since Whitney´s bible on the subject does not provide the answer, maybe you can. With 100/130 fuel plus water injection, what would the dash-111/113 Allison been capable of at WER? My estimate would be about 1900-2000 hp at sea level.

Second cause of wonder is why paddle bladed props were never fitted to the standard P-38. There should have been real technical reason against it. Yet considerable improvement in performance was observed with the P-47 with the new prop. It seems that the improved prop was only planned for the K model plus some protos, but never on standard Lightnings.

[tmcdaid]

Is it because the the V1710s had significantly less power under normal operating conditions than the R2800s? From what I've read, without the paddle blades, the R2800s were somewhat overpowering the propellor. Fewer (and longer) blades are more desirable from a transmission efficiency standpoint, but sometimes you need more and/or wider blades to adequately transmit the power and still fit within the physical limitations of the overall aircraft design.

[jjuutinen]

I don´t buy that. Please see the prop the P-51D had: four wider blades.

[tmcdaid]

Excellent point. Although, what about the diameter of the props? I haven't found anything specific about the prop size on the 38, but I did find vague references that suggest the later 47s had a 13' prop while 51 had an 11'2" prop. The 13 footer gives you more than 35% more disc area (although the useful area is probably closer), so the power difference may not be totally out of the question. Surely someone out there has definitive information on this?

I also found one reference to a single P-38 (H model, maybe?) built with the higher-powered Allison and it mentioned that it had paddle props, although no info on size or number of blades. They weren't put into production because of engine availability issues. I assume that's because of the huge demand for V-1710s for existing planes. Interesting.

Anyone have more and/or better information?