School me on aircraft engines

Oh yeah and at altitude radials open up all their seals and spew oil everywhere. Cowlings were first introduced on radials in the 20s to prevent oil going all over the pilot at altitude, not for streamlining. NACA developed the "close cowling" later, for streamlining, but it was never the original reason for putting cowlings on radials. It was the oil thing.

 

Not to forget the mother of all radials: Pratt & Whitney R-4360 Wasp Major - Wikipedia, the free encyclopedia

Six of them powered the B-36.

 

How many misconceptions will fit in a single post? Aircraft engines are essentially constant speed devices, and are RPM limited by the need to keep the prop tips out of the transonic range. High performance aircraft engines employ variable pitch propellers – also known as constant-speed propellers - which vary the prop’s pitch based on load to maintain a constant engine/prop RPM. Aircraft engine designers know these things, and seek to develop engines with a torque curve that peaks in the usable RPM range. Altitude has nothing to do with it. You want maximum torque in the usable RPM range whether at low or high altitude. Aircraft piston engines, whether inline or radial, do not “overspeed” unless the prop governor fails.

Mechanical superchargers and turbosuperchargers serve the same purpose, and while both have their advantages and disadvantages, one is not inherently better than the other. In fact the P&W R2800 installations in the F6F and F4U used two stage, two speed mechanical superchargers, while the P&W R2800 installation in the P-47 used a turbo supercharger. Do you know something that the Pratt & Whitney engineers didn’t? Turbochargers do not “overspeeds off its dial” unless the waste gate fails.

Since torque is a rotational force, how in the world does the length of the crankshaft figure into torque production?

Hub Zemke flew both the inline-engined P-51 and the radial-engined P-47 in combat. While he thought the P-51 was the better overall fighter, his opinion was that the P-47 was superior above 25,000 ft.

 

Where do you get this stuff? ‘Splain to me why a seal on a radial would open at altitude while a seal on an inline would not. Both the early “Townsend Rings” (also called “Speed Rings”) and the later NACA cowlings were developed for two purposes: to reduce drag and to aid engine cooling. If the early “speed rings” had been designed to “prevent oil going all over the pilot”, they would have failed miserably since the air flow still exits the back of the ring and would do nothing to stop entrained oil from reaching the pilot. Maybe you’re confusing radial engines with rotary engines and their castor oil.

 

As an aside to FJH's comments on the B-29 engine cowling... While in high school I worked w/ an older man who had served as a USAAC mechanic on the B-17 in the US & later the B-29 on Guam. Prior to his military induction he was employed by the Fisher Body Div. of General Motors. They were contracted by Boeing to process the build & design & engineer the fixtures & jigs for the production B-29 engine nacelles. The nacelle was more complicated to build than was the entire fuselage of the aircraft. While Boeing was able to design the nacelle & build prototype versions they needed someone w/ more manufacturing expertise to get the nacelles into production at the rate needed for the war. Even at that the nacelle didn’t perform as Boeing had hoped it would. The actual use of the plane also saw it w/ much greater payloads than first envisioned which aggravated cooling issues.
When he was training on the B-17 he was teased for claiming that soon the US would be operating a much larger heavy bomber w/ great range & bomb load than the B-17’s & -24’s. His fellow soldiers thought it ridiculous to imagine anything larger than a B-17.
Re: The B-36... one of the issues w/ the engine problems w/ the aircraft is due to the decision to place the engines “backwards” on the wing. Parts of the engine designed to be in the airflow were now placed out of it causing overheating & parts expected to be heated by engine heat were in the flow causing icing problems.

 

Speaking of cowlings; "proper" cowling design can minimize (but not eliminate) the drag penalty of a radial over an inline engine. The Vought Corsair put their oil coolers in the leading edge of the wing versus in the cowling in the manner of the Grumman Hellcat (thus creating less frontal area and a thinner air frame over all). The aircraft was definitely faster for the same engine (wing root drag was another difference, but I'm not sure how big of one comparatively). Grumman learned their lesson and applied this to the Bearcat.

 

Well, to the first, it is because the crankshaft is so short.

 

Not all the variants of the 190 had radials. The Dora 9 had an inline engine.

 

A Piaggio, forget the exact designation. But, Piaggios did tend on the pretty side, just look at the P108 bomber.