Aircraft engines

[Ed Rotondaro]

Hi all:

A while back I read "Fire in the Sky" by Dr. Eric Bergerud which covers the aerial struggle in the Solomons. He has several chapters on aircraft and their evolution in the pre-war years that give good insights into how the various designs performed. This brings up my question:

Which type of engine was generally better at high altitudes? Air cooled radial engines of liquid cooled in-line engines? The reason I ask is that I have read conflicting material that confuses me (not a hard thing to do these days). For instance, there are some authorities who feel that the P-47 with its massive radial engine was the best high altitude fighter of the war. The FW-190 had a radial engine and had poor performance above 20,000 feet as did the Japanese Zero. The Germans remedied the problem by creating the long nosed FW-190D the so-called "Dora" which had a liquid cooled engine. Yet the British on the other hand installed Griffon liquid cooled engines into late model Spitfires to improve their medium and low altitude performance, especially against V-1 cruise missiles. They also used their Tempest variant of the Typhoon for similar missions and it gained a reputation as one of or possibly the premier low altitude fighter of the war. The P-38 Lightning even super chargers on its in-line engines still never had the best performance at higher altitudes when compared to the P-47.

I know that no matter what engine design is selected, all aircraft benefit from and indeed require a supercharger for better high altitude performance due to the lower content of oxygen in the upper atmosphere. This certainly was one of the ill-fated P-39 Airacobra's flaws, the lack of any sort of turbo or supercharger to improve engine performance made it sluggish even at medium altitudes where the Zero feasted on it.

Radial engined US navy fighters consisted outperformed their Japanese counterparts at medium and high altitudes due to their massive Wright Cyclone engines. So was it simply better engine design? Or did the type of engine give the aircraft the edge at higher altitudes? Any thoughts or information you can share on this?

Somewhere in sunny Southern California, Dennis the forum hound has picked up the scent and is licking his chops LOL!

[old_pop2000]

Hi all:

A while back I read "Fire in the Sky" by Dr. Eric Bergerud which covers the aerial struggle in the Solomons. He has several chapters on aircraft and their evolution in the pre-war years that give good insights into how the various designs performed. This brings up my question:

Which type of engine was generally better at high altitudes? Air cooled radial engines of liquid cooled in-line engines? The reason I ask is that I have read conflicting material that confuses me (not a hard thing to do these days). For instance, there are some authorities who feel that the P-47 with its massive radial engine was the best high altitude fighter of the war. The FW-190 had a radial engine and had poor performance above 20,000 feet as did the Japanese Zero. The Germans remedied the problem by creating the long nosed FW-190D the so-called "Dora" which had a liquid cooled engine. Yet the British on the other hand installed Griffon liquid cooled engines into late model Spitfires to improve their medium and low altitude performance, especially against V-1 cruise missiles. They also used their Tempest variant of the Typhoon for similar missions and it gained a reputation as one of or possibly the premier low altitude fighter of the war. The P-38 Lightning even super chargers on its in-line engines still never had the best performance at higher altitudes when compared to the P-47.

I know that no matter what engine design is selected, all aircraft benefit from and indeed require a supercharger for better high altitude performance due to the lower content of oxygen in the upper atmosphere. This certainly was one of the ill-fated P-39 Airacobra's flaws, the lack of any sort of turbo or supercharger to improve engine performance made it sluggish even at medium altitudes where the Zero feasted on it.

Radial engined US navy fighters consisted outperformed their Japanese counterparts at medium and high altitudes due to their massive Wright Cyclone engines. So was it simply better engine design? Or did the type of engine give the aircraft the edge at higher altitudes? Any thoughts or information you can share on this?

Somewhere in sunny Southern California, Dennis the forum hound has picked up the scent and is licking his chops LOL!


Sniff! Sniff!:p

Well, Ed. It doesn't make a difference if the engine is air cooled or water cooled. Remember that air density decreases with altitude. Four stroke, Otto cycle gasoline engines require air to function. Specifically, sea level pressure air of a certain density to function at full rated power. As an aircraft climbs, the air density decreases, the power out of the engine decreases. To alleviate that, we use supercharging. Supercharging simply takes ambient air, compresses it to a known density and then pushes it into the combustion chamber. The higher you go, the more the compression ratio has to be between the ambient and the internal air feeding into the engine. So, we add stages to the supercharger. There are two style of superchargers. Turbochargers like those on bombers, transports and the P-38 use exhaust gases to turn a turbine and that turns a compressor. Or, a gear driven supercharger for use on single engined fighters. Normally, you will see an aircraft engine with a two speed, two stage supercharger giving an aircraft excellent high altitude performance. The Zeke's first engine only had a single stage supercharger so it was limited in its altitude performance.

Does that help, or did I confuse me.:D

[Ed Rotondaro]

Sniff! Sniff!:p

Well, Ed. It doesn't make a difference if the engine is air cooled or water cooled. Remember that air density decreases with altitude. Four stroke, Otto cycle gasoline engines require air to function. Specifically, sea level pressure air of a certain density to function at full rated power. As an aircraft climbs, the air density decreases, the power out of the engine decreases. To alleviate that, we use supercharging. Supercharging simply takes ambient air, compresses it to a known density and then pushes it into the combustion chamber. The higher you go, the more the compression ratio has to be between the ambient and the internal air feeding into the engine. So, we add stages to the supercharger. There are two style of superchargers. Turbochargers like those on bombers, transports and the P-38 use exhaust gases to turn a turbine and that turns a compressor. Or, a gear driven supercharger for use on single engined fighters. Normally, you will see an aircraft engine with a two speed, two stage supercharger giving an aircraft excellent high altitude performance. The Zeke's first engine only had a single stage supercharger so it was limited in its altitude performance.

Does that help, or did I confuse me.:D

Dennis:

Heh Heh, that certainly helped with superchargers and turbochargers, but what about which engine choice was better at altitude and why? (He asks knowing full well that Dennis will rise to the bait!)

[old_pop2000]

Dennis:

Heh Heh, that certainly helped with superchargers and turbochargers, but what about which engine choice was better at altitude and why? (He asks knowing full well that Dennis will rise to the bait!)

You weren't paying attention, Ed, me lad. It doesn 't matter.

It depends on the environment of the aircraft. On a carrier, I want a simple air cooled radial. They don't need glycol coolant, they are more rugged and give just as much power. They are not as aerodynamic, but designers have come up with some neat, streamlined cowlings.

On the land, an inline engine is far easier to streamline, and ease of maintence isn't as critical, neither is the flammable ethylene glycol.

My personal preference is the radial, especially the R-2800 with two speed, two stage supercharger. 2000 hp and noisy as the dickens. When they fly over my house, I can always tell.

Now, quick asking so many questions and go to your room. :p:D:D

[old_pop2000]

Quick note:

P-47 had an exhaust driven turbosupercharger. They tend to be more efficient. Superchargers are just another load on the engines crankshaft.

Ok

[Ed Rotondaro]

You weren't paying attention, Ed, me lad. It doesn 't matter.

It depends on the environment of the aircraft. On a carrier, I want a simple air cooled radial. They don't need glycol coolant, they are more rugged and give just as much power. They are not as aerodynamic, but designers have come up with some neat, streamlined cowlings.

On the land, an inline engine is far easier to streamline, and ease of maintence isn't as critical, neither is the flammable ethylene glycol.

My personal preference is the radial, especially the R-2800 with two speed, two stage supercharger. 2000 hp and noisy as the dickens. When they fly over my house, I can always tell.

Now, quick asking so many questions and go to your room. :p:D:D

Dennis:

You live for this stuff LOL! Still it becomes interesting that either engine can do the job providing its putting out enough power and has an effective supercharger to boost high altitude performance.

[Ed Rotondaro]

Quick note:

P-47 had an exhaust driven turbosupercharger. They tend to be more efficient. Superchargers are just another load on the engines crankshaft.

Ok

Dennis:

That makes sense, one less thing to go wrong with the aircraft while still getting the boost needed.

[old_pop2000]

Dennis:

That makes sense, one less thing to go wrong with the aircraft while still getting the boost needed.


They do take up more room. The booms on the P-38 were used to house the exhaust turbines. If you ever get to see a picture, or a real one, look on top of the booms. The circular device with blades is the exhaust turbine. I thing that is what they call it.

[Ed Rotondaro]

They do take up more room. The booms on the P-38 were used to house the exhaust turbines. If you ever get to see a picture, or a real one, look on top of the booms. The circular device with blades is the exhaust turbine. I thing that is what they call it.

Dennis:

Thanks, I will look for more close up pictures of the booms.