An Excellent Introduction to WW2 Aircraft Engines

[Venturi]

Excellent article about piston engine performance fundamentals.

http://www.pacificaviationmuseum.org/pearl-harbor-blog/superchargers-and-turbochargers/

It primarily explains quite accurately and simply (with a few minor technical errors here and there), the basics behind all fighter and bomber piston engines in WW2. It is focused on American aircraft, but all concepts are applicable to Soviet, German, Japanese, and British a/c as well.

As we all know, or suspect after flying in IL-2 for a while, the aircraft, regardless of any other factor, is only as good as the engine in it.

 

Edited August 25, 2017 by Venturi

[I./JG1_Deschain]

Excellent article about piston engine performance fundamentals.

 

http://www.pacificaviationmuseum.org/pearl-harbor-blog/superchargers-and-turbochargers/

 

It primarily explains quite accurately and simply (with a few minor technical errors here and there), the basics behind all fighter and bomber piston engines in WW2. It is focused on American aircraft, but all concepts are applicable to Soviet, German, Japanese, and British a/c as well.

 

As we all know, or suspect after flying in IL-2 for a while, the aircraft, regardless of any other factor, is only as good as the engine in it.

 

 

 

It is very basic though, just general concepts without any numbers to look at, but i guess it fits "introduction" description :D

 

Sadly i dont have enough time to translate this : http://www.palba.cz/viewtopic.php?t=3027 thats pretty exhaustive

Edited August 25, 2017 by Deschain

[Retnek]

One of the most interesting articles I read about piston engines deals with (from a today's point of view) failed concepts - a lot of aero-engines included. It's written in German, but one can download and easily translate it:

 

Translation: https://translate.google.com/?tr=f&hl=en

 

Article: https://www.haw-hamburg.de/pers/Gheorghiu/Labor/SKM/Anlagen/Gescheiterte_Motorkonzepte.pdf

[kestrel79]

I've seen a few videos online with a wooden model of ww2 engines and it's really cool to see everything working and what does what. I'll try to find it.

[Venturi]

Thanks for the other language articles. Understanding piston engines really makes us all better WW2 aircraft pilots.

[[CPT]Pike*HarryM]

It is interesting too how many prototype engines were built and tested but were never reliable enough and not produced. Very hard to make a good, reliable and high-power engine! 

[Venturi]

One more tiny tidbit which might add to the discussion:

 

Turbo-supercharged aircraft had a serious drawback in any kind of a dogfight where the throttle might have to be quickly changed - that is, turbo lag. Quick increases of the throttle did not bring quick increases in power output. Instead, the turbo had to spool up. This was not a big problem at lower altitudes, when the supercharger was engaged and not the second-stage turbocharger. (This is an advantage of superchargers over turbochargers in general)

 

But at high altitudes where the second-stage turbocharger was engaged, quick throttle (and especially RPM) changes did not bring quick response from the turbos. It is somewhat of a moot point in practicality (but not for modelling these engines in a sim). At high altitudes, aircraft do not have the maneuverability they have at low altitudes and denser air. Therefore, quick engine changes were not as needed. Additionally, engines were usually running hard and fast fairly continuously, in any combat situation at altitudes where the second-stage turbocharger would be engaged.

 

The advantage of turbocharging was that the engine had no parasitic loss from the second stage of a gear driven supercharger, which could be around 300hp. Of course, they also did not have the ejector - exhaust power giving them extra thrust, which the supercharged engines had...

Edited August 25, 2017 by Venturi

[ZachariasX]

Not having parasitic loss is a HUGE plus I'd say. About 1/5 of your engine power doesn't make it to the propeller in significantly supercharged engines (or in your AMG Mercedes to the wheels). A 1600 hp Merlin is a 1300 hp Merlin on second stage compressor. Loss is huge.

 

The Jug however had 2000 hp roughly up to 8000 Meters, roughly where its turbocharger reaches its limits over 20'000 rpm. But it has 2000 hp up there on the shaft and not 1/3rd less as competing planes. The Jug really shines up there. A 109 can never dream to follow a Jug through a zoom climb up there.

 

There is the turbo lag, sure. But is this as relevant at 8000 meters as it is for 109 and Yaks casing each other around the trees? I see more of a problem of making the plane look like a guppy to make a supercharger fit.

 

For me, the Jug is a fascinating aircraft. You have all the coolers to operate plus by setting turbo rpm you can even set or influence your manifold temperature. Same as in the B-17. I love A2A simulations version of those planes. There you can really learn to understand the effects of each component. You learn how to use turbos during hot and during cold athmosphere and humidity.

 

It also shows how the B-17 was worlds ahead from everything when it came out. You never find such a complicated piece of technology so simple an logic to operate. It was really made for teenagers to fly it. Safely. And it worked...

[BlitzPig_EL]

Yeah, the B 17 was amazing when you think that is was initially intended to be a maritime patrol bomber, and it's design dates to what, 1934?

[II/JG17_HerrMurf]

I've seen a few videos online with a wooden model of ww2 engines and it's really cool to see everything working and what does what. I'll try to find it.

Yes, please. That sounds pretty cool. I think the US. Air Force museum in Dayton has a cut away R2800. Really fascinating.

 

(might be a different museum - too many to remember anymore)

[Rjel]

Another nice air museum a lot of folks don't know about is at the Kalamazoo Air Zoo at the Kalamazoo, MI airport. They have a lot of unique displays including WWII A/C, a Ford Tri-motor and an SR-71. It was amazing to stand that near to such an iconic aircraft. Its size was mind boggling as was an engine from it mounted on display.

 

They also have a restoration shop to explore with several radials, a Merlin and Allison V-12s to gander at. They are currently working on restorations of an F4F and SBD recovered from Lake Michigan, where they were lost during carrier training in WWII. Well worth the visit if you're ever near the southwestern part of the lower peninsula of MI. 

 

http://www.airzoo.org/index.php

Edited August 26, 2017 by Rjel

[BlitzPig_EL]

I've had a ride in their Ford Tri-Motor.

 

Never been to the museum itself though.

[Field-Ops]

This is a good introduction indeed. I really didn't have the concept down in my head good enough. And I never really had an interest in engines until I wanted to learn more about aircraft. Car engines never did it for me. 

[Rjel]

I've had a ride in their Ford Tri-Motor.

 

Never been to the museum itself though.

That would've been an amazing experience. Unfortunately, they've retired the Tri-Motor now from flight exhibitions but I was able to get on board for a look. If you're near there, I'd recommend a visit to the Air Zoo.

[ZachariasX]

This is a good introduction indeed. I really didn't have the concept down in my head good enough. And I never really had an interest in engines until I wanted to learn more about aircraft. Car engines never did it for me.

 

In principle, there's no difference at all between aircraft and car engines as they use the same technology.

 

In reality, in aircraft you'd solve the question: "How do I make a 200 hp engine run efficiently at 180 hp?"

 

For cars, the question would be: "How do I make a 200 hp engine run efficiently at 20 hp?"

 

That these questions are more than just semantics are illustrated in Porsches failure to make an aircraft engine. The great thing about WWII aircraft engines is that you have everything, turbo, supercharger, NOx injection, etc... you have all of that and you have to manually use those components and you have the gauges to monitor their use. Cars try their best to hide whats really underneath the hood.

[Venturi]

Have to agree the principles are the same. I think of these engines as the pinnacle of internal combustion technology (minus the solid state electronics).

[Guest deleted@30725]

I thought I knew a lot about engines. I learned some stuff though particular to those era engines. Good find.

[Venturi]

It is interesting to note that most relevant engine characteristics boiled down to the type of forced induction the engine had: This characterized the altitude regimes at which the aircraft would shine and the missions it could fly.

 

Something to consider, the V-1710 in the P-40 had a single stage, single speed supercharger. The Sakai 12 in the A6M2 also had only a single stage, single speed supercharger. It wasn't until the A6M3 that a two-seed supercharger was introduced (in April 1942, and at the cost of sacrificing a large portion of the Zero's famously long range, and adding only a little top speed... but increasing critical altitude enormously)

 

People also forget that the Merlin III as used in the Spitfire Mk1 also only had a single stage, single speed s/c. And the DB601 as in the Me109 effectively had a hydraulically clutched single stage, single speed s/c.

 

All of these engines reached critical altitude at about 14-16'000 feet due to their single-stage, single-speed superchargers. This altitude limit was the MAJOR focus of ongoing American and European engine research and design - as everyone knew high altitude bombing (with turbo-supercharged bombers like the B17) was going to occur at some point.

 

So the P-40's reputation as being "altitude challenged" is only in comparison to later engines with more advanced supercharger gearing and multiple stages. It was largely IRRELEVANT at altitudes below 15,000' and was absolutely comparable to most aircraft it faced in the beginning of the war in the Pacific. But in Africa, the Germans had already introduced the Bf109F4 with Db605A - which had a critical altitude of 5.9km. This contributed heavily to the P-40's later reputation, as the German pilots could literally zoom away to altitudes where the P-40 could not fight due to loss of power.

 

However, none of these other engines could come close to comparing to the altitude ability that Turbo-supercharging gave the Allisons in the P-38, or the R2800 in the P47. The Allison engines, as used in the P38, had a supercharger as the first "stage" and a turbocharger for the second stage, enabling them to reach very high critical altitudes indeed, all the way at 22,600ft altitude! 

 

The bottom line, is that the way the RPM, mixture, and throttle were manipulated were the determining factor in how the pilots experienced the engine operation,

 

and the altitude regimes at which these engines could best perform dictated how and where the planes were best flown - and which side had the all important altitude advantage at the start of any encounter.

See attached.

Edited August 27, 2017 by Venturi

[ZachariasX]

Imagine, the B-17 had 4 different critical altitudes (some hundert feet different) on its 4 engines, due to different system components connectected to them. They would fly their mission at or very near critical altitude. Synchronizing the turbos for that was one of the charming tasks flying a B-17.

[novicebutdeadly]

It is interesting to note that most relevant engine characteristics boiled down to the type of forced induction the engine had: This characterized the altitude regimes at which the aircraft would shine and the missions it could fly.

 

Something to consider, the V-1710 in the P-40 had a single stage, single speed supercharger. The Sakai 12 in the A6M2 also had only a single stage, single speed supercharger. It wasn't until the A6M3 that a two-seed supercharger was introduced (in April 1942, and at the cost of sacrificing a large portion of the Zero's famously long range, and adding only a little top speed... but increasing critical altitude enormously)

 

People also forget that the Merlin III as used in the Spitfire Mk1 also only had a single stage, single speed s/c. And the DB601 as in the Me109 effectively had a hydraulically clutched single stage, single speed s/c.

 

All of these engines reached critical altitude at about 14-16'000 feet due to their single-stage, single-speed superchargers. This altitude limit was the MAJOR focus of ongoing American and European engine research and design - as everyone knew high altitude bombing (with turbo-supercharged bombers like the B17) was going to occur at some point.

 

So the P-40's reputation as being "altitude challenged" is only in comparison to later engines with more advanced supercharger gearing and multiple stages. It was largely IRRELEVANT at altitudes below 15,000' and was absolutely comparable to most aircraft it faced in the beginning of the war in the Pacific. But in Africa, the Germans had already introduced the Bf109F4 with Db605A - which had a critical altitude of 5.9km. This contributed heavily to the P-40's later reputation, as the German pilots could literally zoom away to altitudes where the P-40 could not fight due to loss of power.

 

However, none of these other engines could come close to comparing to the altitude ability that Turbo-supercharging gave the Allisons in the P-38, or the R2800 in the P47. The Allison engines, as used in the P38, had a supercharger as the first "stage" and a turbocharger for the second stage, enabling them to reach very high critical altitudes indeed, all the way at 22,600ft altitude! 

 

The bottom line, is that the way the RPM, mixture, and throttle were manipulated were the determining factor in how the pilots experienced the engine operation,

 

and the altitude regimes at which these engines could best perform dictated how and where the planes were best flown - and which side had the all important altitude advantage at the start of any encounter.

See attached.

 

The 109 G2 had the DB 605 not the F4.

 

Have you got a graph for the 109F-4/Z which had the GM-1 Nitrous boost?

[Venturi]

Oh, yes... that's right. The Me109F4 had the Db601E with single stage, single speed hydraulically-clutched supercharger, with critical altitude of 5km (16000 feet).

 

Sorry I do not have a power graph for the 500 some odd aircraft with the heavy equipment for the GM-1 system, which could only be used at altitudes above 6.5km on this aircraft. In fact, I believe the liability was not only in weight, but in explosive decompression of the tanks when struck by enemy fire. And the rear pilot armor had to be removed to fit the system, as well. The increase in critical altitude provided by the DB605A over the DB601E rendered the system obsolete, and for these reasons most G-1s with pressurized cockpit, and all G-2s, were not fitted with the system.

 

Later, after the turbosupercharged American aircraft were encountered, the GM-1 was reintroduced on -U2 variants of the G6 (a small minority). It provided at most 300hp above baseline HP when the engine was far above its critical altitude - in an attempt to compete at 7-9km where the P-38 and P-47 engines really shone. If engaged below the engine's critical altitude, it would detonate the engine, so was otherwise useless weight.

[kestrel79]