March until October of 1940: fighters' ranking

[Jabberwocky]

In WWII, it just so happens that American bombers and their escort fighters had two stage superchargers, allowing them to fly at altitudes above anything the Germans and Japanese were effective at.

B-17, B-24, P-38 and P-47 were all turbocharged. The P-51 was supercharged (but it was a British engine, and in the P-51 it only got a 2 speed supercharger into service in December 1943).

The Japanese did struggle to get engines producing high levels of power above 25,000 ft, but the Germans ... not so much.

The later 1943 and 1944 models of the DB-605 generally had full throttle rated altitudes between 6200m and 8000m (20,500ft and 26,400ft).
DB 605 AS and DB 605 ASM had FTHs of 7800m (25,600ft) - which is only about 1500 ft lower than the FTH of the Merlin 61/63/V-1650-3.
DB 605 DB and DB 605 DB had FTHs of 6800 m (22,300 ft) - which is about 2000 ft higher than the FTH of the Merlin 66/V-1650-7.

 

[tomo pauk]

B-17, B-24, P-38 and P-47 were all turbocharged. The P-51 was supercharged (but it was a British engine, and in the P-51 it only got a 2 speed supercharger into service in December 1943).

P-51 escorting the heavies have had the engine with a 2-stage supercharger.
On ths other A/C listed there, the turbocharger performed the 1st stage of supercharging, the engine-stage superchargers performed the 2nd stage of supercharging. Yes, we call those 'turbocharged engines', but still the number of stages of supercharging there was 2.

The Japanese did struggle to get engines producing high levels of power above 25,000 ft, but the Germans ... not so much.

The later 1943 and 1944 models of the DB-605 generally had full throttle rated altitudes between 6200m and 8000m (20,500ft and 26,400ft).
DB 605 AS and DB 605 ASM had FTHs of 7800m (25,600ft) - which is only about 1500 ft lower than the FTH of the Merlin 61/63/V-1650-3.
DB 605 DB and DB 605 DB had FTHs of 6800 m (22,300 ft) - which is about 2000 ft higher than the FTH of the Merlin 66/V-1650-7.

A big engine has it's appeal
Problem with the DB 605 engines with big superchargers was their too late appearance, IIRC the DB 605AS was available by mid-1944, the DB 605D by late 1944.
Engine power vs. altitude of the late DB 605s is certainly on par on what the 2-stage supercharged Merlins in service were making.

 

[John Vasco]

I just posted it as a "aside" to add to the discussion, part of my background was in ultrasonics which is the same technology as far as spurious signals go, so I find such things interesting. I always understood that Chain Home just viewed outwards to sea, in fact if you read The Radar Pages Radar Pages Home page it "looked" mainly out to sea but also generated signals behind the masts, this presented an additional problem to the RDF operators. To answer your question literally, it was always the case because the operators first task was to establish whether the signal they were looking at was from in front or behind the transmitters. If you havnt read it, it is a great read and explains a lot about the problems of Fighter Command during the BoB especially in October.

Thanks for your previous post - I did not know that before. In the meantime, I looked things up on the internet and indeed read that the Operators had first of all to set the receivers correctly. I'd read through your link also, but when it started to get technical I was quickly left behind! Thanks again for the info.

 

[wuzak]

The later 1943 and 1944 models of the DB-605 generally had full throttle rated altitudes between 6200m and 8000m (20,500ft and 26,400ft).
DB 605 AS and DB 605 ASM had FTHs of 7800m (25,600ft) - which is only about 1500 ft lower than the FTH of the Merlin 61/63/V-1650-3.
DB 605 DB and DB 605 DB had FTHs of 6800 m (22,300 ft) - which is about 2000 ft higher than the FTH of the Merlin 66/V-1650-7.

At what boost/power levels?

 

[BiffF15]

P-51 escorting the heavies have had the engine with a 2-stage supercharger.
On ths other A/C listed there, the turbocharger performed the 1st stage of supercharging, the engine-stage superchargers performed the 2nd stage of supercharging. Yes, we call those 'turbocharged engines', but still the number of stages of supercharging there was 2.



A big engine has it's appeal
Problem with the DB 605 engines with big superchargers was their too late appearance, IIRC the DB 605AS was available by mid-1944, the DB 605D by late 1944.
Engine power vs. altitude of the late DB 605s is certainly on par on what the 2-stage supercharged Merlins in service were making.

Tomo,

I thought the turbo was the "second" or high altitude stage, and the engine driven supercharger was the first stage. Why am I wrong? (I genuinely curious and not being my standard smart arse).

Cheers,
Biff

 

[Shortround6]

Jumping on Tomo's answer.

It sort of depends on which way you look at the air flow.
The air flow goes from the intake/scoop through the first stage and then through the second stage where the pressure builds even further and then to the intake manifold/cylinders.
The engine driven stage (or stage closest to the intake manifold) is the 2nd stage.
The stage that is first compressing the outside ambient air is the 1st stage.

 

[Howard Gibson]

Tomo,

I thought the turbo was the "second" or high altitude stage, and the engine driven supercharger was the first stage. Why am I wrong? (I genuinely curious and not being my standard smart are).

Cheers,
Biff

The Americans were the only ones who got turbochargers into production during WWII. Typically, the various Pratt & Whitney and Wright radial engines had built-in superchargers. The turbocharger effectively was part of the airframe. The engine air entered the turbocharger, and it was then pumped into the engine supercharger. The best place for an intercooler would be the output of the engine supercharger.

 

[Howard Gibson]

B-17, B-24, P-38 and P-47 were all turbocharged. The P-51 was supercharged (but it was a British engine, and in the P-51 it only got a 2 speed supercharger into service in December 1943).

The Japanese did struggle to get engines producing high levels of power above 25,000 ft, but the Germans ... not so much.

The later 1943 and 1944 models of the DB-605 generally had full throttle rated altitudes between 6200m and 8000m (20,500ft and 26,400ft).
DB 605 AS and DB 605 ASM had FTHs of 7800m (25,600ft) - which is only about 1500 ft lower than the FTH of the Merlin 61/63/V-1650-3.
DB 605 DB and DB 605 DB had FTHs of 6800 m (22,300 ft) - which is about 2000 ft higher than the FTH of the Merlin 66/V-1650-7.

As far as I know, all the WWII aeroplane engine superchargers were on centrifugal blowers. To get high pressure on something small, like an automobile engine, you have to consider using a positive displacement blower like a Roots blower.

If you want substantially more pressure into your aircraft engine without sacrificing airflow, the solution is two centrifugal blowers in series. The American turbochargers blowing air into the engine superchargers achieved this, as did the two-stage centrifugal blowers geared to the crankshafts of the Merlin and Griffon engines. The Rolls Royce/Packard superchargers ran at two speeds, allowing good performance at both low and high altitudes. P-47s were successful at low altitude late in the war because the Germans had run out of fuel and good pilots.

Definitely, the Rolls Royce blowers were operating at supersonic speeds. There is only so much you can do with a single stage supercharger. The Germans were in very bad shape at 30,000ft against the two-stage Thunderbolts and Mustangs.

 

[Howard Gibson]

The boys at North American apparently didn't get that memo.

In other words, the Americans got lucky. They designed a fantastic airframe, and they got their hands on a very good engine with a two-stage supercharger. If the Germans had developed laminar flow airfoils and two-stage superchargers, strategic bombing would have been suicidal. Strategic bombing caused combat at altitudes that suited Thunderbolts and Mustangs.

The Mustang was developed into a long range escort. It was not designed to be one.

 

[Thumpalumpacus]

In other words, the Americans got lucky. They designed a fantastic airframe, and they got their hands on a very good engine with a two-stage supercharger. If the Germans had developed laminar flow airfoils and two-stage superchargers, strategic bombing would have been suicidal. Strategic bombing caused combat at altitudes that suited Thunderbolts and Mustangs.

The Mustang was developed into a long range escort. It was not designed to be one.

Right, we got lucky. But -- the laminar-flow wing was just as much a tech advance as a twin-charged engine, no? Superior tech doesn't only exist in the powerplant.

We go lucky with the Corsair as well.

 

[Jabberwocky]

A big engine has it's appeal
Problem with the DB 605 engines with big superchargers was their too late appearance, IIRC the DB 605AS was available by mid-1944, the DB 605D by late 1944.

Maybe shade earlier for the AS

From some quick online research (*caveats for accuracy apply*), the DB 605AS completed testing towards the end of 1943 and the engine entered combat service sometime during the first third of 1944. It seems there were three Luftwaffe units (JG 1, JG 5 and JG 11) had small numbers of 10G-5/AS and 109G-6/AS in service during April 1944 (or at least that's the earliest I can find).

According to a 2008 Il-2 Sturmovik forum post by Kurfurst (noted 109 aficionado and occasional sparring partner ), 109G-6/AS production/retrofit figures were:
1943: 2 aircraft
Feb 1944: 26 aircraft
Mar 1944: 65 aircraft
April 1944: 95 aircraft

May through August records lost

Sep 1944: 14 aircraft
Oct 1944: 2 aircraft
Nov 1944: 1 aircraft

At what boost/power levels?

605 AS: 1200 PS at 8000m (not sure about ata, maybe 1.3??)
605 ASM: 1150 PS at 7800m (assuming that's without MW-50 injection)

605 DB: 1285 PS at 6800m at 1.45 ata
605 DC: 1285 PS at 6800m at 1.45 ata

At least that what the data sheets I have say.

 

[pbehn]

Thanks for your previous post - I did not know that before. In the meantime, I looked things up on the internet and indeed read that the Operators had first of all to set the receivers correctly. I'd read through your link also, but when it started to get technical I was quickly left behind! Thanks again for the info.

The electronics are over my head but it is worth skimming over that, lots of interesting "stuff" in there. When the Germans investigated CH with a Zeppelin all they found was a wall of "noise", they didnt realise how much it had been optimised to make a very primitive system work well. By primitive I mean two or three years behind the best available in research labs. It takes two to three years to get a system working reliably, then mass produced and installed with trained operators.

 

[tomo pauk]

Tomo,

I thought the turbo was the "second" or high altitude stage, and the engine driven supercharger was the first stage. Why am I wrong? (I genuinely curious and not being my standard smart are).

Cheers,
Biff

Shortround6 answered this - basically, we count the stages as the air enters them. In P-43, -47, -38, B-17, -24, air was always 1st entering the compressor 'half' of the turbo-compressor (bear with me here), where it got compreessed, and then was routed to the interocooler (to lower the temperature of the compressed air) and then to the engine-stage compressor via carburetor. In order to avoid over-boosting the engine, waste gates were used so the turbo will be spinning slow at low altitudes (waste gates open), and ever faster up to the rated altitude (waste gates closing with altitude).

The Americans were the only ones who got turbochargers into production during WWII. Typically, the various Pratt & Whitney and Wright radial engines had built-in superchargers. The turbocharger effectively was part of the airframe. The engine air entered the turbocharger, and it was then pumped into the engine supercharger. The best place for an intercooler would be the output of the engine supercharger.

In a radial engine, there was next to no space for an intercooler past the engine-stage S/C, unless a wholesale redesign of an engine is done.
Germans also put the turbochargers in use to help out the BMW 801 on some Ju-388s; granted, this was a very small quantity vs. what the Americans did.

 

[tomo pauk]

In other words, the Americans got lucky. They designed a fantastic airframe, and they got their hands on a very good engine with a two-stage supercharger. If the Germans had developed laminar flow airfoils and two-stage superchargers, strategic bombing would have been suicidal. Strategic bombing caused combat at altitudes that suited Thunderbolts and Mustangs.

The Mustang was developed into a long range escort. It was not designed to be one.

Right, we got lucky. But -- the laminar-flow wing was just as much a tech advance as a twin-charged engine, no? Superior tech doesn't only exist in the powerplant.

We go lucky with the Corsair as well.

Americans got lucky? Let's try 'Americans were usually doing the job right' statement?

 

[pbehn]

Americans got lucky? Let's try 'Americans were usually doing the job right' statement?

To paraphrase Arnold Palmer. The more research you do into engines metallurgy and aerodynamics the luckier you get.

 

[Thumpalumpacus]

Americans got lucky? Let's try 'Americans were usually doing the job right' statement?

We got lucky in that adding the Merlin to the Mustang proved not so troublesome, and gave us a LR fighter capable of tangling with almost anything.

With the Corsair, we got lucky in finding that the inverted-gull wing reduced drag at the wing roots, allowing the plane a higher turn of speed.

 

[Howard Gibson]

Americans got lucky? Let's try 'Americans were usually doing the job right' statement?

In WWII, the Americans had more engineering resources than anyone else. The fact remains that the Mustang was designed mostly in a panic rush by people with limited experience in fighter design. It all worked out in the end, but it was not a good war strategy.

The Germans had their share of good aircraft and engine designers, but they missed the laminar flow wings and two-stage superchargers.

 

[Howard Gibson]

With the Corsair, we got lucky in finding that the inverted-gull wing reduced drag at the wing roots, allowing the plane a higher turn of speed.

My understanding is that the Corsair's reverse gull wings solved a bunch of problems, including good airflow around the wing roots. It was not a lucky guess.

 

[Thumpalumpacus]

My understanding is that the Corsair's reverse gull wings solved a bunch of problems, including good airflow around the wing roots. It was not a lucky guess.

I could be wrong, but I have been under the impression they were designed to allow for clearance for the large prop, and that the reduced drag was an ancillary benefit noticed later. I'm happy to be corrected if I am wrong. Getting good dope is why I read here.

 

[John Vasco]

In WWII, the Americans had more engineering resources than anyone else. The fact remains that the Mustang was designed mostly in a panic rush by people with limited experience in fighter design. It all worked out in the end, but it was not a good war strategy.

The Germans had their share of good aircraft and engine designers, but they missed the laminar flow wings and two-stage superchargers.

I think it is also fair to say that the Americans got the benefit of what was happening in Europe, with regard to what the RAF and Luftwaffe were putting up in the skies in 1940. A Bf 109 and Bf 110 were shipped to the States in 1941, and I expect we also provided info on our own two fighters. What was discovered (and I know Vultee produced a comprehensive report and 20 minute film re the Bf 110) probably helped future thinking and development in some way. Which was no bad thing, given the ultimate performance of the US fighters in the last 12 months of the war over Germany, which was superb! And I say that as a Brit...