Me-410 vs Mosquito combat

[Juha]

Originally Posted by Paul Thompson

... The two-stage supercharger on the Lancaster's Merlin 22 ...

Hello Paul
Merlin 22 had a two-speed supercharger not a two-stage. The 60 series Merlins were the first Merlins with two-stage superchargers.

[Paul Thompson]

Originally Posted by Juha

Hello Paul
Merlin 22 had a two-speed supercharger not a two-stage. The 60 series Merlins were the first Merlins with two-stage superchargers.

Hello Juha,

Thank you for correcting my glaring error. It does reinforce my overall point, since the one-stage Merlins had much worse altitude performance than the American engines fitted with turbosuperchargers.

Since we are discussing the subject, do you happen to know a source that lists the critical altitudes for various Second World War aero engines? Various books that I have suffer from inconsistencies, as well as clearly inaccurate conversions from metric to Imperial units.

Regards,

Paul

[Juha]

Not really but one good place to start is http://www.enginehistory.org/ especially the Model Designations of U.S.A.F Engines (http://www.enginehistory.org/ModDesig/SecI.pdf). In it there is info on the US engines and so also on those Merlin versions produced by Packard. Remember that a static engine has lower critical altitude than a fast moving one so it is important to know if the ram effect is taken in the account or not, also the boost level has effect on the FTH and if in slightest doubt, the imperial-metric and vice versa conversions should be checked by calculating them by oneself.

[Kutscha]

Didn't the P-38 have turbocharger problems?

[Paul Thompson]

Originally Posted by Juha

Not really but one good place to start is http://www.enginehistory.org/ especially the Model Designations of U.S.A.F Engines (http://www.enginehistory.org/ModDesig/SecI.pdf).

Juha,

Thank you, this is a very helpful list! Since I am not an engineer, I am not at all sure to what extent the various data account for the ram effect. The basic data, especially for Soviet engines, usually lists just horsepower-altitude combinations, sometimes with the boost level also provided.

On the specific issue of boost, I am looking for a reliable conversion table. Here is a link to one I've found - http://www.fittings.com.tw/news/Pres...on%20Table.pdf

Taking this table and using the late-war Bf 109G as an example, its boost pressure of 1.42 ata should be equal to 1044.5 mm Hg. How does that translate into the British measure of lb./sq.in ?

Regards,

Paul

[Paul Thompson]

Originally Posted by Kutscha

Didn't the P-38 have turbocharger problems?

Hello Kutscha,

It did, of two kinds as far as I know. First, the turbochargers did not always provide the same power for each engine, creating a problem of assymetric thrust. Second, there were problems with the low ambient temperatures at high altitudes. While these issues were significant, they shouldn't obscure the fact that the P-38 was the first effective long-range escort fighter used by the Allies, making an extremely important contribution to victory in the Mediterranean from December 1942 onwards.

Regards,

Paul

[Kutscha]

Paul, this should help answer your question,

[Paul Thompson]

Originally Posted by Kutscha

Paul, this should help answer your question,

Kutscha, you seem to have lost the attachment to your message. Thank you for your help!

[Kutscha]

I was afraid of that happening Paul.

Do an image search for 'equivalent boost pressure conversion chart'

[Paul Thompson]

Originally Posted by Kutscha

I was afraid of that happening Paul.

Do an image search for 'equivalent boost pressure conversion chart'

No problem, looks like I got it - see ww2aircraft.net/forum/attachments/engines/228489d1363748979t-ata-inches-hg-equivalent-boost-pressure.jpg

It is a fairly low resolution image, but I have got the gist of it. I will have a crack at a couple of caluclations this evening.

Regards,

Paul