DB 601: 1' erhöhte Kurzleistung (1,40 ata)

[41Sqn_Banks]

http://www.scribd.com/doc/71362812/1940-Betriebs-und-Wartungsvorschrift-zum-Mercedes-Benz-Flugmotor-DB-601-A-u-B mentions the use of 1' erhöhte Kurzleistung (1,40 ata) only under take-off conditions.

Was the 1' erhöhte Kurzleistung only allowed for take-off or was it also allowed or used for combat or emergency conditions?

[Kwiatek]

1' erhöhte Abfluglestung in Db 601 A ( 1.4 Ata) and 601 Aa ( 1.45 Ata) was allowed only at low altitude from 0 km to 1.0- 1.5 km.

More over Kurzleistung in Db601A (1.3 Ata) and 601 Aa ( 1.35 Ata) was allowed only for 5 minut rating.

[Kurfürst]

I have always assumed - but could not confirm - it was meant for low altitudes only, probably because the early LW bombers like the He 111P used the DB 601A too and it was a useful extra boost for them when lifting heavy loads.

I was trying to find out a while ago wheter that was a soft limitation ('you really should not - but may - use it for other than takeoff') or a hard one (you really can't use it whatever you do).

The power curves of the DB engines draw the 1-min rating only up to about 1-1.5 km then the line cease. So I wondered, if it can be only engaged in the first supercharger speed..? But there is no evidence to such limitation (yet..?).

Unlike however the 5-min limitation for the Kurzleistung, which was a soft one, the 1' erhöhte Abfluglestung in Db 601 A ( 1.4 Ata) and 601 Aa ( 1.45 Ata) was a hard one: when pushing forward the throttle, a 60-sec clockword was engaged which automatically shut down the erhöhte Abfluglestung after one minute.

[41Sqn_Banks]

I have always assumed - but could not confirm - it was meant for low altitudes only, probably because the early LW bombers like the He 111P used the DB 601A too and it was a useful extra boost for them when lifting heavy loads.

I was trying to find out a while ago wheter that was a soft limitation ('you really should not - but may - use it for other than takeoff') or a hard one (you really can't use it whatever you do).

The power curves of the DB engines draw the 1-min rating only up to about 1-1.5 km then the line cease. So I wondered, if it can be only engaged in the first supercharger speed..? But there is no evidence to such limitation (yet..?).

Unlike however the 5-min limitation for the Kurzleistung, which was a soft one, the 1' erhöhte Abfluglestung in Db 601 A ( 1.4 Ata) and 601 Aa ( 1.45 Ata) was a hard one: when pushing forward the throttle, a 60-sec clockword was engaged which automatically shut down the erhöhte Abfluglestung after one minute.

I always thought that these "special take-off powers" (which is also present in Merlin XII or XX for example) were connected with a extra rich mixture which was only possible at low altitudes and thus limited the use to these altitudes. However I don't know where I've read or heard this.

Where can the description of the 60-sec clockwork be found? It's discusses as a possible game bug here http://www.il2bugtracker.com/issues/40

[Kurfürst]

Where can the description of the 60-sec clockwork be found? It's discusses as a possible game bug here http://www.il2bugtracker.com/issues/40

Olivier Lefebrve (butch2k), one if not the most knowledgeable person on the 109 I know posted this some year ago about the clockwork mechanism. He named this document for DB 601Aa, so I guess its from some kind of 601Aa manual.

I will attempt to give quick and rough translation:

"Increase of output for takeoff (Allowed period: 1 min)

Through pushing the throttle the beyond "Vollast" (Full load, this is probably the 5-min rating - KF) position, without leaving it in the "Abflug" (Takeoff) position.
The holding of the throttle in the "Abflug" position is unnecessary, and therefore pointless; it will repeatedly return to "Vollast" position.

The mechanical clockwork, which is winded by pushing the throttle in forward will disengage the manifold pressure / boost increase automatically after 1 minute, regardless of the position of the throttle. Holding the throttle in the "Abflug" position does not restart or lenghten the increase in manifold pressure, instead it will just increase the richness of the mixture - and therefore no increase in engine output but an increase in fuel consumption - after the throttle has returned to its position."

So basically once activated, it's ON for one minute. I guess its cannot be deactivated either, though given that the clockwork is winded by pushing the throttle forward, its quite clear that the process can be repeated AFTER the one period period has elapsed.

The November 7 1940 issue of Flight magazine (available online) also briefly mentions the clockwork in a DB 601 article, though it does not mention how it works.

[SG1_Lud]

I was unaware of this thread. Thanks Banks for the research.

Dear Kurfürst, that Nov 7th issue of the Flight Magazine could be a good proof. I managed to find it online: http://www.flightglobal.com/pdfarchive/view/1940/1940%20-%203152.html

Thank you very much, I'll update the bugtracker with this document.


Lud.

[41Sqn_Banks]

The "excessively rich mixture" mentioned in "Pilot's Notes General" might prevent the use at higher altitudes.