This report prepeared by the Messerschmitt Projektbüro in December 1944 contains calculated effects on performance expected from new type propeller (VDM 9-12199), which differed in its thinner blades from the serial production VDM 9-12159, that was fitted to late war Bf 109s with high-altitude DB 605AS or D engines. Altough it is believed the so-called Dünnblattschraube VDM 9-12199 was not standardized, this report is of special interest it also shows - as a reference - the performance of the serial production Bf 109K-4 with standard VDM 9-12159 propeller and as such it is a valuable resource for the basic performance figures of this last, potent subtype, at it`s numerous combinations of the engines, manifold pressures and MW-50 boost used.
Actual flight test trials with the VDM 9-12199 Dünnblattschraube, as well as various other propellors of advanced design were also performed at Aspera Gmbh., showing improvements in good agreement with the Messerschmitt Projektbüro report.
The calculations show performance of the Messerschmitt 109K-4 with the DB 605DB/DB engines. Further information is available on these details can be at the appropriate links; it should be also noted that the DB 605 DB and DB 605 DC designations are referring to the same engine, set for different maximum manifold pressure and fuel type; converting DBs into DCs or DCs into DBs was a simple matter. As this powerplant had numerous variations in settings, it is worthwhile to briefly overview their representative outputs at the settings referred by level speed and climb rate graphs of the Projektbüro report.
German operating manuals suggest switching off MW-50 injection above the rated altitude of the engine, because of wasteful nature of operating a boosting system when it it no longer effective, however the system was manually operated by and at the pilot.
Special thanks is due to Mr. G. G. Hopp who did the original research, and kindly made the documentation available for the rest of us. Transcription and translation by Kurfürst.
Special thanks to Herr Henning Ruch for revealing the meaning of some very special technical terms (ein/ausgestrakt) for me, and for the corrections suggested.
A / IV / 294 / 44
Preface for the performance data.
8-109 K4 G = 3400 kg
Retractable tailwheel. streamlined MG 131 bulges, wheel well covers,
without wing weapons.
http://www.kurfurst.orgEngine : DB 605 D for C-3 fuel with MW.
Basic setting 1.98 ata after DB instruction 9-605-2290.
the Steig- Kampfleistung by increasing the revolutions to 2800/min.
Radiators : Coolant radiators Fk = 36 dm2
Fk = 8.5 "
Propeller : Results has been created with the new thin-bladed propeller
In level flight : level speed gain is 12 km/h at
are as equivalents in calculations. Above the Volldruckhöhe
somewhat lower climb rates are to be expected as a result of the
expected worser Ca - behaviour of the thin bladed propeller.
Standardized is the serial propellor 9-12159.
It's effects on Sondernotleistung are shown on the speed graphs.
Mach : Were not taken into account in the calculation.
effects Greatest deviation at the Volldruckhöhe with Sondernotleistung,
: The stated
figures are going to be reached with
threatment to the airframe and surface protective layer on
Secret document !http://www.kurfurst.bravehost.com/
| Pet./Bu. [signed]
Oberammergau, on the 11 December 1944.