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Note: The VDM automatic propellor pitch system -  mentioned in this translation of the Technical Sheet appears to  have been introduced already by late 1939. For more details, please see the notes for this performance trial.

Technical Sheet Issued by the
Quartermaster General
(Air Equipment).

Berlin 14th November 1940.              

Subject:   Increasing the revs of engine types
           D.B. 601A and 601N in the Me 109.

           To increase the performance of the Me 109 an increase in the
revs for a short time at heights over 5.5 km. will be in future be
permissable.  For the DB 601 A engine the normal maximum revs are 2400.
Above full pressure height they may be for a short time be increased
from 2400 to 2600.  For the DB 601 N engine the normal maximum revs are
2600, but may be increased to 2800 for a short time above the full
pressure height.  An increase in the normal revs of 2400 for the DB 601A
or 2600 for the DB 601 N at heights of less than 5.5 km. is still not
permissable, as the engine is damaged without any increase in the
performance of the aircraft being obtained.  The use of the increased revs
places a particular strain on the engine and must therefore, for
reasons of safety, be restricted to the absolutely neccessary.

           To assist the pilot an automatic airscrew pitch changing
device has been introduced. This ensures, without intervention by the
pilot, that the maximum revs are not exceeded and the engine is not
subjected to excessive strain.  In addition, every position of the
throttle lever has a corresponding rev. speed, which is kept within
narrow limits by the automatic device in all flying conditions, including
diving.  In the case of economical flight, in which lower revs are
desirable for each throttle lever setting in order to increase the range,
the automatic device can be switched off and the neccessary changes in
the airscrew pitch carried out in the ordinary way by means of the
thumb swithc.

           The devices for the automatic regulations of the revs
hitherto used will be modified by Messerschmitt and VDM as quickly as
possible so that the short period increase in revs to 2600 for the
DB 601 A and 2800 for the DB 601 N permissable above the full pressure
height can also be made by the automatic device.  Until
this modification is completed the excess revs can only be obtained by
means of the thumb switch after switching off the automatic device.
In doing this the danger of an additional impermissable increase in
the revs must be watched.

          In the interests of the reliability of the technical
equipment it is essential that units should make themselves acquainted
with the above instructions and observe them strictly.  The
instructions must therefore be read out to all pilots and maintance

Sources and References:

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