|Subject:. Influence of high Mach number on Fw 190
During the investigations on the influence of Mach number on
the elevator moment of the Fw 190, a dive was carried out by the
signatory from a little over 10000 m height to 5000 m. The measured
values obtained are summarized on the accompanying graph, while in the
following, the observations of the pilot during the dive in question will be discussed.
Initiation of the dive:
Normal flight, from there a half roll into an inverted flight, over
inverted flight into the vertical, or near vertical (~80°).
General conditions at the beginning of dive or during dive:
Initial height HB = 10100 m. Fin position ß Tr = 2.4° = const.
Engine power n = 2300 RPM = const. (Automatic)
PL = in accordance with the assignment by the Kommandogerät (cruise power).
The course of the dive:
Control stick pressure in the "push" direction initially
light, with growing ram pressure slightly increasing. Around 7500 m
occurred a strikingly greater moment in the direction of "nose-heavy" -
not jerkily, however, suddenly and unmotivated. Due to the irregularity
in the force curve of the elevator, initial impression of instability
in the dive based on the hand pressure. With the occurring nose-heavy
moment clearly noticeable, a rotation of the machine around the
transverse axis into the dive. In response thereafter an attempt to
counteract, to stop the dive by pulling the elevator. The self
induced rotation towards "inverted flight" stopped, whether on its
own or in reaction to rudder operation, could not be clearly observed.
The pilot had the impression that he had pulled the elevator towards
the end stop, because the stick could be changed in the direction of
"push" without feeling any force. Nevertheless, the pitch of the
aircraft did not change over ~ 10 sec, so that an impression of
the ineffectiveness of the elevator arose. The machine dove through
1500 - 2000 m with, by impression of the pilot, elevator pulled fully
against the stop without any noticeable course change. A clearly
perceptible, increasing elevator effectiveness was felt thereafter;
then the plane could be pulled out of the dive, with a smooth pull out
requiring to ease up on the elevator.
The highest Mach number reached was 0.79. The highest speed
result, taking into account the pressure error correction and the
compressibility influence, was Vw = 567 mph (912 km/h).
To what extent the air speed indicator is influenced by Mach effects,
should be clarified by calibration at altitude, on a marked test
course, which is not available here.
Langenhagen, 24 September 1943