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).
Pitch: 80-60°.

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

Fw 190 Wk. Nr. 0022 dive speeds
Fw 190 Wk. Nr. 0022 stick force, elevator angle, dive angle, etc.

Einfluss hoher Mach' Zahl auf Fw 190 (pdf)

Translation by Jörn Dietrich and Mike Williams

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