File:Type91 AerialTorpedo RollRudder.PNG

[Type91 Aerial Torpedo Roll Rudders

Type 91 aerial torpedo has roll rudders to steer the stabilize the roll of the aerial torpedo, both in the air and in the water.

Stabilizing rudder, or roll rudders are put on both side of the torpedo, being steered to produce counter-rolling moment. Each rudder is a small 8cm² size square metal wing. Each roll rudder has been covered with a temporal wooden extended wing of 12 x 20 cm² (4-3/4in x 7-7/8in), tighten with six aluminum sharing pins on both side-edge to get enough aerodynamic force in the air, that is to be shed and broken off when the torpedo gets the hard impact from the water surface on water entry. The remained original metal roll rudders are steering in the water running to converge the rolling movement arisen on water entry.

Angular velocity steering system

Anti-rolling controller system inside the aerial torpedo steers both roll rudders tri-stated to full-up / neutral / full-down in twisting aileron manner. When the controller detect the rolling is coming back to the center position, the system countersteers roll rudders in opposite direction. This system uses countersteering function so as to dump unstable rolling oscillation movement. Type 91 aerial torpedoes has fast period in approx. 0.5 sec time constant in rolling moment. Normal controlling systems of the days in 1940s have long time lags to response, the system had to have countersteering.

The anti-rolling controller

The anti-rolling controller is actually a steering controller to stabilize the rolling motion of the torpedo by roll rudders on both sides. The roll rudders work within angler range +/-22.5 °, twisting in ailerons manner. When a torpedo is rolling or rolls to some degree, the anti-rolling controller twists those rudders in the counter-rolling direction. But the torpedo is rolling over the angle +/-10 ° and rolling back within angle range +/-10 °, toward its neutral position of 0 degree, the countersteering function works. The anti-rolling controller sense it and switches roll rudders in the opposite direction to break angular velocity of torpedo rolling back, or countersteering in the air and in the water. This function is embodied by the mass slider valve in the main controller of the anti-rolling controller, limiting the slide stroke range of the mass slider valve at +/- 10 °, which is moving proportional to the angle of roll within the range. They naval engineers called this operation as countersteer as they modeled it to steer a ship.

For further detail, see Type 91 torpedo or Koku Gyorai Note.] Error: {{Langx}}: text has italic markup (help)

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05-5-2009

Shun Zero

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