Messerschmitt-boelkow-blohm Gesellschaft MIT Beschraenkter Haftung

Messerschmitt-boelkow-blohm Gmbh

Messerschmitt-bolkow-blohm Gesellschaft MIT Beschrankter Haftung

Michael Stephan

Alois Schwarz

Karlheinz Mautz

Karl-Heinz Mautz

The blades or wings of a rotor for example of a rotary wing aircraft, are nnected to the rotor head in a hingeless and bearingless manner by a blade neck section, which is flexible relative to torsion loads, flapping movements and lead-lag movements. The blade angle adjustments are made by a torsion stiff control rod bridging the flexible blade neck section. The control rod is flexible relative to flapping and lead-lag movements. The radially outer end of the control rod is rigidly connected to the respective wing. The radially inner end of the control rod is connected to the rotor head in such a manner that the control rod is movable substantially in the direction of its own longitudinal axis.

Rotor having a hingeless and bearingless blade connection

The blade angle of the blades of a rotary wing aircraft is adjusted by a control rod (5) inside the hollow rotor head operating a control shaft (8) extending radially out of the rotor head in axial alignment with the blade angle adjustment axis. The adjustment movement of the shaft (8) is transmitted to the respective blade (3.3) by a yoke (11, 12) and a torsion-stiff sleeve (7) which bridge the blade root (3.1) and the torsion yielding blade neck (3.2) respectively. The blade root (3.1) is connected to the rotor hub (1) by a forked member (2) through which a portion (11) of the yoke extends for connection to the control shaft.

Rotor structure for a rotary wing aircraft

The wings of a rotary wing aircraft comprise, for example, four wing blades orming two pairs of wing blades whereby the blades of a pair are located diametrically opposite each other. The blades of a pair are connected to each other by a spar extending from wing blade to wing blade. The spar is operatively secured to the rotor head. Each spar has between the rotor head and the respective wing blade a zone with a torsion yieldability larger than in the spar outside said zone. A beam stiff against bending, bridges the zone, referred to as a torque soft zone, from the wing blade toward the rotor head except for a small flexible section between the rotor head and the radially inner end of the beam. The flexible section permits the blade flapping movements and the blade lead-lag movements.

The present four-blade rotor is made up of two blade pairs, each blade pair aving two rotor blades arranged diametrically opposite one another. The blades of each blade pair are coupled to each other by means of a coupling loop for taking up centrifugal forces produced by the rotation of the blades. The present rotor system also has a centering device including a centering body and tension straps for each coupling loop. The tension straps connect the respective loop end to the centering body whereby the two coupling loops may be centered in the rotor head practically without play and without substantially limiting the free movement of the coupling loops.

Four-blade rotor, especially for helicopters

The present four-blade rotor structure comprises two pairs of rotor blades. iametrically opposite each other located blades form a pair and the blades of a pair are connected to each other by coupling belts which are tension resistant and torsionally yielding. One coupling belt extends substantially horizontally whereas the other extends substantially vertically. The coupling belts are centered in the rotor head by respective centering bodies. The centering bodies are connected to their respective belt by bearing elements capable of taking up pressure loads while simultaneously permitting a blade angle adjustment. In a modification the bearings may be slide bearings.

The present hingeless rotor structure, especially for rotary wing aircraft, omprises at least one pair of rotor blades, whereby the blades of a pair are arranged diametrically opposite each other. The blades are secured to a rotor head for proper blade angle adjustment. Each blade has its root or radially inner end secured in a blade root sleeve which in turn is held in a respective blade angle bearing bushing. The blades of a pair are interconnected by a tension resistant, torsionally yielding member. One bearing which is pressure loadable in the direction of the longitudinal blade axis is provided for each blade pair between one of the respective blade root sleeves and the corresponding blade angle bearing bushing. The tension resistant, torsionally yielding member is capable of a certain stretching or elongation during operation. In order to compensate for such an elongation, the tension resistant, torsionally yielding members are installed in such a manner that in the rest or non-rotating condition of the blades, the center is radially displaced from the axis of rotation of the rotor head toward the respective pressure loadable bearing by one half of the length of said elongation.

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Munich, Germany

Michael Stephan