Helicopter Anti-Torque Rotor Bearing Interface for Failure Control
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Solution Overview
Problem
The existing anti-torque rotor systems in helicopters are prone to uncontrollable failures due to damage in the antifriction bearing, which can lead to hazardous situations, and there is a need for a simpler and cost-effective solution to detect failures and maintain control.
Innovation Solution
The anti-torque rotor system incorporates a bearing with a double ring of balls and a transmission unit that includes a sensor and an interface with antifriction coatings to prevent twisting moments and ensure controllability, featuring a redundant transmission path to maintain control even in failure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an antifriction bearing is used to allow rotation of the control element with respect to the control rod, then the anti-torque rotor can be controlled by altering blade angles of attack, but the bearing may fail due to damage from foreign bodies, loss of lubrication, or raceway damage, causing the anti-torque rotor to become uncontrollable
Solution Approach 1:
The patent applies beforehand cushioning by introducing a damping element between the control rod and control element that can absorb and dissipate energy from twisting moments. This damping element is pre-positioned to protect the control rod from damage when the bearing fails, allowing the system to withstand bearing failure without complete loss of control.
Solution Approach 2:
The patent uses an intermediary approach by introducing a damping element as a mediator between the control rod and control element. This intermediary component absorbs the harmful twisting moments that would otherwise be transmitted to the control rod, while still allowing the bearing to perform its primary function of enabling control element rotation during normal operation.
2Reliability
If the rolling bodies and raceways become damaged, then the bearing improperly transfers twisting moments from the outer ring to the inner ring, but this can irreversibly damage the control rod
Solution Approach 1:
The damping element is pre-installed in the control rod to cushion against twisting moments before they can cause irreversible damage. When bearing damage occurs, the damping element absorbs the excessive twisting moments, protecting the control rod from strength failure even though the bearing is no longer functioning properly.
Solution Approach 2:
The patent converts the harmful twisting moments that result from bearing failure into a beneficial effect by using the damping element to absorb and dissipate this energy. The harmful vibration and twisting that would damage the control rod are transformed into controlled energy dissipation through the damping element, protecting the overall system.
3Reliability
If the rolling bodies break and detach from the inner ring, then the bearing can no longer transmit axial load, but the rod can no longer cause translation of the control element
Solution Approach 1:
The patent applies local quality by giving different parts of the control system different functions: the bearing handles axial load transmission during normal operation, while the damping element handles twisting moment absorption during failure. This localized functional differentiation allows the system to maintain control capabilities even when the bearing fails completely.
Solution Approach 2:
The patent uses parameter changes by allowing the damping element to change its mechanical properties based on operating conditions. During normal operation, the damping element has minimal effect on axial load transmission, but during bearing failure, it becomes the primary load-bearing component, changing the system's stiffness and damping parameters to accommodate the failure mode.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents damage to the control rod and ensures the anti-torque rotor remains controllable, reducing the risk of helicopter instability and enabling timely pilot intervention in case of bearing failure.
Implementation Method 1
a plurality of rolling bodies, which roll in respective raceways defined by the radially inner and outer rings
Implementation Method 2
an interface (102) with an antifriction coating, arranged between the control rod and the control element, and configured so as to prevent transmission of a twisting moment from the control rod to the control element
Data Source
AI summary
An anti-torque rotor is described for a helicopter, comprising: a mast rotatable about a first axis; a plurality of blades hinged on the mast, extending along respective second axes transversal to said first axis and rotatable about respective said second axes to alter the respective angles of attack; a control element sliding and rotating with respect to the mast, and operatively connected to said blades to cause the rotation of said blades about respective second axes following a translation of said element along the first axis; a control rod sliding axially along first axis with respect to the mast and angularly fixed with respect to the first axis; and a bearing interposed between the control rod and the control element, sliding along the first axis with respect to the mast and integrally with the control rod; the anti-torque rotor further comprises an interface made of an antifriction material interposed between said control rod and said bearing.