Tail rotor isolation systems for rotorcraft

Patent metadata

Field	Value
Publication number	US-12049304-B2
Application number	US-202217861702-A
Country	US
Kind code	B2
Filing date	Jul 11, 2022
Priority date	Feb 5, 2019
Publication date	Jul 30, 2024
Grant date	Jul 30, 2024

Abstract

A tail rotor isolation system for rotorcraft includes a secondary engine, first and second freewheeling units, an isolation assembly and a tail rotor system. The secondary engine is coupled to the input race of the first freewheeling unit. A main rotor system is coupled to the output race of the second freewheeling unit. The isolation assembly is coupled to the output race of the first freewheeling unit and has a fully engaged position coupling the input and output races of the second freewheeling unit and a partially engaged position coupled to the input race but decoupled from the output race of the second freewheeling unit. The tail rotor system is coupled to the input race of the second freewheeling unit such that in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit isolates the tail rotor system from the main rotor system.

First claim

What is claimed is:

1. A tail rotor isolation system for rotorcraft having a main rotor system including a main engine, a main rotor gearbox and a main rotor, the tail rotor isolation system comprising:
a secondary engine;
first and second freewheeling units each having an input race and an output race such that torque applied to the input race is transferred to the output race in a driving mode and torque applied to the output race is not transferred to the input race in an overrunning mode, the input race of the first freewheeling unit coupled to the secondary engine, the output race of the second freewheeling unit coupled to the main rotor system;
an isolation assembly disposed between the first and second freewheeling units, the isolation assembly coupled to the output race of the first freewheeling unit, the isolation assembly having a fully engaged position in which the isolation assembly couples the input and output races of the second freewheeling unit and a partially engaged position in which the isolation assembly is coupled to the input race of the second freewheeling unit and decoupled from the output race of the second freewheeling unit; and
a tail rotor system coupled to the input race of the second freewheeling unit;
wherein, in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit isolates the tail rotor system from torque generated by the main rotor system;
wherein, in the partially engaged position of the isolation assembly, the tail rotor system is coupled to torque generated by the secondary engine; and
wherein, in the fully engaged position of the isolation assembly, the tail rotor system is coupled to torque generated by the main rotor system and the secondary engine.

2. The tail rotor isolation system as recited in claim 1 wherein the secondary engine is configured to generate between 5 percent and 20 percent of the power of the main engine.

3. The tail rotor isolation system as recited in claim 1 wherein the secondary engine is configured to generate approximately the same amount of power as the main engine.

4. The tail rotor isolation system as recited in claim 1 wherein the secondary engine is a gas turbine engine.

5. The tail rotor isolation system as recited in claim 1 wherein the secondary engine is an electric motor.

6. The tail rotor isolation system as recited in claim 1 wherein the isolation assembly includes an outer housing and a splined adaptor that is disposed within the outer housing, rotatable with the outer housing and translatable relative to the outer housing between the fully engaged position and the partially engaged position with the second freewheeling unit.

7. The tail rotor isolation system as recited in claim 6 wherein the splined adaptor has a splined coupling with the input race of the second freewheeling unit in both the fully engaged position and the partially engaged position; and
wherein, the splined adaptor has a splined coupling with the output race of the second freewheeling unit in the fully engaged position and is decoupled from the output race of the second freewheeling unit in the partially engaged position.

8. The tail rotor isolation system as recited in claim 6 wherein the splined adaptor has outer splines and inner splines;
wherein, the outer splines of the splined adaptor have a splined coupling with inner splines of the input race of the second freewheeling unit in both the fully engaged position and the partially engaged position; and
wherein, the inner splines of the splined adaptor have a splined coupling with outer splines of the output race of the second freewheeling unit in the fully engaged position and are decoupled from the outer splines of the output race of the second freewheeling unit in the partially engaged position.

9. The tail rotor isolation system as recited in claim 6 further comprising an actuator coupled to the splined adaptor and configured to shift the splined adaptor between the fully engaged position and the partially engaged position with the second freewheeling unit.

10. The tail rotor isolation system as recited in claim 9 wherein the actuator is a linear actuator.

11. The tail rotor isolation system as recited in claim 9 wherein the actuator is one of a hydraulic actuator, an electromechanical actuator or a pneumatic actuator.

12. The tail rotor isolation system as recited in claim 1 wherein the tail rotor system further comprises a tail rotor and a tail rotor brake; and
wherein, in the partially engaged position of the isolation assembly and with the main rotor system operating, the tail rotor brake is configured to stop rotation of the tail rotor when the secondary engine is shut down, thereby establishing a ground safety configuration of the rotorcraft.

13. The tail rotor isolation system as recited in claim 1 wherein, in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit is enabled such that the second freewheeling unit is configured for unidirectional torque transfer from the input race to the output race of the second freewheeling.

14. The tail rotor isolation system as recited in claim 1 wherein, in the fully engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit is disabled such that the second freewheeling unit is configured for bidirectional torque transfer between the input race and the output race of the second freewheeling.

15. A rotorcraft comprising:
a main rotor system including a main engine, a main rotor gearbox coupled to the main engine and a main rotor coupled to the main rotor gearbox;
a secondary engine;
first and second freewheeling units each having an input race and an output race such that torque applied to the input race is transferred to the output race in a driving mode and torque applied to the output race is not transferred to the input race in an overrunning mode, the input race of the first freewheeling unit coupled to the secondary engine, the output race of the second freewheeling unit coupled to the main rotor system;
an isolation assembly disposed between the first and second freewheeling units, the isolation assembly coupled to the output race of the first freewheeling unit, the isolation assembly having a fully engaged position in which the isolation assembly couples the input and output races of the second freewheeling unit and a partially engaged position in which the isolation assembly is coupled to the input race of the second freewheeling unit and decoupled from the output race of the second freewheeling unit; and
a tail rotor system coupled to the input race of the second freewheeling unit;
wherein, in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit isolates the tail rotor system from torque generated by the main rotor system;
wherein, in the partially engaged position of the isolation assembly, the tail rotor system is coupled to torque generated by the secondary engine; and
wherein, in the fully engaged position of the isolation assembly, the tail rotor system is coupled to torque generated by the main rotor system and the secondary engine.

16. The rotorcraft as recited in claim 15 wherein the rotorcraft is a helicopter.

17. The rotorcraft as recited in claim 15 wherein the tail rotor system further comprises a tail rotor and a tail rotor brake; and
wherein, in a ground safety configuration, the isolation assembly is in the partially engaged position, the main rotor system is operating, t

Assignees

• Textron Innovations Inc

Inventors

• Olson Eric Stephen

Classifications

• B64D35/08

  characterised by the transmission being driven by a plurality of power plants (for hybrid-electric power plants B64D35/022) · CPC title

• B64D27/026

  comprising different types of power plants, e.g. combination of a piston engine and a gas-turbine (Hybrid electric aircraft B64D27/33) · CPC title

• F16D41/04

  combined with a clutch for locking the driving and driven members (F16D41/02, F16D41/24 take precedence) · CPC title

• F16D2041/0603

  Sprag details · CPC title

• F16D47/04

  of which at least one is a freewheel (F16D47/02, F16D47/06 take precedence; freewheels combined with a clutch to lock the driving and driven members of the freewheel F16D41/04, F16D41/26) · CPC title