A monitoring system for monitoring one or more properties associated with a rotating shaft is provided. The system includes a first phonic wheel which is mounted coaxially to the shaft for rotation therewith, the first phonic wheel comprising a circumferential row of teeth. The system further includes a first sensor configured to detect the passage of the row of teeth of the first phonic wheel by generating a first alternating measurement signal. The system further includes a processor unit configured to determine the durations of successive first speed samples. Each first speed sample is a block of n successive cycles of the first alternating measurement signal, where n is an integer, and in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle. At least one axial location of the first phonic wheel every m.sup.th tooth of the row of teeth of the first phonic wheel has a circumferential thickness which is different from that of the other teeth of the first phonic wheel, where m is an integer, mn, and m is neither a factor nor a multiple of n. When the first sensor is positioned at said axial location of the first phonic wheel and at any given rotational speed of the first phonic wheel, the durations of the successive first speed samples display a characteristic repeating pattern of longer and shorter sample durations relative to the average duration of the successive first speed samples. The amount by which the longer and shorter sample durations differ from the average duration is in proportion to the amount by which the circumferential thickness of the m.sup.th teeth differs from that of the other teeth at said axial location of the first phonic wheel. The processor unit monitors the properties associated with the rotating shaft from the characteristic repeating pattern.

A monitoring system for monitoring one or more properties associated with a rotating shaft is provided. The system includes a first phonic wheel which is mounted coaxially to the shaft for rotation therewith, the first phonic wheel comprising a circumferential row of teeth. The system further includes a first sensor configured to detect the passage of the row of teeth of the first phonic wheel by generating a first alternating measurement signal. The system further includes a processor unit configured to determine the durations of successive first speed samples. Each first speed sample is a block of n successive cycles of the first alternating measurement signal, where n is an integer, and in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle. At least one axial location of the first phonic wheel every m.sup.th tooth of the row of teeth of the first phonic wheel has a circumferential thickness which is different from that of the other teeth of the first phonic wheel, where m is an integer, mn, and m is neither a factor nor a multiple of n. When the first sensor is positioned at said axial location of the first phonic wheel and at any given rotational speed of the first phonic wheel, the durations of the successive first speed samples display a characteristic repeating pattern of longer and shorter sample durations relative to the average duration of the successive first speed samples. The amount by which the longer and shorter sample durations differ from the average duration is in proportion to the amount by which the circumferential thickness of the m.sup.th teeth differs from that of the other teeth at said axial location of the first phonic wheel. The processor unit monitors the properties associated with the rotating shaft from the characteristic repeating pattern.

A system for monitoring the axial position of a rotating shaft includes a phonic wheel mounted coaxially to the shaft for rotation with a circumferential row of teeth. The system includes a sensor configured to detect the passage of the teeth by generating an alternating measurement signal. First and second portions of the teeth alternate around the row and contribute respective first and second components to the alternating measurement signal. The first portion of teeth vary in height in an axial direction of the wheel such that the relative height of the first and second portions varies with axial distance across the phonic wheel, and the sensor is positioned relative to the phonic wheel such that axial displacement of the shaft causes the signal to vary the first component's amplitude relative to the second component's amplitude due to the height variation, to monitor the axial position of the shaft.

A monitoring system for monitoring the axial position of a rotating shaft includes a phonic wheel which is mounted coaxially to the shaft for rotation therewith. The phonic wheel includes a circumferential row of teeth. The system further includes a sensor configured to detect the passage of the row of teeth by generating an alternating measurement signal. The teeth are configured around the row such that the teeth contribute a component to the alternating measurement signal. The teeth are tapered in an axial direction of the wheel and the sensor is positioned relative to the phonic wheel such that, in use, axial displacement of the shaft causes the signal generated by the sensor to vary either or both of the amplitude and the pulse width of the component, whereby the axial position of the shaft can be monitored.

A method and system for operating a gas turbine engine coupled to an aircraft propeller are described herein. The method comprises detecting a command for unfeathering the propeller, inhibiting shaft shear detection logic in response to detecting the command for unfeathering the propeller, detecting completion of the unfeathering of the propeller, and enabling the shaft shear detection logic in response to detecting the completion of the propeller unfeathering.

A system and a method for detecting a shaft shear event in a gas turbine engine are disclosed. The system comprises a sensor configured to detect a shaft shear force exerted by a shaft on a support structure supporting the shaft where the shaft shear force is indicative of shearing of the shaft. The system also comprises a controller operatively coupled to the sensor and configured to initiate a shutdown of the gas turbine engine in response to the detection of the shaft shear force by the sensor.

A system and a method for detecting a shaft shear event in a gas turbine engine are disclosed. The system comprises a sensor configured to detect a shaft shear force exerted by a shaft on a support structure supporting the shaft where the shaft shear force is indicative of shearing of the shaft. The system also comprises a controller operatively coupled to the sensor and configured to initiate a shutdown of the gas turbine engine in response to the detection of the shaft shear force by the sensor.

An aircraft comprising a fuselage and propelled by a turbine engine having two coaxial and contrarotating fans, the turbine engine comprising a power turbine having two contrarotating rotors, one of which drives a fan upstream from the turbine, the other a fan downstream from the turbine, each fan comprising a ring of blades, and the assembly of the fans and the power turbine being incorporated at the rear of the fuselage, in the extension of same. The aircraft comprises, for at least one of the fans, a device for blocking the rotation of the fan and a device configured to modify the pitch of the blades of the fan in such a way as to make it operate as a flow straightener with respect to the other fan.

An aircraft comprising a fuselage and propelled by a turbine engine having two coaxial and contrarotating fans, the turbine engine comprising a power turbine having two contrarotating rotors, one of which drives a fan upstream from the turbine, the other a fan downstream from the turbine, each fan comprising a ring of blades, and the assembly of the fans and the power turbine being incorporated at the rear of the fuselage, in the extension of same. The aircraft comprises, for at least one of the fans, a device for blocking the rotation of the fan and a device configured to modify the pitch of the blades of the fan in such a way as to make it operate as a flow straightener with respect to the other fan.

A guide vane segment 10 for a turbomachine includes a radially inner shroud plate 13 having a shroud plate surface 14 that is adapted to be configured in the turbomachine to face a rotor blade 20 adjacent to the guide vane segment, and thereby essentially extend along an outer conical surface K.sub.1 whose cone axis coincides with the axis of rotation A of a rotor shaft 30. In a radially inner region, a rotor blade 20 for a turbomachine has a base plate 23 having a base plate surface 24 that is adapted to be configured in the turbomachine to face a shroud of a guide vane row 10 adjacent to the rotor blade and thereby essentially extend along an outer conical surface K.sub.2 whose cone axis coincides with the axis of rotation A of a rotor shaft 30.