An aircraft engine having a fan, the fan having at least one flutter-resistant blade, the blade having a leading edge (LE), a trailing edge (TE), a midchord (MC), a minimum radial height r.sub.hub, a maximum radial height r.sub.tip, and a radial extent between r.sub.hub and r.sub.tip, wherein, at every point along the radial extent of the blade, the blade has a modeshape value V.sub.1 for a blade first vibratory mode defined as

[00001]$V_1=\frac{.Math.D_{1\mathrm{LE}}.Math.}{.Math.D_{1\mathrm{MC}}.Math.},$

and wherein, when the engine is operating between its maximum speed and 70% of that maximum speed, at least 80% of the radial extent of the blade has a modeshape value V.sub.1 from 0 to 1.5.

Embodiments of the disclosure provide a method for controlling steam pressure within a turbine component. The method includes calculating a predicted stress on a rotor of the turbine component based on a predicted steam flow with the inlet valve in a minimum load position, a rotor surface temperature, and an inlet steam temperature, and determining whether the predicted stress exceeds a threshold. If the predicted stress exceeds the threshold, the inlet valve adjusts to a warming position. When steam in the discharge passage reaches a target pressure, the exhaust valve partially closes while maintaining the warming position of the inlet valve. If a safety parameter of the turbine component violates a boundary, the exhaust valve partially opens while maintaining the warming position of the inlet valve. When the predicted stress does not exceed the threshold, the inlet valve opens to at least the minimum load position.

Methods and apparatus are disclosed to determine material parameters of a turbine rotor. An example apparatus includes a rotor geometry determiner to determine a geometry of the rotor, a node radius calculator to calculate radial node locations of radial nodes including a first radial node, a thermocouple interface to record first temperature values over an interval, a first thermal stress calculator to calculate first thermal stress values at one or more of the radial nodes over the interval, a node temperature calculator to calculate second temperature values at respective internal nodes of the first radial node, a reference value lookup to lookup first material parameter information, a second thermal stress calculator to determine second thermal stress values, a thermal stress comparator to calculate a difference between the thermal stress values, and, in response to the difference not satisfying a threshold, a material parameter adjuster to determine material parameters.

A gas turbine engine system includes an engine component comprising ceramic matrix composite materials, at least one control system configured to control at least a temperature of the engine component, and a controller. The controller includes a degradation map stored therein. The degradation map includes degradation fields, each field defined by a unique range of temperatures and stresses of the component and correlated to different types of degradation of the component. The controller is configured to determine a first temperature and stress of the component and a first field based on the first temperature and stress, determine a second field different from the first and a second temperature and stress that would locate the component in the second field, and instruct the control system to change the temperature of the component from the first to the second temperature to locate the component in the second field.

Distress models can be generated to model current or future deterioration of components. By correlating distress models with maintenance costs and material consumption, cumulative cost models and cumulative material models can be developed to optimize engine removal timing in order to maximize asset and portfolio value.

A method includes receiving a command to operate a power load of a power system at a command output power while operating the power load at a reference output power; operating a gas turbine engine of the power system in a maximum regulator mode to increase a power generation of the gas turbine engine when the command output power is greater than the reference output power or in a minimum regulator mode to decrease the power generation of the gas turbine engine when the command output power is less than the reference output power; and coordinating an electric machine power draw from the gas turbine engine with a change in power generation of the gas turbine engine to maintain a rotational speed parameter of the gas turbine engine substantially constant while operating the gas turbine engine in the maximum regulator mode or in the minimum regulator mode.

A method for creating a three-dimensional (3D) mark in a protective coating including at least one of a TBC and a bond coating over a metal part, is provided. The method may include positioning a mask over the protective coating, the mask including an opening pattern therein; and performing an abrasive waterjet process on the protective coating using the mask. The abrasive waterjet erodes a first portion of the protective coating exposed through the first opening pattern to create the 3D mark. The mask is removed, leaving the 3D mark in the protective coating. The 3D mark only partially penetrates through the protective coating. A metal part may include a metal body, a protective coating over the metal body, and the 3D mark in the protective coating, is also provided. The 3D mark in the protective coating may include an opening having a width of between 30 and 300 micrometers.

The present disclosure provides methods and systems for operating a multi-engine rotorcraft. The method comprises driving a rotor of the rotorcraft with a first engine while a second engine is de-clutched from a transmission clutch system that couples the rotor and the second engine, instructing the second engine to accelerate to a re-clutching speed, and controlling an output shaft speed of the second engine during acceleration of the second engine to the re-clutching speed by applying a damping function to a speed control loop of the second engine.

Distress models can be generated to model current or future deterioration of components. By correlating distress models with maintenance costs and material consumption, cumulative cost models and cumulative material models can be developed to optimize engine removal timing in order to maximize asset and portfolio value.

A method includes receiving a command to operate a power load of a power system at a command output power while operating the power load at a reference output power; operating a gas turbine engine of the power system in a maximum regulator mode to increase a power generation of the gas turbine engine when the command output power is greater than the reference output power or in a minimum regulator mode to decrease the power generation of the gas turbine engine when the command output power is less than the reference output power; and coordinating an electric machine power draw from the gas turbine engine with a change in power generation of the gas turbine engine to maintain a rotational speed parameter of the gas turbine engine substantially constant while operating the gas turbine engine in the maximum regulator mode or in the minimum regulator mode.