Methods and systems of starting a gas turbine engine are provided. During startup, a fuel pressure associated with a primary fuel supply of the gas turbine engine is monitored. A low-pressure event for the primary fuel supply is detected when the fuel pressure falls below a predetermined threshold. Responsive to detecting the low pressure event, an electric backup boost pump is activated by an engine controller to provide fuel to the gas turbine engine.

Methods and systems of starting a gas turbine engine are provided. During startup, a fuel pressure associated with a primary fuel supply of the gas turbine engine is monitored. A low-pressure event for the primary fuel supply is detected when the fuel pressure falls below a predetermined threshold. Responsive to detecting the low pressure event, an electric backup boost pump is activated by an engine controller to provide fuel to the gas turbine engine.

An gas turbine engine for an aircraft includes, in axial flow sequence, a compressor module, a combustor module, and a turbine module, together with a first electrical machine rotationally connected to the turbine module. The combustor module has a combustor volume V (cm.sup.3). In use, at a full power condition, the gas turbine engine has a maximum corrected core flow Q (m.sup.3/sec), and a ratio T of:

[00001]$T=\frac{\left(\mathrm{Maximum}\mathrm{Corrected}\mathrm{Core}\mathrm{Flow}=Q\right)}{\left(\mathrm{Combustor}\mathrm{volume}=V\right)}$

is in a range of between 450 and 2,500.

Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.

Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.

Aircraft power and propulsion systems, aircraft comprising such power and propulsion systems, and methods of restarting a gas turbine engine of such power and propulsion systems during flight are provided. One such aircraft power and propulsion system comprises: a propulsive gas turbine engine comprising a plurality of spools, combustion equipment, one or more electric machines mechanically coupled with one or more of the spools and an electrically-powered fuel pump for delivering fuel to the combustion equipment; an electrical system connected with the one or more electric machines and the electrically-powered fuel pump, the electrical system comprising an energy storage system; and a control system configured to: responsive to a determination to the effect that a flame in the combustion equipment has been extinguished, control the electrical system to supply electrical power from the energy storage system to the fuel pump during an engine restart attempt.

A method of operating a twin engine helicopter power plant, the power plant comprising: two turboshaft engines each having an engine shaft with a turbine at a distal end and a one-way clutch at a proximal end; a gear box having an input driven by the one way clutch of each engine and an output driving a helicopter rotor; a bypass clutch disposed between the proximal end of each engine shaft and the input of the gear box; and power plant management system controls for activating the bypass clutch; the method comprising: detecting when a rotary speed of an associated engine shaft is less than a rotary speed of the gear box input; activating the bypass clutch to drive the associated engine shaft using the rotation of the gear box input; and starting an associated engine by injecting fuel when the bypass clutch is activated.

A method of operating a twin engine helicopter power plant, the power plant comprising: two turboshaft engines each having an engine shaft with a turbine at a distal end and a one-way clutch at a proximal end; a gear box having an input driven by the one way clutch of each engine and an output driving a helicopter rotor; a bypass clutch disposed between the proximal end of each engine shaft and the input of the gear box; and power plant management system controls for activating the bypass clutch; the method comprising: detecting when a rotary speed of an associated engine shaft is less than a rotary speed of the gear box input; activating the bypass clutch to drive the associated engine shaft using the rotation of the gear box input; and starting an associated engine by injecting fuel when the bypass clutch is activated.

A method of cooling a shaft of a gas turbine engine includes moving a control valve towards a position that inhibits fluid flow from a high pressure air source to an air turbine starter and enables fluid flow from a blower motor to the air turbine starter, in response to a gas turbine engine shutdown. The method further includes operating the blower motor to provide air to the air turbine starter.

A method of cooling a shaft of a gas turbine engine includes moving a control valve towards a position that inhibits fluid flow from a high pressure air source to an air turbine starter and enables fluid flow from a blower motor to the air turbine starter, in response to a gas turbine engine shutdown. The method further includes operating the blower motor to provide air to the air turbine starter.