Gas turbine engine

A gas turbine engine comprising:

• a gear assembly mechanically coupled to an LP shaft of the gas turbine engine, wherein the gear assembly comprises a sun gear, a ring gear, a carrier, and a plurality of planet gears arranged in a planetary configuration, wherein each of the plurality of planet gears comprises:
• a pin comprising a pin outer surface;
• a gearbox bearing disposed within the planet gear and at least partially surrounding the pin;
• an annular planet gear rim comprising an inner surface, wherein the inner surface and the pin outer surface define a clearance, wherein the clearance is greater than zero when a radial component force, a pinch component force, a tangential component force, and a centrifugal component force are applied to the planet gear;
• a planet gear bending stress neutral axis radius, wherein the planet gear bending stress neutral axis radius is a radius where stresses and strains within the annular planet gear rim are zero when the radial component force, the pinch component force, the tangential component force, and the centrifugal component force are applied to the planet gear;
• a pin clearance parameter defined by:
• PCP
• =
• K
• 1
• c
• r
• ⁢
• GR
• GR
• -
• 2
• ⁢
• r
• p
• 2
• [
• K
• 2
• ⁢
• r
• p
• 3
• ⁢
• Ω
• fan
• 3
• -
• HP
• fan
• N
• p
• ⁢
• (
• GR
• -
• 2
• GR
• )
• 2
• ]
• wherein “PCP” is the pin clearance parameter in rpm, “cr” is the clearance in inches, “GR” is a gear ratio of the epicyclic gear train, “rp” is the planet gear bending stress neutral axis radius in inches, “Np” is a number of the plurality of planet gears, “HPfan” is a fan power of the gas turbine engine in horsepower at takeoff conditions, “Ωfan” is a fan speed of the gas turbine engine in rpm at takeoff conditions, K1 is a first constant of 1.96×10−5 per horsepower-minute-inch, and K2 is a second constant of 4.91×10−9 horsepower-minutes cubed per cubic inch, and wherein the pin clearance parameter is greater than or equal to zero rpm and less than or equal to 3,334 rpm;
• and
• a primary lubrication system configured to supply a lubricant to the gearbox bearing of at least one of the plurality of planet gears during normal operation of the gas turbine engine,
• wherein the primary lubrication system comprises a primary pump, a primary lubricant supply line, and one or more tanks,
• wherein the primary pump is in fluid communication with the one or more tanks and the primary lubricant supply line and is operative to pump the lubricant from the one or more tanks to the gearbox bearing of at least one of the plurality of planet gears, and
• wherein a gear ratio of the gear assembly is in a range from 2.5 to 5.