Speed sensor probe location in gas turbine engine

Abstract

A method for a gas turbine engine includes affixing a speed sensor probe in the gas turbine engine. The sensor probe is operable to determine a rotational speed in the gas turbine engine. The gas turbine engine includes a first spool that is coupled at a first axial position to a compressor hub that is coupled to drive a first compressor. The first spool is coupled at a second, different axial position to a fan drive input shaft that is coupled to drive a fan drive gear system. The second turbine is coupled through a second spool to drive a second compressor. The speed sensor probe is affixed at a third axial position that is axially forward of the first axial position and axially aft of the second axial position.

What is claimed is: 
     
         1 . A method for a gas turbine engine, the method comprising:
 affixing a speed sensor probe in a gas turbine engine, the sensor probe operable to determine a rotational speed in the gas turbine engine, the gas turbine engine includes a fan, a fan drive gear system coupled to drive the fan about an engine central axis, a compressor section including a first compressor and a second compressor, and a turbine section that includes a first turbine and a second turbine, the first turbine coupled to drive a first spool, the first spool being coupled at a first axial position to a compressor hub that is coupled to drive the first compressor and the first spool being coupled at a second, different axial position to a fan drive input shaft that is coupled to drive the fan drive gear system, and the second turbine coupled through a second spool to drive the second compressor, and   the speed sensor probe being affixed at a third axial position that is axially forward of the first axial position and axially aft of the second axial position.   
     
     
         2 . The method as recited in  claim 1 , including, prior to affixing the speed sensor probe, removing a used speed sensor probe from the gas turbine engine such that the affixed speed sensor probe replaces the used speed sensor probe. 
     
     
         3 . The method as recited in  claim 2 , wherein the gas turbine engine is accessed for the removing and the affixing through one or more cowl doors. 
     
     
         4 . The method as recited in  claim 2 , including electrically disconnecting the used speed sensor probe and electrically connecting the affixed speed sensor probe. 
     
     
         5 . The method as recited in  claim 1 , wherein the gas turbine engine further comprises a fan output shaft coupled to be rotated by the fan drive gear system and coupled at a fourth axial position to the fan, the fourth axial position being distinct from the first axial position and the second axial position, and wherein the fourth axial position is forward of the second axial position the third axial position. 
     
     
         6 . The method as recited in  claim 1 , wherein the compressor section is axially aft of the fan drive gear system. 
     
     
         7 . The method as recited in  claim 1 , wherein the first compressor is a three-stage compressor. 
     
     
         8 . The method as recited in  claim 1 , including at least one sensor target coupled to rotate with the first spool. 
     
     
         9 . The method as recited in  claim 1 , wherein the fan drive gear system is an epicyclic gear system. 
     
     
         10 . The method as recited in  claim 1 , wherein the epicyclic gear system has a gear reduction ratio greater than 2.3:1.