Provided is a turbo fan engine (TF) provided with a
power transmission device that switches main shafts (MSs) connected to a
starter generator (SG) so as to perform
power transmission, between at startup and after the startup. The TF includes a first MS and a second MS. The
power transmission device includes a first shaft, an intermediate shaft, and a second shaft that are coaxially disposed, and a
clutch. The first shaft is connected to the first MS through bevel gears, the intermediate shaft is disposed outside of the first shaft and is connected to the SG through bevel gears, and the second shaft is disposed outside of the intermediate shaft and is connected to the second MS through bevel gears. When, out of any two adjacent shafts of the first shaft, the intermediate shaft, and the second shaft, an inner shaft tries to rotate at a speed higher than a speed of an outer shaft, the
clutch causes the both shafts to engage with each other and to rotate at the same speed, and transmits power, whereas when the outer shaft tries to rotate at a speed higher than a speed of the inner shaft, the
clutch causes the both shafts to disengage from each other, and does not transmit power.