[macaman]

Our '68 T337C does have the rear hydraulic pump. In the POH it mentions that both do run together but that it is also a backup if the front pump fails, which sounds nice. We have never had either pump fail, however the drawback is that the second pump makes the system that much more complex.

I was lucky, Louie Dubois from Dubois Aviation in Chino, CA had come up for our annual recurrent training in another airplane. Our insurance also required an annual IPC in the Skymaster from an instructor that met the open pilot policy so he would do this with me as well. After takeoff, we looked in the mirror to see the main gears dangling behind like a wasp's tail legs in flight. One of the lines to the rear pump blew, draining the system to both pumps. It was nice having Louie in the right seat as we managed the manual gear extension procedure.

A positive of having both on the Turbo C model (each model's system could and likely is much different, especially the early models) is that you have one less thing to worry about should an engine fail. If you only have the gear driven pump on the front engine, you get to decide weather or not you want to let the windmilling prop power the pump to extend the gear or if you want to immediately feather the prop to minimize drag while if you have the 2nd pump on the rear, you know you can use that at your normal approach position to extend the gear.

Personally, having lost an engine one time and having the line blow on a different flight, I'd be much more comfortable doing the manual extension with power to both spinners than to try and decide if the rear engine had enough power to keep me above all the cumulus granite out west.