Originally Posted by
Uplinker
I am guessing, but I would have thought that intelligent design would mean that only the gearboxes and props would have to be different on the two contra-rotating engines, which is not a massive increase on spares requirement, considering the advantages. The engines would otherwise be identical.
My reading indicates that is the situation, engines the same, difference in the props and gearbox.
Originally Posted by
Uplinker
Not sure why an engine change would take several days?
Well, I don't know if it accounts for "several days" but I can see that having to change gearboxes would take more time, perhaps a lot more time.
Just for example a Herc Quick Engine Change assembly has everything except the prop and associated controls (Valve housing) It even has almost all the cowling installed. You essentially hoist the engine into place. bolt it on, make the electrical and plumbing connections, then install the prop and Valve housing and rig the controls. I know that's simplifying it a bit, but having to install a gearbox on the engine will add to that, perhaps considerably. Installing the gearbox would seem to involve removing cowling and reinstalling , There's plumbing to connect, as the gearbox and engine share lubrication, and the installation itself seems pretty critical. you're making a connection which transmits a lot of power, and it has to be aligned correctly. Perhaps this has been engineered so that a gearbox installation is pretty much "plug and play", but even so, it's a process that isn't required on a Herc engine change.