Originally Posted by
SJCFlyerLG
With the engine fully in the tail, the DC-10 was subject to catastrophic loss of control if the tail engine exploded, as was the case in the UA232 crash. The hydraulic lines controlling flight were severed, leaving only thrust control of the wing engines.
And with the hydraulics running through the cabin floor, if the cabin floor buckled, you lost the airplane. That's why the rear cargo hatch failures in the '70s were so awful. Douglas cheaped out on the hydraulics and did not run a redundant backup through the top of the fuselage. The hatch popped, the floor buckled, the control lines snapped and (in the THY Eremonville case; Windsor was an almost) the plane crashed. If it'd been built like a Boeing it would have come home.
As for lodging the number two engine in the tail rather than using an S-duct: I don't know if it was a 727 patent case, but I do know it was cheap, simple, dirty design, and therefore of interest to Douglas during the race to get the bugger in the air.