What Happened to the Aft Engine Mounted "T" Tail Design?

[Owain Glyndwr]

The VC-10 had rear mounted engines so that the entire wing could be fitted with high lift devices (ie full span slats and flaps/ailerons) to provide an amazing short field performance for hot and high operations off short runways on BOAC's African network. Wing mounted engines required gaps in the high lift devices.

The VC-10 had a CLmax of 2.3, but the A320, from the same Weybridge design team achieved CLmax 3.2, albeit with a lower sweep wing, so it isn't obvious that wing mounted engines have worse high lift capability.

Going back to the original question, a couple of other considerations would be:

Susceptibility of T tails to being blanketed by wing wake at high AoA (deep stall problems), and
Great difficulty today to get clearance for the disc burst case where T tails with engines closely mounted opposite each can rapidly turn into a glider with no hydraulics or electrics.

[Volume]

Another important aspect is the position of the cabin and baggage compartments CofG in relation to the wing. Having the engines far aft you need to position your payload more to the front making the aircraft tail heavy at low loading and nose heavy at full load. With wing mounted engines this is much more ballanced.

The Trident had the forward bulk cargo compartment (requiring asymmetrical nose gear) to give more flexibility in placing the payload.

I seem to recall the IL-62 having huge C of G problems

They call it differently
Illushin claims that a major disadvantage of the VC-10 compared to their IL-62 was the position of the landing gear too far aft of CG producing high nose gear loads and requiring a larger tail for rotation. The IL-62 uses the pogo stick when empty and is balanced perfectly when loaded. But maybe that is just a good excuse

[andrasz]

The IL-62 uses the pogo stick when empty and is balanced perfectly when loaded.

The Il-62 also had a water ballast tank up front that could take as much as six tonnes, to make it flyable with low payloads.

Bit off topic:

Recalling some hazy memories from my early career, Aeroflot used to oprate some weird fortnightly Il-62 services to west african destinations like Brazzaville, Bissau Guinea, etc. via BUD, being the last friendly port of call to uplift fuel. They arrived in the small hours with 8-12 grim looking guys in black leather coats as passengers, and usually there were a few green painted long wooden boxes in the hold that we were not allwed to go near to. They came in with a light fuel load from Moscow with the ballast tank always full, and left a mighty puddle on the apron before departing with full tanks...