I'm not in the aviation business but I will comment anyway with a wind turbine perspective :-)
Many modern machinery need power electronics to control speed anyway, so doing for a DC distribution system will eliminate an additional DC/AC and AC/DC conversion.
Since the driving machine has variable speed, something (CSD/DFIG/Full scale converter) has to be added to convert to a fixed frequency AC.
The most modern and weight and power effective way is to use a PM Generator with a AC to AC converter. (This is in reality a AC to DC to AC converter)
Many systems like (hydraulic) pumps and fans can benefit from having PM motor with a variable frequency drive, since the weight of systems are reduced when the rotational speed is higher.
The efficiency is also improved since the speed can be adjusted, and a PM machine has lower loss than an induction machine.
Another advantage is that DC buses can be connected together without any need for synchronization. (Some fault isolation relays with hall sensors are need)
A disadvantage is that a lot of industrial components like circuit breakers are only rated for 50 to 60 Hz.
Last edited by HighWind; 17th Nov 2013 at 11:50.