Which types of aircraft are required to carry ELTs? According to regulations and recommendations from the FAA, ICAO or other aviation organisations, what types of aircraft are required to carry Automatic Fixed Emergency Location Transmitters (ELT(AF)) devices? In particular, is it required of commercial transport airliners?

CAA (and I guess other aviation organisations/regulators) group aircraft into several categories:


General Aviation (GA) - personal aircraft etc.
Business Aviation - executive jets etc
Commercial Air Transport / Public Transport - Scheduled passenger airliners etc.




AOPA say


  ELTs are emergency transmitters that are carried aboard most general aviation aircraft in the U.S.


(my emphasis) - note GA, not all aircraft.



CAA refer to ICAO Annex 6 


  Aeroplanes - ICAO Annex 6, Part II
  6.12.3 From 1 January 2005, all aeroplanes operated on extended flights over water as described in 
  6.3.3 b) and when operated on flights over designated land areas as described in 6.4 shall be 
  equipped with one automatic ELT. [i.e. designated KK(ii) in the Air Navigation Order]  
  
  6.12.4 Recommendation. - All aeroplanes should carry an automatic ELT. 


But I can't find an annex mentioning ELTs at www.icao.int.



So, I'm not sure whether all airliners are required to carry ELT(AF)s and if so, by whom.
Everything you need to know (at least in the USA) is here.

Regarding airliners, it appears that they are carved out of the general requirement to have an ELT in 91.207.f.2.   I guess that makes some sense.  If you're flying a scheduled flight, presumably we should be able to find the plane, since we know the takeoff time and approximate airspeed, and we have radar tracking by ATC/ARTCC.  Unscheduled (especially VFR) flights are where things get dicey.