[ankara_acc]

ı am writing from turkey, so we appliy rules depended ıcao.For the trafics approaching a field, the first rule is ceeling and visibility.Before starting a vector for visuall approach, controller must be sure that ceeling higher than the first approach altitude. The other main rule is pilot's report of field in sigth.

If pilot reports the field and traffic in sigth, controller may clear the traffic for visual app. But atc still has responsibility of seperation for succeeding aircrafts.For preceeding aircraft pilot responsible.A caution announce for wake turb. may be ıssued by controller.

Question seems a specific application regarding the situation of the traffics and the field. If trff. vector to a point that considered starting point for vis. app., mrva(min. radar vector altitude) values valid.( while ı am in operation, ı use the outer marker as referance point, trff. most probably could have field in sigth untill om.). So the controller at MEM may think that ıls course is the guarenteed way,untıll field in sigth. And in case of unexpected situation( if negative in sigth etc.) pilot can continıue on glideslope and finish his approach.

If a trf. vectored for visual app., you should give a true path for loosing altitude and chance for field in sigth.