The funny thing about "in-charge" is it leaves much to the imagination. In-charge doesn't necessarily bring with it the responsibilities and accountability of appointment of being in command or being in charge.
Within this discussion is also the vagueness of field time which has no connection by it self of requiring the NCO and or commissioned service member to be in charge or to be in command.
So what do you imagine day-to-day and throughout career field time to be considering to be there leading requires significant competence, proficiency and experience.
AFI13-219v1 COMBAT CONTROL AND SPECIAL TACTICS OFFICER TRAINING, 23 FEBRUARY 2009 Certified Current 21 APRIL 2011:
4.4.2. Special Tactics Officer (STO) Training. STOs are first and foremost combat leaders, train and employ them for this role. Simultaneously, STOs must be thoroughly trained in planning, coordinating and working in an Operations Center (STOC, TOC, JOC, AOC, etc.) Provide both the academic training and practical experience to ensure STOs succeed at the C2 level. STOs need to be familiar with all ST mission sets. Recommend all STOs get initially certified as JTACs and receive training in CSAR/PR operations as part of ST Advanced Skills Training. Commanders will ensure that all of their assigned STOs receive training and exposure to CSAR/PR mission sets – especially officers in ST units with assigned PJs who have the greatest opportunity and most pressing need for this training.