 Lieutenant-colonels are addressed by rank and name and thereafter by subordinates as "Sir" or "Ma'am".In the Canadian Army, lieutenant-colonels are often employed as commanding officers of battalion-sized groups, such as infantry battalions, armoured regiments, artillery field regiments, engineer field regiments, signal regiments, field ambulances and service battalions.In the Royal Canadian Air Force, lieutenant-colonels are often seen as the commanding officer of flying or ground squadrons.