65 •  Minimum Turning Altitude (MTA)  - Minimum turning altitude (MTA) is a charted altitude providing vertical and  lateral obstruction clearance based on turn criteria over certain fixes, NAVAIDs, waypoints, and on charted route  segments. When a VHF airway or route terminates at a NAVAID or fix, the primary area extends beyond that  termination point. When a change of course on VHF airways and routes is necessary, the enroute obstacle clear- ance turning area extends the primary and secondary obstacle clearance areas to accommodate the turn radius  of the aircraft. Since turns at or after fix passage may exceed airway and route boundaries, pilots are expected to  adhere to airway and route protected airspace by leading turns early before a fix. The turn area provides obstacle  clearance for both turn anticipation (turning prior to the fix) and flyover protection (turning after crossing the fix).  Turning fixes requiring a higher MTA are charted with a flag along with accompanying text describing the MTA  restriction. •  Minimum Crossing Altitude (MCA)  - An MCA is the lowest altitude at certain fixes at which the aircraft must  cross when proceeding in the direction of a higher minimum enroute IFR altitude. MCAs are established in all  cases where obstacles intervene to prevent pilots from maintaining obstacle clearance during a normal climb to a  higher MEA after passing a point beyond which the higher MEA applies. The same protected enroute area vertical  obstacle clearance requirements for the primary and secondary areas are considered in the determination of the  MCA. The FAA has created new low altitude area navigation (RNAV) "T" routes for the enroute and terminal environments. The  RNAV routes will provide more direct routing for IFR aircraft and enhance the safety and efficiency of the National Air - space System. To utilize these routes aircraft are required to be equipped with IFR approved GNSS. In Alaska, TSO-145a  and 146a equipment is required. Low altitude RNAV only routes are identified by the prefix "T", and the prefix "TK" for RNAV helicopter routes followed by a  three digit number (T-200 to T-500). Routes are depicted in blue on the IFR Enroute Low Altitude Charts. RNAV route data  (route line, identification boxes, mileages, waypoints, waypoint names, magnetic reference courses and MEAs) will also  be printed in blue. Magnetic reference courses will be shown originating from a waypoint, fix/reporting point or NAVAID.  GNSS MEA for each segment is established to ensure obstacle clearance and communications reception. GNSS MEAs  are identified with a "G" suffix. Joint Victor/RNAV routes are charted as outlined above except as noted. The joint Victor route and the RNAV route iden- tification boxes are shown adjacent to each other. Magnetic reference courses are not shown. MEAs are charted above  the appropriate identification box or stacked in pairs, GNSS and Victor. On joint routes, RNAV specific information will be  printed in blue. FAA Chart Users’ Guide - IFR Enroute Terms AREA NAVIGATION (RNAV) "T" ROUTE SYSTEM Victor Route (with RNAV/GPS MEA shown in blue)