to be followed and the criteria that must be met before  the path concludes and the next path begins. Although  there are 23 leg types available, none of the manufactured  database equipment is capable of using all of the leg types.  Pilots must continue to monitor procedures for accuracy  and not rely solely on the information that the database  is showing. If the RNAV system does not have the leg type  demanded by procedures, data packers have to select one  or a combination of available lleg types to give the best  approximation, which can result in an incorrect execution  of the procedure. Below is a list of the 23 leg types and  their uses that may or may not be used by all databases.  • Initial fix or IF leg—defines a database fix as a point  in space and is only required to define the beginning  of a route or procedure. [Figure 6-5]  • Track to a fix or TF leg—defines a great circle track  over the ground between two known database  fixes and the preferred method for specification of  straight legs (course or heading can be mentioned  on charts but designer should ensure TF leg is used  for coding). [Figure 6-6]  • Constant radius arc or RF leg—defines a constant  radius turn between two databases fixes, lines  tangent to the arc, and a center fix. [Figure 6-7]  • Course to a fix or CF leg—defines a specified course  to a specific database fix. Whenever possible, TF legs  Next segment R F L E G  ARC  CENTER  FIX  Previous segment  CF LEG 080°  Course is flown making aGLYPH<df00>justment for winGLYPH<df00>  DF LEG  Unspecified position  $_{F}$A LEG 080°  UnspecifieGLYPH<df00> position  8,000'  FA leg is flown making aGLYPH<df00>justment for winGLYPH<df00>  TF LEG  Figure 6-5. Initial fix.  Figure 6-7. Constant radius arc or RF leg.  Figure 6-8. Course to a fix or CF leg.  Figure 6-6. Track to a fix leg type.  Figure 6-9. Direct to a fix or DF leg.  Figure 6-10. Fix to an altitude or FA leg.  6-6 