The duty cycle of the A320 starter refers to the limitations on how the starter can be used to prevent overheating or damage. For the Airbus A320, the following standard limitations apply:

Starter Duty Cycle Limitations

1. Maximum Starter Engagement Time:
   
   

   • Standard Use: 2 minutes per cycle.

   • Increased Use: 3 minutes per cycle for the ground start (newer engines such as IAE V2500 or CFM56 with updated configurations may allow this).

2. Number of Consecutive Cycles:
   
   

   • A maximum of 3 consecutive start attempts is allowed.

3. Cooling Period:
   
   

   • After three failed attempts or three cycles, a 15-minute cooling period is required before further attempts.

4. Continuous Cranking:
   
   

   • Continuous starter operation is limited to 5 minutes. After this, a 30-minute cooling period is required.

5. Starter Usage During a Manual Start:
   
   

   • The starter should not be engaged when N2 (core speed) is above 20%.

Additional Considerations:

• Always follow the aircraft's specific Flight Crew Operating Manual (FCOM) or Engine Manual, as variations might exist depending on engine type (e.g., CFM56 or IAE V2500).

• Using ground air sources (APU or external air) in conjunction with the starter might have additional restrictions based on pressure settings and procedures.

These limitations ensure engine safety and protect the starter mechanism from excessive wear or overheating.