Final answer:
If both engines are started using APU bleed air, the operating engine thrust must not exceed the maximum thrust that can be provided by the APU.
Step-by-step explanation:
The subject of this question is Physics and it is targeted towards High School level students.
If both engines are started using APU bleed air, the operating engine thrust must not exceed the maximum thrust that can be provided by the APU. The APU, or Auxiliary Power Unit, is a smaller engine typically located in the tail section of an aircraft. It provides electrical power and compressed air for various aircraft systems when the main engines are not running.
Depending on the specific aircraft, the APU bleed air may have a limited amount of thrust it can provide. Therefore, the operating engine thrust must not exceed this maximum limit to ensure the APU can supply sufficient bleed air to both engines.