Final answer:
Hot or Simultaneous Refueling is a special servicing operation involving multiple refuelers or a combination with hydrant-servicing equipment for quick servicing of large aircraft, using different types of fuel for different stages of ignition.
Step-by-step explanation:
The special servicing operation that involves using more than one refueler or a combination of refuelers and hydrant-servicing equipment to rapidly service large frame aircraft is known as a Hot Refueling or Simultaneous Refueling operation. This procedure is intended to minimize the time an aircraft spends on the ground being refueled and is used for large, commercial, or military aircraft where rapid turnaround is essential.
During hot refueling, different types of fuel may be used; for example, the first stage of ignition uses a liquid fuel/oxidant mixture (indicated by a 3 s green flame), while the second, more powerful stage uses a solid mixture (indicated by a 4 s yellow flame).