Thank you PA.
PTOW states for Performance Take off Weight. It is the max TOW due to perf limitations.
You have described how to know if a SID requires special calculations.
I will give you an example of what I want to know.
You are PIC of a 744 and at your arrival to OPS your company tells you are to TO rwy10 using XXX1A SID. That SID requires a 5% gradient for the 2nd segment. Your OPS agent gives you a performance analysis showing that you may accept only 380 of the 400 pax already checked, plus 20 tons of cargo, plus the fuel needed for the flight. That max weight is your PTOW. Therefore you are limited by performance due to obstacles at the 2 segment for the rwy 10.
When you arrive to cockpit, the ATIS has changed and the active is the 28. The dispatcher wants to begin the boarding but the SID XXX1B used for the rwy 28 requires a gradient of 8% for the 2nd segment.
There goes my question. How can you tell to that anxious dispatcher how many pax do you accept? Were do the MAIN COMPANIES search for the new PTOW? Do they use special charts? Will you introduce the TOW into the FMS and checks if it is OK with the obstacles? Or, Will you make your own analysis at the performance charts of the OM?
What is a WAT combo?
Tailwinds