Firstly, that AND/OR drawing is called a Boullian Expression.
Secondly, the PTU is only inhibited when:
1. Y pump PB is off AND
2. Cargo Door OPER
And as a side note the PTU continues to be inhibited for 40 seconds after the cargo door closes.
The other conditions show when the PTU runs, these are
1. PTU pb switch in auto AND
2. Diff pressure between G & Y >500 AND
Either of:
3a. NOSE L/G shock absorber extended (i.e. airborne)
3b. Both ENG Masters off
3c. Both ENG Masters on (These two ensure PTU doesn't run after only one engine is started)
3d. Park Brk off AND NWS not in towing position
You are right about the three inhibitions, as far as I can tell. But your assumption in RTO is slightly wrong. We need to focus on conditions 3a to 3d to understand what will happen, conditions 1 and 2 will be met following a failed engine with the PTU pb in its normal position
When the engine fails the PTU will kick in once diff pressure drops less than 500.
Condition 3a is not met since you are on the ground.
When you stop, set the p.brake, you probably will still have both ENG Masters set to ON, when you finish ECAM actions you'll have one ENG Master off, so both conditions 3b. and 3c. will no longer be met,
The only condition left that will allow for the PTU to run is 3d. Well the NWS is not going to be in towing position, so that condition is met, the only thing left is the p.brake, i.e. when its off the PTU will run, when it's on the PTU will not run. So as soon as you are ready to taxi again and switch the P.Brake off the PTU should start running and will give you pressure again in the Green or Yellow systems.
This is based on how I understand the diagram.
Hi airman another question then:
so we have established that with the RTO condition the PTU will run once we release the parking brake.
Which brings me to my next question:
We are on a taxiway starting engine 2 after push back
NWS is not in the towing position; and
the parking brake is off
i have lime greened the conditions above so it appears the PTU should run, however if you check DSC-29-20 P2/8 PTU pb sw
NOTE: the PTU is inhibited during the first engine start and automatically tested during the second engine start.
