A320 Engine fail PTU question

[Flaperon75]

Hello Airbus Genii,

In the case of an engine fail, if you push the Eng Fire pb, one of its actions is close the corresponding Hydraulic Fire Shut off valve.

In the Engine failure case without damage, where you don't push said pb, what are the implications on the hydraulic system?

I'm pretty sure that in both instances the PTU would kick in (with differential hydraulic press > 500psi). But without the hydraulic fire shut off valve closed, what are the differences??

Ta muchly for your shared wealth of knowledge and expertise ;-)

[Goldenrivett]

Hi Flaperon75,

But without the hydraulic fire shut off valve closed, what are the differences??

The windmilling engine will deliver 3,000 psi Hyds when the demand is low and airspeed is above green dot. Around GD speed, the pressure tends to fluctuate causing the PTU to cycle on and off and the HYD SYS page to cycle into view. Below GD speed, the PTU runs continuously so no more distracting SYS page changes.

[Microburst2002]

That's actually a good question

If the fire push button of the failed engine is pushed, the hydraulic reservoir will be isolated from its pump. How can that system work without the reservoir?

[Amadis of Gaul]

Because the reservoir will only be isolated from the relevant EDP, not from the PTU.