A320 No fault light hyd pumps

[Speedwinner]

Hello folks,

Quick one: why do the generators before engine start show a fault light but the green and yellow pump do not? Any hint on that?

And another one: is the emer cancel button on the ecam panel also a confirmed button?

Thanks!

Sw

[hph304]

Gen fault light illuminates when:
Lights up amber, and an ECAM caution comes on, if:
‐ The associated generator control unit (GCU) trips it.
Note: If a differential fault trips the protection, reset action has no effect
after two attempts.
‐ Opening of the line contactor (except if the GEN pb-sw is selected OFF).

If ENG are off, line contactor will open because the generator field is not energized.

For Eng 1(2) hydraulic pumps:
This amber light comes on, and the ECAM caution appears, if :
‐ The reservoir level is low
‐ The reservoir overheats
‐ The reservoir air pressure is low
‐ The pump pressure is low (inhibited on the ground, when the engine is
stopped).
This light goes out, when the crew selects OFF, except during an overheat. (The
light stays on as long as the overheat lasts).

The button must be confirmed since it is covered according to Airbus procedure. Might be that some operators don't do this however. With my company it is SOP.

Regards

[Uplinker]

In the case of the genny fault lights, the aircraft has electrical power applied, either from the GPU or the APU. So as far as the aircraft is concerned, its electrical system is energized but the gennys are not producing power, so it illuminates the fault lights.

(To confirm this, I will check to see next time I switch on the aircraft from cold if the genny lights illuminate with batteries only or when the AC system is powered. I don't think they come on with battery power only).

In the case of the hydraulics, there will be a non return valve between each (Green/Yellow) system and its ENG HYD pump. This is necessary because otherwise, if the Green or Yellow ENG HYD pump had failed, but the system was being pressurised by the other ENG HYD pump via the PTU, then the ENG HYD pressure switch would 'see' pressure but would not 'know' if that was from its own pump or another one, so it would not be able to tell if its own pump had failed. (The main purpose of the ENG pump non return valve is to prevent fluid loss if the ENG pump were to shatter or to suffer a seal failure).

If an ENG pump fails, but system pressure is maintained by other pumps and the PTU, the non return valve downstream of that ENG pump will close and the pressure switch - situated between the ENG HYD pump and its non return valve- will 'see' low pressure and operate the fault light.

What I can't work out is why Airbus would suppress the ENG HYD pump fault illumination when the engine is not operating.

[Speedwinner]

Thanks Folks!

[safelife]

On the Fokker 100 (similar all-lights-out concept) the GEN FAULT was suppressed as long as the engine wasn't running. I always thought that to be more logical. It's not faulty, after all.
The APU GEN also doesn't show FAULT when the APU is stopped...