airbus a320 question during maintenance

[bEN_]

hi guys would like to know more from forum members regarding an issue i encounter recently.


aircraft type A321.

the aircraft had jacked up(flight configuration) during maintenance and during the landing gear retraction test, the PTU did not come on to pressurize the green hydraulic system . (aircraft yellow hydraulic electrical pump is being turn on and there's 3000psi on the yellow hydraulic system)


but when the de-actuactor is being installed on the aircraft to simulate aircraft on ground configuration, and with the yellow hydraulic electrical pump turned on the PTU activate and pressurized the green hydraulic system as normal.


i would like to know why it happened this way which some other people told me the PTU will be active even in flight config during the landing gear retraction test.


is this a fault condition or normal i could not understand. :ugh:

[tigerstift]

Hi Ben,

Had have this discussion already some ages ago. In general it's not possible to perform a L/G retraction/extension Test with only the Yellow EMP + PTU, due to restricted flow delivered by the PTU.

Available flow minimum on the green system (considering the internal leakage) = approx 9L/min
Available flow for the LDG retraction = approx9L/min at 2175psi (<3000psi)

This would mean difficulties in retraction, and possible pressure drops with priority valve closures.

But this would still not answer the question why the PTU didn't came online!

What my suggestion would be:
The G EDP pressure switch detects a low pressure, the PTU ECAM indication is displayed showing a transfer from Yellow to Green Hydraulic System. If it is a genuine low press, the PTU will start at the same time, if it is a spurious low press (Press switch failure), the PTU will not start refer to AMM 29-23-00.

So i suggest to follow up the AMM procedure again to ensure that the Aircraft would be in proper Flight mode and Hydraulic pressure is applied by a external source.
Just to heads up on the ground mode, try to apply the Parking Brake or disconnect the N/W Steering with one ENG Master ON. If the PTU turns offline i see would suggest that the flight mode was not correctly applied to the A/C.