A350 EDP clutch

[AeroTech]

Hi,

http://www.smartcockpit.com/docs/a350-9 ... pilots.pdf

In the link above (ATA 29, page 29.3), it is said that "The Hydraulic System Monitoring Unit (HSMU) monitors EDP clutch".

I never heard about EDP clutch in other airplanes.

a-Is this clutch a new device in the EDP?

b-What's the function of the clutch in this EDP (engine driven pump)?

c-Besides A350, are there other aircraft that their EDPs (engine driven pump) are fitted with a clutch?

[Lan_Morehell]

a. Well, You should be able to cut off the hudraulic pressure from EDP somehow in case of overheat, or low pressure, or engine damage etc.
b. Most probably to disconnect the pump from engine driveshaft and therefore shut off the pump.
c. Every aircraft has some EDP or EDP fluid pressure shutoff mechanism. 738 has a solenoid for that (Which only cuts off pressure, creating a fluid circuit without stopping pump itself), A350 obviously has a clutch. Why not?

[spannersatcx]

Engine Driven Pump Declutch
The declutch, which is a part of the engine-driven pump, includes a mechanical device that has an effect on the pump shaft level.
The declutch can be used when a pump malfunction occurs.
The disengagement can be done manually from the ground, when the engine is stopped, use a 3/8 inch square drive tool on the reset port. On the Engine Driven Pump, there is a visual indicator which gives the position of the clutch: reset, engaged or disengaged.
When the EDP is declutched, the re-engagement cannot be done from the cockpit.
After trouble identification and correction, the re-engagement of the pump to the engine accessory gear box is done manually when the engine is stopped: Remove the cover, pull release cable and reinstall cover.
The new engine driven pumps include a disengagement clutch at the drive from the engine. This lets the maintenance personnel de-activate the pump for an approved flight dispatch with an inoperative pump.

[AeroTech]

Thanks the feedback.

spannersatcx, very informative post.

a) Can the pilot disconnect in flight the EDP from the engine gearbox? If so is it the guarded switch in the Overhead panel? Please look at the link below:
http://www.smartcockpit.com/docs/takeoff_full-cockpit.pdf (hhttp://www.smartcockpit.com/docs/takeoff_full-cockpit.pdf)

I was looking to the Overhead panel in A380 in the link below and it seems there is a guarded switch to disconnect the EDP in A380:
http://www.smartcockpit.com/docs/a380-overhead-panel-light-test-on.pdf

b) Can the pilot (in flight) or the AMT (on ground) disconnect the EDP in A380?

It seems this feature (the disconnection of the EDP from the gearbox) is useful especially in flight even if each engine is fitted with one EDP. It is useful also on the ground for engine fitted with 2 EDPs for the dispatch.

c) Why Boeing is not using this feature in flight on the EDPs (used by Boeing in the IDG or VFSG, and even the CSD) ? I wrote "in flight" because Boeing (not Douglas) uses only one EDP per engine and there is no benefit for this feature on the ground for the dispatch.

[tdracer]

c) Why Boeing is not using this feature in flight on the EDPs (used by Boeing in the IDG or VFSG, and even the CSD) ? I wrote "in flight" because Boeing (not Douglas) uses only one EDP per engine and there is no benefit for this feature on the ground for the dispatch.
Boeing doesn't use a clutch, it uses a servo valve to 'depressurize' the EDP such that the EDP isn't involved in the associated hydraulic system and is basically just free-wheeling.

[spannersatcx]

A350
Engine Driven Pump (EDP) Operation
The hydraulic system can be pressurized by the Engine Driven Pumps (EDPs).There are two EDPs per engine so two per hydraulic system. The Engine Driven Pumps (EDPs) can be in three different states:
•pressurized,
•Depressurized
•declutch
The pressurization and depressurization modes are controlled from the P/Bs installed on the Main Hydraulic Panel. One P/B per EDP is used to select its depressurized mode. The normal state of the EDP P/B is pushed. In this condition there is no indication at the P/B and when the engines are running the system is pressurized automatically. Pressing the P/B causes the related EDP to operate indepressurized mode.
P/B's with red arrows on pic.
The blue arrows are showing grnd maintenance hyd switches.

To put each EDP in the depressurized mode, you must energize the EDP solenoid valve.
This solenoid valve can be energized:
•Manually by a pump OFF pushbutton switch (direct wiring)
•Automatically when the related engine FIRE pushbutton is pressed (due to Fire SOV closure)
•Automatically by the Propulsion Control System(PCS)in case of engine start. The EDPs will pressurize again after engine start. N3>50%(Flight and GND)
(It wil lnot be depressurised during DRY Crank)
•Automatically by the FQMS if there is a fuel low level and a hydraulic temperature of more than 80 °C. Automatic depressurization is only done if the second EDP of the hydraulic system, which is on the opposite engine, supplies pressure (pressure is measured at the EDP HP manifold). OVHT Threshold in RESERVOIR is now modified from 95 deg C to 115 deg C.

[AeroTech]

Thanks for the feedback.

tdracer wrote:
Boeing doesn't use a clutch, it uses a servo valve to 'depressurize' the EDP such that the EDP isn't involved in the associated hydraulic system and is basically just free-wheeling.



Both Boeing and Airbus use the EDP solenoid valve to pressurize or depressurize the hydraulic system. On recent aircraft Airbus use the clutch as extra feature because it provides more benefits (for example disconnect the EDP from the gearbox in flight because of certain problems. This feature (the clutch) is provided only on recent aircraft (spannersatcx mentioned A350 using the AMM as evidence and may be on A380, I hope someone can confirm it on A380). That's why I am wondering why Boeing is not using the clutch in the EDP (Airbus own patent clutch or other reasons ?)?

The EDP solenoid valve is part of the pump and it is made by the EDP manufacturer (supplier/vendor) and not by Boeing or Airbus.

[really not]

A380 Manual states that following a Reservoir Low Level or a System Overheat (only if system depressurisation is not successful) the pumps may be disconnected from the engine accessory gearbox to prevent damage. Reconnection is only possible on the ground. No reference to a clutch is made, however there is obviously a hard disconnect system.