aerotech777
Topic Author
Posts: 74
Joined: Sat Aug 15, 2009 3:53 pm

A350 EDP clutch

Thu Jan 04, 2018 9:58 pm

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".

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

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

Feedback appreciated.
 
Lpbri
Posts: 46
Joined: Tue Sep 27, 2016 7:18 pm

Re: A350 EDP clutch

Thu Jan 04, 2018 10:48 pm

All aircraft in know of have a depressurization solenoid. This blocks the flow out of the pump when the pump is selected off. Or when the fire handle is pulled, or there is an overheat condition. The solenoid also bypasses the pump during an inflight restart.
 
aerotech777
Topic Author
Posts: 74
Joined: Sat Aug 15, 2009 3:53 pm

Re: A350 EDP clutch

Sun Jan 07, 2018 5:11 pm

Thanks for the feedback.

I am aware of the depressurization solenoid (the switch in the cockpit should remain ON to prolong solenoid life) of the EDP.

Since A350 is[b][b] new[/b][/b] aircraft I said may be the EDP is fitted with a clutch as it is mentioned in link above. So I am wondering if the A350 EDP is fitted with clutch same as the IDG (Integrated Driven Generator) or CSD (Constant Speed Drive) on old aircraft. So I am wondering if the A350 EDP can be disconnected from the engine gearbox same as the IDG or the CSD.
It will be nice if someone (AMT, Pilot, ...) have access to the A350 AMM (Aircraft Maintenance Manual) or may be in the A350 FCOM (Flight Crew Operating Manual) to confirm if it a clutch or just depressurization solenoid. So feedback very appreciated

Lpbri, in the aircraft that I am little bit familiar (737) there is no overheat sensor in the EDP and when the fire handle is pulled the supply hydraulic valve is closed. If I am not mistaken other Boeing aircraft are fitted with EDP overheat switch.

Thanks.
 
User avatar
jetmech
Posts: 2329
Joined: Wed Mar 29, 2006 2:14 am

Re: A350 EDP clutch

Mon Jan 08, 2018 1:24 am

aerotech777 wrote:
Thanks for the feedback.
So I am wondering if the A350 EDP can be disconnected from the engine gearbox same as the IDG or the CSD.


From the looks of the following, I'd say not;

http://www.smartcockpit.com/docs/takeof ... ockpit.pdf

The disconnect push buttons for the IDG's are clearly visible and configured as guarded switches which makes sense as I believe once the IDG's are disconnected they can only be reconnected on the ground

The hydraulic pumps do not appear to have a disconnect function or guarded switch - although the hydraulic supplies do - so I presume there is no clutch.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
User avatar
Starlionblue
Posts: 18084
Joined: Fri Feb 27, 2004 9:54 pm

Re: A350 EDP clutch

Mon Jan 08, 2018 3:39 am

jetmech wrote:
aerotech777 wrote:
Thanks for the feedback.
So I am wondering if the A350 EDP can be disconnected from the engine gearbox same as the IDG or the CSD.


From the looks of the following, I'd say not;

http://www.smartcockpit.com/docs/takeof ... ockpit.pdf

The disconnect push buttons for the IDG's are clearly visible and configured as guarded switches which makes sense as I believe once the IDG's are disconnected they can only be reconnected on the ground

The hydraulic pumps do not appear to have a disconnect function or guarded switch - although the hydraulic supplies do - so I presume there is no clutch.

Regards, JetMech


Correct. The IDG guarded pushbuttons (Airbus nomenclature) disconnect the IDGs and they can only be reconnected by maintenance action on the ground. The hydraulic pumps, however, can be switched on and off in flight with the "Pump" pushbuttons.

To expand, on Airbus the logic is thus:
- Red guard: Irreversible action. Use must be confirmed by other pilot. E.g. Fire pushbuttons, RAT deploy...
- Black guard: Reversible action but use (in the air) must be confirmed by other pilot. E.g. FADEC power supply pushbuttons, tank transfer pushbuttons, flight computer pushbuttons.
- No guard: No need to confirm. E.g. Engine anti-ice.

A couple of special cases: ADIRS rotary switches are not guarded (though you have to pull and twist) but use must be confirmed by other pilot if in the air. Fuel jettison pushbuttons have red guards, but obviously, you can stop the jettison. The logic is that you can close the valves but you can't suck the fuel back in, so it counts as irreversible.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
jetmech
Posts: 2329
Joined: Wed Mar 29, 2006 2:14 am

Re: A350 EDP clutch

Mon Jan 08, 2018 1:24 pm

Starlionblue wrote:
To expand, on Airbus the logic is thus.

I wonder if it was always this way?

For some reason, I have recollection of an incident involving an A340 (SQ?) where the pilot inadvertently shutoff all four hydraulic systems in-flight instead of manipulating four, fuel cross-feed valves.

Part of the reason for this was that all the overhead switches were of an identical, unguarded black push-button design.

Interestingly, I cannot find any information on this so it must be a figment of my imagination?

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
User avatar
Starlionblue
Posts: 18084
Joined: Fri Feb 27, 2004 9:54 pm

Re: A350 EDP clutch

Mon Jan 08, 2018 3:52 pm

I don't know if it was always thus. I only know the 330 and 350 in detail. However no one but yourself can save you from pressing a pushbutton you shouldn't be pressing. That's why the kosher method of pressing anything while following the QRH or ECAM is to name the panel first and be very methodical. For example to turn on Crossfeed 1 on the 340, you'd read "Crossfeed one, on" from QRH or ECAM, then point at the panel with the big letters FUEL on the side (helpful hint) and say "Fuel", then you'd point at the relevant pushbutton and say "crossfeed one", then press the pushbutton, then confirm it goes to on and say "on". Innocent bystanders will think you sound a bit weird but this method really helps to mitigate wrong presses.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
zeke
Posts: 11674
Joined: Thu Dec 14, 2006 1:42 pm

Re: A350 EDP clutch

Mon Jan 08, 2018 9:02 pm

aerotech777

The EDP clutch within the hydraulic pump does act very much like the electrical IDG disconnect on othe Airbus. The aircraft has two hydraulic systems at 5080 psi, each engine has two EDPs connected to the accessory gearbox.

The clutch disconnect can be used by Crew from the cockpit in response to some faults or can be activated on the pump by mechanics to dispatch the aircraft under the MEL with one of the 4 EDPs inoperative.

Once the EDP clutch is disconnected the aircraft needs to be shut down and a spring loaded reset ring pulled on the EDP pump. Run some software tests and then it back online.

While that document says the A350 has a HSMU, that is a simplification for pilots. They have data concentrators that are connected via the network to remote monitoring applications on the main servers.

The A330/340 have depressurization solenoids on their engine driven hydraulic pumps which open automatically on start etc.

The A350 electrical VFG also has a a manual disconnect and a automatic thermal disconnect. If these operate with the engine rotating (dry crank or under power) the VFG needs to be replaced. The reset ring can only be pulled on the VFG for a static disconnect.


JetMech,

The SQ incident happened before the hydraulics had guarded switches, hence their incorporation. Not sure if they were attempting a fuel crossfeed or fuel imbalance.

Starlionblue,

Some guarded switches are reversible, eg the gravity gear, fire, fuel jettison.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
User avatar
Starlionblue
Posts: 18084
Joined: Fri Feb 27, 2004 9:54 pm

Re: A350 EDP clutch

Tue Jan 09, 2018 2:01 am

zeke wrote:
Starlionblue,

Some guarded switches are reversible, eg the gravity gear, fire, fuel jettison.


Fair point but I think there is some element of "Airbus logic" in those three. Granted, we may be entering splitting hairs territory.

- Pressing the fuel jettison pushbutton again stops the jettison, but does not suck the fuel back in. By that logic, the action taken is irreversible.
- Gravity gear lever action is reversible but not with the gravity extension mechanism. You get normal gear operation back if you get hydraulic pressure back. You can then use the normal gear lever.
- Fire pushbuttons shuts off the various hydraulic, pneumatic and fuel valves and deactivates the IDG. Is that last bit really reversible? The FCOM doesn't say explicitly as far as I can find.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
jetmech
Posts: 2329
Joined: Wed Mar 29, 2006 2:14 am

Re: A350 EDP clutch

Tue Jan 09, 2018 1:11 pm

Starlionblue wrote:
That's why the kosher method of pressing anything while following the QRH or ECAM is to name the panel first and be very methodical. For example to turn on Crossfeed 1 on the 340, you'd read "Crossfeed one, on" from QRH or ECAM, then point at the panel with the big letters FUEL on the side (helpful hint) and say "Fuel", then you'd point at the relevant pushbutton and say "crossfeed one", then press the pushbutton, then confirm it goes to on and say "on". Innocent bystanders will think you sound a bit weird but this method really helps to mitigate wrong presses.

I worked with an engineer who was very anal and one of his pet issues to pull you up on was pushing buttons on the overhead panel without doing the procedure you described. He did indeed look funny sitting in the flight deck alone doing this procedure. Fantastic engineer though with an encyclopaedic knowledge.

zeke wrote:
The EDP clutch within the hydraulic pump does act very much like the electrical IDG disconnect on othe Airbus. The aircraft has two hydraulic systems at 5080 psi, each engine has two EDPs connected to the accessory gearbox.

Interesting, must be one of the first aircraft with this feature?

zeke wrote:
The SQ incident happened before the hydraulics had guarded switches, hence their incorporation. Not sure if they were attempting a fuel crossfeed or fuel imbalance.

I'm glad it wasn't a figment of my imagination. It's interesting I can find no information on the incident.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
aerotech777
Topic Author
Posts: 74
Joined: Sat Aug 15, 2009 3:53 pm

Re: A350 EDP clutch

Wed Jan 10, 2018 5:35 pm

Thanks zeke for your post.

zeke wrote:
The clutch disconnect can be used by Crew from the cockpit in response to some faults or can be activated on the pump by mechanics to dispatch the aircraft under the MEL with one of the 4 EDPs inoperative.


a) Does the pilot use a switch from the cockpit to disconnect in flight the EDP from the engine gearbox? If so is it the guarded switch in the Overhead panel?

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.

c) Why Boeing is not using this feature in flight (used by Boeing in the IDG or VFSG) on the EDPs? 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.

Feedback appreciated.

Who is online

Users browsing this forum: No registered users and 16 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos