A320 "GEN 1 LINE" Pushbutton

[hangil94]

hi, all ^^ After struggling with this problems, I finally logged on to PPRuNe ... Please share your knowledge with me...


As you know, on left overhead panel, there is "GEN 1 LINE" pb in EMER ELEC PWR section.

What I know is, This button is used for SMOKE situation in Avionics bay .. and Once I pushed this button off, Gen 1 line contactor opens and .. just one fuel pump in each wing remains powered ....

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Here is my question !!!
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What is the relationship between Generator and Fuel pumps ?
Why these things happens???

Please understand my silly questions !

[vapilot2004]

The A31X/32X series aircraft fuel system has a total of 12 pumps 6 AC powered and 6 DC powered. (with CTR tank). The AC powered pumps are powered VIA the main AC1 or AC2 bus - these two AC busses are powered directly by #1 & #2 Gen, the APU Gen or the RAT turbine VIA the AC ESS bus.

In order to protect the aircraft's power systems in the event of fire and to limit electically generated smoke - the Main AC1 and AC2 busses are in load shed - they drop current loads VIA opening contactors feeding the busses.

In this configuration, GEN1 supplies AC to the wing fuel pumps directly - bypassing the main busses altogether - the AC pumps remain powered directly.

In the total loss of AC1 and AC2 bus, we still have 4 (2 per wing tank) DC pumps available. In smoke configuration - only the DC and AC essential busses are powered - feeding power through overhead CB panel to equipment.

According to the schematic, if you have a smoke condition, the #1 generator is required for AC fuel pump operation.

Have I helped or muddied the waters ?

regards

[Carnage Matey!]

IIRC Pressing Gen 1 Line removes all power from AC Bus 1 so you can try to stop the smoke. AC driven fuel pumps continue to operate so the engines will run. I don't have a QRH handy but I seem to remember you reset the Gen 1 Line switch during the approach to restore primary flight instruments with the risk that the smoke might reappear.

[hangil94]

Of course It helped a lot .
Now I can understand ...

Thank you so much, and always take care !!

[dovish]

Hello all,

I agree to what it is written but doesn't the GEN2 connects to AC1 via the BUS TIE CONTACTOR? if it does so should not make any difference disconnecting the GEN1 from the AC BUS.

I hope I've made myself clear.

Thanks in advance

[PantLoad]

Not exactly...

Please have a look at FCOM 1.28.30 P1 and FCOM 3.02.26 P6a

In smoke config...you can feed one pump from each of the two wing tanks
directly from IDG 1. (Pump N 1) Center tank pumps are unpowered under these circumstances.

As far as I know, there are NO DC pumps. All pumps are either AC with DC control....or Jet Pumps. That is to say....if you have NO AC POWER....you have NO FUEL PUMPS.

If I'm incorrect, please refer me to the appropriate FCOM page(s).

Fly safe,

PantLoad

[dovish]

I agree in what you're saying but my question relies on what is the meaning of disconnecting the GEN1 from the AC1 (in smoke config)?? I could understand that in case of smoke config we should isolate the main components by disconnecting the AC1 BUS BAR (to reduce the chance of fire) but when you do it so by pressing the GEN 1 Line p/b you will continue to have the AC1 BUS BAR because the GEN 2 will then supply it as it is describes in the FCOM 3.02.26 p6a, so I do not see much difference besides the fuel pumps being supplied directly from the IDG!!

Thanks for your help.

[Microburst2002]

Gentlemen

All you have to do is to apply the AVNCS SMOKE/SMOKE/FUMES procedure.

The GEN 1 LINE push button allows to open the generator 1 line contactor, without deenergizing the GEN 1. All the AC and DC networks remain supplied by the GEN 2 (or APU GEN if avail).

The EMER ELEC MAN ON deploys the RAT and this powers the EMER GEN. Essential buses are now powered by that GEN.

When you switch off GEN 2 (and APU GEN just in case you were using the APU) all the AC and DC networks are lost, except the essential buses, and these fuel pumps which are still fed by the GEN 1, from a line upstream of the line contactor.

Then you have shed a large part of the electrical equipments. But the fire might still be caused by one of the remaining ones...

That is why when the smoke or fumes source is not inmediately identified, what you have to do is go to the QRH procedure, push all the buttons you have to push, don the masks if you need and...

DIVERSION........INITIATE
DESCEND to FL100 MEA......INITIATE

Because you don't know how long has fate determined for the fire to become deadly nor if fate is going to give you a chance to fight the source of the fire. Maybe it is a lost battle no matter what you try.

when in doubt...
DIVERT, DIVERT, DIVERT
DESCEND, DESCEND, DESCEND

[dovish]

The question appeared because some people wrote that by pushing the GEN 1 LINE push button it would isolate all the components from the AC1 BUS BAR. And that is not correct, because the GEN2 will then supply the AC1 BUS.

So from what I understood the GEN 1 Line p/b is only a way to have fuel pumps connected to the IDG 1 after completing the SMOKE ELEC CONFIG.

If we would not carry on the SMOKE drill would not make much sense having that p/b at all.
correct?

[Microburst2002]

that's right.

That pushbutton is the last step of a procedure to induce an electrical emergency configuration only without having the problem of the fuel gravity feeding.

[Bubi352]

I was told once you can get limited access to the avionics bay from inside the cabin just behind the carts in the forward section. Never looked into it. Any truth to it?

[Nevermind]

The button is used in a Smoke situation - hence the light on the button illuminating if Avionics Smoke is sensed. It removes the power from Gen 1 to AC bus 1, and when used as per the QRH, in further removing the power from bus 2, you go into EEC and hopefully isolate the problem if it electrical.
It removes over 70% of the aircraft electrical load.

However, as stated above, it prevents gravity feeding, as a pump in each tank stays powered, which wouldn't happen if you removed the power using the Gen 1 button.

Why?
Because the smoke will probably not be coming from a pump in a fuel tank.
!

And just to clear something else up, [from the airbus crew training manual] you don't put the Gens back on before landing to get the instruments back.

It is to regain the anti skid and improve your stopping distance, if required.

[A320_DRIVER]

fortunately, i went through this thread long time ago and i was asked this question in my line check today :ooh: the examiner was stunned when he heard the full answer i had .. thanx to all fellow pilots in pprune :ok:

[Beeline]

Bubi, you can access any part of the avionic bays if you lift up the floor boards.

[FLEXPWR]

vapilot2004,

Can you please tells me which FCOM/Page(s) to refer to the fuel DC pumps? Only flying the Airbus for a few years but never heard of it, maybe I am missing a few pages.

Flex

[primreamer]

Bubi352,
Some of the very early A320's had a lift up hatch in the aisle for access to the avionic bay below. It was situated under the carpet just aft of the forward galley. Didn't really use it a lot because once open, it impaired boarding. On a quick turnround it was much easier to get the ladder out and enter the bay from outside. The hatch was gradually done away with as it became obvious it was more bother than it was worth.

[Citation2]

I disagree with the fact that Gen 2 will stay online and supply the rest of the network.
By pressing the Gen 1 line pushbutton, it will force the electrical system in EMER ELEC CONFIG therefore AC1 and AC2 will remain disconnected
GEN2 will not takeover and GEN 2 will go offline

The only difference between Emer elec and smoke config is that fuel pumps 1 are supplied.

Please review FCOM Elec schematic and check that gen 2 is disconnected as well.

The purpose of GEN 1 line is to keep pump 1 of wing tanks connected.

If you had to shed the electrical system manually , firstly it will take too long , secondly you will end up in gravity fuel feeding.

Smart airbus

[vilas]

Gen2 will be on line. That is why the next action is to put Gen2 off. Then you get into ELEC EMR but with one fuel pump in each inner tank supplied from GEN1 directly. This avoids gravity feeding requirements.

[Fargoo]

Bubi352,
Some of the very early A320's had a lift up hatch in the aisle for access to the avionic bay below. It was situated under the carpet just aft of the forward galley. Didn't really use it a lot because once open, it impaired boarding. On a quick turnround it was much easier to get the ladder out and enter the bay from outside. The hatch was gradually done away with as it became obvious it was more bother than it was worth.

We had those on our 320-100s. Eventually the hatch was carpeted over completely but the ladder and hatch remained.

Like the airstairs, it was a good feature at launch but not really needed in practice. The airstairs were just unreliable junk and heavy junk at that!!

[primreamer]

Fargoo,
It was the A320-100's I was referring to,took delivery of them in May 1988. I remember the airstairs well, unreliable as you say. De-activated after several "door open" indications in flight. Some of our newer A320's still have the 2 step ladder to nowhere under the floor boards in the avionic bay.
Were you BA engineering at LGW by any chance?
Apologies for the thread creep.

[Beeline]

Worked the old bcals for years knew the airstair provision was there but not the hatch.

Cheers

[compressor stall]

When the Gen 1 LINE p/b is pressed, the generator line contactor is opened (i.e. the link from Gen 1 to the AC Bus 1 is broken) The #1 pump in each side are supplied with 115V AC power directly from the generator.

[screwdriver]

If you used some of the information on this thread then ,I suspect , your line checker would probably be stunned by a LACK of knowledge.

VApilot2004 and his 6 dc powered pumps?
Citation 2 and the Gen 1 line p/b putting the a/c into the EEC ??

:ugh::ugh: