A320 ADR 1+2 fault , landing gear gravity ext

[Reverb_SR71]

Hey guys

I was wondering in the Dual ADR fault the ecam status says the lading gear has to be gravity extended .

My question is why is the landing gear system affected ? is there a link between the ADRs and the LGCIUs ?

Thanks

[MrBaldyHead]

Are you thinking of ADR 1+3?

In this instance the landing gear safety valve is locked, requiring the gravity extension

[MrBaldyHead]

From FCOM

Air data information is lost on one PFD.
Note:
In case of an ADR 1+3 FAULT, the landing gear safety valve is controlled closed:
Landing gear retraction is inoperative
Landing gear extension must be performed by gravity.

:ok:

[Reverb_SR71]

Ahhh thank you so much

so what exactly is this safety valve ?

and does a similar thing happen in a IR 1+3 fault ??


Edit -

Got it now , The safety valve closes and isolates the green hydraulic system if the A/c is flying faster than 260kts so this airspeed info is from the ADRs . The IRs have nothing to do with the gear operation.

Thanks again MrBaldyHead.

[kikwon]

my question is, then, why is the safety valve locked?

[vilas]

So no one out of boredom lowers the gear in cruise. Safety valve gets locked when speed increases beyond 260KT and remains locked till it gets speed reference indicating it is below 260kt which is not available.

[kikwon]

i am getting ready for my A320 initial FFS lesson 6 within which adr 1+3 fault scenario is included.

it does say clearly in the fcom abn that during this fault, landing gear has to be gravity extended and also that retraction is inhibited.

i did search the fcom and previously discussed threads regarding the same topic but they don't really say why.

in the fcom system, it says that hydraulic supply is automatically cut off when a/c flying faster than 260 kts, but not much more that i could find.

can an expert explain why for the gravity extension and retraction inhibition?

thank you

[applecrumble]

I think your sim partner probably asked the very same question at the same time. Check out the tech forum. Basically that the safety valve which cuts hydraulic supply to the landing gear is closed above 260kts. If you loose the ADR 1 + 3 there is a loss of the airspeed data to tell the aircraft when it is slower than 260 knots therefore the gear has to be lowered by gravity.

[kikwon]

thank you vilas
so if i carefully rephrase that:
since we won't have the speed reference from ADRs, we won't have the green hydraulics even during an approach at speed lower than 260kts in this abnormal situation, and thus, the reasons for landing gear gravity extension plus the retraction inhibition.
am i correct?

[Fox_one]

I’m not an expert but I’ll try and explain why.

You’ve actually found the answer in your research. If you go to FCOM DSC 32 landing gear doors and normal operation, there is a system diagram which illustrates how the system works.

There is a safety valve connected to the landing gear doors and gear, its feed is from ADR 1 & 3. Above 260KTS the safety valve cuts off the green hydraulic supply. If you’ve lost ADR 1&3 there is no speed input so the safety valve is controlled closed.

I think the Status page following the (ADR 1&3) failure doesn’t mention the fact that the gear won’t extend normally, and once you use gravity extension you won’t be able to retract it.

If you have time it’s always worth referencing the FCOM following a failure in the Airbus as there are a number of failures where the status page doesn’t tell the full story. Obviously, this has to be balanced with other tasks and the time available.

Enjoy the type rating!

[vilas]

Reverb_

The IRs have nothing to do with the gear operation. True! But if you turn off the IR rotary switches 1 and 3 they will also turn off ADRs 1 and 3, leading to same situation where the safety valve will remain locked.

[kikwon]

I think your sim partner probably asked the very same question at the same time. Check out the tech forum. Basically that the safety valve which cuts hydraulic supply to the landing gear is closed above 260kts. If you loose the ADR 1 + 3 there is a loss of the airspeed data to tell the aircraft when it is slower than 260 knots therefore the gear has to be lowered by gravity.

applecrumble, thank you very much!
clearing things up one at a time. this initial training is just pouring information into my brain.

[kikwon]

Fox one, anyone who is more experienced than i am in this field is an expert!
thank you for your clear and simple explanation. it's confusing and tough process, this initial phase but yes, i will try my best to enjoy my type rating.

[vilas]

kikwon
Yes!

[Right Way Up]

Kwikkon,

Just to clarify, green hydraulics are available but the normal gear extension will not be.

Also worth mentioning that you will most likely go straight to conf 1+f when selecting config 1.

[vilas]

I think the Status page following the (ADR 1&3) failure doesn’t mention the fact that the gear won’t extend normally, and once you use gravity extension you won’t be able to retract it. Not true! It does mention gravity extension.

[vilas]

Why should it go to 1+F? As long as one speed reference is correct and two others are switched off it will do as supposed to. This is not UAS situation.

[Right Way Up]

Sorry Vilas,

I was a bit vague after the hydraulics point as I meant to carry on and make a point regarding the original question of ADR 1 + 2 fault. I believe it is to do with the ADR 2 control of flap retraction. When you normally select flap 1 from 0 when airborne it senses you are above 100 kts and selects flap 1. However with ADR 2 failed it cannot sense the speed so I believe it defaults to 1+F which can be quite a surprise if you are not expecting it

[vilas]

Right Way Up
As long as one speed reference is correct that will be used by SFCC so flap will behave normally. It is in UAS situation where if the incorrect speed of being less than 100kts is taken by SFCC then this problem can happen. ADR 1 supplies lot of systems like EGPWS, TCAS, GPWS terrain and are affected. Also as long as ADR1 or 3 is available landing gear can be normally lowered.

[Right Way Up]

Thanks Vilas, that does make more sense.

[Right Way Up]

Hi Vilas.

Just tried it in the sim and ADR 1 and 2 fault, with both switched off (no UAS) the config goes straight to 1+f when conf 1 selected.

[tubby linton]

ADR 2 faults have this note in the MEL-
When the ADR 2 pb-sw is set to OFF, and if the aircraft is in CONF 1+F, the SFCS n°2 Flap channel is unable to crosscheck the airspeed coming from the ADR 1 with the ADR 2 airspeed coming from the SFCS n°2 Slat channel. This may lead to an uncommanded flap retraction during the takeoff. As a consequence, takeoff in CONF 1+F is not permitted when the ADR 2 pb-sw is set to OFF.

[vilas]

Right Way Up
Strange! nothing's mentioned in FCOM. As tubby mentioned it can cause unwanted retraction. So it is important. I will check in the sim next time. Thanks anyway.

[Right Way Up]

Nothing is mentioned in the FCOMs anymore....so frustrating!

I think your reasoning about the UAS is sound, even for the dual ADR fault no speed is sensed so thinks it is below 100 hence 1+f is selected.

[Dracarys]

I think the Status page following the (ADR 1&3) failure doesn’t mention the fact that the gear won’t extend normally

The status page will state as part of the approach procedure that the landing gear extension is by gravity. :ok:

It looks something like this:

- L/G.............GRVTY EXTN

[Escape Path]

Is there any reason to default that valve to "closed" when ADR1+3 fail? The gear is not something critical for such an scenario or that can be easily selected accidentally and it does create a bit more of workload. If the valve would be defaulted to open, would it drop the gear? Or would it need additional inputs (i.e. selecting gear down)?

[vilas]

The ADR 1+3 doesn't close the safety valve but it is closed any time speed goes beyond 260kt. It cannot be opened without ADR 1 or 3 input. The valve itself will not lower the gear. To remove the protection should not be a problem but for such low possibility event why remove a protection which prevents accidental lowering beyond design speed which may happen more under pressure than double ADR failure.

[CaptainMongo]

Reverb_

True! But if you turn off the IR rotary switches 1 and 3 they will also turn off ADRs 1 and 3, leading to same situation where the safety valve will remain locked.

As an aside to this discussion, a few months ago after putting the landing gear handle down we received the ECAM, L/G GEAR NOT DOWNLOCKED. To say the least, that got my attention. At my carrier we have a special procedure regarding this ECAM where we are to cycle the gear handle up to five times in an attempt to get the gear down. On the third try the gear came down.

Maintenance replaced the gear safety valve among a few other things.

[vilas]

Captain Mongo
Previously the procedure was to recycle the lever once. It was not necessary to wait for actual retraction because the purpose was to change to other LGCIU which happens with lever recycle. Some operators reported slow operation of the main landing gear (MLG) door opening/closing sequence, leading to the generation of ECAM warnings during the landing gear retraction or extension sequence. An EASA directive was issued for maintenance and repetitive inspections of the components involved. That led operational procedure change to the present one as you rightly did. You can read the directive at:
http://www2.lba.de/dokumente/lta/ad1003135.pdf

[Escape Path]

Does this procedure applies for specific MSNs or is it for all MSNs? I just checked my FCOM (for A319s up to 23XX and A320s up to 52XX) and apparently it has the "old" procedure of recycling the gear (though it doesn't say how many times, so I'd assume it's just one), waiting for uplock and doors closed before moving the lever down. If unsuccessful, it immediately refers you to gravity gear extension after the 120s "dwell time"

I read the AD and it's specifically says "up to 5 times" as Mongo said and then if unsuccessful, wait 120s and do the gravity extension.

Is the difference because we may have different PN on the whole system which doesn't require the 5 attempts method or is it just that my company has outdated manuals/procedures?

Thanks for the link to the AD, Vilas