A 320 After Landing Action-Query
 

In the latest revision of FCOMS of the Airbus 320 family aircraft, the After Landing Action in the SOP states that, "To avoid damage on the RTLU (Rudder Travel Limit Unit) mechanical stop the SLATS/FLAPS should be retracted before all ADIRS are set to OFF simultaneously.
Can any one offer an explanation for this?

In case of loss of ADR data, RTLU uses slat position. It allows full rudder travel when slats are extended.

My guess is that in case of All ADR's OFF and slat retraction, the RTLU will try to limit rudder deflection. If the rudder is already deflected beyond the RTLU limit, this may cause mechanical damage...

After Landing
 

Thanks Sidestick. Does it mean that one has to activate the Yellow Electric Pump and select SLATS/Flaps before doing a Alignment of the ADIRS as part of the Cockpit Preparation?

After Landing- A320
 

Does it mean that one has to switch on the Yellow Electric Pump and select SLATS/FLAPS before Aligning the IRs as part of the Cockpit Preparation?

well the slats shouldn't be extended if the ADIRS are off

@Boyington,

The potential problem is retracting the flaps with ADR OFF - as this drives the RTLU to "Hi speed" position and can damage it.

Extending the flaps with, or without ADR's shouldn't cause any problem, as both actions will just drive the RTLU to "lo speed" position.

P.S. The above is based on what is written in the FCOM and my understanding of the system. Perhaps someone with access to the AMM could confirm it...

This is a long-standing procedure where I fly.

On a turn-around, we just leave the flaps at 1, because we know for sure that neither ELEC power and the ADIRS will remain on at the outstation. When back at base, where the ADIRS might be de-powered for any length of time for whatever reason (gnd pwr tripping, maint, night stop, etc), we simply retract the flaps.

And yes, if you need to do a full alignment of the ADIRS, the flaps will need to be retracted.

After Landing- A320
 

@ Sidestick & Seagull
Thanks but a doubt remains. The maximum rudder travel deflection gradually reduces as the speed increases to avoid structural loads. At slats extension, full rudder travel authority is recovered. Therefore if the ADIRS are switched OFF when the Slats are extended the rudder travel deflection will be at it’s maximum. During hot weather conditions to prevent AIR L(R) WING LEAK warnings the Slats are kept in Config 1 where OAT is above 30 degree C. Now with Config 1 +F selected, if the ADIRS are set to OFF the Rudder Travel may reach maximum deflection and damage the mechanical stop. So the logical action would be to activate the Yellow Electric Pump after obtaining clearance from ground personnel, and then retract SLATS/FLAPS before doing an alignment. Any difference of opinion ?

Is that so? Thanks for the info, but where I operate, due to high temperatures we keep Conf 1 after landing, and plenty of times I have taken an aircraft and done a full alignment on this configuration. As far as I know nothing has happened :confused:
Would appreciate any more info.
Cheers!

I wouldn't expect the RTLU damaging the mechanical stop due to maximum deflection. After all that's what the mechanical stop if for - to arrest movement and prevent damage... Also, since the A/C is on the ground, RTLU should be already at max deflection anyway...

I'd rather suspect the damage due to RTLU undesired movement to "Lo Speed" position during slats retraction.

I've dug up the AMM a bit and found some additional info:

- RTLU is normally controlled by the FAC's

- in the absence of FAC signal there's an additional "open loop" circut that will move the RTLU to "Lo Speed" position when slats are extendend

- Maintenance procedures for extending/retracting slats on GND make no mention of ADIRS at all. They do, however, call for both FAC's to be isolated by pulling their cb's.

Maybe, with invalid ADR data, there's some conflict between the normal FAC control and the secondary circut? :confused:

Hey, Boyington, if it makes you feel more comfortable to dirty the wing up prior to ADIRS alignment, knock yourself right out. I don't see anything that says you can't, outside of clearing with ramp personnel prior to turning Y Electric pump on. So, if it makes you happy, why not?