adirs alignment and flaps 1

[starryeyedfalcon]

Hi everyone. First time poster here. I would just like to ask the relationship between adirs alignment and flaps 1 (above 30degrees celcius) on the A320.
I have a rough idea but how would you explain it to a a320 newbie?

[MD83FO]

On ground, when the OAT is above 30 °C, a spurious “AIR L(R) WING LEAK” warning may be triggered. To avoid such warning during transit, and after refueling is complete extend the Flaps to position 1+F.

If the ADIRS go offline while the slats are extended, the RTLU goes into a "emergency return to low speed" mode. This allows maximum rudder travel by driving the RTLU to mechanical stops. If this happens regularly it can cause damage to the stops.

the problem is not the retraction of the slats/flaps but instead turning the ADIRS (air data inertial reference units) off. The RTLU is designed to operate in a feedback loop, where its position is controlled based on input from the FACS (Flight Augmentation Computers, which take input from the ADIRS).

Damaged mechanical stops are internal stops of actuating screws (rotating shafts) inside mechanical part of RTLU, not rudder travel (variable) stops. Damage on this stops is generated by repetetive activation of "emergency return to low speed" mode, which drive a rotating shaft inside TLU until reaching mechanical stops. During normal RTLU operation shaft stops rotating before reaching mechanical stops, because system uses closed loop feedback from position transducer. This normal function does not put any load to mechanical stops. Emergency return to low speed condition will be activated on ground if CB for FAC are closed (it means RTLU is electrically supplied) and both FAC P/B are OFF and slat extended or ADIRU OFF (ADR data invalid for FAC) and slats extended. Yes, on ground is RTLU in low speed position, but can be moved further to hit mechanical stops.

This appears to be related to the Indonesia AirAsia Flight 8501 crash. Although this issue was not one of the main contrbuting factors, the report lists this as one of the Technical Followups (TFUs) that Airbus issued as a result of the investigation. It improves the reliability of the RLTU, the failure of which was cited by the investigation.

[starryeyedfalcon]

Awesome, thanks MD.

[Max Angle]

when the OAT is above 30 °C, a spurious “AIR L(R) WING LEAK” warning may be triggered.Makes you wonder why they just don't fix this and remove the need to leave the flaps out in the first place.

[Stan Woolley]

Wish we’d known this. It would have prevented an unnecessary nightstop in Turkey years ago. Still, it was interesting. :ok:

[gnarlberg]

we didn't have this above 30C leave flaps in 1 thing... it was just on the a330 i guess

[starryeyedfalcon]

Some operators do it. Some don't. We used to but not anymore. Guess it's a local thing.
We ceased to because of every time we refueled we had to retract the flaps and slats.