A 320 question

[chrislamb]

A320 question: Is the ground spoiler inhibitor circuit keyed to wheel spin, and, is there a manual reversion mode if ice or other conditions keep wheel spin below the threshold? Is there no role for the squat switch?

[Busterpilot]

Hi!

If I read my FCOM right you get also get spoiler spoiler extension if RA is less than 6 feet and both MLG are compressed.

Partial spoiler extension if at least one thrust lever in reverse with the other at idle and one MLG compressed.

BR

Buster

[chrislamb]

Thanks

That seems to say that wheel spin doesn't enter into the deployment

Is that correct?

[shortfuel]

No, it's not. Busterpilot's answer is correct but incomplete.

Wheel speed is one of the logic conditions for GND SPLRS extension.

Inhibition is also keyed to wheel speed: you have inhibition between lift off and return of wheel speed below 23 kts or touchdown.
(touchdown condition= wheel speed>72 kts OR both MLG compressed and RA<6ft).

Proximity Detectors on Shock absorbers (I guess what you referred as "squat switch") will deliver the compression condition to the LGCIUs, so they have an important role.

(Ref: FCOM 1.27.10 p 12/13 and AMM 27.90.00 p26).

That said, Airbus recently modified the ground spoiler logic (new SEC standard 120 to cope with inappropriate TL position during flare...), but as far as I remember the wheel speed logic remained unchanged.

[Metro man]

If you bounce a landing the spoilers stay extended but would retract if TOGA was applied for a go around. Correct ?

[shortfuel]

It's correct indeed

[Metro man]

Thanks for clearing that up. :ok:

[TyroPicard]

FCOM 1.27.10 p13 - shows an OR gate

Wheel speed above 72 kts
OR
MLG compressed.

Manual reversion: not for ground spoilers, but speedbrakes work if NOT in CONF FULL.
It's all in the books....