A320 Hyd B+Y fail

[vilas]

A320 question gents.
Dual hydraulic failures G+B and G+Y dominance is so much that the B+Y has taken the back seat. Even Airbus isn't helpful.
1. With G+Y fail you are in Alt law, loose flaps and needs adding of 25kts to Vref
2. With G+B fail you are in Alt law, loose slats and half elevator and needs addition of 25kts to Vref
3. With B+Y fail you remain in normal law can extend both slats and flaps but loose half elevator.
And yet the FCOM says (B+Y) if Flap3 Vapp Vref+25. It's silent on flaps full.
If you go to QRH Inflight Performance landing distance chart(now removed) it offers both options in flaps full with zero ∆Vref and Flap3 with only 6kts ∆Vref.
Doesn't make any sense to me. Has anyone got an answer from techrequest?

[Denti]

Just played around with the FCOM, the +25kts for flaps 3 seems to be a NEO only thing. A319/320 CEOs do not have that in the FCOM, there is only a restriction for A321 to use Flaps 3 and Vref +10 in that case. In any case it tells us to use the landing distance procedure which if course requires a calculation with the flysmart landing app. Did a few calculations, NEOs show the Vref +25, CEOs show +6. But of course i couldn’t check every MSN.

[vilas]

Just played around with the FCOM, the +25kts for flaps 3 seems to be a NEO only thing. A319/320 CEOs do not have that in the FCOM, there is only a restriction for A321 to use Flaps 3 and Vref +10 in that case. In any case it tells us to use the landing distance procedure which if course requires a calculation with the flysmart landing app. Did a few calculations, NEOs show the Vref +25, CEOs show +6. But of course i couldn’t check every MSN.
Even in Neo it says if Flap3 Vref+25. It means nothing since you can retract to 2 or go to full. Then what?

[CrazyStuntPilot]

What'the Documentary Unit number for the Status page of the B+Y in your FCOM?
​​​​​​Aircraft with FWC F10 and later have an evolution in every ECAM alert with a mono elevator where the Vapp is faster on some type of aircraft.

A320 question gents.
Dual hydraulic failures G+B and G+Y dominance is so much that the B+Y has taken the back seat. Even Airbus isn't helpful.
1. With G+Y fail you are in Alt law, loose flaps and needs adding of 25kts to Vref
2. With G+B fail you are in Alt law, loose slats and half elevator and needs addition of 25kts to Vref
3. With B+Y fail you remain in normal law can extend both slats and flaps but loose half elevator.
And yet the FCOM says (B+Y) if Flap3 Vapp Vref+25. It's silent on flaps full.
If you go to QRH Inflight Performance landing distance chart(now removed) it offers both options in flaps full with zero ∆Vref and Flap3 with only 6kts ∆Vref.
Doesn't make any sense to me. Has anyone got an answer from techrequest?

[Jwscud]

I have looked at Flysmart and our FCOM which for old MSN CEOs gives:

320:

Flap 3 ΔVref 6
Flap Full - 0

321:

Flap 3 ΔVref 10
Flap Full not authorised

The FCOM DU is dated 9 Nov 21

On reflection it is clear there is no speed increase required on the 320 for controllability but one is clearly required on the 321. Without access to flight test data one can only hypothesise as to why.

[Denti]

Even in Neo it says if Flap3 Vref+25. It means nothing since you can retract to 2 or go to full. Then what?

Yes, the NEO needs Vref +25 if Flaps 3, the CEO only Vref +6. However the +6 does not show up on ECAM or in the FCOM, only in the landing distance calculation, whereas the +25 for the NEO shows up on the ECAM, FCOM and during the landing distance calculation. No delta Vref required for Flaps full, and yes, both flap settings are available with that failure except on the A321 which can only use Flaps 3 (and delta Vref +10). Why? No idea.

[Clandestino]

I am not saying that what I vaguely recall is correct or even if so, has something to do with the subject. I flew 320 last time 14 years ago but ISTR that during my TR I was told that loss of hyd power to one elevator means loss of not half but three quarters of pitch authority as surviving elevator would be limited to half the normal travel to reduce torque loads on rear fuselage.

[vilas]

I am not saying that what I vaguely recall is correct or even if so, has something to do with the subject. I flew 320 last time 14 years ago but ISTR that during my TR I was told that loss of hyd power to one elevator means loss of not half but three quarters of pitch authority as surviving elevator would be limited to half the normal travel to reduce torque loads on rear fuselage.
Half elevator will have to move double to produce dynamic load of both elevators. So they will keep hitting the extremities that can damage the elevator. So it's movement is restricted to less than full. That makes it less than half effective. This is known.

[Zar_1]

Half elevator will have to move double to produce dynamic load of both elevators. So they will keep hitting the extremities that can damage the elevator. So it's movement is restricted to less than full. That makes it less than half effective. This is known.

I do remember flying half-elevator very recently in my (somewhat study-level) A321 Home Sim. Certainly, the roll moments are very non trivial, leading to some pretty uncomfortable flying.
What did help a lot though, was the use of the THS, which worked on both sides of the elevators. (idk if it would work IRL).

As an engineering student, and studying how torsion loads work, it's actually pretty impressive how the fuselage is able to handle these forces so effectively, one eg. where I think it couldn't, was in the Lauda Air crash, where a portion of the right elevator broke off in the dive.

[vilas]

In B+Y fail both ailerons are available and since aircraft is in normal law roll control is automatic. So it may not need any speed addition for roll control. Even after gear down since in normal law Pitch control remains automatic but should need some addition for better control.

[Zar_1]

In B+Y fail both ailerons are available and since aircraft is in normal law roll control is automatic. So it may not need any speed addition for roll control. Even after gear down since in normal law Pitch control remains automatic but should need some addition for better control.

Yeah, sorry, didn't realise that both Ailerons would be operative (albeit on single actuator mode).

So then... THS will operate solely off the G Hyd. Sys. , correct?
Oh, and sorry for the questions, but any clue why the Rudder has all 3 systems working on it (G+Y+B)? Is it cause it's a vital part of the Manual Reversion??