A330 RA1+2

[sonicbum]

Hello boys and girls,

Apologies if this has already been discussed before but I couldn't find some definitive answers. Being (much) more used to the A320 for the above mentioned failure, I am a bit confused if the landing distance procedure of direct law is applicable or not on the A330. As far as I understand it is not, as the airplane goes to Flare law, and not direct law. If someone can shed some light that's appreciated.

Cheers and thanks.

[flying headbutt]

Hello,

This is taken directly from the FCTM for our A319/20 aircraft for dual RAD ALT failure so as you see it actually goes to flare law for the A320 also. Hope tnat helps.

"On approach, flare law becomes active when the L/G is selected down and provided AP is disconnected. At this point, "USE MAN PITCH TRIM" is displayed on the PFD."

[TyroPicard]

sonicbum
You are correct, Flare Mode is the usual law for landing so no CONF 3 restriction, no increase in LDR.

flying headbutt ... A320 goes to Direct Law not Flare Law with this failure, so CONF 3 and L DIST PROC required.

[flying headbutt]

.....well I thought the A320 went to direct law too but what I posted was a cut and paste from an Airbus A320 Flight Crew Training Manual - Abnormal Operations/Navigation/Dual Radio Altimeter Failure.

For info, the A330/340 FCTM that I just referenced defines flare law as follows. FLARE LAW: The control law is a smoother direct law. (FCTM Operational philosophy, Flight Controls)

The A319/320 FCTM in the same section reads - FLARE LAW: The control law is a pitch demand law.

[sonicbum]

Thanks Tyro and flying headbutt. What makes me wonder is that on the A330 you still get the "USE MAN PITCH TRIM" on PFD as you do on the A320 for the same scenario. In the normal flare mode with no failures on the A330 you obviously don't get it as you don't get it on the A320. The subtile difference here as far as I can interpret it is that the A320 FCOM says when LG down -> direct law and the A330 talks about Flare mode only. Handling wise where is the difference ? Looking it this ways it seems that the final stages of the approach (ie AP OFF LG DOWN) will be flown in the same way in both airplanes.

Cheers.

[sonicbum]

Originally Posted by flying headbutt

.....well I thought the A320 went to direct law too but what I posted was a cut and paste from an Airbus A320 Flight Crew Training Manual - Abnormal Operations/Navigation/Dual Radio Altimeter Failure.

For info, the A330/340 FCTM that I just referenced defines flare law as follows. FLARE LAW: The control law is a smoother direct law. (FCTM Operational philosophy, Flight Controls)

The A319/320 FCTM in the same section reads - FLARE LAW: The control law is a pitch demand law.

The FCOM PRO-ABN for that failure mentions Direct Law for the A320. For the A330 it mentions when L/G down... MAN PITCH TRIM USE and switching to flare law occurs if AP is OFF. To me, as I was mentioning before, it looks like the airplane will end up in the same handling characteristics in both cases but legally speaking there is not "direct law wording" for the A330 so technically no correction.

[TyroPicard]

sonicbum
in normal ops the A330 goes into Flare Mode at 100'RA... no autotrim but you don't need to trim at that point, just flare and land.
With RA1+2 FAULT you fly in Flare Mode from L/G down and AP OFF, so you need to trim manually during the approach - hence the caption.

flying headbutt
I have just found your FCTM reference and amazingly that is what it says .. but it's wrong!
Here is the bit from FCOM Abnormal Procedures...
WHEN L/G DN: DIRECT LAW
At landing gear extension, flight controls revert to direct law in pitch, as well as in roll (Refer to PRO-ABN-27 F/CTL DIRECT LAW). ILS APPR mode cannot be engaged, LOC mode is available via the FCU LOC pb.

Handling wise, the major difference between the two is A330 remains in Normal Law in roll, A320 goes fully direct.

[vilas]

Tyro,flying headbut
It is not wrong. In A320 direct law is the only other flare mode. That is why in alternate law with gear down it is put in direct law to give you flare mode.

[TyroPicard]

Have read FCOM again...
A320 in ALTN law, pitch goes into Flare Mode with gear down; this Flare Mode is different to Normal Law Flare Mode, being a direct sidestick to elevator relationship... so what I think of as a Direct law landing is actually an ALTN Law landing because the Yaw remains Alternate ... not Mechanical. True or False?

But with RA1+2 Fault the A320 is NOT in ALTN Law..... FCOM says it goes straight to Direct Law with gear down, which does not have a "Flare Mode" in FCOM DSC, it is just Direct Law. Or does it really go to ALTN Law with Flare Mode enabled but we call it Direct Law for simplicity?

And I thought I understood it...

[vilas]

Tyro
In A320 with RA1+2 it is not in alternate law. Then why direct law with gear down? Only to give you the conventional behaviour during flare and landing. That is, in no auto trim during flare and when you close thrust nose drops requiring steady backward pressure.

[BuzzBox]

Hmmmm, I think I'll stick to Boeing!

[sonicbum]

Hello gents thank you all for the inputs. For the A330 no correction then as the result of the analysis.

Thanks.