PPRuNe Forums - Why does A330 with emergency config will enter direct law after L/G gravity extension

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- - Why does A330 with emergency config will enter direct law after L/G gravity extension (https://www.pprune.org/tech-log/591155-why-does-a330-emergency-config-will-enter-direct-law-after-l-g-gravity-extension.html)

Quote:

Originally Posted by vilas (Post 9683254)

can8 ko
Correction. The pitch before flare is +4 degrees from there it goes down to -2 degrees so total pitch down is 6 degrees and not 8 degrees as I said. A330 has two flare modes when out of normal law. In ALT1 it has flare mode in which roll is normal only pitch is direct stick to elevator and when in ALT 2 it is like A320, landing gear down direct law. In dual RA fail, inability to read radio altitude is the only problem so it uses the ALT1 flare mode. When in ELEC EMER since there are many inop systems that is not possible. So it reverts to complete gear down direct law. In both these cases the nose down pitch comes from speed reduction and the thrust reduction during flare. The FCS does not apply any nose down elevator.

This is another example. Don't take me wrong. I'm aware about the value of knowlege. The question is: to what extent? Going from time to time through official books just to have a general idea and to be able to quickly find information when you need it and keeping up with revisions, takes too much time and memory. On top of it you suggest things that not even in "nice to know" category, but simply useless (IMHO). What exactly from information in your quoted phrase helps you to fly the aircraft and how? Just curious. And I'm ready to accept it if it's reasonable. I have to admit I only remember that aircraft applies pitch down when I read disscusions like this. 6 years. About 10-15 landings per month. I have never thought about it. Just reacting on what aircraft, wind or sometimes another pilot are doing.

Quote:

Originally Posted by vilas (Post 9683254)

So it reverts to complete gear down direct law. In both these cases the nose down pitch comes from speed reduction and the thrust reduction during flare. The FCS does not apply any nose down elevator.

Vilas,
Does the computer in A330 do pitch down during flare mode in normal law?

Rocket
I stated the flare mode of A330 is slight pitch down elevator is applied. It is from FCOM.

Been flying the 330 for sometime now and you can barely feel this pitch down effect.

@Romasik, point taken in knowing all of this wont help with the hand flying but a good background on the failure would certainly help in the overall decision making process.

Hi vilas,
I thought the "pitch down" is a special feature in A320 family only and not for the other widebodies (A330&A340....)....
I am sure the "Pitch down" isnot on A340 but I will read the FCOM for the A330.

Many thanks

At 50 ft slight pitch down , says so in the FCOM for the A330/340

Quote:

Originally Posted by vilas (Post 9681588)

can8
I remember reading in one airbus instructor meeting report that A330 is not a big A320. So I think it will be better to forget A320 during transition. A330 has better redundancy the flare mode and also the AP is available in some situations in alternate law. But in A320 the transition to direct law with gear down is in fact the only flare mode of alternate law. The flare mode of A330 is slight pitch down elevator is applied while in A320 it progressively pitches down by eight degrees. But without Radio altitude measurement there can be no flare mode any way so with gear down it goes in direct law. A330 also does the same in ELEC EMER. That is why you use manual pitch trim. Do not confuse this with A320 Neo not going to direct law with only some failures like double yaw damper fail. Actually it does not even go into alternate law but remains in normal law with flare mode. Airbus wants pilots to carefully handle since there is a failure so only the indication of alternate law is displayed. As I said if you keep comparing A320 you will add to your confusion.

Sorry Vilas would you mind please explaining the dual yaw damper failure regarding the control laws in a sharklet aircraft?
I had a look in my manuals and don't see any differences?
Cheers

The sharklet aircraft do not go into direct law with gear down. They stay in "alternate" law which is actually normal law in this case. Compare the FCOM side by side for a non sharklet and a sharklet aircraft, FCOM-PRO-ABN-22-AUTO FLT YAW DAMPER SYS. The sharklet aircraft omit the line WHEN L/G DN: DIRECT LAW.

Oh yes I see thank you.
You say it stays in alternate law which is actually normal law. Would you have the amber crosses indicating alternate law?
But normal flare law is available?

Pilot James
The sharklet aircraft has better maneuverability so it retains normal law with yaw damper 1+2 and two other failures while normal A320 would go in alternate law and gear down direct law. But since There is a failure Airbus wants pilots to be careful so only indications of alternate law are shown but aircraft is in normal law and normal flare mode is available. This one is also of the many replies I obtained from Airbus.

Thank you Vilas that's great, worth knowing as I fly these regularly.

It is also applicable to three other failures i.e. FAC1+ FAC2
FAC1+YELLOW and FAC2+ GREEN.

When in EMER ELEC CONF, on the A330, the LANDING GEAR must be extended by GRAVITY (and Nose Wheel Steering is LOST in all cases) in order to avoid strong fluctuation of the G HYD pressure, which may cause spurious disconnection of the EMER GEN, when it is powered by EDP.

The reason why the aircraft enters Direct Law when LNDG GEAR down by Gravity is because of the need for using of LAND RECOVERY (to energize ILS 1, SFCC 1, LGCIU 1, BSCU 1, and WHC 1). This, will disconnect the EMERG GEN and will put electricity on BATs only.

Quote:

.The sharklet aircraft has better maneuverability so it retains normal law with yaw damper 1+2 and two other failures while normal A320 would go in alternate law and gear down direct law.

The cynic in me wonders whether a sharkletty aircraft might be an absolute nightmare to fly with the loss of both yaw dampers, hence the increased redundancy.

I understand all A321 aircraft, including early versions, also did not have the problem of reverting to direct law on gravity gear extension due to the extended nose gear not disturbing the airflow around the RAT and thus the RAT keeps running. I don't know if this is the case with early A318/319s?

What I stated is only true for A320/321. It is not tested for A319 yet. There is no increased redundancy. Had it been so Airbus cannot hide it. They will rather publicize it.

Hello guys

Kinds of busy last week! Very appreciate so many back and forth Q & A. I could see not only me but also other one could learn something from this discussion! It's more than my expectation!