A320 DUAL FAIL - Flaps inhibited?

[timmyEGCC]

Hi all,


Consider the following case
• You have a dual engine failure
• You attempt ENG restarts to no avail
• You make a decision to force land
• As per the QRH procedure, you select Config 3 (Flaps lever to 3)


NOW, what are the chances of flaps actually moving because of windmilling engines? Or are the flaps inhibited for some reason?


Cheers

[vilas]

timmyEGCC
At 300KTS wind milling is sufficient to keep hydraulics working. At FL250 start the APU. As speed is reduced for approach wind milling will not sustain hydraulics. You can use yellow electrical pump with PTU OFF as Yellow electric does not have the capacity to support green through PTU. With blue and yellow working you can move both slat and flap but slowly. ECAM should tell you all this.

[ReverseFlight]

If you read the "Hudson" Cactus 1549 report, there was still enough G + Y hydraulics to go Flaps 2 even when there was a significant rollback of both CFM56s. And that was way outside the restart envelope.

[vilas]

ReverseFlight
In Hudson incident engines had not failed. No1 engine had 35% N1 close to idle. That will not be the case when there is a flame out.

[vilas]

captainflash
The fluid turn over from yellow EDP is 140 l/mt while from electric pump is 32 l/mt. So it cannot handle two systems and will lead to failure. I received this reply from AB. Otherwise Blue and yellow are similar pumps and they are capable of running continuously.

[timmyEGCC]

Thanks guys


I also heard from Airbus that Y ELEC PUMP does NOT have enough power to support G and Y through PTU. Thus no mentioning of Y ELEC PUMP ON even after APU start below FL250.


While we are on the subject of DUAL FAIL, can anyone teach me why FAC 1 needs to be 'reset' in order to display Characteristics Speeds and to recover rudder trim?

[vilas]

timmyEGCC
You are misunderstanding. APU start won't tell you to start yellow pump. When wind milling becomes less and G+Y low pressure will tell you that. FAC1 needs to be reset because before emergency gen starts A/C is supplied by only batteries for 8 seconds. That trips both FACs. FAC1 when reset is supplied by EMER GEN and recovers rudder trim although you cannot see the figures. Also characteristic speeds are available. FAC2 is not supplied even on EMER GEN.

[timmyEGCC]

Thanks Villa


I was misunderstanding indeed. I also noticed in our FCOM that newer aircraft has "PTU....OFF" but not in the older ones. Cheers for your explanation of FAC 1 too.

[qwsa]

I recently used yellow elec pump only on ground to retract flaps and slats on brand-new a321,I forgot to swich blue pump on))) so they where both retracted but very slow))