A-320 Using of Engine anti-ice

[aeroslon]

Hi,

From Airbus Supplementary Techniques:

ENGINE ANTI-ICE must be ON during all ground and flight operations,when Icing conditions exist,or are anticipated,exept during climb and crouse when the SAT is below -40C

ENGINE ANTI-ICE must be ON before and during descent in Icing conditions,even if the SAT is below -40 C

Can anyone explain,why we need to swich ON Engine Anti-Ice during descent in such LOW temperatures ? Thanks a lot :D

[Max Angle]

Belt and braces I guess, if you are descending the temperature will eventually climb to the level that you will start to get ice problems. As for the bit about turning it on in the descent if icing conditions are anticipated I don't know anyone in our company who operates it like that, what about other operators?. We just turn it on when we are about to enter cloud or rain, doing it the Airbus way I reckon you would have it on most of time in the descent in Europe.

[A-3TWENTY]

I agree with MAX ANGLE .That´s the way I do.

[kick the tires]

the stall margin in the descent is that much more critical, ice build up in a low power engine will induce a stall much quicker than one at high power.

of course, should a flame out occur the FADEC will sense a sub idle condition and apply the ignitors automatically together with the relight procedure.

So yes, belt and braces it is!

[JuanTerGo]

The descent rule is not intended to require anti-ice in descent outside of icing conditions. Effectively means switch em on just before entering cloud.

As you are moving from a colder to a warmer environment and the nacelle may be cold soaked it is possible to get ice at lower temperatures than you would normally expect since the nacelle may be substantially below the saturation temperature of the air you are flying into.

[SIDSTAR]

Same in all jet aircraft. Descent = low thrust, so ice will build up more readily.

[FlightDetent]

We all obviously operate the same, I was taught to read "anticipated" two ways:

1) it is not neccessary to wait until you are in cloud, it is a good habit (read: procedure) to turn EAI on before entering cloud; same logic for climbs in cloud with TAT say +12 deg C;

2) Aniticipate is a good thing, i.e. for TKOF at OAT 4 deg C and cloud base below planned thrust reduction ALT, set EAI on and calculate performance data accordingly, or I personally would not be ashamed to turn EAI for VMC approach to snow covered airfield with precipitation or cloud in the G/A sector (again, low TAT);

[Cold Soak]

I know it's belt and braces and that Airbus recomends it, but in certain airlines this procedure is not employed. Ironically enough, and I subscribe to this myself, putting Antiicing on below -40c can heat up the ice crystals to ABOVE -40c and actually cause Ice to accrue on the fan blades! Interesting eh? Any thoughts ?

[VMK]

whats belt and braces.....:confused:
yeah i sound lost...or stoned...

[GearDown&Locked]

As found on the internet:

Belts and braces (a.k.a. bracers) are meant to hold one's trousers up. Going 'belt and braces' is a double insurance against having them fall down. The figurative use, as a general term for cautiousness, was coined around the mid-20th century.

In the USA 'belt and suspenders' is used with just the same meaning. That emerged at around the same time too. The first citation in print we have is from the Galveston Daily News, 1935 - in their 'News Behind the News' column:

"A pessimist wears both belt and suspenders."


GD&L:ok:

[safetypee]

Flight tests (not A320) in recent years identified conditions where engine icing (and possibly airframe icing) can occur outside of the generalised certification boundaries of JAR FAR 25 ‘Annex C’. One area is in very low temperatures, including -40C. A particular problem is with mixed phase icing – a mixture of ice crystals and super cooled water, such that on contact with a surface the water froze acting as glue for the other ice particles. Yet again we learn that the physics of the atmosphere and flight are not as well understood as we thought.
Specific engines / aircraft will have different characteristics and thus different limitations – always stay within the flight manual guidance, but allow some safety margin just in case. Very few aircraft have been flight tested in the range and extent of icing conditions experience during line operations, the certification is based on many assumptions; there is no need for you to be the first to prove the assumptions wrong.

[gmb]

hi, could someone tell me why in the 320 family on the SOP during descent states...
speedbrake..... as req (note: the pilot may use up to half speedbrake when engine anti ice is used )
why is the reason to use half speed breake under this condition?
thanks

[kick the tires]

half speedbrake provides enough drag to counter the extra idle thrust caused by selecting engine anti ice on.

[TO MEMO]

exactly!

But actually it doesn`t make much difference! Only if you`re using anti-ice for a long period of time you will notice that you`ll need speed brakes.

[Dan Winterland]

Do any operators witch on the eng anti ice on at TOD if icing conditions are anticipated? I hope they all do. my company does, and Airbus think it's important, hence the use of the word MUST.

I think it's quite unambiguous - and not open to intepretation!

[PantLoad]

Gentlemen,

It's important to remember that the engine anti-ice system is just that...anti-ice. Allowing ice to build up could easily cause severe engine damage, flame out, etc. This is why it's important to have the engine anti-ice system ON prior to entering icing conditions.

It does not hurt anything to have the engine anti-ice system ON (if you're anticipating icing conditions), and then discover it really wasn't needed. Yes, you're burning a bit more fuel. But, the other side of the coin is: How much money do you save over the lifetime of your career by damaging an engine? You can buy a lot of fuel for the cost of such an occurrence.

We've beaten this topic to death many times, here, in PPrune. My advice is to follow your company's SOP. It protects you, and, in this regard, it will protect your engines.

I've flown with many guys over the years who have their own 'techniques'. Not a good idea. And, some guys will pretend that, with having their own 'techniques', they employ some degree of piloting proficiency that others lack. WRONG!!!!!

Follow the SOP.

My philosophy...when in doubt (about the possibility of icing) turn on the engine anti-ice. (This covers the 'anticipated' clause of the SOP.)

Another interesting note...some erroneously believe that, under certain atmospheric conditions, turning on engine anti-ice could actually increase the likelyhood of engine flameout and/or damage due to icing. WRONG!!!!!
If this were true, there would be SOPs/limitations regarding this.

When in doubt, use it. The worst-case down-side...you've wasted a bit of fuel.


Fly safe,


PantLoad

[TheGorrilla]

Bit of an aside. I'm currently on a Boeing looking at going onto Airbus. Why would half speedbrake be an issue only for autoflight? I can appreciate I've why I've not brought this up in the right place. Though this thread has got my brain cells ticking over.

[idg]

TG

On the 320 with either AP on, the speedbrakes are limited to half deflection regardless of the handle position.

[TheGorrilla]

I understand that bit ok. Just cant understand why?

It's an Airbus I suppose....!

[idg]

TG

Without the speedbrake restriction the VLS (lowest selectable speed) would increase dramatically if attempting full speedbrake during an emergency descent at altitude. As VLS increased it could cause the AP to trip off as the AoA protection function became active, clearly not what is best right in the middle of an emergency descent!!

[PENKO]

Ok, before we get hopelessly confused, which is not very hard on an Airbus, what is this talk about half deflection being available with autopilot on? All it says in my (edit: A319) books is that you get half rate when flying faster than .75/315 with AP engaged. No more, no less.

The part about anti-ice, with airbus one must be always very suspect of translation vagueries (French to English). I know, a dangerous statement, but not less true.

[SoundLesS]

1.27.10 P11 bottom it tells about AP spoiler deflection being achieved with half speedbrake lever deflection.

[PENKO]

Ok thanks, can find no such note in the A319 FCOM. Forgive the confusion.

edit

I compared the 319 FCOM with the generic FCOM. There is less speedbrake authority on the 319. And no distinction between manual and autoflight.

[wingattack]

In my company we do not turn EAI on in the descent until just before entering moisture (say 10-15 seconds before). Is this wrong? Should it be on for all the descent/hold if the only moisture anticipated is a layer of FZFG?

As an aside and please excuse the thread creep.... Found myself very high once in an A320 so decided to select full speed brake and disconnect the AP. Cabin crew rang from the the back galley thinking the tail was about to fall off; shan't try that again!

[DesiPilot]

Penko,

In A319 and A321 you will get full speed brakes even with A/P engaged whereas in A320 you get half the speed brakes only.

To achieve full speed brakes in A320 one must disconnect the autopilot!!

[PENKO]

Thanks for clarifying that! However when I compare the actual deflection of the control surfaces it seems that there is more deflection on the 320 than on the 319...so what is considered full speedbrake deflection on the 319 is actually half the deflection on the 320.

FCOM319 (1.27.10)
The maximum deflection for spoilers is :
25° for spoilers 3 and 4
12.5° for spoilers 2 in configuration 3, and 17.5° in other configurations
(NB , the same as on the A320 with AP engaged!!)

Whereas my generic A320 paper manual states someting like:
The maximum deflection for spoilers is :
40° for spoilers 3 and 4
20° for spoilers 2 in configuration 3, and 17.5° in other configurations


Sorry for the thread creep.

[TheGorrilla]

Can understand speed restricting spoiler displacement (?). However I fail to see why manually flying the thing should allow greater amounts of spoiler use. Particularly as the autopilot seems to have access to a higher roll rate than the pilot.

Ho hum... It seems that as I fly more hours my brain gets smaller.

[Dan Winterland]

Half speedbrake on the 320 is roughly equivalent to full speedbrake on the 321.

[TheGorrilla]

sounds like I should just accept this fact!

[manuel ortiz]

Girilla,

Edited after reading Airbus info.

A-320 was modified to deploy only half speedbrakes with A/P ON to avoid:

- Activation of AOA protection when starting emerg desc with A/P ON

- Posible overshoot of VMO at speed brake retraction with A/P ON

- AP pitch authority not sufficient to counteract the pitch up moment at full extension of the speed brakes

Best regards,

Manuel

[pakeha-boy]

Ok, before we get hopelessly confused, which is not very hard on an Airbus


after 15r yrs.....its easy:}

[Jonty]

The theory of below -40 is that all the moisture should be ice crystals and as such should pass through a fast rotating fan without adhering to the surface.

When in the decent not only are the stall margins of the engines much smaller but the fan is rotating much slower allowing ice to build up on the surface of the fan.

Its not just a 320 issue, we also did it on the 757.

As for the speed brake, all I know is you get half speed brake with the AP engaged on a 320 and full on a 321. Why? I have no idea!

[eight16kreug]

EAI is anti-ice so I agree it's a belt and suspenders thing. You asked for plus 1,000 kg fuel anyway, why not turn those heaters on? You don't want the ice until it's for the scotch at the hotel after the flight.

I pull the speedbrake lever when I need to kill the speed due to ATC restrictions. I've been hopelessly confused in the airbus for a long time so I leave it to the engineers to decide how many degrees they want to deploy which panels. (Aren't the speedbrakes those thingies that open up on the tailcone?):)