A320 High speed protection.
 

From the A320 FCOM DSC-27-20-10-20

1. At high altitude, this may result in activation of the angle of attack protection. Depending on the ELAC standard, the crew may have to push on the stick to get out of this protection law. What is the meaning of "depending on the ELAC standard"?
2. On the A320 THS setting is limited between the setting at the aircraft’s entry into this protection and 11 ° nose-up, whereas on the A321 pitch trim is frozen? Why?

1. So high speed protection applies a nose-up pitch demand to control the speed. If you're at high weight / high level, this pitch up may be sufficient to trigger angle of attack protection. At this point the sidestick commands angle of attack directly, and acceleration will actually result in a climb. The only way out of AoA protection is a forward input on the sidestick, which if you're flying level will require a slight descent. This isn't ideal so I suppose that Airbus modified later ELACs to not do it.

2. Result of flight testing, I guess.

Hi Fursty... I am sorry, I didn't understand point no 1. "This isn't ideal so I suppose that Airbus modified later ELACs to not do it." What isn't ideal the AOA or the pitch down.?

The excursions beyond the envelop mostly may happen due to environmental conditions. The philosophy is not to allow the aircraft to stabilize beyond the envelop. So the trim freezes when the envelop is penetrated, even the AP trips. Airbus made some changes to the software with online experiences. So the older ELACs behave in a different manner.

So to understand, in case the aircraft enters a stall while high speed protection is active, the pilot has to lower the nose manually. Was this happening earlier automatically depending on ELAC.

ARe you referring to high AoA protection or high speed?

Hi Vilas I am just trying to understand this following statement from the FCOM

Depending on the ELAC standard, the crew may have to push on the stick to get out of this protection law.

So are getting out of high speed or angle of attack.

What Kay Pam said is correct. AoA has priority over other protections. So if high speed protection triggers an aggressive pitch up and it may end in alpha prot. There was an airprox incident over the Atlantic between the A340 and A330 where due to turbulence and copilot merely disconnecting the AP but not pushing the stick caused the aircraft to rapidly climb through the altitude of the other Aircraft. Perhaps that triggered the change in ELAC with a new software.

Once AOA-prot is passed, the aircraft changes into a flight control law where stick neutral commands AOA-prot and full-back-stick commands AOA-max.

In older ELAC standards, if the passing of AOA-prot was only a temporary thing (for example a short vertical gust), the aircraft would still keep this law, meaning to pitch-up into AOA-prot if stick was neutral, since after passing AOA-prot, flight control law changes, and stick neutral commands AOA-prot, although the AOA would be way below AOA-prot after the vertical gust has passed. To leave this law, some fwd input on the stick is needed. However this is intuitive, since any reasonable good pilot would pitch the aircraft down, if it suddenly begins a climb.

On newer ELAC standards, if AOA goes by itself back to values below AOA-prot, the aircraft does not anymore pitch up to maintain AOA-prot, but leaves this law without stick input.

G'day B737NG_Pilot,

I see you have asked a few questions now about the A320 systems, mainly AutoFlight/Flight Control related. My guess is you are converting, or about to convert onto the A320 from the 737. Hopefully the below can help you understand the "Airbus Way", which is very different to the "Boeing way".

I converted from the Ejet to the A320, then to the 787, then back to the A320. One thing I can say is, despited the 5000 page FCOM, plus the FMGC manual, and all the other Documents (FCTM/QRM) your company may have for you to read, the A320 is actually a pretty simple aircraft, SOMETIMES.

Normal Ops on the A320 is very straight forward. Definitely the easiest aircraft to operate on multi sector days.

Abnormal/Emergency ranges from pretty straight forward to very time consuming.

I did my initial Rating with some ex PanAm guys that had been instructing on the A320 during its development, early 1980's, and they were so knowledgeable. Their advice, if it's not talking to you (ECAM), you don't need to do anything.

While there is lots of information, like that above, it will be a unicorn event where you will need to know it. Eg: Sully, QF32

The Golden Rules seem like fluff when you first read them, but as it says, they are Golden. For example:

Say you end up in this situation you have written above, there will be lots of ECAM noise (Overspeed, AP off etc) from the aircraft, it's really distracting, and some of them can't be cancelled.
You might remember the description of the Protection, you might even remember the ELAC standard the aircraft has. But all you need to do is:

FLY - (Airbus' version of Aviate)

That is Frenglish (French/English) for AVIATE. So, do whatever it takes to stay in the air and control the a/c. Who cares what angle the THS is frozen at, you can't do anything about it anyway. (it will unfreeze once you are out of the protection regime)

Once you have the A/c under control, the Overspeed Warning will disappear and you can re engage the AP, all the noise will stop. Happy days. The FCTM has the recovery procedure. (PR-AEP-MISC)

Unlike the Boeing, which has limited systems information, Airbus has included a lot of info in the DSC section of the FCOM, but would you believe it has been getting less over the years? (There was stuff in my initial Rating notes that had been removed 8 years later)

I found a lot more useful Operational Info that helps understand the DSC info in the ABN/EMERG section, and operational information in the FCTM. Also the DDG, this is where you will find out which system is connected to which. (the thigh bone isn't always connected to the knee bone :-( )

In this example:
PRO-ABN-OVERSPEED

It just tells you when it will Trigger

What the limits are

END

So you apply the Golden Rule:

AVIAT -> Then back to normal Procedures.

I am not saying Systems knowledge isn't a good thing, it certainly will help as the failures get more complex (Dual HYD, Emerg Elec etc), but the ECAM protocol is very robust. The QRH summaries help in the more complex failures to show the switching between the systems.

Aviate - Safe to continue flight
Navigate - as required
Communicate - as necessary

Then if time permits, QRH, FCOM, DDG etc.

Airbus RECALLS seem lame at first. (EGPWS, W/Shear, TCAS, Loss of Brakes, Emerg Desc, Stall Recovery, Unreliable Speed, RTO.)
Until you realise they were all "recalls" on the Boeing too, but then you had the 10 "standard" recalls too, The ECAM takes care of these.

Ie: Engine fire - It is exactly the same.

Fly the Aircraft
At a safe Altitude (abv 400 ft)

"ECAM ACTIONS" (Airbus)
Thrust Lever Idle
Eng Master Off
ENG Fire P/B Push
AGENT 1
AGENT 2
-Engine secure-

"ENGINE FIRE, SEPARATION SEVERE DAMAGE MEMORY ITEMS" (Boeing) (it has been a while so I think I got it right)
Auto Throttle off
Thrust lever Idle
Start Lever Off
Fire Handle Pull
Agent 1
Agent 2
-Engine Secure-

From here you do whatever you need to do to clean up the aircraft, sort out your next move etc. The only real difference is AIRBUS is actioned from a screen, Boeing from memory and checked against a book. (or the Electronic Checklist on the 787/777).

So, don't get buried too deep in the DSC section, spend time in the SOP's, ABN/EMERG, and the FCTM. Once you get in the Simulator your will see it in action. It all works as advertised. Once you have some time in the aircraft, and a few Sims under you belt, you will see it is a very good aircraft.

It is definitely "Different". Is it better than the Boeing 787? No and Yes, but there is 30 years between those 2 aircraft. The eJet sits in the middle of both, Boeing levels of FCOM information, Airbus levels of operational simplicity.

You might not like it, you might love it, but don't let it confuse you, that is a tricky place to come back from.

I hope this helps.

Cheers Roj

P.S. The table is the greatest single thing about the Airbus.

1201alarm thank you.. this is exactly what I was looking for. With regards the newer ELAC once the the AOA is below AOA-prot, does the aircraft pitch down or maintain level flight ?

Thanks Roj,

Appreciate the input, coming from some one who has flown the 3 different systems. Will keep the pointers in mind as I progress further into the type rating.

Thanks Kay....

Hi Vilas was looking for the changes made to the new ELAC, when the AOA reduces on its own with stick neutral.

I don't have access to them but all proposed changes are published by Airbus as MOI Modification Operational Impact. And detailed changes to Aircraft behaviour, QRH and FCOM sections are mentioned there. May be it's in Airbus world but you have to be a member it's not free.

My answer is an educated guess, I am not entirely sure.

However, what I would expect: after the temporary gust has passed and AOA is again below AOA-prot, the Airbus is in normal law and would keep it's current 1g flightpath.

Hi Vilas was able to locate this document.

Safety First 06
However it still doesn't answer the question. When the AOA is reduced, the newer system will get out of the Alpha protection... But does the airplane thereafter fly level or is left in a climb, if no pilot input is given.

Angle of attack
 

Does angle of attack protection available all the time or just at 100 feet?