A320 (ELAC, SEC, FAC)

[StrIA]

HELLO!
I've question about principle work ELAC, SEC, FAC? How is create the roll (bank)? What is algorithm creating of bank?
ELAC 1(2) performs the following functions:
‐ Normal pitch and roll
‐ Direct pitch and roll
SEC 1(2)(3) performs the following functions:
‐ Normal roll (by controlling the spoilers)
‐ Direct roll
Both FACs perform the following functions:
‐ Normal roll (coordinating turns and damping dutch roll)

I wrote here PRO-SUP-27-20 (FLIGHT MODE). But I could meet nowhere decription how making the range of roll
For example: AP - ON, FDs - ON, NORMAL LAW
1. We are flying at FL350 IAS 265kt ~0.78M and take decision on 180-degree turn. You are pulling HDG on FCU and turning to backward direction.
2.The same conditions, except - ALT 2000' IAS (TAS) 200kt
3. If we perform turn on 30-50 degree at those FL and ALT
What will be a bank?

[Cough]

At FL350, TAS 280 you are going to have an IAS of just less than 160. This is likely to mean a full stall, as such your bank angle is likely to be the last of your worries.

Anyhow, for a given turn ELAC will start the turn with aileron, along with SEC with a touch of spoiler. The ELAC will keep the turn level by adjusting the elevators to maintain your flight path and the FAC will balance the turn with rudder.

Normal turns at low levels occur at 25 degrees AoB.

[StrIA]

TAS 280
I corrected. IAS of course.

[StrIA]

Normal turns at low levels occur at 25 degrees AoB.
Where it's described?

[ElitePilot]

At FL350 at 280kts IAS you will be in excess of MMO in a 320 so in normal law speed protections will start to come into play. Not a realistic question.

[Cough]

Normal turns at low levels occur at 25 degrees AoB.
Where it's described?

Just years of watching it...

[StrIA]

At FL350 at 280kts IAS you will be in excess of MMO in a 320 so in normal law speed protections will start to come into play. Not a realistic question
I adjusted IAS 265kt ~0.78M

[StrIA]

Quote:
Normal turns at low levels occur at 25 degrees AoB.
Where it's described?
Just years of watching it...
Can you give link to FCOM, FCTM or AFM?

[Cough]

No longer on type. However just google rate 1 turn.

[StrIA]

Did anyone meet any information about it?

[Togue]

I was also curious about this topic and lost interest because I was not able to find info on FCOM or FCTM. The plane I was flying before had "half bank" function when operating at high altitudes. Airbus do not mention anything about half bank. There's a mention about the g loads limits. Bank angle protection is there also. So I guess the FAC will not let you exceed the +2.5 to -1 g's when clean. How does the FAC calculates it? I don't know.

[compressor stall]

I'd forgotten about this thread. I'll do some digging.

It's one of those things that Airbus don't think you need to know, therefore they don't publish it! The only reason it came about for me was that I was writing a spreadsheet calculating a flight path to intercept a solar eclipse shadow and calculating the turn radii at altitude...

[tubby linton]

Normal law commands roll rate
The normal-law flight mode is a load-factor-demand mode with automatic trim and protection throughout the flight envelope.
When the aircraft is in the “in flight” mode, normal law combines control of the ailerons, spoilers (except N° 1 spoilers), and rudder (for turn coordination) in the sidestick. While the system thereby gives the pilot control of the roll and heading, it also limits the roll rate and bank angle, coordinates the turns, and damps the dutch roll.
With the autopilot engaged At low level you will see twenty five degrees of bank. At high level I dont think I have ever seen it put on more than 10 degrees, probably less, however full roll rate remains available through a manual input

[Metro man]

A rate 1 turn is 3' per second which is really cranking it at jet speeds. Try timing a standard holding pattern with one minute legs, back when we were flying light twins the turns at the end were rate 1 and took a minute each, therefore each hold was 4 minutes total.

See how long it takes now to go around the pattern.

[StrIA]

As I understood, at low level bank will be create by FAC, but no more 3°/sec and restriction 25°. How will be at higher level?

[Microburst2002]

To my knowledge, rate 1 turns is not a thing that airbus fbw airplanes care about.
I once did an assessment for an airline where we had to fly the "figure B", which includes timed rate 1 turns. The speed regimes were 200, 250 and 300 knots. Nobody explained how to do a rate 1 turn at 300 kt without exceeding 30º bank angle...

There are bank limits at speeds below maneuvering speed, and also when close to the buffet boundary, when flying at high levels and high weight. Then, in NAV mode, bank angles can be very small, in order to make very wide turns at intersections and therefore flying less miles (a form of "cheating"?).

Also, when you are in departure and get a DIR and you do just that (use the MCDU for a DIR TO) the bank angle is small, but if you pull HDG to go there instead, bank angle will be maximum. That is why I prefer to use HDG and later on I use the DIR TO.

So not only the ELAC is involved. The FMGC is involved, too.

[compressor stall]

I’ve just looked at my notes and my memory is clearly not what it used to be!

From Honeywell: A320 Roll limits in MANAGED are:

1. between 150KTAS and 300KTAS the bank angle is 30° for flight plan legs
2. 100KTAS to 375KTAS the bank angle is 25° for holding patterns, procedure turns and arcs.
3. TAS 450 and above bank angle 19° for all turns
4. Linear joins for the above.

The difference in bank angle I mentioned in previous post was not due to AP off or on, it was due to NAV vs HDG.

In the sim at FL390 450+ TAS, turning 90° to intercept a HDG gave a HDG of 15°AoB. When NAV was engaged during the turn (to the waypoint off to the right), the AoB increased to 19°AoB.

On the day I assume it went the same, as it all went to plan. I’d have to look at the FOQA data replay to see what it did.

[Microburst2002]

Interesting.

One day we were flying at mas level but we were very light, and I turned with HDG for WX avoidance and got nearly 30º bank. In the PFD I couldn't even see VLS, so margin to buffet was very good

[compressor stall]

http://i663.photobucket.com/albums/uu353/stallie001/aviation/5A96C41C-2216-44D5-BF3A-6FBBBE9F824B.jpg

http://i663.photobucket.com/albums/uu353/stallie001/aviation/8C1BC726-5D1C-49B9-9AB4-4B0814D874F6.jpg

Note the speed - I'm not sure if that makes a difference in HDG?

From memory we were CI 100 at this point getting M0.80. We had to go selected speed to get M0.82 for the intercept leg.

[StrIA]

From Honeywell: A320 Roll limits in MANAGED are:

1. between 150KTAS and 300KTAS the bank angle is 30° for flight plan legs
2. 100KTAS to 375KTAS the bank angle is 25° for holding patterns, procedure turns and arcs.
3. TAS 450 and above bank angle 19° for all turns
4. Linear joins for the above.
Give me link to material, if it possible.
I read the FCOM, THALES_FMS_PG_REV2+, but I've not met description the similar situation.
Have anyone Honeywell described in more detail?