A320 PFD Symbols
 

We are having a debate here about whether the green normal law eyebrows on the PFD are a graphic representation of the 67 deg bank angle limit or not.

Cannot seem to locate any specific reference within FCOM.

Hi,

DSC-31-40 C
in connection with
DSC-27-20-10-30 B

Great. Thanks

FlightDetent

Our debate continued:

FYI Here is the FCOM at std1.6 Not what it now says. Perhaps explains the different views.

“The display shows the symbols in green:

• · On the roll scale at +/- 67 deg to mark the bank angle limits

• · On the pitch scale at 15 deg nose down or 30 deg nose up to mark the pitch limits.”
  

The current FCOM DSC-31-40 P4/32 item (5) uses the words (my italics)

“The display shows these symbols (=) in green

• · On the roll scale to mark the bank angle protection availability.

• · On the pitch scale at 15 deg nose down or 30 deg nose up to mark the pitch limits.”

Cheers ZFT


ok, let's have a look, to see if I make any sense :O and understood you correctly.

In the present wording, the reference to 67 bank "hard" limit is removed in lieu of explanation about B.A. prot. (my bolding in your quote above). No such re-phrase happened to the pitch article.

My FCOM has exactly the same wording as yours, under :
FCOM DSC-31-40 C INDICATIONS ON PFD, the bullet point #5 shows:

(5) Flight Control Protection SymbolsThen I skip to DSC-27-20-10-30 B BANK ANGLE PROTECTION, the last sentence of the first paragraph says:[INDENT]If the pilot holds full lateral sidestick deflection, the bank angle goes to 67° and no further.

Haha, I see now I am not answering your original question at all. :sad: Back to square one.

1. Yes, I believe the = bank protection marks are displayed at 67 degrees.
2. No, I cannot find any reference in FCOM (present version) with the exact wording to declare so.
3. To settle your argument - as long as former versions of FCOM and (unchanged) DMC standard numbers are not allowed as evidence, you would need a test:
   • fly the A/C to the bank angle limit and compare the position of the sky-pointer to the mark, or
   • put an angular ruler / protractor on the PFD. [at least one engine running most likely required]

Splitting hairs, are we not? :E

FD.

Just to confuse the situation slightly, the bank angle protections at 67 degrees are there because this equates to a load factor of 2.5g,(the certified load factor clean) now if flap is extended the load factor limit changes to 2g but do the limits move on the PFD? Discuss

TL, thanks! Your gentle :D poke just helped me to find the answer to a Q I had (being a bookworm): why did AB change the wording in the first place?

Big respect to your knowledge.

tubby linton
It is a bank angle protection it has nothing to do with load factor. You cannot bank more than 67 degrees whatever be the load factor. Although it is true that if you do a turn with side stick fully deflected and maintaining altitude you will see +2.5 G.load factor displayed but that does not mean 67 degrees is always directly related to G.

ZFT
May be Airbus didn't find it necessary to repeat what is given in DSC-27-20-10-30 P 1/2 and 2/2 in chapter 31 which explains displays not necessarily limitations.

FlightDetent,

There was certainly an element of hair splitting going on but was an interesting debate.

Vilas

Maybe so. But DSC-27-20-10-30 pg 1/2 std 1.7 has this sentence ....(indicated by a pair of green bar lines "=" on the PFD) at the end of the 1st paragraph.

Not there on std 1.8 FCOM

ZFT
Yes I checked 1.7 that indication has been removed in later version. Never the less it still holds good.

Vilas, I would be surprised if you could obtain 67 degrees without getting to 2.5 g load factor. Would you explain why Airbus chose 67 degrees not 60.?Also if you have a load factor of 2.5 g before you obtain sixty seven degrees can you continue rolling and increasing load factor, which protection has priority?

Hi everybody,

to state the obvious, in a coordinated turn load factor relates to angle of bank with n=1/(cos(b.a.).

Here is my train of thought, please comment and fire at will:ok::

• The certified limit is 2,5g, just like any other aircraft.
• In a coordinated turn, 2,5G is reached at 66,5 aob.
• Airbus decided (hypothesis) to put a hard stop on bank at 67 deg aob, so in ideal conditions the load limit protection, aircraft certified limit, and bank angle protection intersect at a single point of the 4D situation.
• The B.A. protection indicator "=" is shown on PFD at 67 degree mark, and this was clearly stated in the older FCOM versions.
• There is no black magic about Airbus FBW. All is in the FCOM (somewhere :oh:). Equally important is, what is not in the FCOM!

That was then, and this is now:

a) ZFT discovered that the wording have changed.
b) tubby linton points out, that with flaps out, the bank angle protection set at 67 deg AOB will not stop you from going beyond the certified (+2g) envelope. Personally I feel the FBW designers are way smarter than that.
c) villas reminds us that load factor protection should takes care of the g-loading limitations.

My questions then:
. with flaps out, will the load factor protection change its hard stop to 2g instead of 2,5?
. with flaps out, will the bank limit protection change its hard stop to 60 deg AOB (2 g in coordinated turn) instead of 67 ?

In case the answer to the second Q would be YES (another hypothesis), all snaps together:
- the new limiting angle being 60 deg, the position of green marks on PFD no longer represents where the protection activates;
- Airbus purifies the FCOM wording since ["protection stop" equals to 67°] is not really true at all times.

tubby linton
In a 67 degrees bank you get 2.5g load factor provided you maintain altitude but if you just bank 67 degrees and allow the aircraft to descend as it will if you don't pull back, you won't get 2.5g. Merely rolling does not increase g you need elevator input to do that.

Vilas, thank you for the reminder. I try not to fly the bus to its bank angle limit .
PRO-SUP 27-20:
Steep turns can be made at up to 67 ° of bank. This is the steepest bank at which it is possible to maintain level flight at 2.5 g.