Flare Mode on A320

[FLEXPWR]

Hello there,

Anyone here who can describe when the flare mode would NOT be active during a manual landing (normal law)?

I am referring to a normal landing with no failures, and no CB's pulled.

I was told recently that the 320 flare mode (2 deg nose down over 8 seconds input) was not operative when the FD's were switched off for the approach, but I struggle to find any reference in FCOM's (mind you, info could be there anyways, Airbus has a talent for hiding stuff in hard to find places!).

The FCOM 1.17.20 only describes the flare mode, but does not give any exceptions for its operation.

Any help appreciated, thanks.

Flex

[rudderrudderrat]

Hi Flex,

I've never heard of that one.

I'm sure Airbus would have written that in big bold print somewhere if the handling was going to be so different between a manual landing from an ILS (with FD on) and a manual landing from every other sort of approach with the FD off.

[FLEXPWR]

That would be my guess, but considering where I heard it from, I would like the opinion of a few collegues/experienced pilots/instructors etc...

I am usually quite thorough in finding the information in FCOM's and other docs...but this one I'd like to check before coming forward and start to debate the veracity of the statements coming from my Yoda Master...

Any other mode/situation that could have been interpreted as such?

Thanks

Flex

[fredgrav]

Hi FLEXPWR,
the only thing I know is that sometimes while flying manually (no NAV course or NAV path active) it would be better to turn FD's off in order to revert from THRUST mode to SPEED mode: this may avoid abrupt and uncommanded thrust changes ... but, as far as I know, there ain't any flight mode reversion with FD's engaged !

Best,
fredgrav

[pensador]

Hi! the FLARE mode can never be disengaged in normal law because of the pilot will be rob of the instinctive reaction that needs for flare.

[pensador]

Hi,fredgrav, if I don't mistake whenever you intend to fly manually you MUST turn off FDs. Correct me If not, please!

[Dan Winterland]

I wouldn't use the imperative "must". It's down to your SOPs. My company specifies for visual approaches and the visual part of any non precision approaches.

Not heard that switching the FDs off changes the Flare Law, but that's not to say it doesn't happen. For instance, the rate of change of Rad Alt readings changes Flare Law, if the rate of change increases or decreases rapidly, then the feel is different - apparently. It's not mentioned in the books except for a paragraph which alludes to it in the FCOM bulletins.

It certainly makes for a good excuse for a cruncher at some of our trickier destinations!

[rudderrudderrat]

Hi Flex,

Any other mode/situation that could have been interpreted as such?

During manual Flight, with FD's on, coupled to the ILS - just after 400 radio "Land" annunciates (which has always struck me as being very tricky since both APs are disengaged).

Maybe Yoda Master was saying the "Flare" Mode won't annunciate if the FDs are turned off?

I've never been "looking in" at that stage - so I can't tell you if it does or not with the FDs on.

[NigelOnDraft]

IMHO Airbus have confused us here by having 2 Flare Modes

First is the Normal Law stick v pitch effect noted above from 30R - by itself this actually lowers the nose. This is a "Flight Control Law" mode. AFAIK this mode was removed in the A330/340 i.e. the effect of the pilot "needing" the pull this mode requires seems to have been judged unnecessary.

Second is the Autoland FLARE FMA from ~40R - also called in places 'Flare Mode' - this unsurprisingly raises the nose. This is an AP/FD mode. The manual does state that this mode "disengages" when the AP/FDs are disengaged, which might equate to being turned off.

Our manuals quote a 3rd "Flare Mode" in Altn Law when the gear is lowered (direct stick to elevator relationship). Commonly understood to be "Direct Law"... but then knowing Airbus, maybe it is not quite that

Summary: IMHO landing with the FDs off does not alter the Normal Control Laws / feel / pull required in the flare. One might understand otherwise from the Airbus manuals, but what's new

NoD

[FCeng84]

Boeing 777 and 787 manual flare compensation easier to understand

I wish the Airbus control law were more clearly defined. For the 777 (and identical for the 787) a Flare Compensation function is always active for manual flare and landing. As main gear altitude decreases from 50 feet to zero (i.e., touchdown) an increasing nose down command bias is added that requires the pilot to hold aft column to counter. Flare is accomplished with a monotonic pull until main gear touchdown (target of 15 to 20 pounds at touchdown). Nose let-down is accomplished by relaxing the column thus allowing the flare compensation bias to command negative pitch rate.

[Microburst2002]

Yes.

Maybe they are referring to the case where G/S and LOC are active but at 350 ft LAND does not come green. Then neither FLARE nor ROLL OUT are armed and you land manually (no autoland) and disregarding the FD.

But I don't know the conditions required by the FMGS to give the green light to the LAND mode or the red one.

[FLEXPWR]

Thank you

Thanks to all of you for your inputs, it leaves a big question mark still, but in a way seems to confirm no change in the flare law with FD's off.

I have to insist the example given to me was relating to the law during flare being different the FD's on or off, not any other flight phase, nor any call out, and focused only on the manual landing.

But again thanks, I am looking forward to see other replies as well.

Note: not a rethorical question, but genuine interest to get a better understanding of what the beast is doing.

Flex

[fredgrav]

Hi,fredgrav, if I don't mistake whenever you intend to fly manually you MUST turn off FDs. Correct me If not, please!

Hi Pensador,
the MUST depends on your company's SOP ... however it would advisable to turn FD's OFF whenever you're flying manually, with ATHR active, an off route segment or an interception course (eg. HDH/TRK to intercept, radar vectors, visual approac etc.), this just to avoid unexpected thrust excursions.

[TyroPicard]

FLEXPWR
There is nothing in FCOM or FCTM that backs up your Yoda Master statement. I suggest you ask him/her to show you the reference .. I don't believe there is any difference with FD ON or OFF - that would be a ridiculous design feature. (AP ON or OFF is different!).
With FD OFF the FLARE mode is not annunciated, but it still works the same.

Re Manual flight - of course you can fly with FD ON. It is recommended to turn it off and use the bird in certain circumstances.

I am hoping your YM is not an instructor - his/her info comes from beyond the dark side...

fredgrav

however it would advisable to turn FD's OFF whenever you're flying manually, with ATHR active, an off route segment or an interception course (eg. HDH/TRK to intercept, radar vectors, visual approac etc.), this just to avoid unexpected thrust excursions.

Can you explain further? I am mystified by this statement. How can you use HDH(sic)/TRK to intercept with FD OFF? Radar vectors are easier with FD ON....

[mcdhu]

The jiggery pokery called Flare Law that goes on beneath your feet below 50' in Normal Law in the A320 Family is there simply to make it behave like a non FBW aeroplane in the flare. Therefore, it matters not whether the FDs are on or off, whether the FPV is on or off or anything else for that matter.

The 'Flare' FMA is nothing to do with this and becomes active only during an Autoland ie AP1/2 engaged and 'Land' annunciated.

Cheers
mcdhu

[fredgrav]

Can you explain further? I am mystified by this statement. How can you use HDH(sic)/TRK to intercept with FD OFF? Radar vectors are easier with FD ON....

Hi Tyro,
I'm sorry, HDG not HDH ... just a typing error !
I was referring to an AP OFF + FD + ATHR ON condition: here the A/THR is still in THRUST mode. In THRUST mode the AP pitch mode maintains speed, but as it is not ACTIVE, unwanted thrust excursions may verify while flying manually. It is advisable at this purpose to turn FD's OFF in order to revert from THRUST MODE to SPEED mode, where ATHR maintains a constant speed (selected). Surely radar vectors are easier with FD ON, but if you are being vectored, and flying with AP OFF, FD should also be selected OFF, and FPV alone might help you keeping the path ...

fredgrav

[tom775257]

fredgrav <<but if you are being vectored, and flying with AP OFF, FD should also be selected OFF, and FPV alone might help you keeping the path>>

No! The time you have to worry about taking the FD off (with regards to this) is if you are not following them. You can perfectly happily fly the aircraft around AP off FD/Athr on in thrust or speed mode during vectoring, or most other stages of flight.

<<I was referring to an AP OFF + FD + ATHR ON condition: here the A/THR is still in THRUST mode>> No, it depends on the vertical mode selected, you could easily have a VS selected and a heading to intercept the ILS, hand flying it, FD + AThr on, selected or managed speed, the aircraft will be in Speed, V/S mode HDG and LOC blue AP off Athr on 1FD2



The time it is very important to bring FD's off to get speed mode is really either a visual approach where the flight directors will offer no guidance obviously, or continuing visually after a non-precision approach or a TCAS RA when you will ignore the flight directors hence you need to turn them off to get speed mode.

I take it you have never flown the aircraft?

[Chris Scott]

Autothrust Confusion

Quote from fredgrav:
I was referring to an AP OFF + FD + ATHR ON condition: here the A/THR is still in THRUST mode. In THRUST mode the AP pitch mode maintains speed, but as it is not ACTIVE, unwanted thrust excursions may verify while flying manually. It is advisable at this purpose to turn FD's OFF in order to revert from THRUST MODE to SPEED mode, where ATHR maintains a constant speed (selected). Surely radar vectors are easier with FD ON, but if you are being vectored, and flying with AP OFF, FD should also be selected OFF, and FPV alone might help you keeping the path ...
[unquote]

Can an old fart be permitted a few remarks, to challenge statements that are admittedly off the original topic? As a long-retired A320 driver (Jan1988 - Nov2001) I've been trying to keep my oar out of this thread, but the above remarks seem to betray a big misunderstanding of the A/THR modes. What exactly do you mean by "THRUST MODE"?

On the initial approach, the only thing that will prevent the A/THR being in "SPD" mode is if the FD has been left in "DES" mode or "OP DES" mode. The A/THR mode will then be "IDLE". If at this stage the pilot goes visual, ignores the FD commands (while leaving the FD on), and sooner or later starts to reduce the rate of descent, the A/THR will continue to command idle thrust. This was the prime reason for the Indian Airlines Lahore (?) accident circa-1989, but others had previously fallen (nearly) into the trap. THAT is the scenario in which you MUST turn the FDs off (although improved low-speed protections were installed after that accident).

With AP off, I agree that – any time you are not on radar vectors or flying an ILS – the FD should be switched off, and "SPD" mode of the A/THR verified (assuming you are using it). The "bird" is to be recommended.

On final approach, using auto-thrust, some of the commanded thrust changes can be unnecessary, particularly in gusts. On a single-engine approach, in particular, unexpected thrust changes make smooth yaw-control difficult. A stickler for SOPs, I hope nevertheless that there are still some A320 fleets sufficiently enlightened to permit their pilots the choice of manual thrust, on short-final at least? The A320 manual throttle is the best of the six jet types I flew. But in auto-thrust, the absence of tactile information (throttle movement) is a drawback, as we tried to convince Bernard Ziegler in 1986...

Chris

PS:
tom775257, see you got in first!
fredgrav, I have just looked at your personal profile. I hope the above is helpful, and that you soon enjoy flying Airbus FBW.

[pensador]

fredgrav
and
Dan Winterland
how often do you fly AP-off with FDs-on (I mean do not follow FDs commands) and in what cases?

[fredgrav]

Thanx ChrisScott it more than helpful !
I fully agree with both you (Chris and Tom775) ... though the situation I was thinking for radar vectors was a really basic one: AP OFF + FD OFF + ATHR ON, without any FCU HDG or ALT selection -> (eg. the controller instructs you to fly heading 050 climbing to FL90, then you fly heading 050 manually with NO FCU selection, while starting a climb, to FL90 manually). In that situation, a FD left ON on a previous heading or ALT might also lead to unwanted thrust excursions, that's what I meant ... if wrong, could anyone explain the why ?!

I take it you have never flown the aircraft?

Tom775, haven't flown the bus yet, cause I'm yet a "pilot in the making" ...

Pensador, while flying with AP OFF, it would be best to turn the FD OFF whenever you're not going to follow it ... even if the example I made above is a bit uncommon to be sincere !