Airbus - Flap FULL or Flap 3??

[captainpaddy]

General question:

Under what circumstances would you use Flap 3 for landing as opposed to Flap FULL? And why??

Obviously this question would apply to any aircraft where you have a choice of landing flap settings. Normally most people I have seen will use Flap 3 for gusty or turbulent conditions. However, I am unsure as to the philosophy behind this as we fly the approach 5 knots faster but still 5 knots above VLS (wind conditions permitting). So why use Flap 3??

Any thoughts welcome.................

[dartagnan]

that's right, when u insert datas in the FMS, there is full flaps or 3 flaps choice.
any idea?

[D'vay]

Dartagnan,
What is your current level of experience?

[Yellow Sun]

Our company policy is that Flap Full will always be used unless an abnormal procedure requires the use of Flap 3. I should be interested in whether other companies routinely permit crews to use Flap 3 for landing and if so under what circumstances.

[captainpaddy]

I lean towards the idea of there being no real advantage in the use of Flap 3. The only thing I can think of is that it would result in a slightly higher nose attitude which may be of slight benefit if wind conditions dictate the use of a particularly high VAPP. Other than that, what does it do for you??

[OPEN DES]

My company does not exclude the use of flaps3. But flaps FULL is recommended under normal conditions. No guidance w.r.t. use of flaps 3 for LDG in normal ops is provided.

However I recall from Airbus Industrie FCOM that flaps 3 is recommended in case of reported windshear and/or severe turbulence during the apch.
I think energy is the keyword here. You have better G/A performance because Flaps 2 has a better L/D ratio than Flaps 3 (read: more efficient wing). Same for the balked landing obviously. This provides you with better windshear escape capabilities and gust recovery.
You could also argue that flying at higher speeds (5-6 knots normally) provides you with better stability but I would imagine that this is very marginal.

Personally on a very gusty day, I will have flaps 3 anytime. Provided stopping performance is not limiting.


I think there are some companies using Flaps3 as a standard for LDG because of economy (noise and fuel savings). I suppose they operate on long runways where there is no cost of braking/reverse.

[PhoenixRising]

The argument for CONF 3 landings in strong crosswinds and severe turbulence is that the aircraft has more energy and is in a lower drag configuration. The increased approach speeds will also decrease the required crab angle in crosswinds. Higher airspeeds increase control effectiveness and response.

That said, the only FCOM reference I could find for CONF 3 landings is this:

LANDING
Configuration FULL, or 3, can be used.
However, Configuration 3 provides more energy and less drag.

FCOM 3.4.91

My company doesn't mention the use of CONF 3 for landing in our ops manuals but I've flown with lots of people who use it in strong crosswinds. I've used it myself a few times but to be honest, I couldn't really see any real benefit gained.

[jonesthepilot]

I was led to believe that roll response was 'crisper' in Flap 3 than Flap Full, hence giving better handling at the expense of landing distance. If you then look at the increase in landing distance for a Flap 3 landing then you will see it is only about 70 meters. So, unless you are approaching a runway where you are close to landing distance limits and there is turbulence/windshear Flap 3 is the way to go!

[OPEN DES]

Surely 5 or 6 knots extra on Vapp (VLSconf3 opposed to Vref) won't have a significant effect on crab angle required.


Anyway here another FCOM reference
3.3.16 DESCENT PREPARATION

Check or modify the landing configuration. Always select the landing configuration on the PERF APP page : CONF FULL in the normal landing configuration. CONF 3 should be considered, depending on the available runway length and go-around performance, or if windshear/severe turbulence is considered possible during approach.

[captainpaddy]

Thanks for the FCOM reference Phoenix!

Originally Posted by PhoenixRising

The increased approach speeds will also decrease the required crab angle in crosswinds.

I have heard this before, although the net effect would be to reduce the crab angle by about 1/10th of a degree?

Higher airspeeds increase control effectiveness and response

Same kind of result with this. The change in effectiveness must be minute. Also, since the airbus is fly by wire, any input on the sidestick would surely give the same result regardless of speed. The surfaces may have to deflect a tiny bit more, but the computer will still give you what you ask for?

(Not discounting your thoughts Phoenix! Just giving my own view!!)

The less drag configuration is interesting. I also can see the benefit in a Flap 2 go-around although following windshear the configuration would not be changed intially, but a Flap3 windshear go-around would be better than Flap FULL.

Thanks for the thoughts guys! It's so easy to focus on the approach itself, when perhaps the benefit is only relevant for the go-around?

[Waldo Pepper]

In my Big company, it's SOP on the A320/A321 to land Flap 3 (unless you can think of a reason not to) for the purpose of saving fuel, since the power settings are less.

Most of us are reasonably good at finding reasons not to..but they're not really a big deal, to be honest.

[oldebloke]

Good question-The old question comes up every time one opens the QRH at the overweight landing:Flaps-determine???(so much for the quick reference)
The answer is in FCOM 3.5.35..Missed approach climb gradients.
It's easier to fly the approach in config3 at the faster speed,and have a cleaner aircraft on the missed app climb after "go-around Flaps"(flaps selected to 2)..
The same thinking applies to OEI approaches,or high ambient temps.
The only time one Has to use Config Full is on a CAT2(visual slope)..
Didn't they cover any of this on your line indoc??
Cheers..

[PhoenixRising]

Originally Posted by captainpaddy

Thanks for the FCOM reference Phoenix!!
I have heard this before, although the net effect would be to reduce the crab angle by about 1/10th of a degree?

Absolutely, don't get me wrong, it is negligible. Also, you're right, the roll in normal law is a roll rate, so again there's no gain with the airbus for landing with CONF 3. I was just outlining the general arguments for landing with a lower flap setting in a crosswind, albeit thinking more in terms of a conventional aircraft.

I'm not an advocate for it. Like I said, I've used it myself a few times but didn't see any discernible difference over CONF Full.

[747dieseldude]

I'm no 'bus driver, but since I think the question is fitting to all airplanes with choice of landing flaps, I will offer my view.

Lower flap setting gives you less drag, hence less engine power required, hence less noise. On our airplane in very heavy landing weights we MUST use flap 25 (instead of 30) in order to still be stage III.

Lower flap setting gives you a higher nose attitude. This is an advantage at very low weights, when the nose attitude is low to begin with, and the aircraft tends to 'float' during the flare. I find it makes a low-weight landing easier.

For the case of expected windshear, although this is not the SOP for us, reduced flaps will be superior, since you have better performance, and you are not allowed to change configuration during the recovery maneuver. Also added approach speed for gust compensation might sometimes at heavy weights put you close or above the max flap limit speed. Same is true for some hydraulic / flight control failures that require higher approach speed.

My philosophy is, unless you have a good reason (less crab on crosswind is not a good reason), use max flaps.

Happy Landings and Happy New Year

[Zeke]

Originally Posted by Waldo Pepper

In my Big company, it's SOP on the A320/A321 to land Flap 3 (unless you can think of a reason not to) for the purpose of saving fuel, since the power settings are less.

Correct, however should not be used of wet or worse runways.

Windshear, fuel, noise, missed approach gradients are positives, negative is the higher approach speed, greater landing distance, additional braking and wear, hydroplaning speeds, and possibility of a tail strike.

Judgment is needed, blanket policy for it does not make sense in all situations.

[Dixons Cider]

Windshear recovery on approach calls for no change of config until clear of the shear whilst climbing away with TOGA and following SRS pitch (ie max perf)
Doing this in Config 3 as opposed to config Full will give better climb perf.

[jonesthepilot]

I don't know the answer but I thought I'd throw this into the melting pot: Several folk have mentioned that using flap3 would lead to a higher pitch attitude, but surely the increase in approach speed would cancel that out(or to a degree anyway-no pun intended!)

[amos2]

C'Mon guys...let's not turn this into Rocket Science, what does your Ops Manual say?

What it says is what you do, how hard is that?

[Dozza2k]

F3 in a 321 always tickles me. We get hammered with dangers of tail strikes and then they ask us to adopt a landing config tht increases the pitch att on finals by 1, maybe 1.5 degrees. Its not a lot but if you get a strong sink at 30R and yank back to arrest the rate you creep 1 maybe 1.5 degrees closer towards that 9 degree office meeting.
am I being a bit too cautious?

[MrBernoulli]

No Dozza, you're not being too cautious. Ideas like this are constantly being dreamt up by desk-driving gimps to save fuel or whatever, and improve bonuses for said management monkeys.

Once data about increased brake use (higher landing speeds) becomes available, or a tail-strike occurs for exactly the reason you suggest, then they will invent another policy to 'improve company performance'.

I'm surprised they don't ask for glide approaches!