A320 handling in Flap 3 vs Flap Full

[Sore Higher]

Hi

I have been in the left seat of A320s for over 10 years and have developed the habit of using Flap 3 and Vapp of Vls +10 for an approach in expected turbulent or possible windshear conditions. The reason for doing this is because Airbus says we should, and in fact give us no option but to use Flap 3 if windshear is possible. (FCOM PRO-SUP-91-20 P1)

I find the handling on short final in choppy conditions to be quite acceptable with Flap 3 and Vapp=Vls+10 entered in the MCDU Perf page, whereas on occasions doing a Flap Full with Vapp=Vls+5 approach in unexpected choppy conditions the aircraft handles like an over loaded canal barge by comparison. Yes I know the manuals imply the handling should be the same, but it isn’t… I’m talking about lateral control here.

So I have two questions I would like to ask:

First question, directed towards other experienced A320 pilots out there: Talking to the F.O.s I fly with it appears very few other Captains prefer Flap 3 to Flap Full in choppy conditions, and I am wondering why? Is it me who is missing something, or is it the other guys?

Second question, directed to anyone who has advanced knowledge of aircraft stability and control, and aerodynamics: Is the difference in handling due to the flight control laws, or aerodynamics, or both? I'm just curious, that's all.

Thanks for any replies.

[Capt Scribble]

Flap 3 always seems good in choppy conditions and I always use it, trouble is, you will never know what it would have been like if you had used flap full. I understand the reason is that the lateral flight control laws are different in F3. Our Co wants us to use F3 where conditions allow to save fuel so, I use it most of the time. Not sure why you use VLS plus 10. Just Use the Config3 selection in the FMGC and it gives the correct Vapp, which is about VLS +10 on Full flap as it happens.

[rudderrudderrat]

Hi Sore Higher,

There have been several accidents during windshear conditions:
Accident of an Iberian Airbus A320 in Bilbao (http://www.iasa.com.au/folders/Safety_Issues/others/Bilbao.html) and Airbus and FAA Airworthy Directive AD 2001-08-26 specified using F3 if windshear was forecast on the approach. Apparently the pitch control was modified in F Full to try to avoid some PIO events.

However, if there is an increased chance of making a GA (due windshear) and I may be caught with reduced aircraft performance by not changing the configuration during the windshear event, then I'd have to be stupid to attempt it with Conf Full. You are correct, the others are taking risks despite the warnings.

[Stone_cold]

He said choppy conditions, not windshear..seems like it is an acceptable crew option.

[vilas]

Alpha prot is phase advanced it means depending on how fast the AoA is changing it can trigger before the speed(AoA) actually reaches alpha prot. That was the cause of Bilbao accident because the down draft was severe. So they made changes to the software programme. Also the added 10KTS which keeps alpha prot that much away from Vapp. Flap full in any aircraft is lot of drag with little increase in CL so in flap3 aircraft has more reserve of thrust so better thrust response to drop in speed. Less flap than full landing is easier in any aircraft as aircraft handles better in pitch, the attitude is slightly higher so needs less flare. Some people have undue fears about tail strike and they stick to full flap as they are more used to it but in WS it is not good.

[WindSheer]

Ruderruderat

That article is written by someone (and i am not surprised) in Miami.
I got the sense in the first paragraph that it was a bash at airbus and then spotted the name and location at the top.

I am not knocking some of the technicalities within, but it is not an official document and I fear is worded very carefully towards the Western side of the pond.

Treat such documents with caution.

[Sore Higher]

Thanks for the replies, it is nice to know I'm not missing something.

Some delay on my part because I posted under the 'Tech Log' area and the thread disappeared. Now found it under 'Ground.....' :confused:

I usually only make Vapp=Vls+10 in gusty conditions following the Airbus recommendation.

[Lookleft]

My personal view as to why pilots don't use flap 3 more often is the higher pitch attitude required 5deg v 2.5 deg. Not much of difference but they are constantly pushing the nose down to make the picture look right. Just a further example of the degradation of basic flying skills and the ability to adjust to situations that are different to the other 90% of the time. In gusty conditions Flap 3 also gives you a bit more margin over the flap extension speed when GS mini goes nuts.

[dream747]

With all the revisions that have been introduced in the FCOM, am I interpreting it correctly now that flap 3 is recommended in windshear and gusty conditions (FCTM Adverse Weather - Windshear), while either flap 3/full can be used in turbulent conditions (FCTM Adverse Weather - Turbulent Conditions)?