A320 USE OF FLAPS 3

[Metro36]

Hi
Please don’t judge but I have a question re: “USE FLAP 3”
Why is Flap 3 used when ALTN/DIRECT LAW?
Why is Flap 3 suggested in gusty/windshear approaches?
Is it solely due to Go Arounds because of less drag?
One instructor said “it just cuts thru the air better..” wtf!

[Check Airman]

For windshear, I’d guess it’s for better GA performance. No clue on why we do it for direct law. I’d be way more comfortable with full in that scenario. Haven’t done F3 in months.

[gearlever]

For direct law I would assume a minor trim change with F3 than F4 in case of G/A.

[Sidestick_n_Rudder]

There may be many reasons to use reduced flaps when control is degraded. Might be performance, or pitch authority during landing, or G/A, system considerations, or something else altogether.

Only Airbus test pilots and engineers know actual reasons, which may be very obscure, and/or affect only a tiny part of the flight envelope covered during flight testing and certification. However, if the manual says F3, I would strongly advocate to follow this advice.

Also, this is not unique to A320. A330 procedures dictate using F2 a lot when in degraded modes. On the 787 most (if not all) F/CTL, or hydraulic failures call for F20 instead of the usual F30.

[gearlever]

There may be many reasons to use reduced flaps when control is degraded. Might be performance, or pitch authority during landing, or G/A, system considerations, or something else altogether.

Only Airbus test pilots and engineers know actual reasons, which may be very obscure, and/or affect only a tiny part of the flight envelope covered during flight testing and certification. However, if the manual says F3, I would strongly advocate to follow this advice.

Also, this is not unique to A320. A330 procedures dictate using F2 a lot when in degraded modes. On the 787 most (if not all) F/CTL, or hydraulic failures call for F20 instead of the usual F30.

Same on A300/310

[safelife]

Aileron sensitivity is completely different with flaps 3 vs. flaps full.

[320busboy]

The flap csu provides direct input to the flight control system and adjusts the gains according to lever position. Is also why the csu has a breakout function if jammed. Ref the report from vr-hyu in hkg many years ago.
The Kinematics figure shows that a 5°/sec side-stick demand in Config Full results in aileron and spoiler deflection of approximately 11.5° and 3° respectively. The same side-stick demand in Config 3 results in deflections of 18° and 8° respectively. Clearly the aircraft is more sensitive to control inputs in Config 3 than in Config FULL

[Cropduster]

320 busboy....
If the demand is 5 deg/sec, does it not follow the the greater aileron and spoiler deflections in Config. 3 indicate less response as more surface deflection is required to produce the same roll rate? I know that when the 321 first had PIO problems on approach in ice, the fix was to land in Config.3 as the aircraft was less sensitive.
cropduster

[FlightDetent]

Then it looks like less sensitivity is desirable under DCT law?

[Check Airman]

320 busboy....
If the demand is 5 deg/sec, does it not follow the the greater aileron and spoiler deflections in Config. 3 indicate less response as more surface deflection is required to produce the same roll rate? I know that when the 321 first had PIO problems on approach in ice, the fix was to land in Config.3 as the aircraft was less sensitive.
cropduster

Remember, we're talking about alternate law, so roll control is direct. No roll rate demand.

[Check Airman]

The flap csu provides direct input to the flight control system and adjusts the gains according to lever position. Is also why the csu has a breakout function if jammed. Ref the report from vr-hyu in hkg many years ago.
The Kinematics figure shows that a 5°/sec side-stick demand in Config Full results in aileron and spoiler deflection of approximately 11.5° and 3° respectively. The same side-stick demand in Config 3 results in deflections of 18° and 8° respectively. Clearly the aircraft is more sensitive to control inputs in Config 3 than in Config FULL

Interesting. I guess they want to ensure we have maximum roll authority in altn/direct law.

[Check Airman]

Only Airbus test pilots and engineers know actual reasons, which may be very obscure, and/or affect only a tiny part of the flight envelope covered during flight testing and certification. However, if the manual says F3, I would strongly advocate to follow this advice.

Oh I'll be following their advice for sure, I was just thinking out loud, so to speak.

[FlightDetent]

Remember, we're talking about alternate law, so roll control is direct. No roll rate demand. ALTN and DCT is how the discussion started, yes.

On top of that, the poster has a technical description that explains different surface deflections needed to achieve 5°/sec (clearly NORMAL law) for the different approach flap settings. Now, if Normal Law for F4 needed to provide almost double the deflection compared to F3, guess it must be the same the pilot under ALTN or DCT. To achieve the same response with F4, more deflection of the stick, this time? And for the same stick command, the A/C would feel half-responsive compared to F3.

Speculation.

[dream747]

On newer MSNs (or I think at least the units fitted with Sharklets), dual FAC failure does not result in Direct Law after the landing gear is extended (ref FCOM). Can I assume that the roll characterics for the same failure on different aircraft is very different in this case, one being in alternate law roll rate, the other being in direct law. How confusing considering that we are dealing with the exact same problem.

[320busboy]

On newer MSNs (or I think at least the units fitted with Sharklets), dual FAC failure does not result in Direct Law after the landing gear is extended (ref FCOM). Can I assume that the roll characterics for the same failure on different aircraft is very different in this case, one being in alternate law roll rate, the other being in direct law. How confusing considering that we are dealing with the exact same problem.

could have something to do with the envelope E function being also in the FMGC. The earlier models had the E part solely in the FACs. Unlike the 330 which have it only in the FMGEC. I was told by airbus it was too big a design change to remove the FAC’s so it’s in both on later models.

[vilas]

According to Airbus reply actually Sharket aircraft with double FAC failure remains in normal law. As stated by Airbus:-
The reason behind comes from handling qualities: the Normal Law is more adequate in terms of manoeuvrability and controllability of the A320/A321 Sharklet aircraft when flying with Yaw Damper failure. Nevertheless, we did not want the flight crew to consider that there was no impact of the loss of the Yaw Damper (principally on the protections), and therefore decided the PFD to display Alternate Law.
Please note that this behaviour is true only for A32/A321 Sharklet aircraft, and for the following failures:
1. FAC1 + FAC2
2. FAC1 + Y hydraulic
3. FAC2 + G hydraulic
4. Detected loss of yaw damper

[Check Airman]

could have something to do with the envelope E function being also in the FMGC. The earlier models had the E part solely in the FACs. Unlike the 330 which have it only in the FMGEC. I was told by airbus it was too big a design change to remove the FAC’s so it’s in both on later models.

E function? What’s that?

[vilas]

A320/A321
FLIGHT CREW
TECHNIQUES MANUAL
PROCEDURES
NORMAL PROCEDURES
SUPPLEMENTARY PROCEDURES - ADVERSE WEATHER
A320/A321 FLEET PR-NP-SP-10-10-2 P 3/4
FCTM ← D 22 MAR 17
CONF FULL provides better handling capability in turbulent conditions, however, CONF 3 provides
more energy and less drag.

[Cropduster]

320busboy....
I can see this for Alt.Law 2 ( roll degredation) but not for all other cases of Alt. Law.
Much as Vilas posted, we found that that in very gusty conditions, pilots were often feeling they didn't have enough roll control authority in Config.3, sometimes momentarily reaching full sidestick deflection. The airplane appeared to be be much more stable in Config. Full, with less sidestick inputs needed and the engines spooled up more appearing to make speed control more precise in gusts. Of course this was in normal law, and also several decades ago. I am sure updates are continually changing the airplane. Interesting discussion to try and connect subtle technical features with day to day line flying.

[320busboy]

E function? What’s that?
envelope protection.

[vilas]

Metro36, Side stick, Busboy.
This issue was discussed three years ago. I had quoted an Airbus reply as below that should satisfy everyone:

I had asked Airbus why land in Conf3 in specific case of Hyd G+Y Fail when flaps are jammed slats have no 3 position? I quote from the reply from Airbus"

I agree with you that selection CONF 2 during approach, and maintainingCONF 2 for Go-Around could have been less misleading for the pilot.
But the rationale of selecting CONF 3 for A320 family aircraft ishistorical, as this configuration has been proved, in terms of certification,as being the optimum one in terms of handling qualities in alternate law.”

[Metro36]

Thank you Vilas
Thats the quote I was searching for.
I also appreciate the replies about roll control.
Thanks

[StrIA]

The flap csu provides direct input to the flight control system and adjusts the gains according to lever position. Is also why the csu has a breakout function if jammed. Ref the report from vr-hyu in hkg many years ago.
The Kinematics figure shows that a 5°/sec side-stick demand in Config Full results in aileron and spoiler deflection of approximately 11.5° and 3° respectively. The same side-stick demand in Config 3 results in deflections of 18° and 8° respectively. Clearly the aircraft is more sensitive to control inputs in Config 3 than in Config FULL
Can you give me link to FCOM, where I can read.
Thank's

[sonicbum]

Can you give me link to FCOM, when I can read.
Thank's

It is on the report itself that You can find HERE. (http://ebook.lib.hku.hk/HKG/B35840213.pdf)
Page 33.

[StrIA]

It is on the report itself that You can find HERE. (http://ebook.lib.hku.hk/HKG/B35840213.pdf)
Page 33.
Thank you so much