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Takeoff flap setting

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Takeoff flap setting

Old 17th Dec 2019, 02:43
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Takeoff flap setting

We are having an ongoing debate of the pros and cons of flaps 1 vs flaps 2 T/O on the Airbus 320. Ever since FlySmart has incorporated the optimizer for takeoff flap setting, which has consistently applied flaps 1.
I am hearing a number of completely erroneous arguments; such as better second segment climb ( which has just the opposite effect ) or inertial pitch with engine out changing from 12.5 to 10.2 or to much of increase in takeoff V speeds. To the more acceptable, airport with a rough runway.

What are your operations procedures?

Thoughts?
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Old 18th Dec 2019, 01:38
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I have worked for four companies on A320s and two of them used optimum flap, the other two use or used Flap 2 as standard (one of those companies changed it policy to optimum flap while I was working for them). An other argument for using Flap 2 as standard I heard from one of those companies is that during a takeoff in config 1+F in the event of a failure of ADR2 followed by unreliable indications from ADR1 during takeoff can result in uncommanded automatic flap retraction to Flap 1 and that's why Flap 1+F takeoff is avoided (there is a note in the MEL that Flap 1+F takeoff is not authorized if dispatching with ADR2 inop for this reason ). I can not estimate the likelihood of this combination of failures occurring simultaneously or within a short time frame during the takeoff phase, but I guess it must be rather low considering (probably less than 10^-9...) that the A320 is certified for takeoff in Config 1+F...
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Old 18th Dec 2019, 06:00
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Just my opinion, but why have the extra drag if you dont need it. Quieter for neighbours too!
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Old 18th Dec 2019, 07:34
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.during a takeoff in config 1+F in the event of a failure of ADR2 followed by unreliable indications from ADR1 during takeoff can result in uncommanded automatic flap retraction to Flap 1 and that's why Flap 1+F takeoff is avoided
This is the most ridiculous reason to Avoid 1+F. Most have 1+F as preferred setting. You don't select flap setting for double failures. What about doble engine or double AC bus or double hydraulic possibility?
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Old 18th Dec 2019, 07:49
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There appears to be some misinformation continuing to go around our Airbus pilot group concerning the belief that flaps 2 is better for takeoff and second segment climb performance, when just the opposite is true. All we need to do is use our Flysmart + Takeoff performance optimizer for flap setting to give us the best performance information.
Flap setting has an affect on the wing’s lift coefficient and on the aerodynamic drag. Increasing flap angle increases the lift coefficient, and therefore reduces stalling speed and the required takeoff speed (the same lift will be created at smaller air speed due to greater lift coefficient). This reduces the takeoff distance. In the same time increased flap angle beyond optimum increases drag, reduces acceleration, and increases the takeoff distance.
The net effect is that takeoff distance will decrease with increase of flap angle initially, but above a certain flap angle the takeoff distance will increase again. An optimum takeoff setting can be determined for each type of aircraft and any deviation from this setting will give an increase in the takeoff distance.
The flap setting also affects the climb gradient. Increasing the flap angle increases the drag, and so reduces the climb gradient for a given aircraft mass. If there are obstacles to be considered in the takeoff flight path, the flap setting that gives the shortest takeoff distance may not give the required climb gradient for obstacle clearance.
It is important that we not rely on past standards of companies they have worked for and use standards set forth in our manuals . We unfortunately have a number of items like these and others that are still being propagated by many and are in desperate need of being cleaned up. I truly believe that the best cockpit environments are ones that safe, efficient and with a free flow of ideas and communication. I have found that the best way to accomplish this is to have the correct information be promoted by our training and management Captains.
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Old 18th Dec 2019, 08:15
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I am now getting kick back from our some of our most senior captains against the use of flaps 1+F takeoff.
The latest is in the high OAT we operate in; ME, the increase in V1 speed which is even greater with flaps 1 and the light weight we operate at are too high???
From what I know is V1 is limited by Max brake energy speed, the brake energy speed is dependent on weight and thrust. Even some say that the small saving in fuel do not outweigh the use of flaps 2; try telling that to our CFO. Although I have yet to hear a technical performance reason to not be using and optimizing our performance when ever possible.
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Old 18th Dec 2019, 09:55
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Our software aims for the highest possible flex temperature. The flap setting it spits out is what we use, almost invariably, be it 1, 2 or the occasional 3. I donít ever recall flying with anyone who prefers one flap setting over another for takeoff.
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Old 18th Dec 2019, 10:05
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I believe Airbus FlySmart takes in a number of performance values. Not sure if Flex temp is a primary consideration.
As per Flysmart/NavBlue:
"Takeoff performance The Takeoff module provides the necessary take off performance data that the flight crew needs on board to take off. The Takeoff module provides the following take-off performance: • The take-off performance data for a take-off at TOGA thrust: V1, VR, V2, Engine Out Acceleration Altitude, limitation codes; • The take-off performance for a take-off at flexible thrust: Flexible temperature, V1, VR, V2, Engine Out Acceleration altitude, limitation codes; • The performance limit weight (if applicable), the optimum configuration (if applicable), the optimum engine option (if applicable); • The detailed outputs: provided to the crew depending administration settings on a separate page. Example of generic parameters: runway lengths used, different V1 (min, max or balanced), limiting weights, minimum and maximum altitudes. Recommendations regarding the use of the detailed outputs are given during the Performance Administrator training."

As simplistic as it may seem; (using the software for your takeoff values), It amazes me how based on hairs on the back of my neck, because I like, it is used by professional pilots in today's highly automated environment. Gone are the days where in normal operations we go to RTOW charts for our performance numbers. Using and following performance software would seem to be a no brainier. It is interesting from a human factor how irrational to down right bat shit crazy one can be when confronted with change.

Last edited by jimmyg; 20th Dec 2019 at 11:37.
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Old 18th Dec 2019, 11:37
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The optimum given by Fly smart will consider those nine factors and use that Conf for takeoff is normal. But I know atleast one carrier that prefers Conf1+F.
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Old 18th Dec 2019, 13:49
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Only half a speed-brake
 
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jimmyg tough luck, is it? Fear of the unknown, moreover loss of the person's social position in the group once a large piece of self-perceived wisdom erodes into thin air.

FWIW the software spits results chosen to give the MAX PERF LIM TO weight. It is possible to model a case where forcing F2 will cause a higher V2 speed to obtain max possible gradient. While keeping F1 that perform better would allow for the chosen V2 to stay below the anabolic range.

Having flown long periods with 1+F, once in a blue moon then if you have F2 departure it feels as if the cargo doors were left open - during the acceleration segment.
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Old 20th Dec 2019, 02:55
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Well, normally optimum flap setting will be used, as far as I am concerned and what I've talked with friend, optimization is what the airline and pilot is looking for. Why would you put f2 when you do not have anything on the flight path and not limited by any means?

The only reason ( there's more but in this case...) I could think of to put f2 is being speed limited on SID ( often with the 321LR) other than that runways are usually long enough to put f1, also middle East might be due to the temp I guess.
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Old 20th Dec 2019, 06:45
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This flaps 2 mandate was a pet peeve of mine, when flying the 'Bus. 2 out of 3 operators I've flown for insisted that we always used F2, only one allowed OPT flaps.


The main reason cited, however was tail clearance on T.O., which was better at higher flap setting. I believe this claim is somewhat valid for longer planes such as A321 and A346. However definitely not in the A320, which has plenty of tail clearance margin. Airbus FCTM is also not very clear about it and suggests using higher flap setting due to tail clearance when possible. I guess they just want to play it safe to avoid litigation.

I was, however, frustrated by this blanket approach. We have several flap settings available for a reason - and we should use them according to situation. Optimize when able, be conservative when conditions dictate. Mandating the use of F2 means that the management don't understand how flaps work in a jest transport and/or are insecure.

A great example of this was a heavy A330. On a long runway, the V2 could be some 20-25KT below Vfe F2. Guess what happened on a windy day - during takeoff in a gust speed would jump towards Vfe and people would pull the stick and over-rotate, at high rate cos they were scared of overspeed. But when I suggested using 1+F the answer was invariably 'noooo, F2 gives better tailstrike clearance'

Last edited by Sidestick_n_Rudder; 20th Dec 2019 at 06:59.
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Old 20th Dec 2019, 12:08
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"The numbers don't lie" is a rally cry since my early aviation math and physics days.

"In all of mankind's engineering endeavors, nothing proves the laws of physics and mathematics more succinctly than does the jet airplane" is a quote I have used from my friend teacher and mentor, the late Harry Hurt (RIP).

Aircraft although are flown by humans and we must consistently take that into account. In some recent reading I came across seems most appropriate in today's socio heated political or may I add cockpit environment. Context needs to be part of any mathematical equation.

“Narratives without statistics are blind, statistics without narratives are empty.”

Steven Pinker, the author of The Better Angels of Our Nature, describes this paradox perfectly.

Thank you all for your thoughts and insights,

Jimmy
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Old 20th Dec 2019, 13:40
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Originally Posted by Sidestick_n_Rudder View Post
A great example of this was a heavy A330. On a long runway, the V2 could be some 20-25KT below Vfe F2. Guess what happened on a windy day - during takeoff in a gust speed would jump towards Vfe and people would pull the stick and over-rotate, at high rate cos they were scared of overspeed. But when I suggested using 1+F the answer was invariably 'noooo, F2 gives better tailstrike clearance'
priceless.
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Old 20th Dec 2019, 18:04
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Originally Posted by jimmyg View Post
"In all of mankind's engineering endeavors, nothing proves the laws of physics and mathematics more succinctly than does the jet airplane" is a quote I have used from my friend teacher and mentor, the late Harry Hurt (RIP).
​​​​​​
As in, the writer of Aerodynamics for Naval Aviators? Cool!
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Old 20th Dec 2019, 18:49
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The airlines i have flown with so far on the bus always set flaps 1 as standard in the performance module of flysmart. The first one had the software pretty open, so we would see all possible V-speed combinations and could choose which one fits us best, including a usable V1-range. Another one had the software completely locked down, and we only got one v-speed combination. The flysmart software is highly configurable by the airlines backoffice, and those pre-settings can limit the choices the pilots have considerably. In the end, as always, fly whatever the company wants as long as it is safe, and every performance combination flysmart spits out is deemed to be safe.
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Old 21st Dec 2019, 11:38
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We use our own performance tool for takeoff data computation. It aim's for the highest Performance TakeOff weight with the highest Flex Temp. Depending on input data (ray, weather, a/c weight) it gives an optimum flap setting. In our operation, central europe, mostly flaps 1+F.
If the pilots prefer a different setting they can modify it, taking into account "all relevant factors" 😉
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Old 24th Jan 2021, 14:14
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Hello Guys, I was reading a bit about the performance programs manual for A320 and the logic when OPT CONF is selected is as follow:

1> If takeoff is limited by performance, the calculation returns automatically the configuration that maxmizez the performance- limited MTOW.
2> If takeoff is not limited by performance and flexible takeoff is possible, the calculation returns the configuration that maximize the flexible temperature ( to reduce engine wear)
3> If takeoff is not limited by performance and 2 different flaps configuration provide the same maximum flexible temperature, the calculation returns the configuration that maximizes the V2/VS ratio.

For case number 1, what do they mean exactly by '' limited by performance''? Does it mean that let's say the maximum flex that can be used on on A320 is 60 but due to heavy weight a lower flex must be used and therefore by using optimum config it will chose the config with the highest flex?
And for case number 3 what do they mean '' maximizes the V2/VS ratio. Does it means to minimizes the gap between VR and V2?


Another confusing thing is in the FCOM-Performance- Take off recommendations:

'' If take off weight is not limited by performance, consider using the higher flap setting. Objective: To extend engine life and save maintenance.
I don't undestandhow using more flaps therefore more drags will extend engine life and save maintenance cost...

And last: I was playing on the EFB between Conf 1,2 and 3 for take off, for heavy weight the V speed are higher in conf 3 than conf 2 But not on lighter weight. Another mystery for me!

Any feedbacks from you guys will be much appreciated.

Thanks.



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Old 24th Jan 2021, 18:45
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Originally Posted by pineteam View Post
Hello Guys, I was reading a bit about the performance programs manual for A320 and the logic when OPT CONF is selected is as follow:

1> If takeoff is limited by performance, the calculation returns automatically the configuration that maxmizez the performance- limited MTOW.
2> If takeoff is not limited by performance and flexible takeoff is possible, the calculation returns the configuration that maximize the flexible temperature ( to reduce engine wear)
3> If takeoff is not limited by performance and 2 different flaps configuration provide the same maximum flexible temperature, the calculation returns the configuration that maximizes the V2/VS ratio.

For case number 1, what do they mean exactly by '' limited by performance''? Does it mean that let's say the maximum flex that can be used on on A320 is 60 but due to heavy weight a lower flex must be used and therefore by using optimum config it will chose the config with the highest flex?
And for case number 3 what do they mean '' maximizes the V2/VS ratio. Does it means to minimizes the gap between VR and V2?


Another confusing thing is in the FCOM-Performance- Take off recommendations:

'' If take off weight is not limited by performance, consider using the higher flap setting. Objective: To extend engine life and save maintenance.
I don't undestandhow using more flaps therefore more drags will extend engine life and save maintenance cost...

And last: I was playing on the EFB between Conf 1,2 and 3 for take off, for heavy weight the V speed are higher in conf 3 than conf 2 But not on lighter weight. Another mystery for me!

Any feedbacks from you guys will be much appreciated.

Thanks.
1. Performance limited means MTOW limited by available thrust, no flex possible. In that case select the Conf that gives higher TOW.
2. If Flex is possible select the one that gives higher flex.
3. If Flex is possible and same Flex in two different configurations then selects the one that gives higher V2/Vs, possibly for better second segment climb.
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Old 26th Jan 2021, 03:28
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Thank you Vilas,
For case number 3, I guess it should always be config 1 on A320 since it’s less drag.
any idea why the recommend to use more flaps to save engines life and maintenance cost?!
And why on heavy weight the V1,Vr V2 speeds are higher on conf 3 versus conf 2 but not on light aircraft?
thank you.
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