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klk232

FLEX ?? newwui question

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Hi LeoFlex is a derated takeoff option, you set a temp that is higher than actual to "fool" the computers into using lower epr rating for takeoff and climb thrust.


Karl Kleiber

Proud FS2CREW supporter

i73930k, 12gb ram gtx580 1,5gig

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Guest vrandar

To add a bit more flesh to the previous answer, Flex is a takeoff reduced thrust setting (it is not derated thrust which is a bit different) and is used when the runway is not contaminated by being wet or icy, when the runway is not short and the aircraft is not doing a hot and high departure. If any of these conditions do exist then a TOGA thrust setting must be used. Flex is also not recommended with a tailwind. Flex assumes a higher outside air temperature than actually exists, therefore you never input a Flex TO Temp lower than the outside air temperature. The computers command the engines into using less thrust for the takeoff than they would otherwise do with a TOGA thrust setting. Why do this? Well a TOGA thrust setting pushes the engines to the limit of their capabilities, and though they are designed to take the strain it will age them more quickly so maintenance and replacement costs will be higher. Using a lower thrust setting prolongs the life of the engines and reduces the cost. The thrust that results must not be reduced by more than 25% of the full rated takeoff thrust. The PSS Airbus has a default setting of 42 deg C which means that if you leave it at that the computers will command the engines to provide thrust which would be achieved from a TOGA takeoff with that outside air temperature. One effect of using a FLEX takeoff is that you will need to use more of the runway to take off. This is why you must only use TOGA thrust on a short runway. For many airlines the rule is that the FLEX TO TEMP must not be higher than 60 (ISA+45 at msl) even though the MCDU can go to 99 degrees C.One crucial thing with flex is that it was programmed incorrectly by Phoenix into the MCDU. You need to use a MINUS flex figure to see the correct thrust reduction. This doesn't mean using -60 where you might have used +60. Approximate thrust figures for different minus flex temp figures are shown below:FLEX N1% -10 96.1-11 96.0-12 95.8-13 95.6-14 95.5-15 95.3-16 95.2-17 95.0-18 94.9-19 94.7-20 94.5-21 94.4-22 94.2-23 94.1-24 93.9-25 93.8-26 93.6-27 93.5-28 93.3-29 93.1-30 93.0-31 92.8-32 92.7-33 92.5-34 92.4-35 92.2-36 92.1-37 91.9-38 91.7-39 91.6-40 91.4-41 91.3-42 91.1-43 91.0-44 90.8-45 90.7-46 90.5-47 90.3-48 90.2-49 90.0-50 89.9-51 89.7-52 89.6-53 89.4-54 89.3-55 89.1-56 88.9-57 88.8-58 88.6-59 88.5-60 88.3Rob Elliott, EGPE InvernessPSS Airbus Support andAirbus Fleet Training Captain, British Airways Virtual airbus@speedbirdonline.co.ukhttp://www.speedbirdonline.co.uk/airbus.htmlhttp://www.bavirtual.co.uk

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Guest koldo.np

Hello,I've read many messages about this question in the forum, but no find the answer to it. The question is:Where is the chart that says you which N1% must use? I can't find out it in the "Charts and Tables" manual.Thank you very much.Koldo Navarro;-)>thrust figures for different minus flex temp figures are>shown below:>>FLEX N1% >-10 96.1>-11 96.0>-12 95.8>-13 95.6>-14 95.5>-15 95.3>-16 95.2>-17 95.0>-18 94.9>-19 94.7>-20 94.5>-21 94.4>-22 94.2>-23 94.1>-24 93.9>-25 93.8>-26 93.6>-27 93.5>-28 93.3>-29 93.1>-30 93.0>-31 92.8>-32 92.7>-33 92.5>-34 92.4>-35 92.2>-36 92.1>-37 91.9>-38 91.7>-39 91.6>-40 91.4>-41 91.3>-42 91.1>-43 91.0>-44 90.8>-45 90.7>-46 90.5>-47 90.3>-48 90.2>-49 90.0>-50 89.9>-51 89.7>-52 89.6>-53 89.4>-54 89.3>-55 89.1>-56 88.9>-57 88.8>-58 88.6>-59 88.5>-60 88.3>

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Guest FLEX

One more question when i used ther flex thrust then at 1500 (thrust reduction mode) i switch the thrust to CL mode but the thrust dont deacres instead it goes higher that the Flex n1 setting. is there a patch to fix this prob?Raj,Many Thanks

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Guest leopoldo

Hi.What does FLEX stand for?What ralation is with the runway temperature?RegardsLeopoldo

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Guest FLEX

Post removed. Forum guidelines.

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Guest airbusgek

I'm sorry I'm bringing up this topic again, but I still got a question for Rob Elliot.You know the PSS doesn't simulate the FLEX-temperatures correctly, and you know what N1-settings belong to what temperatures in the PSS, but here's the big question:How do you know what temperature you have to use for a FLEX-takeoff?Here's an example to make my question a bit more clear:You have calculated the FLEX-temperature for your flight by either using real-world charts or the Takeoff Performance Calculator of Roland Wukovits. You know that if you fill in this temperature in the MCDU you'll get the wrong N1-setting. What temperature will you fill in the MCDU to get the same N1-setting as when the PSS would simulate them correctly?Is there a formula you use?Do you have tables which show the real world N1-settings with there temperatures? (As far as I know, there aren't any of those charts, atleast not in the FCOM)Hope you can help us,Sander ParijsTechn. Pilot Airbus AircraftV-Bird Virtual Airline

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Guest Batur77

In addition to Sander's inquiry,I've made some tests of my own as having been a permanent PSS Airbus user for a long period of time about the thrust lever settings and so far the flex to values regarding the calculation methods, especially with Wukovits's calculator programme. As a result of my personal examination, I would like to emphasise that using and inputting the flex temperatures without the (-) minus sign seems to be giving more realistic values in the thrust reduction N1 percentages than the ones you used to keep saying. I really would like to get your own remarks and opinion on the issue, cause as a user i have been trying to become as realistic as i can to feel the realism of an airliner pilot. So far I've been examining anything new about the airbus type planes in real life considering training dvd's and other essential items. Now i seem to be in a turmoil which i am not sure of whether the information i have to use is correct or not. e.g: a flex value let's say 45 C without a minus gives around approx 97.3% N1 power setting which seems accurately more correct and realistic and it works it really works cause you can take in the middle or after having passed slightly the middle length of the rwy..According to your values if we use the same degree with a minus this time, gives us N1 setting of about approx. 90.7%, as to make a choice here what if the V1=135, VR=140 V2=142, i tried that and saw that the aircraft seems to be taking off almost at the end of the rwy which gives an idea of being far more unrealistic than the 1st example. Now which one is really correct ? I really want to know. in this 2nd sample with minus valie, should the aircraft loses only about 3 to 5 seconds, it sure will run out of the rwy before it can take off Thank you

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Guest fullflapsplease

As Rob says, FLEX should not be used on short/contaminated runways.What were your weights at T/O, flap settings and which bus were you driving?Cheers.Mark.747400.jpg

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Guest fullflapsplease

Rob, is the requirement to put a - in the McDoo FLEX applicable to all PSS busses or just the 320 family?Cheers, Mate.Mark.747400.jpg

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Guest Batur77

Hi Mark,Mine is A319 PssWhen i use the flex with minus (-) the aircraft uses most of the rwy almost gives a nose up at the end of the rwy and until the thrust accelaration and reduction speed it does not really ascend so easily but after the thrust acceleration speed which enables you to move the thrust lever to CL position it rapidly accelerates moves forward gains speed and lifts up so quickly, after take off this is too dangerous..flex without minus works well with the same logic when i examined it however i really do not know whether or not it is realistic.ThanksBatur

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Guest Batur77

Nobody would like to help ??Nobody has anything to say about this ?

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Guest cobrafly

I'm afraid that it's a more complicated matter,indeed, V speeds and FLEX temperature settings can be found in a separate documentaion (different from FCOMs) called "RTOW" stands for :regulatory takeoff weight chart. this document is computed by each airliner (a spetial softwear provided by airbus makes it possible). There is a specific chart for:- aircraft type (A319, A320, A321..)- engine type (V2500, CFM56B1A1, CFM56B4 211, 214...)- airport elevation..- runway lenth, runway slope..- limitations (runway lenth, obstacles clearance after takeoff, second segment..ETC)- flaps setting- wind- air conditionning ON or OFF- engine or TOTAL ANTI ICE ON or OFF- QNH correction- runway condition (WET or DRY).i.e: *for a giving runway and giving weight, you find a different chart with diff speeds and FLEX whether you fly a CFM56B4 214 or CFM56A1 211.* for a giving runway lenth, elevation and aircraft type, you find a different chart whether you take off from paris CDG or FRUNKFURT because of obstacle clearence after take off (different terrain conditions arround the airport on take off path)FLEXIBLE temperature (witch is different from DERATED take off), is an assumed temperature, that has to be higher than actual temp in order to be used, simulates high temp condition of the day witch causes a lower N1 computation by the FADEC thus, extend engine life.to be more clear let's take an exemple:let's say that we'v calculated a maximum permissible takeoff weihgt of 75000kg for the day. that means tha under no circumnstances we can take off with more than this weight according to the conditions of the day (T

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