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Guest JTH

"Drag required" message on descent?

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Hi everyone, whenever the autopilot starts a descent at the T/D I start to get an FMC message saying "drag required". Sometimes I get it and clear it multiple times during the initial stages of my descent.So my question is what exactly does "drag required" mean and how can I stop this message from occuring? Thanks a lot... Paul.

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Hi, (Unnamed, so please sign your post with your real name)The Drag required message means your plane is accelerating in your descend, under VNAV control.To stop this message you need to use your spoilers (air brakes) to deaccelerate to the calculated (or selected) descend speed on your MCP/FMC.On a big bird it is hard to maintain a speed when descending, so using your spoilers to keep it on the selected speed is not a bad thing, and is used many, many times.Good luck,Stefan van Hierden

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Thanks for the reply. Do you mean use the actual spoilers (/ key) or just arm them (shift + / key)? And would it be a good idea to do this every time at the top of descent, even before I get this message?Oh and P.S. I did sign my name in the original post, check it out! Thanks, Paul.

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paul. no, use the actualy spoilers./ not armed. it will only go as far as the flight detent section. it won't deploy spoilers all the way. have fun, and slow down! :)

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When the aircraft is descendeing at a high rate, it will need help maintaining its selected speed by deploying the speed brakes.It depends on your rate of descent. If you keep it around 2500 FPM, you should not get the message. Doug

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Well is it standard to need speedbrakes on descent? I am basically going with default settings so it's strange that the plane is speeding up at descent. When I apply speedbrakes do I just leave them on and will they turn themselves off when the plane has slowed down enough? Or how exactly will I know when the plane has slowed down enough so that I don't need speedbrakes anymore?Thanks a lot for everyone's continued help.

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When I fly the 747 PAX version and it asks for drag on descent, i wait a few seconds and if the message is still there I deploy the speedbrakes as all people have explained here. If I leave them on, when the speed has reduced to the magenta arrow on the speed tape, if the speedbrakes are still deployed I get an error message on the right hand glass instrument which tells me that i still have the speedbrakes deployed, so i then put them back to armed or turn them off and wait for the next time it asks for drag and repeat the processregardsJohn CallejaBAW352

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Drag or not may be also depending on the cost index. When I take 100 there is no need to use the spoilers, but when I take 250 CI I had to use drag.

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Thanks for all the replies, very helpful.

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>Drag or not may be also depending on the cost index. When I>take 100 there is no need to use the spoilers, but when I take>250 CI I had to use drag.How is a drag requirement linked to cost index?

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"How is a drag requirement linked to cost index?"It shouldn't be... That is to say, the FMC will take CI into account and order a later/sooner top of descent point.Perhaps the pilot forgot to enter WINDS? Or the actual winds were different from the forecast (and entered) winds. Tailwinds tend to put the aircraft above the descent path. Use of TAI (Nacelle Anti-Ice) can also raise the idle levels of the engines, producing more thrust. FMC entries also have to be made to compensate for this. Cheers.Q>

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I did not enter any winds into the FMC, as I was not aware you had to this. Is this standard procedure for the 744 before takeoff? If it is would you mind telling me:a) how winds are determined?:( how I program them into the FMC?Thanks a lot once again, Paul.

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Hi, Paul... I was kinda hoping someone had already created a tutorial for this... or that it was in a manual/FAQ/previous posting somewhere. I'm too lazy to do this kind of stuff... so I use the speedbrake like 99.9% of the flyers here :(Cheers.Q>

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It was a flight without wind and the descent started automatically. But with CI 250 it started later and with a higher descent rate. Therfore I was instructed to use drag.

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