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Guest Paragon

D-TO and the charts jon b provided.

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Guest Paragon

I have a question for using derated takeoff using the charts jon b provided. I very much appreciate them as I fly out of heathrow all the time. I was wondering if you could provide an example or tell me if I'm using them right.Say I'm at heathrow rwy 9R and my GRWT, taken from the FMC, is 748,3lbs ~ 339,5kg do I just go into the chart, using the correct chart of course, and locate the weight closest to mine and then enter that deg C in the place where it says SEL in the FMC? So that would be something like 54 I would have to enter in my case?

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Guest Paragon

Excellent, thank you. Looking at the chart could you tell me what the N1 what number represent? Is that the number if I choose not to derate, because I think that I got someting like 97% with 54 entered. Could you explain, or point me in the direction where it does, the numbers at the bottom of each chart...ie the headwind tailwind and how to use them?-Mikkel

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Guest Paragon

The charts were on the PMDG forum, I'm sorry I can't remember which post, but do a search for jon_b and you should find them.The charts were specifically for EGLL, do I still have to take rwy length into account?-Mikkel

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I don't know the meaning of N1 column. Perhaps you can skip it. I know however the meaning of the wind compensation because it is self-evident. When they say for example ADD KG/KT HEADWIND 600 it means that if there is a headwind you can simply add 600 Kg of 'fake' weight for every 1 kt of headwind and then after modifying your weight this way - find the new values in the table. They simply translate wind into more/less weight - very clever. You get two numbers because there are two columns (two runways per page). Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

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I just realized that this adjustment for weight may get confusing. Because one might ask why add weight for a headwind - headwind should benefit you not penalize you. I am willing to elaborate if your are interested...Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

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Guest Paragon

Sure go ahead...I would like to know how to use the charts proper.-Mikkel

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I realized that with the wind the correction is not made to the aircraft weight but to the weights specified in the table. In other words the equivalent table for the wind is derived from the zero-wind table by adding so many kilograms per 1 kt of wind. If you then use such table then you will get proper result - headwind will result in being able to derate more, not less. Tailwind will then result in less derate.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

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Guest Paragon

Sorry to bring this old topic back up, but could you explain a little more how to use the weight adjustments found in the jon_b charts?-Mikkel

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Guest theflyer

The way I understand it is a little more complicated than it comes across in the charts. Before ever coming to calculate an assumed temperature to use, you need to figure out the regulated takeoff weight (RTOW); I think this figure is achieved after makeing various additions/subtractions as necessary based on headwind/qnh etc and applying it to your actual TOW. To get an assumed temp, the idea is to apply the total of your corrections (headwind/qnh) back to your actual TOW but in the opposite manner...... this sounds a bit messy and unclear, but I gleaned as much from the very thread in which Jon provided the data, I would advise you search for the thread, and let's hope maybe one of the drivers can clarify.Tony

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Guest Paragon

Yea I guess it's done in the same manner as on the LDS...if so then I think I've got it.-Mikkel

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>Sorry to bring this old topic back up, but could you explain>a little more how to use the weight adjustments found in the>jon_b charts?>Not sure by what you mean weight adjustments. In my opinion there are none. Every row already has a different weight. This is the maximum weight for the OTA temperature specified on the left. If your own weight fits between two different table weights - you pick the higher. The only real adjustment is for winds. As I said it is important to understand how it is supposed to work - the headwind should allow you to derate (use higher OAT) even more. If you incorrectly apply the wind adjustment you will get the opposite (erroneous) effect. I have a computer based training course developed by Boeing (or someone affiliated with Boeing) on this very topic. Unfortunately I installed it on my PC from a CD that was handed to me by someone from the PMDG beta team (name witheld). I no longer have this CD so I can't share it. But it explains exactly how to use the derate tables.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_747F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

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Guest Paragon

Let me see if I remember this correctly, I don't have the LDS manuals right here now. What I meant was that I add 330kg per 1kt headwind for the 9L departure plus I subtract 437kg for every mb over 1013 standard. I then find the number closest to this weight.-Mikkel

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