What version of TOPCAT do you use?

I'm using 2.70I am also getting limits over +40, just showed them as a reference. But there is differences between mine and yours.At first one you are saying: +64C 59646 OBS© 115-116 116 120 2706M 86.3%. I have limit up +65C 57019 OBS© 115-116 116 120 2611M 86.8%2nd you got: +54C 65215 CLIMB 143 143 144 1649M 87.6% and i got +50C 65531 CLIMB 143 143 144 1603M 88.7%3rd you got: +65C 56078 CLIMB 114 114 119 2725M 86.2% and i got +65C 54295 CLIMB 114 114 119 2637M 86.8%4th you got +47C 65181 CLIMB 140-141 141 142 1877M 88.6% and i got +43C 65366 CLIMB 141 141 143 1841M 89.7%So i confirm that i calculated these rates by using:TEMP 0C ALT two eight decimal eight zero (eightzero is showing smileyface so i write altimeter as nato alphabet) WIND 040/05 (04KT HW) ** FLAPS 5 (and) 10 ** TO ** DRY ** ** AIR COND ON ** ANTI ICE OFF **Summa summarum: am i doomed?

Edited February 1, 201214 yr by Kazzukki

TEMP 0C ALT 28.

Oh THERE is the problem! I was using Q1008, i.e. A29. If I use the Q0975 (which is almost impossibly low BTW - OK that might be a bit of an overstatement. But it is very unusual.)then I get the same results.In that case, I am not sure what is the problem, if it is that at that specific derate of +40 you always get 90.2% N1, then that is correct.The assumed temperatures works in this manner:-For every (real) temperature, there is a maximal permissible N1.This is because the higher the N1, the higher the EGT, and also the higher the air temperature, the higher the EGT.So for every given temperature, there is a specific N1 (at a set density altitude) that will get the EGT to the limit. So at +40 the engine will have limiting EGT at 90.2%N1, at +50 it will already have limiting EGT at 88.8%.-Thrust is a function of N1 (in otherwise stable conditions, e.g. the ones you input for takeoff). The performance calculator basically calculates how much N1 you need to take-off safely by comparing heaps of data inside it. It compares various situations, accelerate-stop distance, OEI take-off distance, climb requirements, obstacles..... etc.Then it looks up at which temperature the N1 would be limiting, and tells you that.-When you input the temperature into the FMC, it will look up what is the limiting N1 and set that as a limit (note that it will only set the limit precisely after engines are running and AI and air conditioning is set up as required)

Edited February 1, 201214 yr by Fabo

Fabo thank you very much for your special effort. Guys like you are few and far between! But then there is only one problem left for me. Please try to put a real weather value to TC (example EDDF realtime weather from ASE) and then calculate with that. Note the calculated N1 and start the simulator. Go to EDDF to that same runway and make the preparations. In my system there it goes wrong. If i use any value different then 29.92 at TOPCAT to calculate N1, TC's calculations doesn't match with NGXs'. Have you tried? So it's like my NGX is always at 29.92 no matter what altimeter is set in the simulator conditions (or what ASE has setted). Hope you follow. And yes - +40 value is allways the same, no matter flap position and weight. Of course TO, TO-1 and TO-2 +40 values are different. It is extreamly hard to explain but it seems that my NGX thinks allways that it is 29.92 preassure even through by pressing "B", it automatically sets baro to the one that ASE is using (real world one). Damn ;)

So it's like my NGX is always at 29.92 no matter what altimeter is set in the simulator conditions

I will look at that, but if this is true that NGX disregards air density, then that is a question for the PMDG...

Note the name of the button: "Estimate"Estimate is another word for 'guess'.Basically, TOPCAT is a takeoff and landing calculator, not a fuel planner, but they put that feature in there to help you out if you needed a rough guess of how much fuel. Therefore, it's not going to have fuel planner accuracy, or any of the advanced inputs for wind/altitude/etc.

Thanks Kyle

Thanks Kyle

You're welcome!

'windshearDK' timestamp='1327961675' post='2243400']

 

I am using TOPCAT and the NGX with great precision!

Remember to have pneumatic pressure running through the aircraft, ideally from the APU(APU bleed on).

 

Thanks WindshearDK, I started using a cold and dark startup and was wondering why my N1 readings were always off.

Turned the APU on and now both readings are perfect.

Mystery solved. (Now to solve my intermittent CTD's) :Thinking:

Not to be devil's advocate here but does anyone here use the old method? I mean PMDG/Boeing were generous enough to give us the performance charts so can't you interpolate the correct N1 from there? I know you have to do the math yourself but surely it's possible...

 

I know, I know....don't call me surely...

 

I use perf charts, its much more interesting and Im sure values are correct, while with any calculator, I just cannot be sure...

 

It takes only few minutes to do perf dispatch.