Hi! First I like to apologize my bad english!So my problem is this:I start a flight, let's say from LPMA to EDDF. I start from CLD AND DRK (as always) and i do all the preflight procedures correctly but when it's time to do some performance calculations with TOPCAT, i ran into a strange problem. TOPCAT seems to calculate TO-Rate correctly only, when i set Altimeter to 29.92 inHg from TOPCAT's Take-Off menu. QNH is set correctly at the cockpit but if i dont use value 29.92 inHg or 1013 hPa at TOPCAT's "Conditions", the calculated N1 doesn't match with the value that NGX had calculated. For example:LPMA 010/07KT +14 QNH 1027 hPaUsing Flaps 5 and TOW 56 t. Air Conditioning ON and TO-1.At these conditions, TOPCAT calculates N1 93.5% but NGXs' CDU calculates 93.8%. This same, about 0.3-0.8% difference between TC's and CDU's calculations comes at all possible TO / assumed OAT conditions. Only way to make these two (2) different N1 rates to be the same (what TC calculates), i have to set TC's "Conditions" Altimeter-setting to STD (29.92/1013) before calculating take-off performance. When this is done, TOPCAT calculates correctly in nearly all situations. Conversely if i enter a pressure under 29.92 inHg, like 29.50 to TC, it calculates 94.1%, which is now even bigger that CDU's calculated value. This just makes me wonder that either TC cannot co-operate with any different pressure/altimeter settings than 29.92 inHg/1013 hPa, or NGX uses only STD pressure to calculate N1 rates so i have to manually set STD pressure to TC before calculating.Any ideas?

Seems to be to hard for you guys ;) No seriosly, this has an huge impact to realism, if things are what i suspect (hope im wrong)!

I seem to remember the TOPCAT manual saying the only thing to take notice of is the assumed temperature produced by TOPCAT and use that in the FMC. If you change the QNH in TOPCAT do you get different assumed temperatures ?

If many people ask for a tutorial i may do a video about it in the next hours. I use Topcat all the time and always get the same values.

If many people ask for a tutorial i may do a video about it in the next hours. I use Topcat all the time and always get the same values.

bakaman there are many many many people, who are interested to see that video! Also i cound link it to fsnordic.net if its OK to you. Please do a tutorial!

bakaman there are many many many people, who are interested to see that video! Also i cound link it to fsnordic.net if its OK to you. Please do a tutorial!

Hi my friend,I'd be glad to help you. What i need to know is:What would you like to see in the video that you can't reproduce at home. (differences between what topcat calculates and what you get in the cockpit right ? anything else?)

I seem to remember the TOPCAT manual saying the only thing to take notice of is the assumed temperature produced by TOPCAT and use that in the FMC. If you change the QNH in TOPCAT do you get different assumed temperatures ?

I think that I didn't compleatly understand, what you mean. Do you mean, that by changing the "Altimeter" in Conditions field, there will be different range of assumed temperatures? For example: at LIPX 060/05, +0, 29.92 i get assumed temps from +30 to +62, but if i change Altimeter from 29.92 to 31.50, i get D-TO range from +30 to +67. Did you mean that? Also, i have to check with FSX that will the FMC always calculate the same N1 no matter what is the surrounding altimeter setting.

Hi my friend,I'd be glad to help you. What i need to know is:What would you like to see in the video that you can't reproduce at home. (differences between what topcat calculates and what you get in the cockpit right ? anything else?)

Hello. Yes, differences between what i get in TC and what i get in the cockpit for start. It would be nice to see that will TC's calculations match with NGXs' in preassures different then STD (29.92/1013.25). If you gonna include some cockpit material to the video, please provide the testing conditions (temps, wind, altimeter and of course location). I think that for N1, the weight and flaps are redundant. So use some typical weight/flap configuration. Also it would interenting to see, that how TC's calculations match, when we take-off in a situation, where Air Conditioning (Packs?) are OFF.Yours faithfullyKasperi

Hello. Yes, differences between what i get in TC and what i get in the cockpit for start. It would be nice to see that will TC's calculations match with NGXs' in preassures different then STD (29.92/1013.25). If you gonna include some cockpit material to the video, please provide the testing conditions (temps, wind, altimeter and of course location). I think that for N1, the weight and flaps are redundant. So use some typical weight/flap configuration. Also it would interenting to see, that how TC's calculations match, when we take-off in a situation, where Air Conditioning (Packs?) are OFF.Yours faithfullyKasperi

Alright, what I'm gonna do is a flight from GQNN to GOOY, which is region that i know very well and where temps are above STD but i can't guarantee for the QNH . I'll do that tomorrow morning. It'll include full prep (not talking about the cockpit prep): with TOPCAT AS2012 EFB FSbuild.

Superb mate! The whole AVSIM + FSNordic community owns you one for that!

which model to people chosethe fs2004 pmdg one, or ifly?1

which model to people chosethe fs2004 pmdg one, or ifly?1

FSX PMDG NGX -800 WL of course. I think that nowadays that is THE 737 sim aircraft which most of the people use (at least it provides simulation closest to real life of them all).

Edited January 30, 201214 yr by Kazzukki

FSX PMDG NGX -800 WL of course. I think that nowadays that is THE 737 sim aircraft which most of the people use (at least it provides simulation closest to real life of them all).

You mis read my post, I am refering to TOPCAT, I don't think it has an "NGX" option

You know, the weight sheet handed to you by the ground crew is perfect every time, too. Same with the flight attendant's passenger count. Clearly we're going to get the exact weight of the aircraft using averaged passenger weights, and bag weights.Your aircraft will catastrophically fail as soon as you hit Vne.You'll stall as soon as the tape runs into the lower red stall indication.You'll burn the exact amount of fuel you'd planned on your dispatch release....so on.(the above lines are utter nonsense, if you couldn't tell)Basically, all that to say aviation is hugely planned and calculated, but it's a fallacy to think that all those calculations will be spot on, every time (especially if you're not feeding the aircraft all of the important information).

Edited January 30, 201214 yr by scandinavian13

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).Also remember to use real world weather in both TOPCAT and FSX when calculating the take off data for a specific runway.I would say that I have 0,1% accuracy at best. But 0,3% is not bad at all! Set the thrust at 0,3% higher than recommended for added safety :)