Topcat with the NGX

[bakaman 28]

Hey, i have done some ABC... and got the calculation right! but there's a different between the thrust before engine start and after engine start, should i consider the after or before engine start? thanks!(:

thats right. same here ! the one after start is the correct one.

[Daniel choen 23]

Huh?

Buha!

[shuoxing 0]

Regarding performance calculation, there can be ONLY ONE correct solution. Whoever models the real data is correct. I don't have TOPCAT so I don't know what value it gives, however I did realize and get extremely FRUSTRATED with PMDG FMC output. I'm a serious simmer so I use only reliable source. I use AFM-DPI (from my friend) with exactly the same airframe and engine model to help me calculate performance data.To show how PMDG FMC differ from real value, I use standard weather in FSX (standard temperature + atomosphere) + ENG Bleed OnHere OAT is standard 15 CPMDG's full rate 98.0% Matches the output of AFM-DPI 98.0%. That's the ONLY thing it can get correctly!Let change Assumed Temperature!Assumed Temperature 20C, PMDG result 97.1%; AFM-DPI result 98.0% (Not changed!*)Assumed Temperature 30C, PMDG result 95.5%; AFM-DPI result 98.0% (Not changed!*)Assumed Temperature 40C, PMDG result 94.0%; AFM-DPI result 94.8%Assumed Temperature 50C, PMDG result 92.5%; AFM-DPI result 91.9%Assumed Temperature 60C, PMDG result 91.1%; AFM-DPI result 89.3%....* PMDG FMC simply doesn't understand there is something called "Takeoff Thrust Break Temperature", it's 30.0C!! Everyone knows that the engine outputs FLAT RATE unitl a OAT but PMDG FMC don't even know this simple thing!!And also PMDG FMC is always giving a significant higher value! Whatever, I'm not feeling too bad since at least higher thrust means I use shorter field and have larger obstacle clearance. Luckly VMCG calculation is not based on assumed temperature but only on derate, if not, higer rate can endanger my safety if the takeoff is VMCG limited! But you must know, high N1 means high EGT means high maintenance cost. No kidding, 11% derate can save 25% of MMC! Little by little, these higher values are going to waste a lot of money $$$What's more. PMDG's calculation of VREF for landing seems also 4 to 5 knots higher than that calculated by AFM-DPI!!! This invalides my Landing analysis if I use PMDG FMC speed.In all, I feel extremely frustrated about PMDG product now. It claims to be real but it cannot even do the math correctly :( :( :(Howie Wong

[Guest dlrk]

Howie, TOPCAT uses the same real world performance data, and it matches up perfectly. Also, PMDG got their data from Boeing. So, your wrong.

[lexsis 1]

LOL, just saying that PMDG got their data from Boeing doesn't mean that it has to be perfect. So that's not a valid argument.You can only say that he has it wrong with a valid argument. Because any company can say that it's correct within a percentage of 0.0000000001%.Sonny

Edited February 29, 2012 by lexsis