Assumed Temp. B747-8 GE nx-2867

[kevinh 409]

On 11/7/2018 at 9:02 PM, downscc said:

Understand.  Same problem as the B77W... no TOPCAT there either.

My solution was to create a pseudo -300 profile from the -200 base by increasing the maximum TO weight to the -300 value. Seems to work well enough. Same engines, same wings just heavier weights.

Edited November 10, 2018 by kevinh

[Oskar Speer 22]

On 11/10/2018 at 3:30 PM, Wakner said:

Have you tried QSim Planner? 

No, but I will take a look at QSim Planner today.

[Volleyball 1]

When I fly the -400, I used the OPT APP for takeoff performance calculation.

There's some differences between the N1 calculated on OPT and PMDG almost all the time with the same assumed temperature.

I have reported to PMDG with this issue but with no positive answers until now. They just keep telling me that they're using the manual from Boeing, but my OPT program is used in real world operations. Hope PMDG can find the reason why there are differences between the real world data and what they build.

 

Chi-cheng Liu

.

[Olympic260 415]

2 hours ago, Volleyball said:

When I fly the -400, I used the OPT APP for takeoff performance calculation.

There's some differences between the N1 calculated on OPT and PMDG almost all the time with the same assumed temperature.

I have reported to PMDG with this issue but with no positive answers until now. They just keep telling me that they're using the manual from Boeing, but my OPT program is used in real world operations. Hope PMDG can find the reason why there are differences between the real world data and what they build.

 

Chi-cheng Liu

.

Your OPT also takes under consideration obstacles around the airport and all the rest of the info needed. We use the actual Boeing Manuals which are not airport specific

[skelsey 765]

57 minutes ago, Olympic260 said:

Your OPT also takes under consideration obstacles around the airport and all the rest of the info needed. We use the actual Boeing Manuals which are not airport specific

However - whilst that is absolutely true and would account for different V speeds and assumed temperatures, it doesn't account for the fact that the calculated N1/EPR should be very close if the assumed (and outside) temperature is the same in both cases.

My assumption is that any discrepancy is likely down to the vagaries of the MS/LM atmosphere as much as anything!