Best 2017 solution for performance calculation

[Mephic 129]

Hi all

 

Is there any new product on the market which allows us to calculate takeoff performance without too much hassle? I have TOPCAT, but that one only works for NGX in my case. 777-200  profile seems to be broken as the outcome is always nowhere near what FMC shows when I enter same values.

 

Anyone tried TOPER? Also, I plan to get 777-300 expansion, so I guess TOPER would cover it too. My only concern is it's not calculating derates, only temps?

[Budbud 227]

 

 

Anyone tried TOPER? Also, I plan to get 777-300 expansion, so I guess TOPER would cover it too. My only concern is it's not calculating derates, only temps?

 

TOPER does calculates derates as well. I have found some discrepancies between TOPCAT and TOPER for some loading situations of the B77L but TOPER usually works fine and is still regularly updated by his autor who is active on the TOPER forum.

[Mephic 129]

Fantastic! Thank you. I guess next month I'll get myself 777-300 + TOPER package. 

[downscc 1,327]

TOPERs main limitation is that most variants of the product do only derate and not flex temperature and none that I tried include obstacle clearance considerations in the calculations.  We really need something better but TOPCAT is still the best, TOPER fills some gaps, and nothing works as well as we all need.

[Mephic 129]

I'm no rw pilot but isn't climb gradient requirement part of charts and are we not able to calculate it?

 

Let's say I need 7% climb gradient and climb at 160 knots so my fpm should be roughly 1120?

 

Now I am not sure how to check if we can meet this requirement (maybe would make sense to set custom way point with minimum altitude restriction and if aircraft couldn't make it FMC would give this info? That's just a guess :-), but yeah Topcat would definitely be better in this area. I just don't get it why it does not match fmc calculations for n1.

[downscc 1,327]

 

 

I just don't get it why it does not match fmc calculations for n1.

 

It would be surprising if it did.  Afterall, TOPCAT is not a professional product; it is what it is, an inexpensive tool by hobbyists for hobbyists.  The FMC, while also primarily for hobbyists, has enough realism in it to allow the product to be sold to professionals as a "study sim."  None of us could afford the stuff that the professionals use.

[Budbud 227]

Hi,

 

Don't forget that the V speeds calculated by the FMC can be also slightly off. They are calculated with the balanced field method. You may find sometimes that the V speeds calculated by TOPCAT or TOPER on a specific runway are more accurate than the FMC ones.

[skelsey 765]

Now I am not sure how to check if we can meet this requirement

 

As a pilot, you can't easily (other than in the way you describe).

 

In real life the airline performance department would have pre-calculated whether you can make the various gradients and published weight/temp restrictions for the departure if you can't make the gradient AEO at MTOW and/or an emergency turn/EOSID to follow if you can't make the gradient OEI.

[MarkW 1,491]

i have TOPCAT as well and use it with the NGX, 777 but what about other aircraft?  Biggest challenge for me is with say the A320 the FMGS give you the V-speeds close enough for simming but don't consider runway length.  If you put in an assumed temp of 60C is that at sea level on 10,000ft runway or at altitude, hot humid day, on a 6000 foot runway?  Would be great if there were some guideline charts that you could use and then let the FMC determine the V speeds.

[skelsey 765]

If you put in an assumed temp of 60C is that at sea level on 10,000ft runway or at altitude, hot humid day, on a 6000 foot runway?

 

An assumed temp of 60C is an assumed temp of 60C. That's the point....

 

Of course, on a short runway or with a hotter OAT your V speeds will change and thus you will need a different amount of thrust to meet the various requirement, which will affect the assumed temperature.

 

The Airbus FMGC does not calculate any speeds IRL - in the Aerosoft version if you put in a flap setting it will give you a flex temp and V speeds based, I think, on the ambient conditions and known runway length from the nav database.

 

The 777 (and other) FMCs do not take obstacles in to account when calculating the speeds - it just does a very basic balanced field length calculation. TOPCAT does take obstacles in to account.

 

There are many reasons why the N1 may not match up - the chief one that springs to mind is the limitations of the FS jet engine model.

[Mephic 129]

Funny thing is that in case of NGX it's always spot on (n1% matches fmc). So I still think there is just sth wrong with triple 7 profile.