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Simicro

Which tool for take-off performance calculation?

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Hi all,

 

Until now I was using the assumed temperature (65°C) and flap settings () from the tutorial flight Maldives-Dubai for... all my flights! Yeah...  :lol: Believe it or not: I ran short of runway only once with the "Long Haul" Fuel preset in FS Actions (150 tons or something like that). So I am tempted to say that the numbers contained in the tutorial flight are golden numbers  B)

 

Seriously, now that I am more comfortable with the general operation of the 777 and have a better understanding of the concept of thrust limit for airliners, I want to make it to the next level (step by step ^_^ ) and select the right flaps and assumed temp according to the winds, runway lenght, altitude and so on.

 

I made some investigations and I've come up with:

 

1. THE MANUAL COMPUTATION click here

- That is not for me

 

2. UTOPIA 1.2 (Universal Take Off Performance Information), a freeware available in the AVSIM library (utopia12.zip)

- I like it because it's simple and straightforward

- Apparently it has a airport/runway database

- The only 777 profile available is for the PSS 777-200

 

3. TOPCAT click here

- The famous one everybody is talking about

- As I understand it is comprehensive and accurate

- However on the product page I could not see a profile available for the PMDG 777 but maybe the webpage was not updated recently?

- I don't like it much because it is overwhelmed with data

 

4. AURASIM click here

- Seems nice but it has been on "release soon" status since last october...

 

5. TOPER CALCULATOR TOOL - B777 click here

- Simple but lacks airport/runway database

- User Interface not as nice as just released TOPER CALCULATOR TOOL - B737 NG

 

I like nice, easy-to-use and straightforward interface and as a beginner I am not looking for a millimetric accuracy in the calculations. General consistency will be fine. Also, if a computational feature is already built in the PMDG 777 FMC I prefer to use it rather than use third-party.

 

Could you please advise me?

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3. TOPCAT click here
- The famous one everybody is talking about
- As I understand it is comprehensive and accurate
- However on the product page I could not see a profile available for the PMDG 777 but maybe the webpage was not updated recently?
- I don't like it much because it is overwhelmed with data

 

You don't like it much because it is overwhelmed with data?

 

What do you mean by that?  Remember that, when it comes to computing values, you're always subject to TRASH IN : TRASH OUT.  If you only give a program limited data, you're going to get a limited (less accurate) result.  While more data isn't always a good thing, it usually is.  Sure, it asks for a lot of information, but in doing so, it's going to give you a more accurate result.

 

It does have a profile for the 777 (it may still be only in beta, I'm not sure, but it's publicly available).  The profile isn't as accurate as it should be, but it's close enough for me.

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How is in the performance intitation page of the FMC. All parameters are there. People spend a great deal of time programming it to be as accurate as any FSXer will ever require.

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Not sure you guys are on the same page...

 

The FMC's calculations do not provide recommendations for derates or assumed temps, which, I believe, is the reason this thread got started.  So, Rendi's recommendations aren't quite accurate to that end.  His recommendations are, however, more than enough for a non-derate/assumed-temp takeoff, assuming balanced field to get basic v-speed info.

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@Kyle: I agree that a certain amount of data is required for a good computation. I will  give an example from PFPX (just to make myself understood): "overwhelming" is when you split the passengers weight into adults, children, infants... Yeah I know it's more realistic etc but it adds more data fields while a total passenger weight will do.


The FMC's calculations do not provide recommendations for derates or assumed temps, which, I believe, is the reason this thread got started.

 

Right!  ^_^

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@Kyle: I agree that a certain amount of data is required for a good computation. I will  give an example from PFPX (just to make myself understood): "overwhelming" is when you split the passengers weight into adults, children, infants... Yeah I know it's more realistic etc but it adds more data fields while a total passenger weight will do.

 

Which is why you can make an entry in the payload and baggage fields instead (payload - baggage = ???, yep)  :wink:

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It is not necessarily overwhelming because data has to be entered, but visually I mean.

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What you should do is use PFPX AND TopCat. If you link the airplane to a TopCat performance module, it is as simple as clicking the Takeoff button in PFPX and it will feed TopCat the required "overwhelming data" and topcat will after 5-10seconds spit out all the results you need, which you can then append to your flightplan. It literally is as simple as clicking a few buttons.

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It is not necessarily overwhelming because data has to be entered, but visually I mean.

What I do is skip the payload page of TOPCAT and go straight to the takeoff page, update weather for the airport, select runway and enter my takeoff weight. I leave the flap and thrust options at optimum, then hit calculate

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Hi Guys,

 

TopCat works for me and has the 777LR/F profile available by public Beta.

 

Have not run out of Runway yet on my takeoffs. :unsure:  

 

Kind Regards

Simon Ward

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I use PFPX + TopCat and enter ZFW from PFPX into Load page of TC, then  go to take off page etc etc.

There is an issue in TC beta for the T7, it will not generate TO and Landing  report.

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Thank you all for the info on public availability of the 777LR/F profile, the skipping the load page on TOPCAT and your practice experience.

 

I do not want to make a fancy choice so I will go for TOPCAT.

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What I do is skip the payload page of TOPCAT and go straight to the takeoff page, update weather for the airport, select runway and enter my takeoff weight. I leave the flap and thrust options at optimum, then hit calculate

I never thought of that. It will be a real time saver.

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Garbage In - Garbage Out is always a problem in writing expert system programs such as this. An expert system is a rules based model of the problem you're trying to solve. The programmer can limit inputs to the "relevant range" of acceptable practice but then if it changes the program is obsolete or needs to change the assumptions. The alternative is to write in an "expert" option but IRL, everybody's an expert and we're back to gi-go. When writing programs for true expert users I opt for a combination of both that queries the user for an input but warns him/her when and if something's a little "off". You know - something like "Are you completely out of your fricken mind? Just exactly how many passengers do you want to kill?" will usually give 'em a heads up.

 

As far as how much information to present in your output fields it again depends on the level of interaction you're expecting from the user and whether or not he/she is expected to manually verify the results being presented. If the program is being used in a time critical section of flow then "management by exception" is appropriate. MBE highlights or presents only that information requiring attention from the user. Presenting date in green for good or red for danger is an example.

 

Many expert systems are used in optimization decision making known as parametric sensitivity testing. The program uses a range of inputs and prepares a solution matrix that can show all possible solutions or limit itself to only those solutions that fall within a relevant range of acceptable or standard practice. Instead of looking at a snapshot of the problem, the program runs a movie. The truth is though - unless your qualified through training, education or practice to make the decision promised by the software, you shouldn't be using it in the first place.

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I don't like topcat. No sense in calculations! using utopia v1.2 and waiting for aurasim! in only use topcat for the NGX and nothing more

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It's not as accurate as it should be, but I wouldn't throw it out entirely.  It gets the job done for now.

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For now, if you want just for 'enough' data for takeoff rather than 'extremely precise' one, I'd recomment get used to manual calculation using 'the documents'..

 

I really tried hard to understand takeoff performance recently, but all the methods results different output.

Manual calculation using FPPM, the excel sheet for 777, Utopia.. All different output with same data.

(Utopia is based on 'experience' record according to readme file in it - so I think it is generally acceptable for PMDG, too.)

 

But ultimately, I realized that with these calculations(including FMC calculation that does not care about RWY length), there's no way to get perfect V speeds without getting TODR, ASDR.. (maybe I'm wrong at some part of this..)

 

So if you want a 'complicated result' with 'simple' method, TOPCAT is your answer.

(But I doubt that buying this program is worth for everyone because the update for their whole product  is a little bit slow.)

 

I do use manual calculation, and double check with Utopia when I fly T7. Both two results have no big differences, so I'm happy with this. (I know the actual V speeds will be less than these values but it is acceptable for me..)

 

Hope this helps you to decide.  :lol:

(If my English is readable though  :wacko: )

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Thanks for the additional information guys. I went for TOPCAT. I tried UTOPIA but got inconsistent results.

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Is Topcat still supported?

I don't believe anyone knows. I know it's not supported by the TOPCAT Forum since it has been a read-only forum as of Jan 2015. Support tickets can be submitted here - http://flightsimsoft.com/support/. Maybe you will receive a reply. I think TOPCAT is dead in the water. What you have is what you are going to get.

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TOPCAT only has a 'beta' profile for the 200LR/F, no 300-ER. 

 

For what it's worth, I have access to a real world 777 EFB (300-ER/F/200-LR in GE and RR engines) and have tested it against both the TOPER and TOPCAT calculators. The results varied wildly, as you might expect. The TOPCAT one spat out the most accurate results in terms of speeds and margin but the derate N1 figures were a long way off and were up to 10 or 15 degrees lower than the real one. Using these figures we managed to drag the gear through the lights at Dublin on the departure - whoops. 

 

The 777 FMC automatically generated V speeds are incredibly accurate however, within a knot or two of the Boeing EFB for 'balanced' field conditions. Great job, PMDG.

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