TOPCAT for the NG and 777

[Nyxx 6,993]

I use PFPX for every flight. I try to do everything by the book, its just the way I like to do it.

 

Now Q

To me Topcat seems to add very little, as I use the CDU for V speeds and landing speeds.

 

So please explain what extra Topcat brings to the table. Does it make very little difference or just add that extra touch?

 

Is it worth it?

 

I like the way it works with PFPX and yes I do know its a different program to PFPX  :wink: for take off and landing calculations. 

[aceridgey 330]

Basically TOPCAT is there for calculating takeoff performance, the fmc is very limiting in it's function.

 

Topcat gives you derate settings dependant on weight and it is very rare to use full thrust.

 

I did a 306,000kgs 777-300er flight from London to Hong kong and with a different tool I got a derate of nearly 50C (to thrust)

 

Yes, I think it's a really worthwhile investment for takeoff

[scandinavian13 5,192]

 

 

So please explain what extra Topcat brings to the table. Does it make very little difference or just add that extra touch?

 

Your FMC is providing what they call "balanced field" calculations. While this takes into account runway length (one of the reasons you don't get prompted with v speeds until you select a runway from the database), it's assuming whatever thrust rating you've thrown in there (which, unless you've used a takeoff calculator, it's a best guess).

 

Basically, you can work forwardly or you can work backwardly. What the FMC is doing is working forwardly: for a given thrust setting (or derate), with these conditions, and this runway, your v-speeds will be this. What TOPCAT allows you to do is work backwardly: for this runway and these conditions, you can use a thrust setting (or derate) up to this level, with these v-speeds and still safely operate on the runway. This is done for engine cost measures (not fuel savings). The calculator will also give you a table with the relevant margins. This margin is the runway remaining by the time you come to a stop if you were to abort the takeoff at V1. The size of an acceptable margin is up to the SOP or the PIC. I prefer my margin to be at least 500', but that's just me.

 

Additionally, the FMC is only concerned with the field itself. There are also restrictions for climb gradients and so on after the departure that a takeoff calculator would take into account (this is shown by TOPCAT in a CODE column that reports "FIELD" or "CLIMB/OBS", which you can see below).

 

(The CODE in this case - "OBS" - shows that the performance limitation is not the runway itself, but the performance necessary to climb above obstacles on departure. Image provided by AVSIM.)

 

Essentially, what you're getting is field-specific values that allow you to operate a little more realistically regarding de-rates (and/or assumed temps), and climb gradients.

[Nyxx 6,993]

OK, good info, thanks Kyle for all that info, since I own PFPX and fly 90% of the time the NG/777 i will get it.

 

Thanks.

[scandinavian13 5,192]

OK, good info, thanks Kyle for all that info, since I own PFPX and fly 90% of the time the NG/777 i will get it.

 

Thanks.

 

Welcome. Just as a heads up: while TOPCAT does have the option to adjust the weights in aircraft.cfgs, do not utilize this function with PMDG aircraft.

[Nyxx 6,993]

OK thanks for the tip.

[Driver170 42]

I would checkout TOPER 777 you also get it for the 737NG, this software takes uses the climb segment 1 and 2 gradients into account when performing calculations. Unlike TOPCAT

[scandinavian13 5,192]

I would checkout TOPER 777 you also get it for the 737NG, this software takes uses the climb segment 1 and 2 gradients into account when performing calculations. Unlike TOPCAT

 

This isn't true, actually. TOPCAT does address climb segment one (as shown in the above screenshot).

[Driver170 42]

Yeh from VLOF to gear up! But i think the second segment is more demanding as you'll be away from the TODA

[scandinavian13 5,192]

Yeh from VLOF to gear up! But i think the second segment is more demanding as you'll be away from the TODA

 

Where, exactly, are you getting this information?

 

Also, TODA is "take off distance available" - if you're into the climb segment, you're definitely not worried about TODA anymore...

[Driver170 42]

Also, TODA is "take off distance available"

 

Yeh plus clearway

[thepilot 571]

I only use TOPCAT to see how much of a de-rate is possible, then I use the CDU reference speeds which slightly differ from what TOPCAT calculates.

[Driver170 42]

Well the 1st seg starts at VLOF

 

Operations manual from a 737 NG pilot

[scandinavian13 5,192]

Yeh plus clearway

 

No. TODA is TODA. TODA is not TODA plus clearway. TORA plus clearway is TODA.

 

Well the 1st seg starts at VLOF

 

Operations manual from a 737 NG pilot

 

Yes, but again, TODA isn't a concern when you're in the climb.

 

...and I highly doubt an FCOM refers to TOPCAT, here. I meant "where are you getting this information about what TOPCAT does and doesn't do, related to climb calculations?"

[Driver170 42]

No. TODA is TODA. TODA is not TODA plus clearway. TORA plus clearway is TODA.

 

You have it wrong.

 

TORA is just runway length nothing more.

 

TODA - RUNWAY + CLEARWAY.

...and I highly doubt an FCOM refers to TOPCAT, here. I meant "where are you getting this information about what TOPCAT does and doesn't do, related to climb

 

Nope its not an FCOM. Its far away from that. The pilot got it issued from his company about performance of the 737NG

 

Very highly detailed

I read on the TOPCAT forum it doesn't use it and thats from the producer