"ATM calculations not possible yet"

[Jeff Nielsen 1,386]

2 minutes ago, mfrantz said:

Not new news at all.

It is stated clearly in the message displayed on the EFB and also in the EFB Manual that:

"TO-1, TO-2 and Assumed Temperature calculations will be implemented in a future update"

Roger that, still at work and haven't picked up the-8 yet.  Real world aviation job getting in the way of me having fun 😁

*edit* We are hiring in Flight Control.  You're more than welcome to take my shift tonight...lol

Edited September 22, 2018 by Jeff Nielsen

[Ephedrin 418]

1 minute ago, Jeff Nielsen said:

Real world aviation job getting in the way of me having fun

LOL! 😁

[PinkPony 171]

The temporary workouround is really quite simple. 

Lets assume:

PANC, RW33

TOW: 933k/ 423t  

Temp: 11C

Wind: Calm

QNH: 29.97

- Run the CALC 

Result: OK

 

Now up OAT to 40C 

-Run the CALC

Result: Unable to CALC 

 

Let’s try OAT to 39C

-Run the CALC

Result: OK

*** 39C is the max assumed temp you can use. 

At this weight, and with these conditions, anything above 39C results in a RTOW < 933k / 423 t 

While the OPT takeoff tool can’t yet do this on its own, it only takes you a extra minute or two. You also get the benefit of learning something from it!

In summary: First run the calculation for your actual conditions. Then start off with a arbitrary high OAT: 60C. The goal is to determine the temp. that definitely won’t work, and to work your way down to one that does calculate  (aka the MAX ATM). That is how you can figure out  the MAX ATM.

Once you do this at a few weight ranges, you will quickly learn to judge the (ballpark) MAX ATM. Like that you don’t bother trying 60C at a TOW of 987k / 447t. 

 

 

 

Edited September 23, 2018 by calzonister

[Richardnunez 5]

5 hours ago, Ephedrin said:

If it was answered in one of those 'n' pages long teaser threads, no.. I won't search for it in there.. But I have seen a topic about PFPX profiles. 

TOPCAT has had a profile for the 744 that matches very well with the PMDG 744. Given that this data must have come from somewhere and given the circumstance that PMDG has advertised the 748 with its great new feature "EFB" to show charts and do performance calculations, I am sure they will find a way to implement calculations for one of THE main features of this EFB in the real world. That's what it actually is used for and no airline in the world is going to take off with full thrust (TO-1 and TO-1 might be optional, but not assumed temp) with a load of 25t of fuel and 200pax. Sure, we can guess a temperature, but that's definitely not the way PMDG aircraft are meant to be flown.

 

All required data is actually available. What do they have to pay for? the engine data is there, it's simulated. The weather is there, it's filled in. The runway length and elevation comes from the sim. 

It’s really a disappointment to be honest not having this feature 

richard Nunez 

[Wothan 173]

It should be possible.

I can see that the Quality Wings 787 EFB features calculation of Assumed temperature thrust reduction and Derates, so I´m sure PMDG will be able to do that too.

 

I guess the way they calculate this isn´t 100% accurate.

Personally, if realworld data isn´t available, I could live estimates.

But let´s see, they clearly say that it will come in a later update. Until then Calzonister's way of doing might suffice.

Maybe the Topcat 744 profile can be "tweaked" to get into the right ballpark for the 748.

 

FinnJ

Edited September 24, 2018 by Wothan

[Farlis 2,287]

On 9/23/2018 at 1:28 AM, Jeff Nielsen said:

"TO-1, TO-2 and Assumed Temperature calculations will be implemented in a future update"

Not to mince words here, but I very well remember that ACARS was announced for the future in FS9's 737NG. 

So yes that was not technically wrong, ACARS is here now, but that was a very long future. 😉

[Skyrock 4]

1 hour ago, Wothan said:

It should be possible.

I can see that the Quality Wings 787 EFB features calculation of Assumed temperature thrust reduction and Derates, so I´m sure PMDG will be able to do that too.

 

I guess the way they calculate this isn´t 100% accurate.

Personally, if realworld data isn´t available, I could live estimates.

But let´s see, they clearly say that it will come in a later update. Until then Calzonister's way of doing might suffice.

Maybe the Topcat 744 profile can be "tweaked" to get into the right ballpark for the 748.

 

FinnJ

Dito. It's kind of funny that TOPCAT was able to do those calculations back when we were still flying in FS9 (and the 747 calculations were and are still spot on to the PMDG models!) and QW has now pushed it for the 787 but PMDG says it's impossible due to costs. Lol?

Screw real world data, don't forget we are still flying in a flight sim! Some things are not as real as it gets, we don't even have sloped runways (except XP Users), let alone real world obstacles or realistic friction models. It still bugs me that I can't use the DynamicFriction.lua in P3D v4 anymore! Taxiing the 777 is a pain...

[JRBarrett 3,070]

29 minutes ago, Skyrock said:

Dito. It's kind of funny that TOPCAT was able to do those calculations back when we were still flying in FS9 (and the 747 calculations were and are still spot on to the PMDG models!) and QW has now pushed it for the 787 but PMDG says it's impossible due to costs. Lol?

Screw real world data, don't forget we are still flying in a flight sim! Some things are not as real as it gets, we don't even have sloped runways (except XP Users), let alone real world obstacles or realistic friction models. It still bugs me that I can't use the DynamicFriction.lua in P3D v4 anymore! Taxiing the 777 is a pain...

Gathering data to create assumed temperature predictions by measuring the sim’s actual performance under various combinations of weight wind and temperature is probably not a quick or easy process. It’s not a simple matter of doing some calculations.

It would obviously be much easier if PMDG had access to Boeing’s proprietary data, but as has been explained, that’s not an option.

I’m sure that EFB performance calcs for derated and/or assumed temperature takeoffs will be added down the road, but having them ready for the initial release of the -8 would probably have delayed the project for many more weeks.

[Jeff Nielsen 1,386]

On 9/24/2018 at 5:44 AM, Farlis said:

Not to mince words here, but I very well remember that ACARS was announced for the future in FS9's 737NG. 

So yes that was not technically wrong, ACARS is here now, but that was a very long future. 😉

I remember seeing the video of the ACARS pages they showed at the FS convention in Vegas recently.  It's online if you want to see it, so I suspect this wouldn't be a very long future.  They also showed off GFO.  I don't remember seeing that back in the days of FS9.  Also back then there wasn't a infrastructure for ACARS or CPDLC to work on, so it wouldn't have done any good.  I think this is a completely different 'bright' future.

Edited September 28, 2018 by Jeff Nielsen

[DEHowie 269]

There is a way to calculate a flex temp now with the EFB.

It involves working in reverse to determine the max temperature you can use at a particular weight.

it is fiddly to do but it works.

I will describe and in short this is the technique used when using paper charts in the real world.

Ok lets say your taking off at 380000KG.

First step plug in a take off weight of 380K in the EFB using the real OAT to ensure that you can actually depart using rated thrust IE TOGA at that weight.

Having done that I would start at around 40C as a first value to plug in as the OAT. What we are doing is "ASSUMING" the OAT is 40C is Assumd temperature method.

If the box(EFB) result says you can lift 380 do it again with say 50C. If the box says you can lift your 380K at 50C keep going in 5 or 10C intervals.

When you reach the point where the box says you cannot legally depart say for example at 60C it says unable.  When the box rejects your take off as being to heavy you now know the max temp you could take off at is between the previous value that was ok say 55C and the value which just failed ie 60C.

Personally i would go with a ATM/Flex of 55C using the speeds determined at that calculated value.

If you had time and really wanted you could try 56,57,58 or 59 to determine the real max ATM/Flex value going with the highest temperature you can get a positive result out of the EFB from..

To me within 5 is good enough.

Using paper charts in the real world this is EXACTLY the way a flex is determined.

You simply go to the tables using your take off weight and find the max temp you can legally depart at where the limiting weight is your current planned take off weight.

That temp is your Flex temp/ATM.

Note i am not talking about climb-1 or 2 primarily as it takes enough time to work it out at a base value but there is nothing to stop you using them.

Note lots of airlines do not using derate due to the dubious legal grounds. If a performance related accident was to occur as to the nature of the thrust reduction being greater than the legally max rated thrust less 25% This is legally the maximum thrust reduction permitted by law and convincing a jury that derating a 70000Ib thrust engine to 55000 and then flexing(ATM) it to 42000Ib is somehow less than a 25% reduction of its original 70000 will be fun!.

And note DERATE and FLEX/ATM are very different things. In the sim world they seem to be used interchangably but they are far from the same thing and mean and have entirely different applications.