747-8 Assumed Temp Reduction?

[realDonaldTrump 0]

Hi everyone, I'm pretty happy flying with the new PMDG 747-8 V3, but right now applications like TOPCAT and TOPER are not able to calculate Assumed Temp Reduction for the 747-8 yet and I don't know when there will be an update for it. I also tried to use the EFB on the 748 but it says that this feature will not be available until PMDG releases an update. So there's the problem, I am not able to calculate the assumed temp reduction. I asked some people around and they said that I can use something like this 👇 to calculate, but I really don't get it, so can anyone explain it to me how it works, or give me some other suggestions on this problem? Thanks!

[xkoote 57]

It is not a problem per se. Just that the data is not available yet. Those charts are not widely available for the B748. So you can either,

1. Use TO thrust as per the OPT

2. Invent your assumed temp based on past FS experience (or maybe other types) and "risk it"

Don't count on TOPCAT for anything else and be patient for the ATM data.

[MauB 74]

1 hour ago, realDonaldTrump said:

Hi everyone, I'm pretty happy flying with the new PMDG 747-8 V3, but right now applications like TOPCAT and TOPER are not able to calculate Assumed Temp Reduction for the 747-8 yet and I don't know when there will be an update for it. I also tried to use the EFB on the 748 but it says that this feature will not be available until PMDG releases an update. So there's the problem, I am not able to calculate the assumed temp reduction. I asked some people around and they said that I can use something like this 👇 to calculate, but I really don't get it, so can anyone explain it to me how it works, or give me some other suggestions on this problem? Thanks!

Lets consider the runway you are going to takeoff is 3600m long and the outside air temperature at your origin airport is 22ºC. The limiting weight for this condition is 438500kg (just cross the runway lenght line with OAT column).
Now lets say your takeoff gross weight is 410000kg. So you take the runway lenght line to the right all the way to 411500kg (as the next one is less then your expected TOGW) and you'll notice the OAT column is 38ºC. So this is the temperature limit for your weight, with flaps 10 at sea level, packs on, anti-ice off, dry runway. Of course you have to adjust for different conditions (and there are many other things you have to consider as well), as depicted on the charts. But for simulation pourposes, you can go with 38ºC assumed temperature at sea level, flaps 10 takeoff.

Edited September 28, 2018 by MauB

[VHOJT 172]

Here is the workaroun at the moment.  This is a perfectly legitimate way to get an assumed temperature.  Albeit, it might not take into account obstacles, but then neither does TOPER.  I doubt PMDG has obstacles in the EFB database.  Not something to worry too much about in the FS world anyway.

Edited September 28, 2018 by VHOJT

[DEHowie 269]

I just put up a quick how to in the post in the 747 forum...

[mfrantz 45]

2 hours ago, VHOJT said:

I doubt PMDG has obstacles in the EFB database

Obstacle information for a runway can be added in the EFB by creating a temporary NOTAM (see EFB manual page 82). This will allow you to define one obstacle. If you want to add many obstacles you can "overwrite" the runway data by creating a new temporary airport (see EFB manual page 78).

 

[Wothan 173]

Adding this to MauB's post...

Inorder todetermine the Assumed temperature thrust reduction via the FCOM.

PAX: Using FCOM pages 261-274 (PD10.1-10.14)

Freight: Using the FCOM pages 317-330 (PD20.1-20.14)

 

Example:

Aircraft= 747-8F

TOGW: 311.352 Kg => 686.400 LB

Flap 10

EKBI Runway: RWY27, Elev= 247 ft, RWY Length= 2950m => 9680 ft, Slope= n/a, Dry

Weather: Baro=1026 Hpa, Wind=210/5, Temp.= 9°C

 

First go to FCOM page 317 (PD20.1)

Since slope is not known (and not simulated in P3D for EKBI) wi don´t use the first table.

Using my E6B converter app, I find that with a runway heading of 264° and a wind at 210/5 kts I get a 3 kts headwind.

Using the second table on page 317 (PD20.1) I find, by interpolating, the values for RWY length 9400 and 9800 and 0 and 10 kts headwind that wind corrected rwy length is 9715 ft

 

Going to page 318 (PD20.2) -> Flaps 10 at Sea level with Packs On and AI Off, I go to runway length 9400 (closest smaller value to 9715 ft) and 10° OAT (closest higher value to 9°C) and find my Field & climb limit weight to be 886.200 lb.

My actual TOGW is 686.400 lb, so I´m far from reaching that limit.

For my assumed temperature I look at the same line for the higher temperatures, and see that even at 50°C I´m way below the Field & climb limit weight, so I can use an assumed temperature of 50° (and probaly higher, but I got no figures for that).

 

Had my TOGW been 800.000 LB ( 362.874 kg) then the max assumed temperature would have been 38°C

 

Had the runway been Wet, then I had to use the tables starting from page 324 (PD20.8).

Also if the airport had been at higher altitude, tables for these are on page 319-323 (PD20.3-20.7). The altitude tables comes in steps of 0, 2.000, 4.000, 6.000, 8.000 and 10.000 ft.

Use interpolation where adequitein all tables. In my opinion You can use closets guestimate instead of detailed interpolation, since in the end it´s only "in the ballpark" figures anyway - simply use closest safe figures.

 

FinnJ

 

Edited September 29, 2018 by Wothan

[DEHowie 269]

As i detailed in the other post you can just use the EFB with your actual take off weight guestimating temperatures until you find the highest temperature you can depart at without a exceeded max warning...

Then use that temp as your ATM/Flex value...