... getting ready for takeoff (assumed temperature ...)

[Zinger]

Hardy,
just to make sure it's clear, it isn't that the thrust is lower below 15 (or up to  35 degrees C in other cases, depending on manufacturer spec) but rather that the parameter limiting available thrust is reduced to maintain nominal FRT.

[Hardy Heinlin]

it isn't that the thrust is lower below 15

The thrust limit is lower ...

When I mention those peaks, I refer to the max allowable (full rating) takeoff thrust, i.e. the takeoff thrust limit. This limit rises and falls with rising OAT (CF6 engines).

This is not the thrust generated when the levers are at the firewall or anything like that, in case my comments sound like that. That's not what I meant.

Do we mean the same thing?

What is FRT?


|-|ardy

[Hardy Heinlin]

It would be also nice to know what the FMC would do with the "fake" thrust limit when the actual OAT were rising above the assumed temp in the time between preflight check and takeoff. Would it self-delete the entered assumed temp?


|-|

[Peter Lang]

....when the actual OAT were rising above the assumed temp in the time between preflight check and takeoff...

Hi Hardy,

I just tried to check what happens with the EDDF1.ini (EDDF - SAEZ)
There an OAT of 14° C is indicated with 70° C as selected temperature.

Playing around shows the following conditions at TO-1:

14° -> N1=102,7
15° - 54° -> no entry possible.
55° -> N1=102,5
60° -> N1=101,6
and so on...

Checking this roughly with several ini files, shows that obviously an assumed temperature less than 40° over the OAT is not accepted.

I just think, if the OAT within this half hour or give them one hour for preflight preparations raises about 41° C to trigger this condition this planet has serious problems.

Do you want to model global warming, vulcano eruption or sun explosion?  

I'm not sure if my thoughts are right, but I think this condition will not exist. Nevertheless I will ask my friend. Perhaps in the real 747 there is no 40° difference.

Peter

[Hardy Heinlin]

Hi Peter,

if you rise the pressure altitude, the max thrust limit peak will drift to colder temps. E.g. at 2000 feet (or 959 hPa) and 30°C the N1 limit will be at 108.6%, while at 35°C it will already drop to 107.8%.


Cheers,

|-|ardy

[Peter Lang]

Ok, here the answer:

" the assumed temperature will remain in the FMC and not be deleted.
But it will be automatically calculated with the actual OAT"

If you need the German text, please let me know.

Hope this helps
Peter

[Hardy Heinlin]

Aha.

Thanks!

In other words:
When the real OAT rises above the entered value in 1L, that value in 1L will be replaced by the real OAT. And the mode remains in "D-TO".

...

I'll use this principle also in case of a manual OAT change on the Instructor/Weather pages.


Cheers,

|-|ardy

[Hardy Heinlin]

As we all know, the FMC uses OAT and pressure altitude to compute the thrust limit.

Does anybody know in what intervals the value is updated on the EICAS and CDU during the flight? Is it updated when N1 changes by 0.1%? Or perhaps in bigger intervals, e.g. whenever the pressure changes by 30 hPa or something like that ... or the OAT by 1 degree?

I'd be grateful for any hints or thoughts.


Cheers,

|-|ardy

[martin1006]

Long time ago this topic but as I started to fly PS1 again after al these years I'm struggling a bit with the assumed temperatures en derated takeoff's.

Herefore i found this topic and this link
http://aerowinx.de/downloads/Englim.zip
However the zip file is password protected.

Anybody knows the password? I think must be a word in the 744 manual.

Thanks

[Garry Richards]

The password is the last word on page 221 of the ps1.3 manual.

[martin1006]

It can not be opened. I get the message "file does not excist"

Has somebody another link for me?

[Garry Richards]

The link worked perfectly for me. The zip contains Readme.1st, which is a Word file, and Engine limitations.pdf, which is password protected.

[martin1006]

Hi Garry

THe problem is I can not open the zip file.

Get the message "file does not exists.

[John Golin]

Worked for me too?   Try emptying your browser cache, then downloading again to a different location on your computer.

[martin1006]

Solved it in a unix terminal with unzip

The name is the terminal gives Englim\\ \\(2\\).zip

Anyway. Solved