In order for me to use the SEL/OAT function in the FMC would I need to have the actual take-off table from that specific airport and runway I'm taking off from? Or does it not depend on the airport?

temperatur????:D :D :DSorry, I couldn't help myself!

Right...temperature. Well in Danish it is spelled temperatur. :D

Hi,The assumed temperature is usually based on the next items:- Gross Weight of the airplane- Outside Air Temperature- Barometric Pressure- Runway Length- Airport ElevationSo it isn't really dependable on the airport as it is dependable on the conditions of weather/airport/aircraft.Check tomaflex.net for a recently introduced "performance calculator" for several add-on's. As yet it is only available for PSS but it will be updated also for the PMDG and PIC add-on's.cheers,Bj

Yea that looks good, but I'm only interested in finding the assumed temperature. Maybe there's a chart for the 737-800 where I can look up the correct value?

There aren't really "charts" for the assumed temp as it depends on so many factors. They come with huge operation manuals owned by the airlines, containing this info per airport. Even a Quick Reference Handbook doesn't give complete info about this (that's probably why it is called ...."quick"... reference.. LOL). cheers,Bj

Okay so the SEL/OAT in the FMC is basically useless, since it's not really prudent to make a guess, and I would have to use the other ways of reduced TO and climb in the FMC.edit...just to clarify, I'm not saying this function isn't working correctly, but since I don't have that huge manual I won't know what to put there.

Bjorn,The way I use Assumed temp. is to determine runway length and weight of the aircraft, then go to the Takeoff section of the manual and read the "Runway length limit weight" table. By reading the row for the given runway length and moving across until you get to the aircraft weight you will be using, you can then read the maximum assumed temp possible at the top of the column. You also have to make sure that the weight of the aircraft will be under the climb limit for that assumed temp. The climb limit weight is the bottom row of the table (in yellow).I've used this method to find assumed temps, and it seems to work well.Bill

Bill,You can use your method and probably not run into problems in the "sim," but it's not technically accurate in a real world sense. for one thing, notice that the runway length on the left is the "corrected runway length" (corrected for wind and slope), not the actual runway length. Also, and more importantly, the table does not indicate what flap setting and pressure altitude that it is good for.Don S.

I can only agree with Don et al and add a little more...The take-off data is also dependant on obstacles in the extended runway path as well as climb performance. As I understand every major operator ships a set of tables for every flight for different runways and conditions. On airports at higher altitudes you also take into account tire speed limits as well as brake temperature limits. The least of these six weights (structural limit, field limit , climb limit , obstacle clearance, brake temp and tire speed limit weight) is your MTOW for that runway under those cirumstances and conditions.To further complicate things you first have to establish what runway distances you have to play with. You have a TORA (take off run available). That is the actual runway and this is corrected for wind and slope. You can actually have a theoretical runway length available that is longer than actual runway if slope is negative and you have head wind. You also establish the TODA (or take off distance available). This distance is any runway + any stopway (extension of runway that can hold the weight of the aircraft in a RTO situation) + any clearway (obstacle free ground and suitable to fly over). See this very informative pdf-file for further explanations. http://www.aviationshop.com.au/avfacts/sample/perinst1.PDF These corrected lengths are used to establish the weights discussed in the previous paragraph.Now. If your PTOW (Planned Take-Off Weight) is less than MTOW you will not use the full length of the runway before you are airborne. This length is called the TODR (Take off distance required) . You can adjust the temperature fed into the EECs and fool them they are not as efficient as they could be and thus extending the TODR towards the limit, TODA. As I understand all these calculations are done by flight engineers and flight dispatch before the crew even gets the documents in their hands. It's a really interesting subject. And if I've got anything completely wrong, please feel free to correct me! :-)http://forums.avsim.net/user_files/95931.jpgCheers, :-beerchug

Interesting PIC you have there.Where did you get it??? Or is it something from your VA???

Hi,That is indeed a very great lookin' program you got there!! Where do I get it?? You are right Mats, the FE and Dispatch is making the plan complete with all the necessary calculations before the flight crew gets it. In the first place, using reduced thrust is used to prevent wear of the engines. Since there are programs made for FS, like the virtual dispatcher, it is now possible to make such a plan ourselves...cheers,Bj

The Queen will have that too.

The Queen will have what?...I believe that is a program from Scandinavian VA?I was really hoping someone would answer my question if the SEL/OAT function is pretty much useless in the FMC?

Why do you think that???The SEL/OAT is used for a D-Rate takeoff.An Example about the OAT: It's 15 degrees Celcius and the ATIS gives a change in temperature to 16 degrees in about 15min. So, you could calculate ahead for the Temp. and Select that in the OAT box. In this example it should look like: /16 and enter that value in the OAT box. For the SEL temp, it's just the TEMP you enter for a derate takeoff seperate from the TO1 or TO2. For example you could enter in the SEL/OAT box: 48/16Hope it helps,