Hi,Seeing as flying the NGX is almost a continuous learning curve, I guess I need to learn something today. On the N1 limit page of the FMC, in the top left, there is SEL/OAT.I know that OAT is Outside Air Temp., but what does SEL do? And how do I know what values to put in so it functions properly? I used to just put 40, but something tells me that isn't right...Thanks,

It's the derate temp for the engines for takeoff. The higher the temp you set, the higher the derate (the less thrust they will produce). If you derate to much, you may run out of runway before you reach takeoff speed.

Hi Jackson.The N! limit page allows you to select reduced thrust by either using a fixed derate or by using what is called " Assumed Temperature "( you can even have a mix of both )Reduced thrust can never be more than 25%.The assumed temperature comes from a runway/flight analysis program used by dispatch. (usually Boeing software)The temperature is then entered in the SEL/OAT line.The tutorial flight uses a mix of both derate and assumed temperature.I don't know if there is any good flight sim software that makes a runway analysis.Maybe someone knows ??Fred.

Hi,So if I don't want to derate the engines, what temp. do I put in? because if I don't put a number there, the VNAV doesn't calculate...Thanks,

I have never had a problem with not putting a number in there causing the VNAV not to calculate (I have done it on rare occasion for short runways). Sure you aren't missing something else? But if that IS the case, put 1 degree higher in there, say your temp is 12 degrees, put 13 in should be a work around?

You leave it blank ! (if you do not have an acurate source for the temp then always leave this blank)When airborne you will notice that the N1 Limit page changes and will be set to " Auto " for N1 calculations.( if it is a fairly short flight with let's say 1/3 fuel, a derate will work very well.)Fred.

To calculate the correct derate you could get hold of a program called Topcat. Once the local weather is known it can calculate the correct derate for you. Nick

To calculate the correct derate you could get hold of a program called Topcat. Once the local weather is known it can calculate the correct derate for you.Nick

Does it give the assumed temperature ?Fred.

Hello Fred,There is a screenshot from TOPCAT. It may help who think to buy the software.http://uppix.net/c/e/b/da0e40d1c171065b49e322c15de51.png

Thanks !It looks interesting.I will check it out.Fred.

Thanks !It looks interesting.I will check it out.Fred.

Hey Fred, I have been using it since I got the NGX, and it works very well (I think anyway, not like I am a real pilot or anything). Only thing I don't like about it is that it doesn't have the 600 in there.

Does it give the assumed temperature ?Fred.

Indeed it does Fred. I've been using TOPCAT for the last couple of years and think its really good for flight planning from weights and limits to runway selection etc.Nick

Thanks for the good tip on this. Needed it

Where is the SEL temp displayed in TopCat?

Where is the SEL temp displayed in TopCat?

I don't believe it is displayed in TOPCAT. The only temp I have ever seen in TOPCAT is OAT. It is the assumed temp you SELect for takeoff and enter on the N1 LIMIT page based upon the recommendation of TOPCAT. I believe that page is the only place SEL appears.