Hello. Normally I have auto step climb enabled and noticed that FMC wants to climb higher then optimal level.

For example Right now I cruise at FL340, Opt alt is FL351, maximum FL391 and using LRC and step size 2000 but FMC tells me to clime to FL360 though optimal altitude is FL351.

 

 

That’s correct behaviour as you have 2000 step size selected.

You're climbing 2000 feet from FL340 to FL360 the FMC will tell you to start your climb once FL360 becomes nearer to your optimum level than FL340 is so an optimum of FL351 

The next step climb would therefore be to FL380 at an indicated optimum level ofFL371

If you had 1000 foot step size for example it would tell you to climb to FL350 from FL340 once optimum was FL346

En-route winds if you have them entered should also feature in the calculations 

Edited July 31, 20205 yr by jon b

I'm not sure about the rest of the world but here in the US Flight Levels are generally assigned 2000 feet apart.  For instance, on a IFR course between 0 and 179 degrees Flight Levels are assigned to odd numbered Flight Levels, i.e. - course 90 degrees FL330, 350, 370, etc.  Courses between 180 and 359 degrees, Flight Levels are assigned to even numbered Flight Levels, I.e. - course 270 degrees, FL320, 340, 360 etc.  VFR flight below FL180 (18,000 feet) add 500 feet the the above rule. 

Jim Driskell

It's been ages since I had to step climb lol, I can climb right to planned cruise in a Gulfstream. But, I did it a lot in C141Bs and KC/DC-10s. In those jets, we used a 4000ft altitude rule when step climbing and didn't have a fancy FMS that calculated it, the flight engineer did it. Basically you climbed to 2000ft above your optimum and stayed there until 2000ft below your optimum, rinse and repeat. Depending on your direction of flight, you would adjust it for your initial cruise altitude and then jump on schedule with the first climb. You would level off and the engineer would give you the weight and time to initiate the next climb. About 15 minutes or so prior, you would put the climb on request. This process kept you within 2000ft of optimum.

Auto Step climb is there so you can do a long flight and not have to monitor the aircraft every single second. IRL the pilots would handle the step themselves not the aircraft. 

 

Unless you want to sit at the keyboard for 8 hrs...

Edited August 18, 20205 yr by Snowfalcon