Learning to fly , I always had to glance at the ball under the turn coordinator to see if I was slipping or skidding when I climbed, descended , or turned. Step on the ball, was the rule that I learned by. I am contemplating buying a set of CH Pro Rudder pedals and it suddenly occured to me that there is no ball anywhere on the 737. How can you tell if you are slipping or skidding, or is it just not relevant and the rudder is only used for runway alignment in crosswinds?

Well, you pretty much answered your own question. Modern day airliners automatically compensate during turns. The rudders are used in crosswind landings and aborts due to engine failures. They're probably some other senarios but I can't think of them at the moment.

I really can't comment on the 737, but on the RW 757 the ball is located under the Electronic Attitude Indicator.Tim757

Ok first of all, correct, the 737 NG has no ball. The classics did, however. On the NG you have a digital representation of the ball, and its located on the top of the PFD. Its a slip/skid indicator, like on the B747/B777. Just look at the top of the PFD and kick in a bit of rudder - you'll notice it.Secondly, the only times you need to apply rudder is-engine failure-crosswind takeoff/landing-controlling aircraft during takeoff and rollout-trimming an unsymmetric body (don't worry about this in flight sims)Modern a/c have yaw dampers which automatically add rudder input during tunrs to make sure you are always turning coordinated. Don't mix this up with the default MSFS yaw damper, which is just a disaster.Regards,Mark

"-trimming an unsymmetric body (don't worry about this in flight sims)"I use my stairmaster for this, doesn't interface well with the PC but when I interface with a bowl of ice cream it helps.Tim__757

For Asymmetric flight, you can still use rudder trim as the yaw damper doesn't compensate overly well. I must admit coming from a 732 in real life, the lack of the "physical" ball is a bit of a mindset change for me!Then again, most things are a bit of a mindset change for me - see, I'm blonde!Cheers all, Chardy