I have an issue while flying in VNAV. Coming in on an arrival with a published speed reduction, it will fly it perfectly up until that point and once I pass it, it starts an uncommanded speed reduction. So lets say you are crossing fix A at 250kts and it will show that on the legs page. Everything after that will generally show 240kts unless there is another published speed. However once passing the fix, it will SLOWLY bug itself down to stall speed at any given configuration. The legs page still shows 240kts over every fix, the decent page shows either 250 or 240kts. I even enter 250kts manually on the decent page as a restriction, yet the speed bug continues to go down. I commute a ton in the jumpseat of 738's and I have never seen this. If ATC gives a specific speed, they type it in and it does it. I have never seen a gradual reduction in the speed bug to where they had to overide their own speed in on the MCP. Am I missing something big here or is this a software issue?

This is energy compensation mode. Check out page 880 of FCOM 2.

I was in the same boat, check out my thread http://forum.avsim.net/topic/342541-explain-this-for-me/ and as Mike said 880 to fcom2

Wow, I have never seen this. Is there a way to turn it off? I mean, I can understand if you are doing the ELDEE5 into DCA where you have a couple of hard altitudes, but I was on the CANUK into KATL. I made the ONE published crossing restriction but what if I am not following the FMC's "recommended" VNAV decent. Will it not let me overide this and still be in VNAV mode?

Hi Ken, Just press the little button marked "SPD INTV" this will let you control the speed while still in VNAV. Otherwise you can go "FL CH" and calculate it all your self Regards,

Ok, I just read that post, but again, I am impressed that even the real plane does this, but 9 times out of 10, in RW you are given a speed to maintain for flow/metering or in trail and you cannot just slow down at your leisure. Can I stay in VNAV and overirde this or must I do it via the MCP?Ok, I tell you what, I think I was messing it up myself. I kept decending in FL CH instead of VNAV because I didn't know what it was doing. Ok, back to flying. Thanks guys.

Wow, I have never seen this. Is there a way to turn it off? ..........

SPD Intervention