This happens to be a lot and I'm trying to figure out what I'm doing wrong.

 

This is the KAYOH4 (HEC trans) into KSNA John Wayne, CA.

 

As I approach HDF (coming from DAWNA), the FMS slows me down.  I'm not sure why because the speed and altitude at HDF is 269/11000.  I'm only 2000 ft above that target but it wants to slow me down 60+ knots?  In the second picture you can see the speed coming back up.  

 

Any ideas?

 

 

 

 

 

 

 

This happens to be a lot and I'm trying to figure out what I'm doing wrong.

 

To be honest, it looks a lot like the energy compensation feature.  Is ATC holding you at an altitude so that you're ending up above path?

Ryan,

 

If this is happening to you "a lot" then what you are doing "wrong" is not resetting your MCP altitude soon enough thus forcing the energy compensation to kick in (what Kyle said) which lowers your airspeed to potentially allow you to recapture the VNAV path.  Judging from your screenshots and your vertical deviation indication, that's what's happening.

 

If energy compensation has kicked in, the technique I like to use (a r/w pilot posted this once) is to use the SPD INTV button and then crank your airspeed back up to say 280 kts (when above 10,000 feet obviously) on the MCP.  Now you're trading altitude for airspeed and your V/S should increase significantly until the target airspeed is reached.  Once the vertical deviation is back on track, press VNAV again on the MCP to get back to VNAV PTH mode.

 

If possible, reset your MCP altitude before TOD is reached and this won't be an issue.  You should get the FMC MESSAGE to do that just prior to that point.

 

I hope that helps a little.

Request a descent before you get to TOD and this won't happen unless you're held up at altitude for other traffic. (Not uncommon in California.)

Unless they're issuing the HDF at 11k restriction (which I don't believe they will) you can delete that from the FMC. Typically you'd get DEJAY at 8k, and probably a speed restriction. You might get an initial descent to 10,500 or so after DAWNA. Is this happening on other STARs?

 

Don't forget you can (and should) always take over with SPD Intervene if the plane isn't doing what you want it to.

Energy conservation... probably it.

 

I'm flying online so they issue the restrictions like socal would in real life...  There was 2-3 step downs.  So at this point I might as well just use VS and IAS modes?

 

 

I'm flying online so they issue the restrictions like socal would in real life...  There was 2-3 step downs.  So at this point I might as well just use VS and IAS modes?

 

Yeah.  It would be cool to have someone who's flown the STAR chime in, but I bet they either just allow the compensation to assist in the descent, or override it with VS/IAS.