Sloeed to 220 kph close to the end of my flight?

[Dragonmount 5]

I was cruising along happily and suddenly I noticed a massive drop by my lnav speed bug. I haven’t flown this aircraft in quite some time and want to know why this happened? It caused me to miss the next descent checkpoint. Is this new? I don’t remember it from before. I was attempting to descend to fl 111, but it wouldn’t go down while the speed was decreasing. I’m assuming this can be changed in the fmc?

 

Pattick Boynton

[Budbud 227]

Hi,

Most likely a speed restriction along the way. Check in the leg page to find that restriction. The pitch mode whether it is VNAV PTH, VNAV SPD or FLCH will reduce the descent rate to bleed to the speed in order to meet a speed restriction.

Also check the FMA to confirm in which autothrottle and pitch modes are active.

What STAR did you follow?

[Dragonmount 5]

None though there might have been a waypoint  on the flight that is part of a star? I’ll check things but as I said it’s been some time since I flown.

Patrick Boynton 

[downscc 1,327]

15 hours ago, Dragonmount said:

None though there might have been a waypoint  on the flight that is part of a star? I’ll check things but as I said it’s been some time since I flown.

Patrick Boynton 

Patrick, I urge you to always look at the terminal procedures charts (arrivals, departures and approaches) before flying them. You don't want surprises.

[Ephedrin 418]

Additionally, you are the pilot. Speed or altitude restrictions do exist and it‘s your responsibility to match them. If the magenta line modes (LNAV/VNAV) cannot handle them (the 737 is a slippery airplane) then reach up to the MCP and use less automated modes like VS. Or use the spoilers, flaps, gear if necessary. Or violate the restrictions, you won‘t be executed for a few knots more..