VNAV SPD RESTR in idle path

[Hardy Heinlin]

Good morning,

has anyone any experience in using the SPD RESTR feature in a VNAV IDLE descent?

We have ...

SPD TRANS
SPD RESTR

To maintain the path with idle thrust and the elevators, VNAV allows an airspeed tolerance of -10 to +15 knots. Hence, for the typical speed transition of 250/10000, VNAV uses 240 knots. This keeps the max at 255 knots which is allowed.

I'm wondering if VNAV applies the same tolerance to a pilot entered SPD RESTR. Say, ATC requires 230/8000, would VNAV go as far as 245 knots in case of an idle path overshoot? If so, would you enter 220 instead of 230 -- i.e. minus 10, similarly to the FMC subtracting 10 from the SPD TRANS?


Cheers,

|-|ardy