FMC : Desc path not achievable

[GSalden 1,181]

Today I got the message 'Desc path not achievable' on the CDU. I was doing a DME Arc approach to Monastir ( DTMB ) and during the last 30 miles I got the above message.The calculated speed was 240 knots. To my surprise the V/S was just -800.Surely with higher V/S this would not have been a problem.I tried with Speedbrakes on, but then the throttles came up .... Of coarse I can use V/S instead of VNAV, but normally this should have been possible. Where did I go wrong ?

[NGX 1]

On the ND, how high above the VNAV path does it show you are?

[Jordan 0]

View this video by a real NG pilot about catching up with you VNAV path - http://forum.avsim.net/topic/344441-do-you-really-need-speedbrakes-video/page__view__findpost__p__2065410

[GSalden 1,181]

Thanks for the link ! When looking at the ND I was about 400ft too high.Without VNAV I could manage it, but I am sure it has to work with VNAV too. I arrived well in Monastir