Hi Guys I really do need a bit of help. The problem is the V Nav diconnects on every flight i fly, at the same time as the Alt Hold comes on .It appears to happen, regardless of height or speed,even if i adjust the descent path to make it even easier for the FMC to cope it still occurs. [i use adware to plan my flights] If i repeat the flight the same thing happens, but not usually at the same point of the descent.OK i still manage to land but its not a realistic way of flying is it. I have looked thro the manuel, tutorials and searched this forum But i am still baffled. [Yes your right, i am fairly new at all this] Any help from any of you Stars out there,would be much appreciated. Cheers Alan

Alan,You are encountering the frustration from VNAV DES that most new NG simcaptains do.Take some time and do an advanced search for VNAV descends. THis topic has been discussed widely over the years the NG has been out.Short story is that during a VNAV PATH DES you are controlling the speed while the AFDS is controlling the path. Most difficulties arise due to over/under speeding, incorretly applied altitude contraints during descent or winds not entered into DES FORECAST page.Hope it helps,