If you're in VNAV PATH, the aircraft is slaved to the vertical path to meet the alt restriction...it will prioritize path over airspeed so to speak. You want to descend but must control the airspeed, so extend the inflight spoilers  

If you're really in trouble, consider to fly in spirals, the pitching energy is wasted while you still have high speed drag.

I'd use LVL CHG and dial in 250kts, in this way the aiorcraft will fly with throttles retarded but wont exceed 250kts, but I rarely have to do that.

Who makes this hard constraints btw, you or the FMC?
See the stored procedures are designed so your aircraft would have no problem in meeting the restrictions.

now this is a longshot and shold not have so much influence but do you  input values in  the DES FORECAST page. If you fly with lots of headwind, the descent can be very miscalculated, hence putting you too high before the hard alt. constraint waypoint.

Real pilots types in values on this page, even though they are not 100% sure of how the winds enroute actually looks like.

Is that correct, NOPE!

Ask yourself this, is it possible that in 4nm (distance between SINRA and DRAMO) you can loose 3000ft and at the same time decrease airspeed with some 20kts?

Of course you won't make it. You have simply interpret the charts wrong.

Yes at SINRA you should be at FL 060, but at DRAMO you would NOT put a hard alt constraint. Instead the 3000ft hard constraint should be set at the FAF for runway 04R. The FAF for 04R is 9,4nm from the Localizer (ident: NA 110.70mhz). To do this correctly, keep the 6000ft constraint at SINRA, but do NOT manually enter a constraint a DRAMO, instead go to the FIX page and type in NA...in the RAD/DIS line, simply create a fix 9.4nm from the NA...copy the newly created fix into the scratchpad, go to LEGS page and insert it right before the RW04R waypoint.

Great, we now have the FAF in our legs page, only thing left is to set the 3000ft alt. constraint, I also added the speed constraint, but that's not really important, I won't be flying the approach in VNAV anyway  


I can guarantee you VNAV won't disconnect now, and if you want to be on the safe side, use SPD INTV to change the VNAV target speed.  

I was lucky I had the STAR, and the ILS approach (including DRAMO transition) in the FMC database.
here's how it SHOULD look like



Good luck!  

the green circle is a function of the FIX page, as I wrote in my previous reply )
Go to the FIX page, and type in NA.

Now below you have 3 lines where you can enter a RADial and DIStance. We will disregard the radial input for now, but we must tell that to the FMC so we put a SLASH "/" infront of the distance input, which is 9.4

So correct would be /9.4

Okay now you have the green circle, but no actual waypoint where the circle crosses your flight plan. Now on the FIX page, click the LSK where we have the /9.4, if you did this right, you'll have a waypoint in the scratch pad, this wpt is where the circle is cutting though the magenta flightpath
So all that remains is to enter the waypoint in the LEGS page, DONE! 

In fact I did not have to use LVL CHG much (just completed a flight from Paris to Nice), I descended a bit earlier than the T/D calculated by the FMC, reduced the VNAV target speed and below 10.000ft I switched to LVL CHG (speed 220), when vertical speed was stabilized I switched to V/S mode...that's how you do it, smooth transitions from 3 different descend modes