Hi guys, this may sound stupid, but i am having problems with the vnav descents. It descends way to slow. When i reach the airport, i am always way to high, arround 6000 AGL. No problems with climb, but yes with descent. Please, i´d like to know what i am doing wrong, because i know there is something i´m not doing.

 

THANKS IN ADVANCE!!

 

Tatin 98

Please, i´d like to know what i am doing wrong, because i know there is something i´m not doing.

 

It's probably that you're not entering in the proper descent points. Try the tutorials and see how those go. If you're descending well using the tutorials, then it's just your procedure.

Do you assign a STAR and approach in FMC? Do you examine legs page and assure there are proper speed and altitude restrictions published in charts.

 

You see, FMC is not a magic box that will manage all phases of flight for you just by itself. Its a powerful tool, but it requires constant human supervision.

 

Usually, when I try to examine FMC problems i find out that it's not one missed step in FMC setup, but whole wrong "FMC will do everything for me" mindset. It can be corrected with a good training sessions and patience.

 

That mindset is consequence of modern and very powerful PC based aircraft simulators, so for a "young" sim pilot its very tempting to imagine radionavigation, pilotage or performance calculations are not really required because there are a FMC and TOPCAT things do all that stuff for you.

Wind entry & Anti ice will affect your your VNAV profile, it also doesn't hurt to back up with some old fashion manual descent calculations. It's better then pushing and hoping for the best.

 

At the very least remember you have many tools at your disposal. If VNAV is not doing the job switch to another mode, or shock horror click off the automatics and fly the machine

The NGX VNAV is a thing of beauty. If you take the time to complete the Descent and Descent Forecast page ACCURATELY and fly published procedures it will handle most STARs perfectly. Accurately inserted AI altitudes and computed average descent temp deviation and landing QNH are important. When that is done, despite albeit rare in RW flight, a continous descent to ILS platform height at intercept is NOT rare in the NGX world (when VATSIM/IVAO controllers do not require something else).

 

When the FMC does not like something it will usually advise you of this with appropriate messages. These messages then require thought and action. A speed restriction inserted, or an altitude hard coded will usually result in complete VNAV descent ability. Sometimes, both are needed to do the trick. Unlike the VNAV of old, this one requires application of the grey matter in the intercranial cavity. Unlike aeroplanes of old, this one requires pilot response in the most literal sense- it requires a pilot.

 

Get everything in the box well BEFORE TOD and she does an admirable job of handling most published vertical profiles. If things go slightly different than planned, 10-15kts in SPD INTV usually result in VNAV PATH happily reacquired.

 

The thing about this girl, is that she flies like an aeroplane, not like a formula without variables-and therefore infinitely predictable. Don't tell G-CIVX this, but the baby Boeing is miles ahead in flight replication and computational dynamics. The end result being that she flies more like a Boeing, than anything else in the FSX world- currently. That said, she flies best with an attentive and prepared pilot at the controls.

 

In our sim world, time in the manuals is the best preparation possible. I recognize not everyone wants to do that, however, if the pilot is interested in accurate operation of an accurate airframe simulation, time spent with the accompanying documentation is a necessary obligation.

What route and arrival are you using?

 

If you're in Level Change it's really simple. The thrust will be at idle (ARM) and the speed which is in the left-hand (Mach/ speed) window of the MCP.

 

If you're in VNAV the aircraft will typically follow the profile when all parameters entered correctly. It does this by varying the speed - slower than computed if below profile, higher than computed if above profile. I don't like this. it's a bit of a roller-coaster ride for the pax. But what you do get with VNAV is compliance with any vertical speed or altitude constraints, which on most STAR's is important. But same story as in the climb, if ATC clears you to a level or altitude lower than a constraint then you'll need to clear (delete) that restriction if you want to maintain in VNAV.

 

The initialization of the descent is handled very well in VNAV but then I find it most comfortable to do the major part of the descent in Level Change and convert to VNAV in time to take advantage of the altitude/ speed constraints on the STAR. Some guys will use VNAV for the entirety of the flight. Nothing wrong with that & it's the modern thinking way to leave it all automated. I prefer a little more control when I fly.