Thanks for the suggestions!  I never heard of PF3 or Pilot2ATC, after doing some research on them they both look awesome and I'm definitely going to give both a try.

Staying higher for longer (adding power to stay in path) is ALWAYS more efficient in terms of fuel burn, than a dive and drive profile.  TAS is higher with a lower fuel burn at the higher altitude, equaling compounded efficiency.

Exiting VNAV Speed in favor of Level Change doesn't usually make sense.  VNAV Speed is functionally just Level Change with a few extra protections; it will never be low at a restriction for example, won't over speed below 10k etc 

 

4 hours ago, jon b said:

There’s many occasions where what VNAV thinks is the correct profile obviously isn’t and if left to it’s own devices it will eventually admit it was wrong  and start asking for speed brake, so I’d always preempt that situation from an energy management point of view.( on the jumbo at least, on the 787 I’d just throw VNAV away and use FLCH)

If you’re flying something with a narrow gate like F230B/F220A followed by another similar constraint  and you were asked for a greater speed then yes I take your point remaining on path and adding power would be preferable. 
 

However for most constraints which just have a straight crossing altitude I’d say descending at idle and pitching for speed then coasting in level flight is much more fuel efficient than adding power in a descent when you already have gravity for free.

In short I’d much rather be in a situation of being below the calculated descent profile carrying high speed energy which is easy to dissipate in level flight and speed brake  if required once level ,  than maintaining a badly calculated VNAV path and adding power to get a specified speed. You have the potential to not only find yourself high once VNAV realises it’s wrong, but also fast as well and no way to dissipate all that energy as you’ve no fly level period, and end up in a “won’t go down AND slow down” dilemma.

Yes, I’ve heard the tip about EIA on the descent forecast , but surely that just proves the point that the default calculations without that modification are not to be trusted ?

I believe the opposite is true, and that dive and drive would be less fuel efficient., assuming that you end up in the same place at the same energy state. 

In any case I don't disagree with getting below the profile but I don't see why you'd want that to happen out of PATH. If that's your aim then just use FLCH - the entire point of PATH is to keep you on the path, so if you don't want that then use a basic mode. 

Regarding putting something in the descent forecast, you're just giving the FMC something to work with. If the winds are out of date/inaccurate or the drag factor is wrong then it's just garbage in garbage out. 

The HJET does a great job with VNAV.  It is why I fly nothing else.

sp

I will not say - never trust VNAV but it is always recommended to make a question mark behind.

Take your charts, compare them with your flightplan entries and make a rough calculation. The rough calculation is easy and you will get used to. Other than for convinience, there is no need for VNAV.

 

Best regards, Detlef

7 hours ago, stratone said:

Other than for convinience, there is no need for VNAV.

That's not really true (though in the sim it might be.). In reality, flight plan fuel burn is calculated based on an idle path descent.  If you do something different, you're going off plan and you're going to overburn.  That's not just a matter of convenience ;).

Then there's the workload side of things.  On a complex STAR (or SID) with multiple speed and altitude restrictions, safety data clearly shows a trend towards more deviations in flights that don't use VNAV to accomplish these procedures.  Altitude deviations in crowded airspace aren't good.

7 hours ago, stratone said:

The rough calculation is easy and you will get used to. Other than for convinience, there is no need for VNAV.

I doubt if real world pilots (and the companies they work for) would agree.

 

 

59 minutes ago, tup61 said:

I doubt if real world pilots (and the companies they work for) would agree.

But the simmers on Avsim, know so much more than real airline pilots, just ask them....😉

Sorry ... I missed the title of this thread -  "Is VNAV actually used by RL pilots?....."

Of course there are several reasons to use VNAV in RL and in RL it is not only for convinience. 

 

In general - it is never a bad thing to be able to (rough) calculate the VNAV profil, in RL and in the sim. How often does it happend to you (in the sim), that you've noticed: this can't be right ? Never ? Really ?

@Bobsk8  BTW: The sentence: "I will not say - never trust VNAV but it is always recommended to make a question mark behind." is RL. A friendly advice by a RL flightinstructor A320 in my neighborhood.

 

Best regards, Detlef

 

I did a straight-in approach into PAJN / RWY26 and got a message when engaging  that obstructions were not factored in the approach.  This was using the HJET  WT G3000.

Sure enough the terrain got to close on the VNAV descent near the airport and had to hit the ALT to freeze the altitude for a few miles.

sp

Edited March 7, 20233 yr by Sky_Pilot071

57 minutes ago, stratone said:

Sorry ... I missed the title of this thread -  "Is VNAV actually used by RL pilots?....."

Of course there are several reasons to use VNAV in RL and in RL it is not only for convinience. 

 

In general - it is never a bad thing to be able to (rough) calculate the VNAV profil, in RL and in the sim. How often does it happend to you (in the sim), that you've noticed: this can't be right ? Never ? Really ?

@Bobsk8  BTW: The sentence: "I will not say - never trust VNAV but it is always recommended to make a question mark behind." is RL. A friendly advice by a RL flightinstructor A320 in my neighborhood.

 

Best regards, Detlef

 

I think what your neighbor means is to not instinctively trust the VNAV to do everything. Trust, but verify. I don't think he's insinuating that you should toss it out and do simple 3-in-1 rule calculations, and forsake VNAV.

VNAV optimizations and CDAs have saved millions if not billions of dollars, improved fuel savings across the board, and improved accuracy of flying procedures immensely. It's an indispensable tool, but it's a tool - you have to understand the automation, understand what it's doing and why, and how to use it. It's not just a "magic button," which is what I think he/she was getting at.

1 hour ago, mspencer said:

I think what your neighbor means is to not instinctively trust the VNAV to do everything. Trust, but verify. I don't think he's insinuating that you should toss it out and do simple 3-in-1 rule calculations, and forsake VNAV.

VNAV optimizations and CDAs have saved millions if not billions of dollars, improved fuel savings across the board, and improved accuracy of flying procedures immensely. It's an indispensable tool, but it's a tool - you have to understand the automation, understand what it's doing and why, and how to use it. It's not just a "magic button," which is what I think he/she was getting at.

Exactly ....

Cheers

2 hours ago, Sky_Pilot071 said:

I did a straight-in approach into PAJN / RWY26 and got a message when engaging  that obstructions were not factored in the approach.  This was using the HJET  WT G3000.

Sure enough the terrain got to close on the VNAV descent near the airport and had to hit the ALT to freeze the altitude for a few miles.

sp

So...?

1 hour ago, mspencer said:

I think what your neighbor means is to not instinctively trust the VNAV to do everything. Trust, but verify.

Obviously that goes for EVERYTHING when you fly. You could say 90%of the pilot's job is to verify things. The fact that you have to verify things however doesn't mean you might as well do without them. Stratone DID say 'there is no need for VNAV'... If you say 'just calculate the descent and you won't really need VNAV' you might also say 'just figure the course and you won't need the NAV'. All systems are there to aid the pilot and the pilot has to check and verify all systems all the time. In the end NONE of the systems in a cockpit are really needed: you might as well fly as the Wright brothers did.  Yeah, that's a bit over the top but I hope you get the idea. 😉  When push comes to shove a pilot may have to fly without the systems but not a pilot in the world will ever say 'Oh, that's okay, those systems were only there for my convenience'. 😉

Edited March 7, 20233 yr by tup61

3 hours ago, stratone said:

"I will not say - never trust VNAV but it is always recommended to make a question mark behind." is RL. A friendly advice by a RL flightinstructor A320 in my neighborhood.

 

This is true for every single thing in an aircraft.  😁

2 hours ago, Sky_Pilot071 said:

a straight-in approach into PAJN / RWY26

😬 THAT'S not going to end well lol.

In reality, we have an RNP approach to 26 that snakes through the Gastineau channel.  It gets impressively close to terrain.... And it's still way safer than a straight in would be!