1 minute ago, LRBS said:

 

What that guy is doing by dialing "next altitude for the waypoint" in VNAV with multiple step-downs on STAR or SID, IT IS NOT A BOEING/AIRBUS PROCEDURE, it might be a company procedure, or someone who does not understand the systems.

Thank you!  This is what was so confusing. I wasn't sure if he (and others) were doing this because its required, it's a backup, or VNAV is broken or what.

So what I understand is if you have a programmed flight path, and you enter your FAF altitude (like 3000 feet) at ToD, then the plane will fly the profile adhering to all constraints on the way down, automatically.

8 minutes ago, Virtual-Chris said:

Thank you!  This is what was so confusing. I wasn't sure if he (and others) were doing this because its required, it's a backup, or VNAV is broken or what.

So what I understand is if you have a programmed flight path, and you enter your FAF altitude (like 3000 feet) at ToD, then the plane will fly the profile adhering to all constraints on the way down, automatically.

Yes, but keep in mind that during a VNAV approach, when at least 300 feet below the missed approach altitude, set the missed approach altitude on the MCP; otherwise, it will level off and will not perform the missed approach procedure correctly. 

11 minutes ago, Virtual-Chris said:

Thank you!  This is what was so confusing. I wasn't sure if he (and others) were doing this because its required, it's a backup, or VNAV is broken or what.

So what I understand is if you have a programmed flight path, and you enter your FAF altitude (like 3000 feet) at ToD, then the plane will fly the profile adhering to all constraints on the way down, automatically.

You are %100 correct in your understanding. The only thing you MUST have is an E/D point. (End of descent point)

If you don’t have this, you will not get a TOD or a VNAV path. Most of the time, the E/D will be the final point of an arrival or the runway if an approach is loaded. 
 

If you load an arrival and connect it to an IAF of an approach, you can dial in the TDZE right before your TOD and VNAV will fly you to the ground respecting all speed and altitude restrictions as long as your FMA says VNAV PTH. Not only that, once the FMC goes into approach mode (you won’t see any indications of this.) it will slow you to your flaps up maneuvering speed and then when you start configuring to land, it will even slow you to your target speed. Great stuff this VNAV.

29 minutes ago, NovemberUniform said:

I guess so. It may be how they do it irl.

In the sim, I can tell you that both Airbus and Boeing aircraft can descent to platform altitude (let's say 3000ft) from cruise altitude in VNAV without ever changing the dialed in ALT. Depending on conditions or how accurate the VNAV is modeled, you may have to use speed brakes to stay on the profile.

If that's the case, as you describe, we have BAD PROGRAMMING! Just out of curiosity, which of the two developers, Airbus or Boeing, does this? Personally, I never see this happening. 

 

 

8 minutes ago, ahsmatt7 said:

You are %100 correct in your understanding. The only thing you MUST have is an E/D point. (End of descent point)

If you don’t have this, you will not get a TOD or a VNAV path. Most of the time, the E/D will be the final point of an arrival or the runway if an approach is loaded. 
 

If you load an arrival and connect it to an IAF of an approach, you can dial in the TDZE right before your TOD and VNAV will fly you to the ground respecting all speed and altitude restrictions as long as your FMA says VNAV PTH. Not only that, once the FMC goes into approach mode (you won’t see any indications of this.) it will slow you to your flaps up maneuvering speed and then when you start configuring to land, it will even slow you to your target speed. Great stuff this VNAV.

Just a clarification to avoid misunderstanding. I understand what you're saying, but we need to clarify that the exact TDZ cannot be dialed on the MCP window; it can only be rounded up. And in case of a go-around, VNAV will get stuck down there. 

Edited August 5, 2025Aug 5 by LRBS

49 minutes ago, T_Bone said:

How would you descend without dialing in a lower altitude?

I thought that much was clear.

1 hour ago, LRBS said:

If that's the case, as you describe, we have BAD PROGRAMMING! Just out of curiosity, which of the two developers, Airbus or Boeing, does this? Personally, I never see this happening. 

 

 

I edited my post. I thought that much was clear, but I see my way of writing it was not very good.

1 hour ago, LRBS said:

Just a clarification to avoid misunderstanding. I understand what you're saying, but we need to clarify that the exact TDZ cannot be dialed on the MCP window; it can only be rounded up. And in case of a go-around, VNAV will get stuck down there. 

Fair point lol 😂 I’m so used to teaching our SOPs in an environment where everyone knows what I mean when I say what I mean. Thanks for the addition. The OP does need to know that. lol a go around would be uummmm…interesting lol

41 minutes ago, ahsmatt7 said:

I’m so used to teaching our SOPs in an environment where everyone knows what I mean when I say what I mean. 

100%, same problem here. Very difficult to explain to a PC pilot, regardless of how much they educate themselves. We hope to create a positive and pleasant experience. Thank you for your dedication. 

To answer the op's question: The ifly max has issues with vnav descent path calculation, its been that way for a while.  Real 737 vnav works quite well.

3 minutes ago, Pilot53 said:

To answer the op's question: The ifly max has issues with vnav descent path calculation, its been that way for a while.  Real 737 vnav works quite well.

So in the iFly... what do you do to get it to follow the path?  Do you have to dial in the altitude for each waypoint as you go as some of these tutorials show?  Or do you need to use speed breaks or increase V/S to help it descend quicker?  

I tried a flight tonight... From Kona (PHKO) to Honolulu (PHNL) and used an ILS arrival into runway 4R.  It worked perfectly. As I approached the T/D and prepared to dial in my IAF altitude, the FCU prompted me about 2 miles out from T/D to dial in a new altitude on the MCU... Nice!  From there it flew all the way down as expected. At one point, a message on the FCU said "add drag" or something to that effect and I engaged the speed brakes. It didn't tell me when to disable them, so I just assumed it didn't need them anymore once the next altitude constraint was met. 

I really don't understand the tutorials I've been watching where the pilots are dialing in altitudes at every waypoint on the way down... and using V/S etc. The VNAV works very well, at least this time.

Thanks to everyone who helped out... much appreciated!

 

16 hours ago, LRBS said:

I understand what you're saying, but we need to clarify that the exact TDZ cannot be dialed on the MCP window; it can only be rounded up.

We round down, actually, exactly to avoid a reversion to altitude hold and destabilization down low.  We then get the missed approach altitude set in the MCP as part of our standard missed approach profile.

5 hours ago, Virtual-Chris said:

I really don't understand the tutorials I've been watching where the pilots are dialing in altitudes at every waypoint on the way down... and using V/S etc.

Yep, it's mostly people not understanding the systems.  You find things like this that are systemic in simming.  Another example would be many sim pilots religiously arming VOR/Loc first, and THEN approach afterwards.  No need or reason.

One other consideration about setting intermediate altitudes though: in reality (and in the sim world on Vatsim etc) you do not want to descend below your cleared altitude by ATC, so you'll always set that in the MCP.  If you're cleared to "descend via" with no exceptions, sure, set the bottom altitude and let VNAV do it's thing.  But if you're given a "descend via except maintain", or a discretionary descent etc, you'll want that cleared altitude in the MCP to ensure you don't bust it.

6 hours ago, Stearmandriver said:

We round down, actually, exactly to avoid a reversion to altitude hold and destabilization down low.  We then get the missed approach altitude set in the MCP as part of our standard missed approach profile.

Indeed, I've seen various SOPs as well. The goal is to build strong situational awareness.