9 hours ago, cowpatz said:

That 2800A at GRITY is the reason. It is not possible to have a higher crossing altitude following a lower one on a descent path.

Yes, the question is, should it be? I see what he's saying. He's on the ground trying to enter this restriction, which should just become a hold down on the climb. There's room to cross his point at 2000, climb to reach the cruise altitude of 4000, and then create an idle path descent that honors GRITY above 2800. The box is acting as though it's in descent mode before takeoff.

That doesn't seem right, but like I say I'm not really certain it isn't. I fly flights shorter than this occasionally in the real airplane, but I'm never modifying altitudes when I do it. I think that if you were already in flight and this close to a computed T/D, I could see the box already being in descent mode. But before takeoff? That seems less likely. But I'm not certain.

6 hours ago, Stearmandriver said:

Yes, the question is, should it be? I see what he's saying. He's on the ground trying to enter this restriction, which should just become a hold down on the climb. There's room to cross his point at 2000, climb to reach the cruise altitude of 4000, and then create an idle path descent that honors GRITY above 2800. The box is acting as though it's in descent mode before takeoff.

That doesn't seem right, but like I say I'm not really certain it isn't. I fly flights shorter than this occasionally in the real airplane, but I'm never modifying altitudes when I do it. I think that if you were already in flight and this close to a computed T/D, I could see the box already being in descent mode. But before takeoff? That seems less likely. But I'm not certain.

I'm afraid that @cowpatz isn't familiar with how Boeing VNAV manages low-altitude level-offs, climb, cruise, and descent, including SID/STAR crossing restrictions and user-defined conditional waypoints.

In this scenario, the vertical profile is valid. The FMC has a properly defined climb segment, a distinct Top of Climb (T/C), a cruise segment, and a Top of Descent (T/D), with no conflicting altitude or speed constraints. 

As you suggested, I also entered the restriction before activating the route. That avoided the initial error message. However, after passing CRI, VNAV still became confused. Instead of immediately resuming the climb and accelerating to the scheduled climb speed, it remained level at the crossing altitude and speed for a period before eventually recovering and continuing the climb profile normally. That behavior is inconsistent with Boeing VNAV logic, where, once the crossing restriction has been satisfied and no further constraints exist, VNAV should promptly transition back to the commanded climb schedule.

The interesting part is this: prior to takeoff, assuming an ATC clearance such as "Cross CRI at or below 2,000 ft and 180 knots," entered on the LEGS page as a manually defined conditional waypoint, the FMC sometimes fails to accept or process it correctly, resulting in the message shown. What's particularly puzzling is that the issue is intermittent. The exact same setup may work correctly on one flight and fail on another.

That makes me wonder whether this is an edge case in the VNAV coding, perhaps related to the recalculation of the active vertical profile when user-defined conditional waypoints are introduced before departure. Since it isn't consistently reproducible, it's difficult to determine whether it's a logic flaw, a timing issue in the FMC's path generation, or another intermittent condition within the VNAV code. I can't quite put my finger on it, precisely because of its intermittent nature.

Speaking of RNP approaches, anyone know if one exists for RWY 14R at RJOO? Or at least a RNAV Visual? None exist in Navigraph, but I wonder if one of the Japanese airlines might have designed one. Not sure how common that sort of thing is in Japan.

Here is the approach:

1 hour ago, RNAVV19R said:

Speaking of RNP approaches, anyone know if one exists for RWY 14R at RJOO? Or at least a RNAV Visual? None exist in Navigraph, but I wonder if one of the Japanese airlines might have designed one. Not sure how common that sort of thing is in Japan.

Here is the approach:

Last time, over a year ago, there were no approach plates published for that 14L/14R runway. We had an additional chart, similar to JFK CRI lead lights. As you can see, there are 7 lead lights that provide only lateral guidance, with no vertical guidance unless on very short final/turn and seeing PAPI. That was a visual procedure assigned by ATC: circle to land from RWYs 32L/R when minimums were good. We used it with 3200 VIS and MDA 760 crossing LEAD #1. They use it quite a lot for the locals and still wonder why there is no published procedure for it. They spent time putting those LEAD lights; why there is no full approach or visual chart is beyond my understanding. 

Edited 10 hours ago10 hr by LRBS

38 minutes ago, LRBS said:

Last time, over a year ago, there were no approach plates published for that 14L/14R runway. We had an additional chart, similar to JFK CRI lead lights. As you can see, there are 7 lead lights that provide only lateral guidance, with no vertical guidance unless on very short final/turn and seeing PAPI. That was a visual procedure assigned by ATC: circle to land from RWYs 32L/R when minimums were good. We used it with 3200 VIS and MDA 760 crossing LEAD #1. They use it quite a lot for the locals and still wonder why there is no published procedure for it. They spent time putting those LEAD lights; why there is no full approach or visual chart is beyond my understanding. 

Yep, no publicly available approach. But I was wondering if an airline may have created their own approach, in which case the chart (and the approach itself) wouldn't be available to anyone other than that airline and anyone else that they sold it to. It's a long shot that anyone here would have this knowledge, but was just wondering.

Deleted.

Edited 4 hours ago4 hr by cowpatz