Remaining fuel on the FMC page "progress"

[Valentiner79]

Hello to all lovers 737
Hello developers,
Hi Jan!

I noticed that on the CDU "Progress" page, the expected remaining fuel at the waypoints is showing an incorrect value. For example, at the next point, the remainder is greater than at the previous one. Is this a bug or not yet implemented?

For clarity, a screenshot:

[Litjan]

Hi Valentiner,

it is not implemented correctly yet.

To save you the trouble of finding and listing all deficiencies not implemented yet or missing, I would like to direct your attention to these two pinned posts:

 

https://forums.x-pilot.com/forums/topic/8526-things-that-are-not-going-to-be-in-v133/

https://forums.x-pilot.com/forums/topic/17981-version-133-known-bugs-and-workarounds/

 

Cheers, Jan

 

[Valentiner79]

Hello, Jan!

Of course I read the information on you links earlier, but i was confused by the fact that on screenshots of other users everything looked more correct. 

[Litjan]

1 hour ago, Valentiner79 said:

Hello, Jan!

Of course I read the information on you links earlier, but i was confused by the fact that on screenshots of other users everything looked more correct. 

We run a "rough" calculation based on total distance of the route, but omit other factors (speed, altitude,...) so it may or may not be fairly accurate.

The fuel consumption of our plane is fairly accurate, though - so you can use real performance charts to plan the fuel needed (if you have them).

I often just do a quick calculation in my head:

Distance/400 = flight time in hours

2400kgs * flight time in hours + 1500kg ascent/descent fuel + 2400kgs alternate/holding fuel

Adjust this a bit for head/tailwind (if known) and for heavy/light aircraft.

We are currently doing a rewrite of the VNAV calculations (you can notice them not being very good especially on descent with restrictions) and this will also give us a better way to calculate and total up the different route segments with regard to speed and fuel burn - which will make predictions on the PROG page more accurate.

Cheers, Jan

 

[Valentiner79]

Hi, Jan! 

Thank you for response.

I have no problem with calculating the fuel for the flight. If you look at my screenshot, i was confused by the fact that the fuel remainder at the point "Menbo" is 10, and in next point "Noret" the scanned fuel remainder is 22.7 although it should be less than 10. 

I'm sorry, I may not be able to express my thoughts clearly, since I am not an English speaking man.

[Litjan]

Hi Valentiner,

you are doing fine!

It is my fault for not looking at your first post closely enough!

The waypoint "MENBO" is your "FROM" waypoint - you have already passed it. The waypoint "NORET" is your "current to" waypoint and "KISIL" the "next" waypoint.

The PROGRESS page is built like a standard ICAO position report that pilots had to make (and still do in some regions) where radar coverage does not exist. You would need to call ATC with a position report that would go like this: "Flight XYZ, position MENBO at 1558, estimating NORET 1602, KISIL next".

Airline pilots also use this page to fill out the flightplan when they track fuel usage. So you can use it to check how much fuel you had at the last waypoint (FROM) that you passed. Because often you forget (or are too busy) to read off the fuel right as you pass the waypoint, so you can use the PROG page to check it.

The fuel at MENBO should definitely be more than the fuel at your next waypoints, though - which is clearly a bug.

Cheers, Jan

 

Edited February 3, 2021 by Litjan

[Valentiner79]

Thank you, Jan!

I'm really surprised to meet such helpful people here!