How To CHANGE FPAS HOME WP Selection

[Habu_69]

I know how to set the FPAS HOME WP. After an initial selection, however, the adjusting arrows disappear, so how can the selection be subsequently modified??

[Tholozor]

HOME selection and remaining fuel calculations on the FPAS page become disabled when indicated Mach is 0.9 or above.

[Habu_69]

Thank you. Very valuable information, but you missed the point of my question.

[Harker]

Thank you. Very valuable information, but you missed the point of my question.

You need to be below Mach 0.9 and the arrows will appear again.

[Habu_69]

Well, the key or me is that the aircraft also must be moving for the arrows to appear. I was trying to change the HOME WP while the aircraft was still parked. No go.

[CBStu]

13 hours ago, Habu_69 said:

Well, the key or me is that the aircraft also must be moving for the arrows to appear. I was trying to change the HOME WP while the aircraft was still parked. No go.

That is funny as heck. Most car navs limit what you can do while moving. This limits what you can do when flying.

[ultrablue2258]

Make sure you are in the nav master mode and not in burner. 

[Frederf]

It's possible to get the FPAS point stuck if you do something to disable the waypoint being used. Not being a valid point you never get the arrows to change the selection.

[AstonMartinDBS]

On 11/29/2021 at 10:04 PM, Tholozor said:

HOME selection and remaining fuel calculations on the FPAS page become disabled when indicated Mach is 0.9 or above.

On 12/1/2021 at 8:19 AM, ultrablue2258 said:

Make sure you are in the nav master mode and not in burner. 

All those restrictions doesn't make any sense for me.

Why do the HOME selection arrows disappear under certain conditions?

[Tholozor]

43 minutes ago, AstonMartinDBS said:

All those restrictions doesn't make any sense for me.

Why do the HOME selection arrows disappear under certain conditions?

When TAS reaches/exceed Mach 0.9, range and endurance calculations become invalid. If the HOME FUEL caution cannot be calculated by FPAS, the HOME waypoint selection arrows are removed.

[Frederf]

3 hours ago, AstonMartinDBS said:

All those restrictions doesn't make any sense for me.

Why do the HOME selection arrows disappear under certain conditions?

Above that speed FPAS gives up because you're clearly not trying for fuel economy. You'd just be getting alerts all the time and maybe the prediction isn't that accurate beyond a certain speed. I don't know why it prevents you from changing the reference point as a design decision though. Lot 20 is pretty old. Computational resources could be pretty limited.

Edited December 3, 2021 by Frederf

[Nealius]

On 12/3/2021 at 7:01 AM, Frederf said:

It's possible to get the FPAS point stuck if you do something to disable the waypoint being used

I would like to know how to disable the waypoint being used. I'm tired of the deedle every three seconds as I'm jockying the throttle in the groove and want the whole thing silenced. 

[Andartu]

10 hours ago, Nealius said:

I would like to know how to disable the waypoint being used. I'm tired of the deedle every three seconds as I'm jockying the throttle in the groove and want the whole thing silenced. 

Because of that I made it part of the start-up to set it to the max WP59. Wrong behavior I know, but the Home Fuel warning always annoyed me. I rather live with the FPAS advisory than with a Master Caution going off in the groove. I monitor fuel all the time anyways.

[fagulha]

3 hours ago, Andartu said:

Because of that I made it part of the start-up to set it to the max WP59. Wrong behavior I know, but the Home Fuel warning always annoyed me. I rather live with the FPAS advisory than with a Master Caution going off in the groove. I monitor fuel all the time anyways.

Yes i do the same but usually only when inbound.

[Nealius]

Even on WP59 I still get the FPAS deedle while working the groove.

[Frederf]

Keep a point nearby. If your FPAS point is off the coast of Africa (0°N 0°E) that's quite a distance.

[boerdi]

I set my FPAS home waypoint to 58 while starting up on the carrier (to disable the warning sound)

Customised waypoints 0 to 2 while in transit

But now the FPAS page doesn't let me change HOME to something else
Speed definitely under Mach 0.9

What did I miss?

[Q3ark]

4 minutes ago, boerdi said:

I set my FPAS home waypoint to 58 while starting up on the carrier (to disable the warning sound)

Customised waypoints 0 to 2 while in transit

But now the FPAS page doesn't let me change HOME to something else
Speed definitely under Mach 0.9

What did I miss?

You’re not in NAV master mode, that might be it. 

[boerdi]

12 minutes ago, Q3ark said:

You’re not in NAV master mode, that might be it. 

No dice

[Minsky]

1 hour ago, boerdi said:

But now the FPAS page doesn't let me change HOME to something else

As long as I'm aware, this behavior is true to the real aircraft.

Within 5 seconds after the HOME waypoint is selected, and with weight off wheels, the system attempts to calculate the home fuel. If failed, it crosses out the number and removes the arrows.

You can sorta circumvent this by altering the coordinates of the currently selected HOME waypoint. Re-entering "N00.00.00" would suffice.

[boerdi]

Hm, even with weight on wheels the button will be crossed out after selecting the empty "bypass" waypoint 58

Back in the air, re-entering N 00.00.00 works to "unlock" the ability to select again
But now the HOME FUEL advisory/warning pops up, even with "empty" waypoint

Edited September 1, 2023 by boerdi

[Tholozor]

10 hours ago, boerdi said:

But now the HOME FUEL advisory/warning pops up, even with "empty" waypoint

N 0°, E 0° is not an "empty" waypoint. It's a calculatable position.

[boerdi]

Indeed, but doesn't WP 58 technically have that value already when the plane starts up? And then fails to compute home fuel. But when I enter the zero coordinates the computation picks up? (all within a reasonable range of numbers of waypoints set up for a mission and WP 59 being the Bullseye populated WP)

i.e. like NULL values and "0" as value in a database?

I don't mind it being how it is. Just curious that I can't change HOME anymore after those five seconds.

Edited September 1, 2023 by boerdi

[escaner]

Indeed, but doesn't WP 58 technically have that value already when the plane starts up? And then fails to compute home fuel. But when I enter the zero coordinates the computation picks up? (all within a reasonable range of numbers of waypoints set up for a mission and WP 59 being the Bullseye populated WP)
i.e. like NULL values and "0" as value in a database?
I don't mind it being how it is. Just curious that I can't change HOME anymore after those five seconds.

You are right. Those points are undefined. They display 0, but they actually are not defined, which is different from a point defined with coord 0. Also being able to set an undefined point as home and the system locking because it is undefined is stupid. Aircraft systems are not designed like that. I already reported this, but ED does not care to investigate how it really works.

[boerdi]

(Please correct me if I am wrong!)

To sum up the infos I could gather, these should be the necessary conditions to prevent HOME from being stuck/crossed out:
- Speed below Mach 0.9
- Set HOME to a valid waypoint
- No afterburner (no factor)
- NAV master mode (no factor)

 

Notes:
- "Valid waypoint" means a "prepared" waypoint, either entered manually or set up in mission editor. (e.g. an "untouched" waypoint 55 is not valid and HOME gets stuck)
- Default HOME waypoint is 0
- Calculation of home fuel starts 5 seconds after selecting the HOME waypoint on FPAS page
- The HOME FUEL warning is the plane telling you that you will have less than 2000 lbs of fuel left at that designated HOME waypoint
- Entering bogus "N 0 E 0" coordinates makes the waypoint valid but the calculation to "Null Island" in the Gulf of Guinea near the coast of West Africa will trigger HOME FUEL warning

So you got HOME stuck on an invalid waypoint and want it to be available again?
-> Check the "stuck" HOME waypoint number on the FPAS page and manually enter coordinates for that waypoint via HSI->DATA->WYPT tab to enable HOME computation again (best case would be a location where you think you will be landing)

Or do you just want to shut up the annoying HOME FUEL warning and don't care that the button is stuck?
-> Select a likely "untouched" waypoint like 58, 57 or 56 etc
Note: waypoint 59 is automatically populated with the mission's bullseye coordinates and enables HOME FUEL calculation

Edited September 15, 2023 by boerdi