FUEL_SYSTEM discoveries

In laying out the simple fuel system for our next aircraft, which is quite
exciting :D, I’m finding some interesting things that are either bugs or
incorrectly documented. Firstly I think there is a typo in the FUEL_SYSTEM
Junction.N

section when describing Option. It says at the bottom of its description:
If no options are defined then all connecetd lines will be considered as
closed.
However, if that were the case, then why does the A320 fuel system
work when there are NO options declared. That would mean that all fuel
coming into those junctions cannot go anywhere. Is it perhaps meant to say:
all connected lines will be considered as OPEN. __ Second, for those
Junction.N definitions that DO have options an error is reported in the
console when building/resyncing. For instance, my FuelSelectorJunction has 5
options (Off, Left, Both, Right, Off) and I get the error:
[FuelSystem]Attempting to set junction FuelSelectorJunction to invalid
option: (Is 0, should be 1 to 5)
Seems like the system is trying to set 0
index but junctions are expecting 1 index Finally, as with everywhere else,
the documentation is missing ALL units in the description so we don’t know if
we are talking about lbs, gal, slugft, etc: e.g. This is used to calculate
the effect of pressure on fuel flow. Value is in

per second, and if not set will default to 0.1.

Note that the unit is missing when talking about the value per second. This is
consistent throughout the documentation.

1 Like

Other users have pointed out two of the issues you’ve mentioned, namely:

  1. " Is it perhaps meant to say: all connected lines will be considered as OPEN " - This is correct!
  2. " Finally, as with everywhere else, the documentation is missing ALL units in the description so we don’t know if we are talking about lbs, gal, slugft, etc: e.g. " - Sorry about this, it was a failure in the build tools for the documentation that we missed.

BOTH of these issues will be addressed in the next update to the SDK.

What about the other issue I reported?

Second, for those Junction.N definitions that DO have options an error is
reported in the console when building/resyncing. For instance, my
FuelSelectorJunction has 5 options (Off, Left, Both, Right, Off) and I get the
error:

[FuelSystem]Attempting to set junction FuelSelectorJunction to invalid
option: (Is 0, should be 1 to 5)

Seems like the system is trying to set 0 index but junctions are expecting 1
index

By the way, it is interesting that for a valve for a liquid or gas, the
terminology is such that “open” means that the material can flow and “closed”
that it can’t flow. For an electric switch, it’s the opposite. A closed switch
permits electricity to flow, and open switch is, well, open, no electricity
can flow.

Yes because of the physical reality of each :wink:

1 Like

Another interesting example of quirky terminology is that certain types of electrical switches (circuit breakers) are said to be “pushed” or “pulled”. Without knowing a priori what these mean (“pushed” = ON, “pulled” = OFF, right?), that is about as informative as calling the states “purple” and “mauve”. And sadly, the SDK uses this terminology without explaining what it means. Like:

BATTERY_BREAKER_PULLED — b (BOOL) — Whether the battery breaker has been pulled (TRUE, 1) or not (False, 0).

So, if “pulled” means that no electricity flows, the switch is OFF, the logic here even is inverse to what would perhaps be intuitive. The intuitive thing would be that switch that is ON is True, and one that is OFF is False. This is the other way around.

This is perhaps one of those cases where it is easy to assume that “everybody knows”. But that is a fallacy, and the terminology is not universal. For instance, not even the Wikipedia page on circuit breakers mentions “push” or “pull” at all.

And some circuit breaker manufacturer pages use the “trip” and “reset” terminology, apparently meaning “trip” = turn OFF, “reset” = turn ON. It is actually surprisingly hard to find a clear definition of “push” and “pull” for circuit breakers. Not even this page says it excplicitly: Push/Pull Circuit Breaker - Wicks Aircraft Parts

This is a good Youtube video that shows how such devices actually work: https://www.youtube.com/watch?app=desktop&v=9CR5LJW5Yyw