MobiFlight Community Support

Hello,

Is it possible to add precondition feature to the switches ?

Say, i've got a 3-way switch for the Strobes and Nav Lights just like in 738. Down position enables Nav Lights, up position enables Strobes and Nav Lights together and Middle position closes them both.

What i want is to activate the Nav Lights first, on RW Hold Point i want to activate the Strobes without closing the Nav's (no OnRelease function), then after landing and taxiing out, i want to close the Strobes and let Nav's open (the point i'm stuck), and at the gates i'll close the Nav's as well. So, the logic works kinda like this;

Pos. 0 - Strobe + Nav
Pos. 1 - Close
Pos. 2 - Nav

If Pos.2 is enabled; switching to Pos.1 and Pos.0 in order, will NOT close the Nav's while passing Pos.1, only enable the Strobes at Pos.0
If Pos.0 is enabled; switching to Pos.1 and Pos.2 in order, will NOT close the Nav's while passing Pos.1, only enable the Nav's at Pos.2.
If Pos.0 is enabled; switching to Pos.1 will close the Nav's.

Kind of a one-way-bypass of the Pos.1. Seems kinda confusing, but actually it's not Just look at Boeing 737's Nav Light switch and u'll get it.

Any ideas ?

Hi slammer88,

first you need a truth table for your switch with the three statuses to look if it is possible and logical.

Facts: switch with three statuses to switch from off to on the nav's and the strobes without switching off one of them while actuate the switch unless you want to have both switched off.

For the truth table the first condition is all off and this is the initial situation

truth table: (P=Position of switch - N=NAV-Lights - S=Strobes - 0=Off - 1=ON)

P N S
1 0 0
2 1 0
1 1 0
0 1 1
1 1 0
2 1 0
1 0 0

1. both off
2. NAV on
3. NAV keeps on
4. NAV ON and STROBES ON
5. NAV keeps on - STROBES OFF
6. NAV ON
7. both off
You see that the problem is not position 0 and position 2. Tricky is pos 1. You want two conditions with different outputs if you change from #2 -> #3 and from #5 -> #6
I think, that this is not resolvable with preconditions and I assume pizman will confirm this.
What you need is a variable that can store temporarily the last status of the switch so that it can be traceable from wich position the switch comes.
So you need a variable then you can write a new truth table:

P N S V
1 0 0 0
2 1 0 1
1 1 0 1
0 1 1 1
1 1 0 2
2 1 0 2
1 0 0 0

So if you come from the initial situation to #2 (NAV ON) you set the variable to 1. This 1 can be held until you come from #4 to #5. On #5 you set the variable to 2. So the NAV's keep on at #6 if you test the variable on 2 and if you the reach #7 and the variable is 2 both can be switched off.

I think pizman will check this and can give you hints how to install a variable that can be used for preconditions. I can explane the logics but do not know how to implement this in Mobiflight.
You see for yourself that #3 and #5 and #7 are the tricky-points.

Hi Guys.

Holy crap what are you doing ???
Sorry but i can not understand the problem at all.
Maby i miss translate this ( sorry my english is not the best)

WHAT is the exact Problem ? If i see it correct the professional Simulations like PMDG, Prosim and so on work simmular like the Real B737 here....
The Switch got 3 Positions.... Down Position = Only Nav Lights on.... Middle Position is Both Off .... Upper Position is Navlights and Strobe on.

Why do you wan´t to change this logic.... When you on the Holding Poiont before takeoff you push the switch from 0 to 2 .... Yes in the millisecond you have Pos1 there is no lights... But who cares..... Same after landing.... here you switch back from 2 to 0 and have again maby 0,5 seconds without nav lights. Again not important.
Finaly on Shoutdown you switch from Down Position to the Middle and disable the Navs.

Maby i´m wrong but this is the original Warkflow like in a real B737. Here the NavLights will go off to when you swith the Strobes ON/OFF
If not please show me a link that explane the situation in a real Aircraft


If you like for better handling a other system as you request above, why you not think about a chaning of switch positions....
Best way is... Lower Position Both off..... Middle Position Nav ON Upper Position NAV+Strobe ON
That will do what you like i think !


Finaly a logic like you wan´t is not posible i think ( And make no sence)..... Not with Preconditions and not with another software... Even not in a real Plane !

Simply question / Example
You Turn ON Nav Lights after Startup but then you get attend to stay on Gate cause the airport is closed ( Stupid i know)
How can you disable the Navlights now..... Narmal you push it from Lower Position to Middle Position..... With your System you need to set it 0-1-2-1-0-1 .
The switch then can´t know if you like to disable the Navlights realy or if you like to change to Strobes.