Fire warning lights on fuel control switches

[killairbus 3]

Hello,

When I did the IND LTS test I noticed that the asterisk like fire warning lights on the fuel control switches did not light up. 

They only did so with the overhead fire test. 

-Angelo Busato

FSX:SE 747-400

Edited December 25, 2018 by killairbus

[Olympic260 415]

14 minutes ago, killairbus said:

Hello,

When I did the IND LTS test I noticed that the asterisk like fire warning lights on the fuel control switches did not light up. 

They only did so with the overhead fire test. 

-Angelo Busato

FSX:SE 747-400

Correct behavior these will light only with the fire test 

[killairbus 3]

14 hours ago, Olympic260 said:

Correct behavior these will light only with the fire test 

Interesting, why is that?

-Angelo Busato

[Olympic260 415]

6 hours ago, killairbus said:

Interesting, why is that?

-Angelo Busato

You can ask Boeing for this 🙂 As far as I know this is the case on all Boeing planes.

[rcoultas 21]

16 hours ago, killairbus said:

Interesting, why is that?

-Angelo Busato

Not sure why, but more common than  you think.  The CRJ works in the same manner.

[berts 97]

19 hours ago, killairbus said:

Interesting, why is that?

-Angelo Busato

I believe it is because these lights are an integral part of the Engine Fire/Overheat detection system and not merely simple Indication lights.  As such, their sole purpose is to illuminate only when there is a fire in the associated engine, or during the fire/overheat test.  Pushing the FIRE/OVHT TEST ENG switch actually introduces a fire/overheat signal into the Engine Turbine overheat detectors. 

[Qavion2 39]

On 12/27/2018 at 9:21 AM, berts said:

Pushing the FIRE/OVHT TEST ENG switch actually introduces a fire/overheat signal into the Engine Turbine overheat detectors.  

Technically speaking, the test induces an artificial fire signal in the AFOLTS* cards, not the overheat detectors themselves.

*Automatic Fire/Overheat Logic Test System

The turbine overheat detectors are only found on the RB211. These are overheat "switches", which talk directly to the AFOLTS (computer) cards.

The normal (cowl) fire detectors (or "loops" as they are known) are found on all engine types. The loops feed into specialised detector cards. These determine if the signals from the loops are faults or fires. The detector cards then talk to the AFOLTS cards.

The AFOLTS cards process test pushbutton and fire/fault signals and then send signals to the rest of the aircraft to produce lights, bells and messages.

There are very few indicator lights on the flight deck which are not illuminated by the Master Dim and Test System. The engine/APU fire and squib tests lights are some of these (including the fire handles). Other lights that come to mind are the big orange EVAC light on the pedestal and the Stab Greenband forward/aft lights.

On some Boeing aircraft, some light tests may be affected by the configuration of aircraft switches.

 

 

[berts 97]

On 12/30/2018 at 1:54 AM, Qavion2 said:

Technically speaking, the test induces an artificial fire signal in the AFOLTS* cards, not the overheat detectors themselves.

*Automatic Fire/Overheat Logic Test System

The turbine overheat detectors are only found on the RB211. These are overheat "switches", which talk directly to the AFOLTS (computer) cards.

I agree and should have obviously explained this in more detail!