Engine Fire Loop Alert

Gulfstream G450

Eddie sez:

This can be confusing, so let's reason it out.

  • If you get the Engine Fire Loop Alert CAS message with one of the engine fire test switch capsules illuminated, that means the one loop on the indicated engine says there is a fire but the other loop disagrees.
  • You test the system which checks both loops on both engines.
  • If all the lights illuminate that means all four loops think they are okay, including the faulty loop. But it is faulty, what does it know? You can disable it and now rely on the remaining loop.
  • If one of the loops fails to test that means one of the loops is correctly reporting a fire and the other is incorrectly not reporting it. You have a fire.

Everything here is from the references shown below, with a few comments in an alternate color.

Last revision:


Engine Fire Loop Alert


Engine Fire Loop Alert

Just the CAS, no light in the fire handle or fuel control switch.



Since engine fire warning (FIRE handle lights and FUEL CONTROL switch Lights) are dependent upon sensing fire / overheat in both loops simultaneously, the possibility exists that a loop could fail undetected or un-annunciated, or that a system fault could develop which causes a signal output similar to a fire warning (i.e., lighted LOOP A or B red fire test light), but not both. In these cases, fire could develop without triggering fire warnings, or false fire test light could result, again without fire warning. The pilot would be alerted to a single activated fire loop by a LOOP switch segment illuminated red on the FIRE TEST switch on the cockpit overhead panel, coupled with an Engine Fire Loop Alert warning message displayed on CAS, and the associated tones. Should this occur, re-test the system. If the system does not check properly, the loop has failed and the fire indication is genuine; execute the appropriate Engine Fire checklist. If the system does check properly, the LOOP warning is false; disable the faulty loop.


[G450 AFM, § 4-11-10]

    In the event of a single FIRE TEST LOOP light:

  1. FIRE TEST Switch For Illuminated Loop ... DEPRESS AND HOLD
  2. If normal fire test indications ARE displayed:

  3. FIRE TEST Switch light ... RELEASE
  4. FAULT Switch on FIRE DETECTION Panel for Illuminated Loop ... DISABLE
  5. If normal fire test indications ARE NOT displayed:

  6. FIRE TEST Switch ... RELEASE
  7. Applicable Engine Fire (In Flight or On Ground) Checklist ... COMPLETE
  8. NOTE: See Engine Fire In Flight, or Engine Fire On Ground.

Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013