B737-300 Engine Fire

[Flying_Tuur]

Hi everybody,

If you have an engine fire on the B737, and the fire extinguishes, is there a possibility that the Fire Loops have failed because of the fire, e.g. burned in the engine pylon?? If this is possible, you would have NO engine fore warning indication anymore, but the fire is NOT out... You can only assume that the fire is out after a fire warning test which is ok, and therefor you can assume the fire loops are still intact...
Is this scenario one bridge too far, or is it in reality a good idea to do an engine fire warning test after a fire is supposed to be extinguished, just to be sure..???

Many thanks,

FT

[7p3i7lot]

Not only is it a good idea it is in our checklists and FOM (flight manual).
If it doesn't test consider getting some smart eyeballs on the engine and/or shooting the second bottle to it. Land ASAP:O

[LEM]

Flying_Tuur, I don't think the Kidde loops can be burned .
You mean melted ? Impossible, I think. Of course they could melt after an hour at those temperatures, but certainly not in 30 seconds!
And even if severed somewhere they will still work (the signal is between the two wires, not between one extremity to the other).
Boeing is considering nowhere such a possibility in the manuals.
No test required after the warning has extinguished.
Of course, very academically, the loop could fail at the worst possible moment, but...

7p3i7lot , somebody in your company must be smarter than Boeing...

[DanAir1-11]

LEM, with all due respect, I beleive anyone in our industry should
never say never. Anything IS possible, highly improbable with odds at millions to one maybe, but never impossible. Priot to Sioux City, most would have viewed total loss of primary and redundant hydraulics "impossible" in the 10, indeed the manuals had no contingency, but that happened. As aviation professionals, we have an absolute obligation as far as safety is concerned, again I mean this respectfully, but we cannot ever become complacent in any aspects of flight operations.

Best regards

[LEM]

Generally speaking I agree, of course.
But sincerely I still think the loop cannot be melted in 30 seconds.

Anyway, as far as fire protection is concerned, you know we have two loops, A and B.
If one fails, it is automatically deselected, and the remaining one will perfectly work alone.
However , if you do the fire test it won't work! You'll have to troubleshoot by alternatelively select Loop A and then Loop B, to exclude the failed one.

I've never seen people doing a fire test after it has extinguished, and personally I won't change my SOP: that's basically because we have two loops, troubleshooting for the failed loop would increase the workload too much, and lastly because Boeing doesn't say so.

Don't get me wrong, I'm the first one not to blindly thrust the rules or the manufacturer's manuals.
More than once I've criticised some procedures established by test pilots who have some strange ideas.
Boeing too changed some of it's procedures and it's manuals through the years.
There's no absolute truth.

But in this particular case, I guess somebody in 7p3i7lot's Company's brass one morning had a brilliant idea, but forgot to consider all the consequences...

[Touch'n'oops]

If you loose BOTH loops, the FUALT light will illuminate. So a fualt test is not required!!!!

[Dr. Red]

That's right, if both loops fail a fault warning is generated.

See here: http://www.b737.org.uk/fireprotection.htm

There MAY be situations where the loops fail and the fault warning doesn't activate, but how likely that is I have no idea.

[SMOC]

I'm not sure about the 737, but this is from the A330 FCOM (RR T700)
The fire warning appears in case of :
-breaks in both loops occuring within 5 sec of each other (flame effect).

SMOC