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Nick Dobda

Accidental discharge left fire bottle

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So like the title says while checking APU fire protection prior to startup, I accidentally discharged the left engine fire knob, the big red one. I figured go to maintenance menu and service the aircraft... which I did. And yes the green fire bottle indicator came back to life.

 

Problem solved..

 

OR so I thought?

 

After pushback and starting left engine... well trying to start the left engine - when it comes time to give it fuel... well... nothing. No fuel flow.

 

After some thought, I figure it must be connected to the firebottle discharge. Sorry folks.. taxi back to the gate... see you next time (if I still have a job).

 

Anyway, am I right? Is that why it wouldn't start? I'm quitting for the night, It's too late to start fresh again.

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And once ya get that handle pushed back in just defer the bottle - better yet - get the off-base engineer to swap it with the APU bottle and just defer the APU fire protection. ;)

 

PMDG should really include a MEL with their docs!

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PMDG should really include a MEL with their docs!

 

They kind  of  have its called  a QRH  

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So like the title says while checking APU fire protection prior to startup, I accidentally discharged the left engine fire knob, the big red one. I figured go to maintenance menu and service the aircraft... which I did. And yes the green fire bottle indicator came back to life.

 

Problem solved..

 

OR so I thought?

 

After pushback and starting left engine... well trying to start the left engine - when it comes time to give it fuel... well... nothing. No fuel flow.

 

After some thought, I figure it must be connected to the firebottle discharge. Sorry folks.. taxi back to the gate... see you next time (if I still have a job).

 

Anyway, am I right? Is that why it wouldn't start? I'm quitting for the night, It's too late to start fresh again.

When you engage the engine fire handle, it does several things: the spar valve closes, shutting off the engine fuel supply, the bleed air valves close, the generator is shut off, as is the hydraulic pump. All these things are done to completely isolate the engine from the rest of the aircraft systems in case it really is on fire.

 

If you accidentally discharged the extinguisher, you would need to reset the fire handle (push it in) in addition to using the maintenance menu to "refill" the fire bottle.

 

On a real aircraft, if an extinguisher is discharged, it has to be physically removed and a replacement unit installed, as it cannot be refilled on the aircraft. The empty extinguisher has to be returned to the manufacturer to have a new pressure disk fitted, refilled with pressurized halon and leak checked, and a new explosive squib installed.

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When you engage the engine fire handle, it does several things: the spar valve closes, shutting off the engine fuel supply, the bleed air valves close, the generator is shut off, as is the hydraulic pump. All these things are done to completely isolate the engine from the rest of the aircraft systems in case it really is on fire.

 

This is kind of what I was looking for, thank you.

 

I am not 100% sure if I pushed the handle back in... I thought I did.  So if I'm understanding, you think if I would have reset the fire handle the engine would have started?

 

You mention the bleed air valves close, I was able to get the apu bleed air to spin the motor to start, just didn't get any fuel flow when I turned the fuel on. How does everything get reset to un-isolate the engine? Does simply resetting the fire handle bring everything back to normal?

 

 


just defer the bottle

 

Can you do this in the PMDG or is this just what you would do in real life?

 

What about all that fire extinguisher chemical sprayed throughout the engine... that cant be good? Would they have to take apart the engine to clean it out? I was looking for a non-realistic way to continue with the flight in the sim since it was just a stray mouse click that did me in... in real life I would have thought the flight is over and theres nothing you can do about it. 

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in real life I would have thought the flight is over and theres nothing you can do about it.
Plus, I would imagine whoever pulled the fire handle gets his final paycheck within a couple of hours.

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This is kind of what I was looking for, thank you.

 

I am not 100% sure if I pushed the handle back in... I thought I did. So if I'm understanding, you think if I would have reset the fire handle the engine would have started?

 

You mention the bleed air valves close, I was able to get the apu bleed air to spin the motor to start, just didn't get any fuel flow when I turned the fuel on. How does everything get reset to un-isolate the engine? Does simply resetting the fire handle bring everything back to normal?

 

 

Can you do this in the PMDG or is this just what you would do in real life?

 

What about all that fire extinguisher chemical sprayed throughout the engine... that cant be good? Would they have to take apart the engine to clean it out? I was looking for a non-realistic way to continue with the flight in the sim since it was just a stray mouse click that did me in... in real life I would have thought the flight is over and theres nothing you can do about it.

Yes, resetting the handle should re-energize the various valves and solenoids that shut off fuel and other connections. The bleed air OUTPUT of the engine is shut off by the fire handle, because if a real fire exists, you would not want the engine discharging flame into the bleed air ducts. The bleed air supply to the engine starter is an INPUT, that does not connect to the internal parts of the engine, so it would not be closed off by the fire handle.

 

The most single most important thing that gets shut off by the fire handle is the engine fuel supply. If a real fire exists, one would not want additional fuel coming in to feed the fire.

 

Inspection requirements after an accidental discharge vary by manufacturer. The extinguishing agent does not get injected inside of the engine itself - it is discharged into the space between the external engine case and the cowl. The engine, of course, is designed to have a fire burning "inside" in normal operation. The danger exists when that fire breaks through the case and gets outside of the engine - which often happens if there has been a disintegration of internal moving parts (turbine blade failure or the like).

 

The Halon agent usually employed can indeed be corrosive - especially to certain types of rubber or plastic. The Halon is stored as a liquid in a pressurized tank at about 600 psi. When it is released, it expands into a gas (or more correctly a fine mist). In the case of an accidental discharge, maintenance manuals will usually require that the engine cowling be removed, and the engine case and external accessories be inspected for any residual liquid Halon, and cleaned as necessary.

 

The fire extinguishers definitely can NOT be deferred under an MEL. They are considered to be a critical-to-safety component, and must be fully functional at all times if the engine is to be run.

 

It MIGHT be possible to "borrow" the APU extinguisher IF it is the same type used on the engine (often the APU extinguisher is a completely different make and model than the one on the engine). But if this were done, the APU would have to be disabled so that it could not be started, as no aircraft manufacturer would permit an APU to be operated without a fully functional extinguisher connected.

 

In this scenario, you would have to use an external engine start cart to supply pressurized air to start the first engine, as there would be no way to use the APU to supply bleed air.

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The most single most important thing that gets shut off by the fire handle is the engine fuel supply. If a real fire exists, one would not want additional fuel coming in to feed the fire.

 

Cue the old Prodigy track...

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Cue the old Prodigy track...

 

Which one?

 

Firestarter (Fuel)

Breathe the Pressure (APU bleed air)

Smack my B up (the pilot getting the business after explaining what happened to the boss)

Take Me to the Hospital (after explaining to the wife you're out of the job). 

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Which one?

 

Firestarter (Fuel)

Breathe the Pressure (APU bleed air)

Smack my B up (the pilot getting the business after explaining what happened to the boss)

Take Me to the Hospital (after explaining to the wife you're out of the job). 

 

haha - glad someone got that.

 

Given the line I quoted, it was a reference to Firestarter. The rest you added are actually pretty clever - nicely done.

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Which one?

 

Firestarter (Fuel)

Breathe the Pressure (APU bleed air)

Smack my B up (the pilot getting the business after explaining what happened to the boss)

Take Me to the Hospital (after explaining to the wife you're out of the job).

Nice :)

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