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extricate
14th Oct 2018, 16:28
Hi there,

B777 type - This is a hypothetical question but just want to hear your thoughts. It involves some system knowledge too. If right eng suffers fire, after fire is extinguished, left eng fails and can't be restarted, will you try to start the right eng considering the urgency?

Side ques:

With regards to the Eng Fire Switch, are those below actions irreversible?

In (normal position, mechanically locked) – unlocks automatically for a fire
warning, or when the FUEL CONTROL switch is in CUTOFF.
Out –
• arms both engine fire extinguishers
• closes the associated engine and spar fuel valves
• closes the associated engine bleed air valves
• trips the associated engine generators off
• shuts off hydraulic fluid to the associated engine–driven hydraulic pump
• depressurizes the associated engine–driven hydraulic pump
• removes power to the thrust reverser isolation valve.

Goldenrivett
14th Oct 2018, 17:54
will you try to start the right eng considering the urgency?

I can't find the report to BA Flight 9 June 1982, but seem to remember the first engine which failed (No 4) was shut down using the "Fire Engine Checklist" which involved pulling the Fire Handle. After all 4 engines had failed, No 4 was the first one to successfully be re-lit.
Volcanic Ash Forces British Airways Flight 9 To Land (http://avstop.com/news/Volcanic_Ash_Forces_British_Airways_Flight_9_To_Land.htm)

BAengineer
14th Oct 2018, 20:37
With regards to the Eng Fire Switch, are those below actions irreversible?



The only things that are irreversible are tripping the IDG (needs re-connection on the ground) and firing either (or both fire bottles)

tdracer
14th Oct 2018, 21:01
Going from memory here, but restoring the fire handle to the normal position re-opens (or at least re-enables) everything that was isolated when the fire handle was pulled.
I know that the fuel valves will reopen, not absolutely sure about bleed and hydraulics. There was a rather infamous incident years ago on the Boeing flight line where, after a pre-delivery check flight, the operator pilot shutdown all four engines on a 747-400 via the fire handles. Problem was, he then restored the fire handles without setting the fuel control switches to cutoff, which reintroduced fuel into still hot engines as they were still spooling down. Massive tailpipe fires and major turbine damage was the result. Whoops...

Wizofoz
14th Oct 2018, 21:33
Yes, putting the Engine Fire Switches back down resets all valves and switches.

In answer to your question, I'd try a re-start if a suitable landing site was not in gliding distance.

galdian
15th Oct 2018, 04:03
Why wouldn't you try a start regardless of whether there's a suitable landing place within gliding distance or not?

Gliding in you've only got one chance to get the profile reasonably correct - no repeats allowed!

One engine running gives options.
Options damn fine things IMHO!

B2N2
15th Oct 2018, 13:34
Let me be a stick in the mud here for a second.
Engine shut down as a result of fire and fire handled pulled.
Resetting the fire handle and relighting the engine would result in an engine fire...very likely, which means it will take you to the site of the crash.

VinRouge
15th Oct 2018, 15:30
Let me be a stick in the mud here for a second.
Engine shut down as a result of fire and fire handled pulled.
Resetting the fire handle and relighting the engine would result in an engine fire...very likely, which means it will take you to the site of the crash.


Not necessarily true on a podded engine with decent airflow. And depends upon what started the fire. HYD leak for example could subside . HYD pumps would run dry, however the engine would still be producing. I think in an unlikely circumstance like this, anything that has applied logic to it is worth a shot.

Whinging Tinny
15th Oct 2018, 18:18
Skydrol is fire resistant and pretty hard to ignite let alone sustain a flame.

GE90 PW4000 EDPs are under the t/revs attached to the accessory g/box, there is a titanium heat shield to prevent any combustable fluids spraying on to the hot section and protect the g/box from heat.The area is cooled and ventilated by fan air and LP compressor air.

Trent EDP under the fan cowls - area cooled and ventilated via ambient.

Engine hydraulic fire?
I'd doubt it.

VinRouge
15th Oct 2018, 19:14
Skydrol is fire resistant and pretty hard to ignite let alone sustain a flame.

GE90 PW4000 EDPs are under the t/revs attached to the accessory g/box, there is a titanium heat shield to prevent any combustable fluids spraying on to the hot section and protect the g/box from heat.The area is cooled and ventilated by fan air and LP compressor air.

Trent EDP under the fan cowls - area cooled and ventilated via ambient.

Engine hydraulic fire?
I'd doubt it.
Engine TR hydraulic feed split near the jet pipe. There are things on the engine that use HYD pressure too. And you better believe skydrol, atomised as it exits a spit pipe and onto a hot section of an engine can spark.

https://www.fire.tc.faa.gov/pdf/tn90-19.pdf

galdian
15th Oct 2018, 21:46
Wasn't being specific about the fire cause, just interested in any thoughts of pro's/cons in restarting.

I'm assuming the 777 same as 737 with 2 bottles that can be fired in sequence as/if required.

If you'd had a fire but only fired one bottle - why wouldn't you try a restart?
If you'd had a fire and had fired BOTH BOTTLES to extinguish? Now the question gets more interesting.

Apologies if the 777 is a very different system to the 737.

tdracer
15th Oct 2018, 22:14
Wasn't being specific about the fire cause, just interested in any thoughts of pro's/cons in restarting.

I'm assuming the 777 same as 737 with 2 bottles that can be fired in sequence as/if required.

If you'd had a fire but only fired one bottle - why wouldn't you try a restart?
If you'd had a fire and had fired BOTH BOTTLES to extinguish? Now the question gets more interesting.

Apologies if the 777 is a very different system to the 737.

It's similar - one bottle each side which can be fed to either engine (it's pretty standard Boeing design philosophy).
I suppose it's a judgement call, but best case you're looking at something around 100 mile glide range for a complete power loss at cruise altitude (obviously dependent on how high and how heavy, but 100 miles is a good rule of thumb). But if you previously shut one engine down and you've already dropped down to the engine out cruise altitude then your potential range will be quite a bit less. So if you don't have sufficient range to make a runway, restarting the 'fire' engine is at least worth consideration. If the fire warning went out shortly after shutdown (without firing a bottle), there is a good chance it's a pneumatic leak or possibly even a false alarm where there is little harm in restarting (the detection systems have gotten better, but we did a study during the 777 development on fire warnings - the number of false alarms was roughly the same as the number of actual engine fires).
OTOH, if you had to fire both bottles to eliminate the fire warning, restarting that engine could well just make things worse.

BluSdUp
15th Oct 2018, 23:02
First, put the fire handle back and it all works.

Second , A fire goes out when, Fuel lever to cut off or when fire handle is pulled or when first squib is fired or after 30 seconds plus after second squib is fired.
We do not know in this example.

Here is my take.
Start regardless.Unless You are Canadian! ( Gimli , Azores)

If getting to an airport , the Firebrigade will put out any potential or real fire.

If over water or remote area the engine will separate , most likely, and a controlled touchdown makes all the difference.

And if the sucker stays quiet You are a Hero.
I am not a gambler, but I take the odds of this one not burning the wing off.
If not reset sim!

Regards
Cpt B

NSEU
15th Oct 2018, 23:30
The only things that are irreversible are tripping the IDG (needs re-connection on the ground) and firing either (or both fire bottles)

Pilots don't disconnect the IDG for an engine fire. They only trip the generator fields (by pulling the fire handles).

Whinging Tinny
16th Oct 2018, 03:30
Engine TR hydraulic feed split near the jet pipe. There are things on the engine that use HYD pressure too. And you better believe skydrol, atomised as it exits a spit pipe and onto a hot section of an engine can spark.

https://www.fire.tc.faa.gov/pdf/tn90-19.pdf

There are no hydraulic components in the hot section of the engine.
Why would there be?

The t/rev components are on the forward face of the C duct and the pipelines go via the pylon.
Any pipework into the t/rev is contained in the C duct housing itself and sealed from the engine when closed.
Go and have a look at a fully opened engine and you will see.

Read my quote again about Skydrol............doesn't say it can't be ignited, but says difficult to and hard to sustain a flame.

Pleease tell me what uses hydraulics on the engine because I'm curious.

The EDP supplies aircraft hydraulics and the t/revs utilise hydraulics to work, what else?

FullWings
16th Oct 2018, 13:27
If right eng suffers fire, after fire is extinguished, left eng fails and can't be restarted, will you try to start the right eng considering the urgency?
Yes?

There are some scenarios where I might give consideration to leaving it alone but they would normally involve an assured safe landing. Remember that with jets an engine fire indication doesn’t mean that the wing is engulfed in flames, just that the temperature somewhere inside the nacelle has gone over a pre-defined limit, which can be as low as 250C (IDK what the GE/RR/P&W on the 777 use). It could even be a false warning, although with dual loops this is much less likely.

Considering the remote and/or unlandable areas a LH aircraft like the 777 often flies over, the chances of surviving the dead-stick landing/ditching *and* the subsequent waiting around for someone to rescue you could be fairly slim. Even if the restarted engine gives more warnings, as long as it produces thrust I’d be minded to keep it running while I headed for an alternate...