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And now the Boeing 777...
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coppercone2:
how does it stay burning at 600mph? it must be either very flammable, very hot or pilot lighted by something

is the engine like still sustaining itself by oil dripping into the middle and igniting and the flame being pushed out to make it look like its on fire on the outside despite the outside not burning? i.e. combustion occurs in the same place as it does with the fuel but instead occurs with residual oils but the amount of fire is excessive so it gets pushed out, operating kinda like a reflux condenser, in terms of liquid being sucked into the middle then fire being pushed out, not in the sense of condensation?
tom66:
An explanation I heard was that hydraulic fluid or oil is present in that area.  The significant internal failure of the engine may have ruptured some pipes and the engine is consuming those fluids. 

However I don't know if the engines have independent hydraulic fluid supplies for the thrust reverser and any other actuators, because I don't recall the pilots reporting a hydraulics failure.
drussell:


Also of note:


--- Quote ---Hey Juan, really enjoy your reporting.  I'm a career engineer here at P&W in East Hartford.  Dialed in to a zoom call with out President (Chris Calio) today and he stated all Hollow Fan Blade segments have been recovered and are in our lab in East Hartford.  Just passing this along, thanks.
--- End quote ---
coppercone2:

--- Quote from: tom66 on February 24, 2021, 07:17:27 am ---An explanation I heard was that hydraulic fluid or oil is present in that area.  The significant internal failure of the engine may have ruptured some pipes and the engine is consuming those fluids. 

However I don't know if the engines have independent hydraulic fluid supplies for the thrust reverser and any other actuators, because I don't recall the pilots reporting a hydraulics failure.

--- End quote ---

do they end up having thrust from the oil being leaked into them?
ve7xen:

--- Quote from: coppercone2 on February 24, 2021, 06:55:24 am ---how does it stay burning at 600mph? it must be either very flammable, very hot or pilot lighted by something

is the engine like still sustaining itself by oil dripping into the middle and igniting and the flame being pushed out to make it look like its on fire on the outside despite the outside not burning? i.e. combustion occurs in the same place as it does with the fuel but instead occurs with residual oils but the amount of fire is excessive so it gets pushed out, operating kinda like a reflux condenser, in terms of liquid being sucked into the middle then fire being pushed out, not in the sense of condensation?

--- End quote ---

The aircraft isn't travelling at 600mph, nor is its indicated airspeed (which would represent how much the fire 'feels' the air) 600mph. They would've been at an IAS of about 280kts or 322mph. Ground speed would have been somewhat higher, maybe 320kts. They were fairly low in the climb, not at altitude in cruise.

Where you see the fire emanating from is the thrust reverser 'translating sleeve' with many vanes to redirect the air to the rear. The thrust reverser doors appear to be closed, so no significant airflow from the fan duct (or fuel or anything else from the engine core) can reach this area in this configuration. Since the purpose of these vanes is to direct air rearward, the pockets are 'out of the wind' so to speak, and yeah maybe there is an element of negative pressure helping to suck fuel from whatever the fuel source is. From the reports so far, it doesn't sound like there were any major fuel leaks and the fuel shutoffs worked as designed, so I'd guess this is either residual fuel from ruptured lines or hydraulic oil, possibly from the TR mechanism itself, but could be anything mounted on the outside of the engine. This will be a focus of the investigation for sure.

It's definitely not that you're seeing combustion in the core, the TR doors are closed, and even if they were open, you'd only see inside the fan duct, not the core. Any flame you might observe (extremely unlikely) inside the combustion chambers due to catastrophic damage would be much deeper inside the engine than is observed here which is clearly near the surface. If that were happening, you'd probably see it inside the fan duct as well from the front/rear.

Thrust from this would be negligible, it's clearly not a very significant amount of fire, and it's happening in 'free air'.
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