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Posted

Maybe some of the jet jocks here can opine on why it burned for so long.   I'd have thought shutting off the fuel would be a priority in that situation.   On some (many?) jets arming the fire system is supposed to disconnect the fuel, hydraulic, electric, etc., on the selected engine, but I don't know if that's true on a 777.

 

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Posted
7 minutes ago, EricJ said:

Maybe some of the jet jocks here can opine on why it burned for so long.   I'd have thought shutting off the fuel would be a priority in that situation.   On some (many?) jets arming the fire system is supposed to disconnect the fuel, hydraulic, electric, etc., on the selected engine, but I don't know if that's true on a 777.

 

Was thinking the same thing, maybe the oil system?

Posted

By trying to make airplanes lighter they use materials that have some weaknesses that can lead to this kind of failures.

Yves

Posted
4 minutes ago, yvesg said:

By trying to make airplanes lighter they use materials that have some weaknesses that can lead to this kind of failures.

Yves

Now let’s not bad mouth the light weight weight materials. The company I work for makes a lot of machines For Hexcel. We have that stuff all over the place. 
 

The stuff is amazing, you can take a 4 foot square piece, 1 inch thick and hold it out at arms length with no effort.

Posted (edited)

Pulling the fire handle will close fuel, hydraulic, and bleed Shut Off Valves. I assume it's residual burning. The video clip I saw was only a few seconds. 

I had an engine failure 15 years ago. A guide vane came off a turbine wheel and shot everything out the back of the engine. The fire warning never came on in the cockpit. Once on the ground, all we could see was a little smoke. Yes, we ran the emergency checklist for severe damage/fire, it's the exact same. It was weird pressing a fire button that never lit like it does in the SIM.

Edited by Rjfanjet
Added info.
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Posted

There are engine failures that sometimes cut the controls to the fire switch. The Qantas A380 incident comes to mind where after safely landing the airplane the crew could not shut down number 1 engine. The ground fire crew tried flooding it with water but that didn’t work. Finally they used a foam agent and got it shut down but it was almost an hour after touchdown by then.  

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Posted

My guess is that was a failure of the CSD (Constant Speed Drive aka gear accessory drive). N1 is still spinning and appears all blades are present. If I remember correctly the CSD cases are made out of magnesium and can burn. I’m not a mechanic and never flew the 777. Just a guess. We had a CSD fire once on a DC8 on takeoff before V1. Burned for a while even after the fire department doused it. Water makes magnesium fires worse by releasing hydrogen gas.

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Posted

Glad this didn't end in tragedy as did the Southwest 737 in 2018 that lost a fan blade causing engine and cowl fragments to penetrate the fuselage, including a cabin window, killing a lady seated next to that window.

More often than not, a safe return with no one hurt is accomplished, but the potential to hurt or kill someone on board or on the ground is real.

Well done to the flight and cabin crew.

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Posted (edited)
On 2/21/2021 at 1:26 AM, EricJ said:

I'd have thought shutting off the fuel would be a priority in that situation

This was ground testing of a brand new aircraft where engine was stuck running for 10h due controls malfunction after a series of human errors (putting wheel chocks to start with)

http://news.bbc.co.uk/2/hi/europe/7098547.stm

There was another one by AF B747 but it was an electrical failure, 

I am not sure if crew are allowed to make “quick shutdowns before losing control” but surely cutting fuel would be the quickest way, the biggest risk is usually shutting down the live engines before understanding what’s going...

On testing benches, you can just cut it off after glitches but crew don’t have that luxury while in the air 

Edited by Ibra
Posted

It burned a while because:

It takes time to run the check list.

The fire loop burned through because likely there was no fire warning, fire loops were destroyed.

The fuel control cutoff was damaged, so when you activate the fire switch, it cuts off at the spar valve so you have a lot of residual fuel making its way through the system

The halon manifold was probably destroyed, but even if intact a little hard to get a halon concentration in a 200 knot slip stream with no cowl.

On a pylon hung engine, it can burn forever, it can burn until the engine falls off and the airplane is not in danger. There is no reason on a jet aircraft to get in a hurry. Move methodically correctly identifying and verifying the correct fire switch and bottles. 

To expand on V1VrV2's theory of CSD magnesium fire here is how hard that is to put out:

 

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Posted
7 hours ago, Mark89114 said:

Looks like it did lose a blade.  The blade also penetrayed up through the fuselage and wing root.

153477497_3733473023395437_7326827992586333430_o.jpg

Are all modern turbofan blades hollow like this?

Yves

Posted
12 minutes ago, yvesg said:

Are all modern turbofan blades hollow like this?

Yves

No, not all. In fact in this thrust range the P&W is the only one with hollow blades. One of the reason the Emergency AD only covers P&W engines.

 

 

Posted

Some turbine stator and rotor vanes are hollow, too.   Bleed air is forced through them for cooling.

That's interesting that a separated fan blade would result in that kind of damage.

 

Posted
4 hours ago, GeeBee said:

To expand on V1VrV2's theory of CSD magnesium fire here is how hard that is to put out.

Anybody old enough to remember burning VW engine cases in camp fires knows this.  ;)

Typical Class D fire.

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Posted
5 hours ago, EricJ said:

Anybody old enough to remember burning VW engine cases in camp fires knows this.  ;)

Typical Class D fire.

Don't do it at the Imperial Sand Dunes. The gendarmes will hunt you down! They will get there before it goes out!

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