777 Loses Engine Parts Over Denver

[JRBarrett 3,048]

4 hours ago, psolk said:

but the biggest concern for me is why the extinguisher system did not "extinguish" the fire.  Had they been somewhere they could not have returned immediately and that fire continues to burn uncontrollably we most likely have a total loss.  Either that or we see some WWII bomber type extinguishing going on!!  

The fire extinguishing system depends on the cowl surrounding the engine being relatively intact. It discharges halon gas into the space between the external engine structure and cowl. With the cowl missing, the gas would just be immediately swept away by the slipstream.

[psolk 3,037]

1 hour ago, JRBarrett said:

The fire extinguishing system depends on the cowl surrounding the engine being relatively intact. It discharges halon gas into the space between the external engine structure and cowl. With the cowl missing, the gas would just be immediately swept away by the slipstream.

Good point and we don't know if that is fresh fuel being burnt (aka fuel cutoff didn't work or was severed) of just the remaining fluids from lines that were torn apart... 

[scott967 62]

With the massive fans on these twins, vibration induced from imbalance seems like a real issue for the plane maker to deal with.

 

scott s.

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[Matthew Kane 1,343]

4 hours ago, psolk said:

Good point and we don't know if that is fresh fuel being burnt (aka fuel cutoff didn't work or was severed) of just the remaining fluids from lines that were torn apart... 

All though this video looked scary but to be honest that fire was contained within the engine area and never spread anywhere else, with that kind of damage it may have been impossible to shut off the fuel entirely. Goes to show the durability of the 777 once again

Edited February 23, 2021 by Matthew Kane

[Matthew Kane 1,343]

Worth Watching:

 

[Chock 17,769]

4 hours ago, Matthew Kane said:

All though this video looked scary but to be honest that fire was contained within the engine area and never spread anywhere else, with that kind of damage it may have been impossible to shut off the fuel entirely. Goes to show the durability of the 777 once again

To be honest I think the flames - whilst undeniably looking quite dramatic, were the the lesser problem than the damage occurring as the engine lets go and the control difficulties thereafter. The footage of this most recent incident appeared to show the engine vibrating quite a lot, presumably from an unbalanced fan, which would obviously be putting a fair bit of strain on the mounting bolts. In addition to this, as we know, the shrapnel from the departing engine and cowling parts caused a fair bit of damage to the structure of the aeroplane, as well as causing it to shower debris over a town, as it usually is in such cases. After that you've got a big lump doing not much other than creating drag, particularly when it's the only engine on that side of the aeroplane, and so it's handling that becomes the tricky bit.

It's fortunate too that lessons learned from the fatal crash of American Airlines DC-10 Flight 191 at Chicago O'Hare, and the crash landing of United Airlines Flight 232 (another DC-10) at Sioux City, both of which were principally caused by control difficulties as a result of damage to hydraulics from engines either fracturing, or departing completely in the case of Flight 191, has meant that now aeroplanes are designed to seal off the hydraulics if a fracture in the system is caused. Not that, as far as I know, there were any hydraulic lines damaged in the most recent incident, but it's obviously a possibility with such misadventures.

However, as scary as all this is, like you say it is remarkable that these engines are durable enough that the cowlings and casings of these huge things can manage to stop a good deal of shrapnel which has a lot of energy. I don't know exactly how fast a departing fan blade would get fired out from an engine doing high RPMs, but I do know the tips of the fan blades can easily be traveling at around Mach 1.5, so if they depart at full throttle and retain that speed as they fly off, they're potentially hitting a structure which is already resisting a 500 mph wind, with the energy similar to that of many rifle bullets.

[martin-w 3,234]

9 hours ago, Chock said:

 After that you've got a big lump doing not much other than creating drag, particularly when it's the only engine on that side of the aeroplane, and so it's handling that becomes the tricky bit.

 

 

I'm just wondering how the autopilot would behave in that scenario? I mean its not like an engine slowly spooling down and still generating residual thrust. Rather, this is a sudden and complete loss of thrust. So if the autopilot is engaged would it automatically disconnect, or attempt to trim out the sudden extreme yaw?

In manual flight, no auto rudder trim on the 777, or the Airbus of course, so purely down to the pilot.

Edited February 24, 2021 by martin-w

[jon b 2,041]

It’s not the autopilot strictly speaking but the FBW system that will handle things.

The 777 has the same thrust  asymmetry protection (TAP) system as the 787, the FBW will apply the rudder and ailerons as required To keep the aircraft straight, so there is little difference in the handling of the aircraft really. It’s quite different to a 747 with both engines on one wing out , that’s a real handful (and foot full ! )

[Christopher Low 5,341]

I remember that happening on the 747 that crashed into a block of flats close to Amsterdam Schiphol

[martin-w 3,234]

38 minutes ago, jon b said:

It’s not the autopilot strictly speaking but the FBW system that will handle things.

The 777 has the same thrust  asymmetry protection (TAP) system as the 787, the FBW will apply the rudder and ailerons as required To keep the aircraft straight, so there is little difference in the handling of the aircraft really. It’s quite different to a 747 with both engines on one wing out , that’s a real handful (and foot full ! )

 

Oh right, I didn't realise that. With the Boeing FBW philosophy of more pilot control (compared to Airbus) I assumed it would leave it to the pilot. 

[jon b 2,041]

For large power asymmetry and engine failure on take off it’ll back drive the  rudder pedals a small amount  so  know what it’s up to and can recognise the problem .

[fluffyflops 1,847]

Long-tail aviation also had a similar problem in Liege, the same day. 

[WingZ 547]

I am wondering if there is any correlation with an engine having been being mothballed?

It's quite a big ask to get precision machinery carrying on with Business as Usual after sitting about for an extended period.

[Chock 17,769]

9 hours ago, WingZ said:

I am wondering if there is any correlation with an engine having been being mothballed?

It's quite a big ask to get precision machinery carrying on with Business as Usual after sitting about for an extended period.

Seems more likely that it's potentially a manufacturing defect on fan blades given the fact that they were grounding all aeroplanes with that powerplant and even looking at aeroplanes which were parked up and which have not been operating at all. There has been an early suggestion that it may have been the processes which give the fan blades a protective coating during manufacture which caused a weakening of the titanium, but this isn't yet confirmed.

[martin-w 3,234]

New information is emerging. Seems TWO of the engines fan blades were ripped off. Both showed signs of metal fatigue.

 

New Details Emerge About Boeing 777 Explosion Ove…: https://youtu.be/Mhm0_rYsy-Y