777 down.

[Softus]

The chances of the engines dying just at the final approach (both of them) is greater odds than doing the lottery.

If you picked a set of lottery numbers, and then Dale Winton eliminated all but one other (hidden) permutation of numbers, what is the probability of the hidden set being more likely to win that your set?

And would that probability change if Dale had just given hand relief to a goat?

And what's the probability of Dale being 50:50?

 

[tim west]

As they used to say to Derek Nimmo, Oh Brother!

 

[empip]

PPrune through the back door, new thread on subject again !
http://www.pprune.org/forums/archive/index.php/t-309337.html

They will have covered every conceivable fault before they finish... All good fun.

 

[Softus]

PPrune through the back door, new thread on subject again !
http://www.pprune.org/forums/archive/index.php/t-309337.html[/QUOTE]
How does that 'back door' report differ from the one that's publicly available?

They will have covered every conceivable fault before they finish.

I disagree. That would be (a) impossible and (b) pointless. They'll stop when they find the fault and when they've made recommendations for preventing the fault from recurring.

 

[empip]

PPrune through the back door, new thread on subject again !
http://www.pprune.org/forums/archive/index.php/t-309337.html[/QUOTE]
How does that 'back door' report differ from the one that's publicly available?

They will have covered every conceivable fault before they finish.

I disagree. That would be (a) impossible and (b) pointless. They'll stop when they find the fault and when they've made recommendations for preventing the fault from recurring.

Because that address gets one 'in' - read only - useful when the main normal entry to PPrune is blocked... Which it has been on and off with the recent event.
http://www.pprune.org/forums/ try it first.

'They' in reference to the forum posters.. Not the investigation team.

-0-

 

[Softus]

Because that address gets one 'in' - read only - useful when the main normal entry to PPrune is blocked.

I completely misunderstood, and I apologise.

'They' in reference to the forum posters.. Not the investigation team.

I completely misunderstood, and I apologise.

And I agree.

 

[empip]

Just found these pictures...
Here posted by Maverick... He achieved some telling shots.
Left side

Right side engine.

Large edit following picture enlargement.

Left side front fan 'foils demolished at around the radius of the casing 'flat'... engine was running at some level on impact.

The visible fan blade tips on the right side engine look ok but not clear enough, if they are intact and undamaged it would not be far wrong to suppose this engine was under no power on impact.

Relationship - spinner to shaft to fan easily seen here
http://www.kembrey.co.uk/gallery/e_trent_800.jpg

 

[joe-90]

Wouldn't air pressure turn the blades like a windmill? It's damaged on the left engine as the case has a flat spot but doesn't appear to have a flat spot on the right engine. Therefore the spinning blade would have slowed naturally.

 

[empip]

Reasonably tight tolerances between the blade tips and inner casing we would be talking thousandths of an inch, not much distortion required for tip strike...
If a fan was 'freewheeling' then I would expect some damage maybe a few buckled blades... but not broken around the full circumference, that would require some power.
I have seen a few from military stuff - smaller diameter - Pieces broken out of Titanium fan foil with no visual sign of change in manufactured curvature !!

Imagine even 20% of the forces imaginatively described here :-
http://www.rolls-royce.com/education/schools/facts/default.jsp

 

[Softus]

If a fan was 'freewheeling' then I would expect some damage maybe a few buckled blades... but not broken around the full circumference, that would require some power.

I can hardly believe I'm being drawn in to this, but that's all a bit vague, empip.

The deflection of, or damage to, a blade, resulting from hitting the casing, would be in proportion to (a) degree of case intrusion, and (b) speed of blade.

If the impeller was under power, then it's reasonable to conclude that a small of case intrusion would be far outweighed by the energy being applied by the engine.

If the impeller was not under power, then the impact on each blade would have a slowing effect. Whether or not the impeller would stop rotating within one revolution, or continue being damaged, depends on the size and number of those impacts and the original rotational speed.

Apart from the general principles, all based on Newtonian physics, this is all subjective opinion, since we don't know any of the following:

. degree of case intrusion
. original speed of impeller
. whether or not the engine was running at all
. engine torque (if it was running)

Bear in mind, though, that the first stage blades, although small[er], are really quite strong, viz:

The force on the small first stage turbine blade is about 10 tonnes. This is equivalent to hanging a double-decker London bus on each blade.

 

[empip]

We are none of us experts and of course it is all subjective opinion.

Think about containment, the case must be able to contain a pretty hefty breakup, therefore it is pretty strong from a penetration point of view, deflect the case enough and the blade tips will rub, with no power applied, merely windmilling they would pretty soon brake to a halt.

I reckon the visibly broken bladed engine was under some unknown amount of power when it impacted the ground... Blades don't shatter under windmilling.

The other engine appears to have intact fan blades but the picture is not too clear.

Yep, the first stage turbine blades are quite small unlike the first stage compressor fan blades at the sharp end with near 3m diam. hole to fill.

-0-

 

[megawatt]

I would expect the momentum of the fan spool to be sufficient even at windmill to deform the blades if they were to impact the casing.

Looking at the shots (which are excellent BTW) I wouldn't say either engine was producing much thrust when it hit the ground.

One thing's for sure, Trent's make great ploughs ... And great brakes

MW

 

[Trazor]

I can hardly believe I'm being drawn in to this,

 

[megawatt]

The other quite obvious point Empip is that, if the left engine was producing any significant level of thrust, the aircraft would have made the runway

 

[tim west]

What if the runway was a conveyor belt?