The tail camera view includes all four engines. It does not include the end of the wing.

There's a lot of rotational energy in the fan. Once the flange failure began its progress, the fan would wobble and remove whatever beside the containment ring that was in the way, mostly cowl.

There have been accounts of propellers coming off the crankshaft. The prop departs forward until gravity directs it down. Likely the fan took a similar trajectory.

Kudos to the containment ring.

Quite so. After all, a fan isn't much more than a big prop. :O

In a typical high-bypass engine, the fan provides about 80% of the thrust, so Mr Newton tells us that liberated fan is only going to head in one direction (initially, at least).

As for the cowl, the intake lip diameter is typically less than the fan diameter, so a departing fan isn't going to leave the cowl behind, whether wobbling or not.

The suggested failure modes still don't fully add up. The fan would have been producing a leisurely five or six tons or so of thrust, which wouldn't have troubled anything compared to the previous take-off loads, so this isn't an overload failure.

If the LP drive shaft end had failed first, say from fatigue, there would not have been such a clean failure of all the fasteners on the LP compressor drive flange. The flange is pretty well undamaged apart from secondary impacts. And if the failure had been caused by all its fasteners being unsecured and falling out one by one, you would expect the final ones to have ovalised their holes. Which I can't see.

Broadly agreed and my knowledge of the coupling between angular momentum and linear momentum is far too stale to argue convincingly, but consider the hammer thrower in his cage. As a professional wobbler, he’s an effective converter of one to the other, albeit with no propeller attached! There surely was wobble here, however brief, and the last part of the fan case to let go might largely determine the ultimate trajectory, do we think?

Fan would not exit like a prop at all. At the rotational sppeds they do the fan would be absolutely rigid (like a toque converter,) As soon as it encountered something fixed it would start chewing it but it would also 'rotate around that point' then it would most likely roll around the inside of the containment (or cowl) until it chewed or forced its way out. By then it might have generated quite a lot of transverse energy and would depart perhaps forward but also in the random direction where it finally got free. Unless it hit something really rigid gyro effect would keep it 'upright.' 20% chance it chews into something important like the fuselage or No 2?

FWIW - agree with the above but must also include gyroscopic action to the trajectory calcs. Observation of the phot showing leading edge outboard **seems** to indicate fan and part cowl departed down and to the right. However, IF it went above the wing, seems to me to be a fair chance it would hav hit or dinged the right horiz stabilizer. I'll bet a detailed analysis after full examination of parts and external dings will provide a better trajectory analysis AND why-where fracture started

To reparaphrase Ernie Gann- re aircraft accidents -- sometimes an unknown genie doesn't unzip his pants and urinate on the pillars of science..

Are high-time GP7200s still flying? Given that, as CONSO notes above, physics never takes a holiday, should they be?

Incorrect, there is an additional flange joint to the front of the compressor drum.

Once the fan has parted company from the shaft that was driving it, how does it generate any more energy?

Voice recording
 

If you will forgive a non-professional intervening.

There are obvious benefits to having long term voice and other audio recordings. There are also obvious dangers, especially in an era of management by surveillance.

Understanding that what is suggested is a non-survivable recording, and given that 12 hours of CD quality audio will fit on about 12GB, would the solution be recording onto an SD card in some non-rugged outboard of the CVR system, with the SD card being the property of the captain, to be removed at the end of the flight unless there's a need of the recording?

It doesn't generate more, new energy. It uses the rotational energy, in the form of angular momentum, that it already has.

I think what ChrisVJ is suggesting is that it will have converted a portion of its rotational energy into transverse energy -- not that it will magically generate more total energy.

All that is not that easy.

You cannot just put consumer HW into a unit like that. There are far higher requirements with regards to reliability (temperature, high altitude radiation ...)

Furthermore: after 1-2 years consumer chips will no longer be manufactured. So the whole process would need to be started again. The certification surely costs > 100.000 USD and takes many months. That can't be done all the time. Therefore HW like that relies on special industrial chips that are made for a long period of time. Those chips are not developed like consumer HW.

he may have meant it, but as a free body it divides it's energy according to segment size. The worst case is approx 1/3 segments. as two half segments a great deal of energy is tied up in rotation and it generally just falls away after going through a case structure.

FlightlessParrot wrote:

"Understanding that what is suggested is a non-survivable recording, and given that 12 hours of CD quality audio will fit on about 12GB, would the solution be recording onto an SD card in some non-rugged outboard of the CVR system, with the SD card being the property of the captain, to be removed at the end of the flight unless there's a need of the recording?"

Convince a French prosecutor it's OK the Captain takes home the CVR recording at the end of shift, ever.

Back on the subject of the failure itself, it is clearly understatement to suggest that a lot of extremely complex thought has gone into the scenario over the years - it seems there are a number of papers on the subject of computer models for fan containment and of non-axisymmetric loads generated when something goes wrong (typically an FBO), but I am not sure any address the possibility of the loss of the fan rotor and fancase in their entirety as I suppose that actually counts as ... ehm ... uncontained in one major sense!

For those interested, a start point might be the bright-coloured pictures - especially Figs 2, 5, 6, 7, 8, 9 in this (matching?) pair of papers. They share the same title but the second was published later so may be a revised version of the first - apologies, but I haven't managed to fully compare them:

• Sinha, Sunil & Ojha, Sujit. (2012). Rotordynamic Analysis of Asymmetric Turbofan Rotor Due to Fan Blade-out Event with Contact-Impact Rub Loads. 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 2012. . 10.2514/6.2012-1481.
• Sinha, Sunil. (2013). Rotordynamic analysis of asymmetric turbofan rotor due to fan blade-loss event with contact-impact rub loads. Journal of Sound and Vibration. 332. 2253–2283. 10.1016/j.jsv.2012.11.033.

Just guessing here: The fan hub to shaft coupling is designed to withstand quite a bit of thrust (produced by the fan). But the fan hub to LP compressor barrel coupling not nearly so much. It's more for the torque of spinning the compressor. So an initial failure of the shaft to fan (where a jagged piece remains) would allow the fan to pull forward. The 24 (?) bolts holding the compressor stage failed under tension (photo in #194). That may be by design. To let the fan go forwardvwithout trying to pull the compressor rotor through the stator.

Not true in ether the the presumptions in photo #194 nor the design intent of saving the compressor rotor.

The preference is that given a major fan failure all you want is a safe shutdown with the engine staying on the wing with no fires. You gladly give up scrapping every darn piece of the engine to keep the bits from leaving. However given that the fan hub itself splits into pieces you must expect the movement of these pieces will result in tensile shear of any attachments to other rotating bits like compressor spools and/or drive shafts.

I take it that some have not noted what looks to be an intact fan blade and its attachments lodged in the vanes behind the fan?

Possibly a fan blade, but can't say for sure from the available photos. Cowl pieces are the other possibility, some fragments in the vanes look like composite.