The AN124 uncontained engine failure a few posts earlier shows I think is what one really looks like.
From this I believe the containment ring worked.
The hole in the hull looks fairly low energy compared to the AN124, which went straight through destroying things on the way.

The integrated band idea
 

bsieker

Hi bsieker and others,

Probably I didn’t explain the idea very well - think of the band as a rim and the fan blades as spokes of a rigid or semi rigid wheel.

This rim looks a bit like the metal tyre round a wagon wheel and is attached directly to the all blade tips.

In this way the blades are stabilised and supported by each other. There may even be an aerodynamic benefit due to the fencing effect at the tips.

Now imagine you are a blade, hanging on to the disk hub but also being held in there by this band. Before you can fly off you have to compress all the opposite blades which are supporting the band in turn. The band doesn’t have to take the 100 tons - the hub does that and the band provides support to stop it getting ideas.


It is the sum of the forces working like wagon wheel spokes in compression but like bicycle wheel spokes in tension. (Wagon sits on its spokes - a bicycle hangs from them)

So the blade doesn’t get much chance to get fatigued and won’t want to depart. If the blades expanded there would be a bending moment so the rim material should be the same as the blade material. If composite, then composite too.

A tight cord around the blade tips would be lighter and have a similar effect but could be more difficult aerodynamically.

I am VERY out of date on jet engine design, but I do not think there is any practical material that could exist as a hoop at the relevant speed and radius without bursting.
Unless I dropped a 0 or two in my calcs.
So the blades would be holding on to the hoop, not vice versa.
That is why engine discs concentrate the material near the hub, where it is best value.

How we got to where we are
 

Originally posted July 2020 - updated a number of times - including as recently as today.

NDI Process Failures Preceded B777 PW4077 Engine FBO

DType

Yes, I ran some rough numbers for thin wall hoop stress with a 120" diameter and some rough guess as to load; a hoop 'retainer' sort of device does not look realistic. Any serious load would quickly over stress it.

WHBM

The fan blades on the GE90 series are carbon composite construction, with a TI leading edge (GEnx uses the same basic fan blade design). The GE90 blades have proved to be amazingly durable - I can't recall a single fan blade release or failure on a GE90. I don't know if it's still true, but back in the early 2000's GE had a sign in their training center stating that a GE90 fan blade had never needed to be scrapped due to in-service damage.
Memory says the Trent engine uses a TI skin over a TI honeycomb matrix material - and I believe they use the same construction on all their wide-cord fan blades. Rolls has had issues with fan flutter with their fan blades - the RB211-524G/H, Trent 800 (777), and Trent 1000 (787) have all had to implement fan 'keep out zones' which prevent engine operation in a defined RPM range without forward airspeed. I recall a Trent 800 FBO event back around year 2000, although IIRC it wasn't the blade that failed - the blade 'dovetail' root failed due to improper lubrication.

WHBM

From what I read, this particular PW4000-112 series engine (PW4077?) is the only hollow-bladed version. I don't know about the GE90 engine (except that it has part composite blades in the larger variants at least), but RR Trents nearly all have hollow titanium blades. These are made of three pieces which are placed in a mould, heated to very high temperature and are then internally inflated with high pressure gas to form them to the shape of the mould. The third piece between the two halves of the outer blade faces is corrugated and it stretches into shape with the vertices of the corrugations melting into or fusing with the outer pieces effectively forming a one-piece finished structure.

Feathers McGraw

"From what I read, this particular PW4000-112 series engine (PW4077?) is the only hollow-bladed version."

All PW4000 series engines with the 112" fan (PW4074 to PW4098) have the hollow blade.

Juan Browne spoke with the CA of the 2018 777 near HNL.

Very interesting comments about the hazards downstream of the fan blade release -- not just with 777s and PW4000-series engines.

Big pieces of departed cowlings can introduce serious aerodynamic and flight control issues.

DaveReidUK


Right, I see, I didn't realise that the thrust rating of the PW4000-112 varied so widely, but I now realise that it's the 112 that decides the fan size and blade construction, the 40xx gives the thrust rating. Engines now seem to come in many flavours while all aircraft have become twins with few real differences, just the wingtips.

Didn't see this one posted:


"Page last modified: February 23, 2021 8:13:59 PM EST

The FAA issued an Emergency Airworthiness Directive (AD) (PDF) tonight that requires U.S. operators of airplanes equipped with certain Pratt & Whitney PW4000 engines to inspect these engines before further flight.

The FAA is taking this action as the result of a fan-blade failure that occurred Saturday on a Boeing 777-200 that had just departed from Denver International Airport. Although the aircraft landed safely, the failure resulted in damage to the engine, an in-flight engine fire, and damage to the airplane.

After reviewing the available data and considering other safety factors, the FAA determined that operators must conduct a thermal acoustic image (TAI) inspection of the large titanium fan blades located at the front of each engine. TAI technology can detect cracks on the interior surfaces of the hollow fan blades, or in areas that cannot be seen during a visual inspection.

As these required inspections proceed, the FAA will review the results on a rolling basis. Based on the initial results as we receive them, as well as other data gained from the ongoing investigation, the FAA may revise this directive to set a new interval for this inspection or subsequent ones.

The previous inspection interval for this engine was 6,500 flight cycles. A flight cycle is defined as one takeoff and landing.

This AD is effective immediately upon receipt. The FAA will share this information with other international civil aviation authorities."

https://www.faa.gov/news/updates/?ne...oc&cid=101_N_U

Seat4A

"The FAA issued an Emergency Airworthiness Directive (AD) (PDF) tonight that requires U.S. operators of airplanes equipped with certain Pratt & Whitney PW4000 engines to inspect these engines before further flight.

The FAA is taking this action as the result of a fan-blade failure that occurred Saturday on a Boeing 777-200 that had just departed from Denver International Airport. Although the aircraft landed safely, the failure resulted in damage to the engine, an in-flight engine fire, and damage to the airplane."

It's curious that while the FAA (and everyone else) correctly refer to the event as a fan blade failure, the authors of the AD quaintly describe it as the "1st stage LP compressor", as if we've somehow jumped back 60 years in time.

All air carriers opr (taking-off/landing) within the territory of Japan are requested to avoid using aircraft equipped with PW4000-94 series engines until further notice applicable engine types are as follows


PW4052 PW4056 PW4060 PW4062 PW4062A PW4152 PW4156A PW4156 PW4158 PW4460 PW4462 RMK : EXC MIL ACFT

Flightmech

"All air carriers opr (taking-off/landing) within the territory of Japan are requested to avoid using aircraft equipped with PW4000-94 series engines until further notice applicable engine types are as follows

PW4052 PW4056 PW4060 PW4062 PW4062A PW4152 PW4156A PW4156 PW4158 PW4460 PW4462 RMK : EXC MIL ACFT"

That doesn't seem to have made it into any of the mainstream or aviation media. What's your source, and what does it say is the reason ?

It's a NOTAM. Effective today. Already affecting our own MD11PW operation into Japan.

I believe the 777PW is banned along with aircraft powered by the engines above.

Thanks - yes, we learned about the Japan PW4000-112 ban 3 days ago (see post #100).

The new ban on the PW4000-94 (B744, MD11) doesn't seem to have any obvious connection to that, unless anyone knows otherwise.

Yes. That's why I didn't mention the 777 in my original post.

DaveReidUK

That is probably related to the Netherlands incident, which was a PW4000-powered B744. There is little information available, but it looks like multiple turbine blades and/or vanes (and not much else) were ejected. Nothing to do with the fan.

Feathers McGraw

This process is known as superplastic forming and diffusion bonding (SPF/DB).