My experience, from the mid 1970's, when I started boroscope inspections of JT8D engines, the issue was sulphidisation, the Operator was in the Arabian Gulf where the fuels uplifted had a higher sulphur content and lower lubricosity also causing premature failures in their RB211 fuel contol units. For the JT8D regular water wash was introduced. By chance they also leased ANA L1011's and had serious trouble with their RB211 engines. For the FCU's modified bearing materials helped; as these 787 seem to mostly operate within Japan local fuel might be a contributing factor.

Yes, engine boroscope is a scheduled maintenance item - frequency depends on the engine and where in the engine (hot section is more frequent), typically cycle based. When there are known issues the interval is often shortened - often if there is a finding, they are allowed to continue operation but need to re-check at a very short interval (I've seen as little as 10 cycles) to make sure it's not getting worse. Obviously at some point the problem will drive the engine off-wing.

Thanks tdracer. So this must be a known phenomenon with narrow body engines with higher cycle rate and should be a easy fix.

BTW, cynic in me still thinks even a good engine goes bad as soon as it is hung on jinxed 787. Honeywell sold thousand+ of same ELTs, on a B787, it went up in flames.

aeromech3

I heard another operator needed early overhaul of their CFM56s, apparently they were failing prematurely by flying to ME. Is this something to do with sand??

To notapilot15, the silica from sand deposits in the engine, in the hot section it forms what is commonly known as glass, this is not a problem when molten but on engine shut down / cool down, it solidifies and causes the most problem on the T1 blades where it blocks the cooling holes; on engine start when max temperature is critical, the blades have reduced cooling and suffer extra thermal stress, hence life shortening, especially when this occurs on more times on short cycle operation. One has to remember the Operator of short cycle flights has a modified maintenance schedule which should capture this accelerated degredation by more emphasis on cyclic life. As stated earlier ANA are fleet leaders and 1st to experience such unpredicted events.

I wonder if the recent (very low) sulfur standards for automotive diesel might be pushing more high-sulfur crude into jet fuel production. (I doubt any crude can meet the new diesel standards without additional processing, but it seems reasonable that it would be easier if you had less sulfur to start with.)

notapilot15:Not unique to any particular engine type. Helos (turboshaft) operating in Vietnam suffered much distress due to sand & dust - airfoil erosion esp. in the compressor, and blocked cooling passages in turbine airfoils.

My own experience in the ME saw small compressor airfoils worn so badly, the sharp-cornered leading & trailing edge corners resembled the semielliptical wingtip of the Spitfire!

Actually you have the right effect but the reason is different. Typically, Jet (whether Jet A or Jet A-1) is sold to a spec and the parameters are strictly controlled. In the case of Sulfur/Sulphur (S) the spec is, in theory, independent of the source crude, its just that the refinery will need to carry out additional processing (e.g. by hydrotreating) if the source crude is high in S. Its not just elemental S either - it is active S compounds such as mercaptans and the spec has come down over the years, which is why you have seen many "Jet Merox" plants bolted on to Refineries in the ME for example over the last 20 - 30 years to reduce these S species. High levels of active S compounds like mercaptans cause the fuel to fail the "Doctor Test" and are bad news in Jet.

The problem has been that as road fuel S specs have tightened, hydrotreating has become oriented to the biggest cut (diesel and catalytically cracked gasoline) where mercaptans are less critical. As more gasoline selective hydrotreating units are placed on stream, the levels of mercaptans in the higher fractions like Jet have been rising. But the spec willl still have been met, probably through additional after-treatment.

We continually see specs tightening in response to better engine technologies (and even environmental initiatives eg from ICAO) as well as problems like the introductions of road biofuels which caused the bleed of biodiesel or "FAME" from multi product pipelines into Jet. You need to be a bit careful of characterising S as "the enemy" however. S does provide lubricity for injectors and the New Zealand case where ultra-low S Jet caused serious problems in the domestic fleet (not L/haul which only filled up in NZ on departure) is instructive.

Worked for a company that used a laser to harden the 1000 blades. I can assure you that they are titanium.

Depends on which stage you're talking about. The further back you go, the higher the temps.

Main fan blades

https://www.ana.co.jp/group/en/pr/787/pdf/20160826.pdf

https://i.imgur.com/qRhY7Qe.jpg

lasernigel,
Look at the engine cross-section in the ANA letter provided by p.j.m. I guarantee you the turbine blade in question isn't titanium. If it were, it wouldn't be there for long as it would have melted very quickly.

Fan blades are part of the compressor (in front of combustor, i.e., relatively cold) whereas the turbine follows behind the combustor (pretty hot).

Turbine blades get cooler the further back you go, compressor blades hotter.

The turbine blades are made from single crystal nickel super alloy.

Incident: ANA B788 near Tokyo on Aug 30th 2016, engine vibrations
 

I did state in my second post the "Main fan blades".

It is disturbing.......that one or two posters don't know the difference between Fan, Compressor & Turbine blades.

50 twin-engine 787's - One hundred installed T1000's. If retrofit is needed, it will also no doubt include spare engines. Any Idea how many spares?

I presume that it's OK to fly if no more than one engine per flight is at high risk

If a couple come off every day and a spare goes on per aircraft it doesn't seem like any more spares than usual are needed.

In the end the risk analysis should ensure that its extremely unlikely that more than one engine loses power or has to be shut down in the life of the retrofit program.

On the other hand if one becomes too aggressive in swapping out engines like two at a time. human error becomes a more significant risk

Based on ANA statements initial problem was noticed in long haul fleet, later found in short haul fleet. This contradicts initial reports claiming ANA high-cycle short haul was unique. What about other Trent 1000 operators.

RR fanboys are not happy with ANA demanding RR to fix all engines, same fanboys who quickly claimed GE was the reason for BA276@LAS.

Who or what are "RR fanboys" ? Are they to be found in Thailand ?

The guys from Barnoldswick always referred to the ones we treated as the main fan blades.
Did 500's, 700's and 1000's. Plus discs for the BR710 series. A lot of it has transferred to Singapore now.

lasernigel,

Let's get the terminology correct. This thread isn't about fan blades, it is about an intermediate turbine blade that is apparently problem on the Trent 1000 as experienced by ANA.
Fan blades are in the very front of the engine and run cool. Turbine blades are towards the rear of the engine, aft of the combustor and run hot. Fan blades, some early stages of the compressor (low pressure) and some discs in the fan or early stages of the compressor may very well be made of titanium. In the turbine, there are no titanium blades, vanes or turbine discs because of the high temperatures being experienced. There may be titanium aluminide turbine blades in the very last stage of a five or six stage low pressure turbine of certain engines dependent on temperatures being experienced, but that is only because titanium aluminide has somewhat improved high temperature capability verses common titanium alloys.

Main fan blades are not intermediate turbine blades.

lasernigel:Could you share with us the approximate dimensions of these blades?

Seems to be some disagreement re the engine components. This may help: How jet engine is made - material, manufacture, history, used, parts, components, dimensions, product, industry and http://www.azom.com/article.aspx?ArticleID=11454

Wow. Ugh. The How Products Are Made article has several factual and historical errors that need to be addressed. I've seen better stuff in Popular Science.

I didn't even get as far as the manufacturing processes; i hope this section is more accurate & up-to-date.

Well after reading the linked explanations above it would seem that you can't even trust the internet to know the differences between fan, compressor and turbine blade materials or manufacturing.

Now back to the thread subject. Suffice it to say that the Subject engine problems are turbine blades which are quite different in design, manufacturing, operation and repair from the blades in fans or compressors.

got to the "intricate feet of engineering" in the second sentence of that article and knew the rest wasn't worth reading!

Pity, apart from that one unfortunate typo/spellcheck fail the rest of the article is actually a pretty reasonable rundown on what materials are used in which parts of a turbofan.

As one might expect from a publication that specialises in Materials Science, in fact.

They did fine with materials, but not the where they are used part, which seems to have misled some folks in this thread :)

I've yet to hear of a common usage of the "lost wax" process in compressor blades

Except for the aluminum compressor blades which I am unaware of. I don't think they would fare well in a sandy environment due to erosion. Also, investment casting, aka, lost wax process, is not used for compressor blades for good reasons. Compressor blades are forged for mechanical property reasons, fatigue strength, grain control, etc., beyond what the investment casting process can produce.

Turbine blades are investment cast because of the high temperature materials now required. In the olden days, turbine blades were forged, but the forged alloys didn't have the higher temperature or the internal air-cooling sophistication capabilities that investment cast turbine blades can provide made with ceramic cores, forming the intricate internal cooling passages. Investment cast turbine blades can be produced with random equiax grain control, directionally solidified grain control or as a single crystal where the entire turbine blade contains no grain boundaries.

Fan blades have been made for many years using titanium alloys and forging processes. Today fan blades on newer engines are being produced using composite materials to reduce weight, improve strength and improve resistance to foreign object damage (bird strike, etc.).

Hope this information is helpful as the articles referenced left quite a bit to be desired and are misleading in some instances.

The challenge for forging turbine blades (in the old days) and turbine discs, is that the materials used are the ultimate available in resisting deformation at high temperature. Sort of Catch 22!