Pontifications: Engine problems are getting worse

By Scott Hamilton

May 14, 2018, © Leeham News: The engine problems are getting worse.

These have moved beyond the technical issues with the Rolls-Royce Trent 1000, GE Aviation GEnx, Pratt & Whitney GTF and CFM56.

The problems are trickling down to the maintenance, repair and overhaul shops.

LNC previously touched on the back-up in MRO shops due to the RR Trent 1000 problems, affecting even Trent 700 (Airbus A330) MRO scheduling. We’ve also reported the knock-on effect of the GTF MRO on other engine shop visits.

The mandated-inspections of CFM56 fan blades in the wake of the Southwest Airlines accident last month inundated MRO shops with unexpected visits.

Now, a European appraisal company forecasts that the “bow wave” of CFM56 shop visits will create a crisis for spare engines and parts.

Critical demand

“IBA forecasts that the engine lease market will be unable to meet critical demand for spare engines and parts as bow wave of shop visits for the CFM56-7B and-5B hits,” the company said last week.

“The engine lease market will not be able to support the 25-35% increase in shop visit rates forecast for CFM56-7B and -5B engines and continuing strong demand for V2500’s in the period 2019-2024,” IBA wrote. “There is currently very limited availability of spares and unless more spare engines are generated by retirements and aircraft teardowns, or airline held spare stock absorbs some of the demand, IBA expects engine inductions and longer turnaround times (TATs) will create a log jam further intensified by the impact of compound shop visits.”

TATs for Trent 700 and GE90 engines powering the A330 and Boeing 777 have balloon by months, market intelligence says, as MRO shops are overwhelmed by demand, exacerbated by the special problems in the market today.

Power by the hour

The increasing trend toward power by the hour (PBH) agreements adds to the backlog.

The engine OEMs have long considered MRO and after-market parts as a profit center. Selling engines, especially in a competitive situation (which is increasingly rare), typically comes at a steep discount. Engines on the Airbus A380 saw discounts of 80%. I know of one case in the MD-11 days in which the winning OEM gave the engines away in exchange for the MRO contract.

Pratt & Whitney and CFM want MRO contracts with every GTF and LEAP deal they do, whether it’s on the competitive A320neo or the sole-source 737 MAX.

The market is in general agreement that despite PW’s current (and excruciating long-running) problems with the GTF, it will eventually be a good engine. The LEAP likewise will be good, but there are some teething problems and its on-wing time initially will be less than the CFM56, an engine that despite the blade issues in 2016 and last month, is a phenomenally durable and reliable engine.

PW and CFM each pursued MRO contracts and now, with the warranties, are on the hook. These responsibilities also put pressure on the MRO shops.

Emergency inspections

The emergency inspections required by the US FAA and Europe’s EASA on the CFM56 following the Southwest accident illustrates only a fraction of the problems. Here in the Seattle area, there was an unexpected and steady stream of Southwest 737s into Everett’s Paine Field where MRO ATS is located. In just one weekend, there were more than a dozen Southwest airliners on the ground. This picture was repeated throughout the country.

Although the inspection requirements are short-lived, the underlying problems are not.

The GEnx icing problems are years old and there’s no end in sight. RR says its Trent 1000 issues won’t be fully resolved until about 2022. PW puts final resolution for the GTF at 2021. There’s no estimate when the TATs for the Trent 700 and GE90 will get back to normal.

36 Comments on “Pontifications: Engine problems are getting worse

  1. You could say we are suffering a perfect storm of issues as so many engine programmes new and old struggle with reliability. An alternative perspective is that engine manufacturers, aircraft producers and the regulatory authorities have colluded to downplay issues as they arise. Those issues have not been resolved and as the volumes churn out the risk of significant problems rise. The whole industry seems beholden to get units out of the door regardless.

    • Whow… hold back a moment!!

      This is a typical “Denial Syndrome”:
      “engine manufacturers, aircraft producers and the regulatory authorities have colluded…”

      Really??

      I recall the endless number of airlines that have downplayed OEM recommendations for initial provisioning and started operations with no spare engines, no spare nacelles, no spare parts. And then, when the shugar hits the fan, they throw a hissy fit, blame everyone … else and some even went bankrupt.

      It became a fashion that airlines respect only mandatory (AD) requirements. AOG is not a matter of flight safety! ADs do not cover issues with only financial impact. This is not “collusion” but the freedom of ignorance.

      Years ago some Civil Aviation Authorities would not release a CoA without spare engines on site… Airlines pressured them to accept contractual spare engine coverage and now… nothing.

      • Colluded? The Civil Aviation Authorities are supposed to hold the whip hand in terms of ensuring safe operation of airlines. Lets put it another way…. they are pressured into allowing promises from the OEMs to make things right cloud their better judgement.

        • SW was fighting the Blade inspection issue on the CFMs until they killed a passenger. Its not like there was not an Red Flag Alert on that one. I have long known that if one piece of equipment has an issue, you need to make sure its identical partners don’t as well. SW did nothing until they had to. The could have gotten on top of it easily.

          We hear that Boeing is the go between RR and the FAA.

          Why in the world is RR not reporting to the FAA and not going through Boeing?

          I agree there is a all too casual and close relationship involved and not properer oversight.

          P&W puts a lip seal out that is not tested (failing almost immediately ).

          RR has known for years that there is an issue with the harmonics in the flow and they are allowed to go on building engines.

          The first engine that failed on the SW 737 should have alarms screaming as it failed differently than modeled and it takes a second one to raise the alert?

          This has a great deal of the same feeling that the pilots not understanding or being able to fly their aircraft when the automatic hands it to them.

          • Today (May 14) another SW Airline plane made an emergency landing due to loss of cabin pressure. Maybe them employees are down right correct about maintenance being circumvented. Loss of cabin pressure can indicate some very serious occurrences.

          • Theres more catastrophic failures that have happened and apart from the CF6 on the 767 are in ‘investigation limbo’.
            None RR.
            GP7200 on the Air France A380
            PW4000 on the United 777
            GE90 on the British Airways 777

            As for waiting for the ‘second failure’ to hurry things along, thats what it took for the Aloha 737 fuselage failure and maybe 3 failures of the 737 rudder reversal.

          • Hello TransWorld,

            Regarding: ” SW did nothing until they had to. The could have gotten on top of it easily. ”

            According to the excerpts below from the FlightGlobal article at the link after the excerpts, Southwest had completed inspecting 17,000 of its 35,500 CFM56 fan blades prior to the April 17 accident, and was planning to complete inspections of all of them this year, which would have been within the time guidelines of the original CFM service bulletin. After the accident inspections were accelerated to be completed by May 17. With about 10,000 fan blades to go as of 4-26-18, only one cracked blade had been found. Additionally, the blade involved in the accident would not have been covered by the AD that was proposed by the FAA prior to the accident.

            “Southwest had been inspecting its CFM56-7B engine fan blades prior to the 17 April accident, following an August 2016 inflight failure of the same engine type on another 737-700 in its fleet. Van de Ven says the carrier had inspected about 17,000 engine blades before last week’s accident, which killed one passenger.

            “We were on a path to complete the inspections of the remaining 18,000 by year-end and that would have met the recommended service bulletin timeline,” he adds, referring to a service bulletin issued previously by engine manufacturer CFM International.

            The engine involved in the 17 April accident had not yet been inspected as it had accumulated 10,000 cycles since its last overhaul, below the 15,000-cycle threshold for urgent inspections in a proposed US Federal Aviation Administration airworthiness directive. That directive was still in the process of being finalised at the time of the accident last week.

            But the accident prompted Southwest to accelerate the inspections, and to complete them within 30 days or by 17 May. Van de Ven says the airline has roughly 35,500 fan blades, which means the airline has about 10,000 fan blades left to inspect at this point.”

            “An inspection in May 2017 found a single cracked fan blade which was subsequently discarded, says Southwest chief executive Gary Kelly. Van de Ven stresses the rarity of engine fan blade cracks on the CFM56.”

            https://www.flightglobal.com/news/articles/no-signs-of-fatigue-found-in-ongoing-737-engine-chec-448081/

          • See below for the final results of Southwest’sCFM56 blade inspections.

            “Last week, the airline completed inspections on more than 35,000 fan blades – an effort that began in 2016 after a similar accident in August of that year, also involving a cracked fan blade. The carrier accelerated inspections of the remaining fan blades following the 17 April accident.

            Chief executive Gary Kelly says there were “zero findings” from the inspections that recently wrapped up, but says the airline removed a couple dozen blades that showed coating anomalies. These were sent back to CFM for further checks that will be more invasive beyond the airline’s ultrasonic inspections, he adds.

            “There is a more precise and more invasive step that can be taken if you have some indeterminate results from that [ultrasonic] inspection,” says Kelly. “This is an extra cautionary step we are taking.

            Van de Ven says that about 20 to 30 blades were returned to CFM, but stresses that the coating anomalies could be simply due to wear-and-tear. The airline is also completing an audit of its records to ensure that it has inspected every fan blade that requires the checks.

            “What I want to be able to say is that every fan blade with more than 3,000 cycles has been inspected and is in a programme to be inspected every 3,000 cycles,” says Van de Ven.”

            https://www.flightglobal.com/news/articles/southwest-launches-fan-blade-tracking-after-april-en-448654/

  2. Yeap, this is not a new issue. Fluctuations in the spare engine market are always there, determined by
    – fluctuations in the Global Oil price that will trickle down into variation in the airline retirement plans for older aircraft and consequential cannibalizations
    – specific technical issues generating AD Notes and mandatory removal waves that can easily overload the Global engine repair and overhaul infrastructure
    – status of the spare engine pool influenced by the above
    – historical experiences that drive forecasting plans and that may not meet with actual reliability/durability of new products

    As (1) the airlines have continuously followed more restrictive spare engine coverage policies and (2) the OEMs have continuously reduced the level of “freely available” spare engine pools (to improve ROA), the resilience of the Spare engine support infrastructure is continuously weakening.

    This is why Airlines need Aircraft Engineering experts => https://www.linkedin.com/pulse/why-airlines-need-aircraft-engineering-experts-ferenc-koncz/

    Whoever has better experts, will be better prepared for the future storms.

  3. Issues with the Leap 1B on the 737MAX have received little attention in the aviation media. But this engine can take really long to start. And it appears to have been a known issue from the outset, as there is an automatic procedure for it. Leap 1A rotor bow issues have been mentioned for the A32xneo but I do not know if they are worse than on the MAX. From the 737 Tecnical site (facebook, not affiliated with Boeing):

    “The LEAP-1B engine start sequence is slightly different to the current CFM-56. After the engine start switch is moved to GND, the EEC performs Bowed Rotor Motoring (BRM). This is to straighten the N1 and N2 shafts which may have bowed due to thermal buildup after the previous shutdown. BRM will be active from 6 to 90 seconds and MOTORING will be displayed on the N2 gauge between 18-24%.

    At 25% N2 or max motoring when you move the start lever to idle, the EEC then performs a test of the Thrust Control Malfunction Accommodation (TCMA) and Electronic Overspeed System (EOS) functions. This manifests itself as the fuel flow indicating zero, the engine fuel shut off valve opening and closing repeatedly and the ENG VALVE CLOSED light illuminating bright blue until the test has finished whereupon the start sequence continues. It certainly takes longer to start an engine on a MAX than an NG”
    Once a Max is pushed from the gate, it can take 5-6 minutes at worst until it is ready to taxi, which is a very long time blocking taxilanes or others from pushing back. I am wondering if this is a long term issue or if there will be anything done to alleviate this in future? Otherwise as the Max fleet grows, this will contribute to additional delays on airports. At least startup times have been MAXimized.

    • as I understand it, rotor bow is caused by a hot engine being shut down and allowed to sit without the shafts rotating, resulting in differential cooling rates top and bottom, causing the rotor to bow.

      why don’t they just keep them rotating constantly at a low rate (say 10 RPM) using the MGU or bleed air from the APU until they cool below the bow threshold?

      • I’ve wondered about that too.Its so obvious that there must be a good reason why not.On a breezy day they often windmill all by themselves.

      • To bilbo: Engine bow after shutdown is affecting every gas turbine engine.

        The phenomenon of asymmetric cool-down between the top and bottom of the engine (faster cooling on the bottom section) bows both the stator case and the rotors. This is a short time (30-90 min) temporary distorsion that disappears 1-3 hours after shutdown, influenced also by atmosferic conditions (wind), may cause problems (vibration and rubbing) with some operators only, depending on turnaround schedules and operating environments.

        As bowing is also influenced by the installation of the engine in the aircraft, the bowing problems cannot be fully excluded before engine in-service operation in a given aircraft installation and adding to it the diversity of operational environments.

        As engine OEMs try to improve gas turbine efficiencies, they need to reduce clearances (gaps) between rotors and stators while fighting engine bow. It is not easy to fine tune a balance in this improvement process.

        Every modern engine family I know of (eg. CF6, CFM56, JT8D, PW2000, PW4000, V2500) experienced in the past minor in-service issues with bowing that were resolved through various minor adjustments in build standards, operating procedures, EEC Software upgrades, etc.

        • Thanks @ferenc. I have operated 4 out of the 6 engines you mention and none of them had any special operating procedures due to rotor bow. Is this a case of tighter clearances on the new engines?

          • @oceancrosser: the fact that you were not aware it did not mean that the issue was not there. If you read the Specific Operating Instruction for some Engines at Normal Operation, Starting you will find a short paragraph for “rotor bow”. Hinting to bowing was a slightly higher vibration during motoring and start-up that would disappear in a couple of minutes.

            On some JT8s it could happen that the LP Rotor (Fan) could not be rotated by hand some time after shutdown. The engine could still be started, but if a thorough mechanic would do a manual check for “free rotation” (especially on the B737-200 where the engine was easily accessible), it could cause some heated discussions and delays.

      • It is more the casings deforming than the stiff rotors as heat raises and heat up the top of the casing deforming the engine, the result is kind of similar with interference between rotors and casings and its shrouds.

        • ok, but keeping air flowing through the engine at a reasonable clip should prevent differential cooling from occurring in the first place as the whole engine will be receiving constant and equal air flow.

          again, this seems like a very simple and relatively low cost solution (that would also have the knock-on effect of keeping the oil flowing through the engine reducing the chance of coking)

          • @bilbo: Aircraft design is a painfully and a narrowly negotiated solution between reducing and increasing weight, complexity, durability, reliability etc., etc. and cost.

            The intent is to have engine bowing an “unknown problem” for 99% of operators.

            However, presently every teething problem in the learning from entry into service is exaggerated by the huge marketing machineries of the opposing and competing parties.

          • An old way to avoid most of it was motoring the Engine on the starter after shut down for some minutes. In test cells that is common practice on some Engine types when the testers go for lunch or dinner break to avoid coming back to an Engine that is stuck. Normally you use the Engine shop starter during test not to wear on the customers unit.

  4. Over the last 8 years GE/CFM marketing have tried to transplant the CFM56 reliability track record on the LEAP. Which is / proved a kind of non-sense, because it is an entirely new engine. You can not copy products 1 performance on to a different product 2, without testing / proving first. Still they played with just that. I hope CFM will be out of the woods with the LEAP’s in Asia.

    https://www.bloomberg.com/news/articles/2018-04-12/airbus-set-to-win-china-approval-for-delayed-a320-neo-deliveries

  5. Another thing in the pipeline for Boeing – and perhaps Airbus – and CFM is the fact that two fan blade failures each removed the air intake cowl from the aircraft which, presumably, went back over or under the wing, narrowly missing the horizontal stabilizer (look at the aircraft geometry).

    A fan blade failure is supposed to be a non-Hazardous Event.

    If an object that size hit the horizontal stabilizer then a hull loss would very likely result. Safer – though by no means safe – if it hit the wing. It could remove an entire flap if it happened during approach for instance. That too would likely result in a hull loss.

    This ought to result in some re-certification of the engine/nacelle assy IMHO.

    • As noted above, and it should have been investigated as a failure to test/model correctly and a solution come up with.

      Realistically we are stuck with the situation with (15,000?) of the CFMs out there.

      The approach is two fold.

      1. Increase inspections on the blades to much higher levels.

      2. Come up with a test that covers that (or a model( and come up with a design that prevents that. Its in the reg, not just that a blade does not but other parts do not penetrate the cabin.

      And clearly debris going aft as it did could wreck the horizontal stabilizer and or its functioning.

      Shades of Foam hitting the shuttle wing all over again.

    • There will be a discussion if the blade inspections will reduce the chance for a blade-out below an agreed value or if a small risk for blade failure * a big fleet makes logic for an AD that reinforces the inlet by means of sculptured titanium beams or carbon beams between the inlet fwd and aft bulkheads keeping the inlet pretty straight at blade outs not deforming and catching the +500kn wind crumbling the inlet. The UK CAA would have gone for 4ea reinforcement beams pretty quick I think. Otherwise they can do a 500kn blade out event on a 747 test aircraft with the CFM56-7B and nacelle installed then let the explosives set off and see what happens, there is maybe less risk using the AN225 for this test, having #1 engine a CFM56-7B propulsion unit and release the fan blade at +500kn.

      • I am not sure if the trajectory of a fan blade airfoil liberated through classic explosive detonation would be similar to the trajectory of a fan blade airfoil liberated from a natural rupture. Probably not.

        • Also, the detail of the effects of a blade failure likely vary depending where the blade is in its rotation when the failure occurs. Obviously no way to predict this.

        • The blade is almost fully sawed thru to reduce the amount of exposives needed and from the centrifual load it moves radially out an hit the fan runstrip and containment within milliseconds, the angle of release might effect the inlet more or less but a release at around 3 or 9 o’clock sounds like worst case for the inlet areo loads.

    • While I do not have specific data, what I can say is that Nacelle Maintenance is a highly neglected issue. Nacelles, that is Inlet Cowls, Cowl Doors, Thrust Reversers, Exhaust Nozzles are “on-condition” components that may stay on wing quite a considerable time without structural overhauls.

      The issue is complicated also by the fact these components are now complex composite structures that exhibit another deterioration mode than previous simple metallic structures.

      Lately we’ve see several incidents with serious Inlet Cowl deterioration….

  6. We could well see the same effects that upturned the financial markets.
    The “ablative skin” over any risk has been carefully and evenly whittled down to condom thinness. If it gives in a single place the perturbations flood the complete area with problem ringing.

  7. “GENTLEMEN, YOU CAN’T FIGHT IN HERE! THIS IS THE WAR ROOM!”

    [Fade to: Mushroom Clouds – OR – Coming Greater Global Depression]

    REMEMBER: Reported 1st here at LEEHAM News and Comment….

    All the best, Scott
    Norm (75)

  8. From EASA Certification Specification CS25.1309;

    The requirements of CS 25.1309(b) apply to powerplant installations as specified in CS 25.901(c).

    (b) The aeroplane systems and associated components, considered separately and in relation to other systems, must be designed so that –

    (1) Any catastrophic failure condition
    (i) is extremely improbable; and
    (ii) does not result from a single failure; and

    (2) Any hazardous failure condition is extremely remote; and
    (3) Any major failure condition is remote.

    If a fan blade on a CFM56 comes off, and that single event leads to the detachment of a sufficiently large portion of the air intake, and that detached structure then goes on to remove a flap or the horizontal stabilizer, then it will likely result in a catastrophic or extremely hazardous condition – a likely hull loss.

    You can’t inspect your way out of this, since the catastrophic condition does plausibly originate in a single failure – a fan blade release. You can mitigate the risk by inspection certainly, and also by hard lifing the blade.

    Nonetheless, as it stands, there’s evidence in the form of two air intake detachments that the 737 at least does not meet CS25.1309. There’ll be a near identical FAA requirement I’m sure.

    • Yeap, I kind of agree…

      Theoretically one can argue that a certain failure mode is impossible to happen until it does actually occur.

      Some may argue at first occurrence “oh, it’s an isolated event”, but oopps, two ✌ events following each other at short intervals… ??? What does Weibull say?

      In addition, Airworthiness will always act on factual occurrences.

  9. Re: “Now, a European appraisal company forecasts that the “bow wave” of CFM56 shop visits will create a crisis for spare engines and parts.”

    Do the final results of Southwest’s CFM56 blade inspections, as reported in the following excerpts from the FlightGlobal article at the link after the excerpts, support this forecast?

    “Last week, the airline completed inspections on more than 35,000 fan blades – an effort that began in 2016 after a similar accident in August of that year, also involving a cracked fan blade. The carrier accelerated inspections of the remaining fan blades following the 17 April accident.

    Chief executive Gary Kelly says there were “zero findings” from the inspections that recently wrapped up, but says the airline removed a couple dozen blades that showed coating anomalies. These were sent back to CFM for further checks that will be more invasive beyond the airline’s ultrasonic inspections, he adds.

    “There is a more precise and more invasive step that can be taken if you have some indeterminate results from that [ultrasonic] inspection,” says Kelly. “This is an extra cautionary step we are taking.”

    https://www.flightglobal.com/news/articles/southwest-launches-fan-blade-tracking-after-april-en-448654/

    • Fan blade inspections does not effect CFM56-7B Engine shop visit rates as a fan blade set is removed on-wing. An inspected, moment weighted optimized and dry film lubricated set is installed, some Airlines will also swap out the fan blade spacers for overhauled ones and put on a newly painted spinner.

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