text: FAA New AD Against B787 - GenX Icing - Airliners.net
  FAA New AD Against B787 - GenX Icing
  budalb
  Joined: Wed Feb 17, 2016 3:26 am
  Fri Apr 22, 2016 10:51 pm
  http://www.bloomberg.com/news/articl...-after-dreamliner-in-flight-damage
  Another GenX icing issue.
  RE: FAA New AD Against B787 - GenX Icing
  Fri Apr 22, 2016 10:58 pm
  SUMMARY: We are adopting a new airworthiness directive (AD) for The Boeing Company Model
  787-8 and 787-9 airplanes powered by General Electric (GE) GEnx-1B engines. This AD requires
  revising the airplane flight manual (AFM) to provide the flight crew a revised fan ice removal
  procedure and a new associated mandatory flight crew briefing to reduce the likelihood of engine
  damage due to fan ice shedding. This AD also removes certain dispatch relief. For airplanes with
  certain engines, this AD also requires reworking or replacing at least one engine. This AD was
  prompted by a recent engine fan blade rub event that caused an in-flight non-restartable power loss.
  We are issuing this AD to prevent susceptibility to heavy fan blade rubs, which could result in engine
  damage and a possible in-flight non-restartable power loss of one or both engines.
  http://rgl.faa.gov/Regulatory_and_Gu...57f9d0049d985/$FILE/2016-08-12.pdf
  Fri Apr 22, 2016 11:07 pm
  Fortunately the fix seems pretty straightforward and can be performed while the engine is on the plane.
  Joined: Sat Jan 26, 2008 12:15 am
  Fri Apr 22, 2016 11:19 pm
  Before I completely mock Mr. Gates at the Seattle Times, maybe I should ask, do airlines really put two different types of engines on the same plane? Meaning would there be a GE on one side and CFM on the other? I can't imagine that would even be possible.
  On planes with the same engine model on both wings, the problem could cause a potentially catastrophic dual shutdown of both engines.
  http://www.seattletimes.com/business...ers-engine-fix-on-176-boeing-787s/
  Fri Apr 22, 2016 11:23 pm
  Quoting rgreenftm (Reply 3):
  Before I completely mock Mr. Gates at the Seattle Times, maybe I should ask, do airlines really put two different types of engines on the same plane? Meaning would there be a GE on one side and CFM on the other?
  No, per the Bloomberg article:
  Airlines operating 787s with GE engines have 150 days to make sure that they have made repairs or have installed at least one older version of the GEnx engine on each plane so that they won't risk losing power in both, the FAA said.
  Sat Apr 23, 2016 12:19 am
  Before I completely mock Mr. Gates at the Seattle Times, maybe I should ask, do airlines really put two different types of engines on the same plane?
  They can, but it is two types within the same family.
  So say a GEnx-1B67/P1 (PiP1) on one wing and the affected GEnx-1B67/P2 (PiP2) on the other.
  [Edited 2016-04-22 17:19:54]
  Sat Apr 23, 2016 1:53 am
  I thought BI also had a similar shutdown eveet ?
  Sat Apr 23, 2016 3:31 am
  The title should be "New AD against GenX icing to affect B787s" I think the angle of reporting by the Wall Street Journal is more accurate because this is more of an engine supplier issue than one caused by the plane manufacturer.
  http://www.wsj.com/articles/faa-mand...-to-150-boeing-787-jets-1461334638
  I am not an Airbus or Boeing fan, just an aircraft fan
  Sat Apr 23, 2016 6:33 am
  Quoting alyusuph (Reply 7):
  The thread title is correct - the FAA issues the AD against the plane.
  787-8 and 787-9 airplanes powered by General Electric (GE) GEnx-1B engines.
  Quoting budalb (Thread starter):
  Isn't this really the SAME engine icing issue that caused a service bulletin in early April? I thought they were already working on making the changes and were at least a third of the way into it.
  Sat Apr 23, 2016 1:35 pm
  Isn't this really the SAME engine icing issue that caused a service bulletin in early April?
  The earlier issue concerned ice forming inside the core of the engine behind the fan. This issue concerns ice forming on the fan blades themselves.
  Interesting observation. I wonder if this has been an issue on all fan blades over the years, however with metallic blades there was some heat transfer along the fan blade from the core providing de-ice.
  That might very well be. Spinning up the blades for a time via adding power clears them so perhaps such a maneuver causes additional friction heating of the blades to melt / dislodge the ice.
  Sat Apr 23, 2016 3:51 pm
  This issue concerns ice forming on the fan blades themselves.
  Does this suggest that this section of the engine should be running hotter ? Or am I stating the obvious?
  [Edited 2016-04-23 08:52:22]
  Sat Apr 23, 2016 3:59 pm
  The issue was caused by circumferentially uneven ice shedding from fan blades, creating fan imbalance. The fan imbalance caused the shaft to whirl, similar to an imbalanced laundry load. So the fan tip ground the casing. Heat transfer doesn't play significant roles, due to the relatively thin fan blades. Such imbalance in icing more or less exists in every engine. This one is a lot severe due to reduced tip clearance.
  Sat Apr 23, 2016 5:22 pm
  Quoting budalb (Reply 15):
  This one is a lot severe due to reduced tip clearance.
  I believe the goal is to reduce that clearance as much as possible, is it not?
  I wonder if other engine designs that have more pronounced reductions in tip clearances might be susceptible to this condition, as well?
  Sat Apr 23, 2016 5:43 pm
  So it would appear that GE now has a very big problem with the basic design of the GEnX engine. The engine seems to be very prone to icing at different altitudes and in different parts of the engine structure, both in the core and in the propulsor.
  Given that GE just performed initial startup on the GE9x engine, I am left to wonder if that that engine will suffer similar issues, given how much of the GE9x engine is derived from the GEnX.
  My understanding is that the conditions in which this phenomenon occurs are difficult (to the point of impracticality) to simulate on the ground and that it is difficult to find these conditions even during flight testing, since it takes a "perfect storm" of temperature, pressure, altitude, and humidity to induce these phenomena. With the GE9x being built already, a major change to the engine's design is not feasible.
  So how are they going to dig their way out of this one?
  Sat Apr 23, 2016 6:56 pm
  So it would appear that GE now has a very big problem with the basic design of the GEnX engine.
  Well they redesigned a large portion of it between EIS and PIP1.
  GE's been using the information they've learned about icing in the GEnx to improve the GE9X's resistance.
  Sat Apr 23, 2016 7:03 pm
  Two different issues on two different versions of the engine. The first problem has been resolved. This problem is a new one that was recently introduced in a pip. They are not going to dig their way out of it, they are going to machine some material off of the ends of the fan blades. For those engines already installed, the repair can be made on the wing.
  The point is that there is no basic design flaw that runs throughout the line.
  Sat Apr 23, 2016 8:24 pm
  On a sidenote, what's the GE vs RR score on the 787 family thus far? I understand RR have been catching up though I doubt issues like the present AD are significant factors in airlines' engine decisions.
  Joined: Thu Sep 29, 2011 1:46 am
  Sun Apr 24, 2016 11:28 pm
  Does this affect the ETOPS rating of those planes where the fix hasn't been applied yet?
  Mon Apr 25, 2016 1:20 am
  Quoting sejtam (Reply 24):
  ETOPS is influenced by the In-Flight Shutdown Rate. While one or two planes had IFSDs from this issue, with the new fixes, it should no longer be an issue in terms of IFSDs. The original icing issue was more severe and that did not affect ETOPS.
  [Edited 2016-04-24 18:21:09]
  Mon Apr 25, 2016 2:48 am
  In this way its not really possible. I guess in theory it could be done but no one would pay to have say a CFM56-5B on one side of a 321 and a V2500-A5 on the other.
  having said that the biggest issue here would be software. The hardware side can be handled pretty easy if you want to pay for it. Not sure if the computers could run different OEMs. I don't think going from say a CFM56-5A to a CFM56-5B is really possible.
  Having said that the 787 was designed with quick switching between the Trent and GEnX in mind but I believe that the plan was not done.....for the most part. (still have to change the pylons)
  Mon Apr 25, 2016 12:30 pm
  Quoting nikeherc (Reply 21):
  The fix is to basically unpip the pip then?
  Mon Apr 25, 2016 12:49 pm
  Do we know the list of airlines impacted ?
  Mon Apr 25, 2016 3:00 pm
  Quoting RickNRoll (Reply 27):
  Fan blade changes were made in PiP1, as I recall, but not sure clearances were changed. Based on what the initial media report indicates, the "fix" is just to shave them down a bit - and as it can evidently be done with the engine on the plane, I am guessing it's really bit.
  Quoting nikeherc (Reply 16):
  They just cut the clearance between the blades and the case a bit too tight.
  But see the Seattle Times article linked to in reply 3:
  "When the ice abruptly shed, it caused the blades to move slightly forward and because of the contour of the fan case, this was enough to make the blade tips rub against the case."
  "...the shaving [i.e., repair] occurs in front of the fan blades..."
  so it sounds like it's not strictly a blade clearance issue but a blade movement issue into an unusual portion of the fan cowl where the clearance is not adequate.
  Fan blade changes were made in PiP1, as I recall, but not sure clearances were changed. Based on what the initial media report indicates, the "fix" is just to shave them down a bit
  They're shaving the fan cowl, not the blade tips.
  [Edited 2016-04-25 08:39:50]
  Mon Apr 25, 2016 4:28 pm
  Quoting hivue (Reply 32):
  That makes more sense as if it has been a true clearance issue.
  As does that.
  Tue Apr 26, 2016 12:10 am
  Quoting hivue (Reply 30):
  Sounds similar to one of the GTF problems. To get improved fuel economy the manufacturers are pushing the clearance limits of the fans to the limit.
  I would assume this will create a slight loss in performance for the latest pip as the cowling will not be the designed shape any more.
  Tue Apr 26, 2016 12:17 am
  Quoting RickNRoll (Reply 32):
  Well it will still be optimum where it counts - the space where the fan blades normally occupy - so I would expect it to not affect normal operational performance at all.
  And if the fan blade is out of normal position, well, that's probably a bigger hit to performance than a millimeter or two of intake cowling.
  Tue Apr 26, 2016 9:47 am
  A better thread title would be " New FAA AD For GenX.. (748, 787 )
  Quoting iahcsr (Reply 30):
  Not really, given the AD is issued only for GEnx-powered 787s.
  Tue Apr 26, 2016 9:59 am
  Have any 747-8 had PIP2 applied to the GEnx engines?
  Tue Apr 26, 2016 11:24 am
  Quoting scbriml (Reply 8):
  No, thread title is incorrect. The snippet you posted says as much:
  Don't see an "Against" anywhere.
  Tue Apr 26, 2016 12:09 pm
  Quoting neutronstar73 (Reply 33):
  There's no requirement for a thread title to be a direct quotation. It's common English usage, old chap.
  Tue Apr 26, 2016 1:52 pm
  Quoting scbriml (Reply 34):
  Then we have a fundamental difference of opinion on the use of "against" and "for", specifically when it comes to the adoption, acceptance, or issuance of things.
  Against: in opposition to; contrary to; adverse or hostile to: in resistance to or defense from: in an opposite direction to: into contact or collision with; toward; upon:
  For: with the object or purpose of: intended to belong to, or be used in connection with: suiting the purposes or needs of:
  I think the CORRECT usage is "for", as they are issuing the AD "intended to belong to, or be used in connection with" the Boeing Company Model 787-8 and 787-9 airplanes powered by General Electric (GE) Genx-1b engines.
  But different minds, different opinions.
  Thu Apr 28, 2016 5:18 am
  Quoting neutronstar73 (Reply 35):
  Given that this AD would adversely affect 787s in service by requiring additional maintenance and requiring two different versions of a given engine type to be installed on a single airframe, I would argue that the use of the word "against" is not unreasonable.
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