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Boeing, and FAA oversight

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Boeing, and FAA oversight

Old 15th Feb 2020, 07:17
  #221 (permalink)  
 
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What a lame response by B - “pulling out the wires risks chafing the other wires...”
Disconnect the wire, leave it in place and route a new wire externally to the bundle.
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Old 15th Feb 2020, 10:37
  #222 (permalink)  
 
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Originally Posted by Bend alot View Post
Are the NG and MAX actual manual trim wheel forces the same or is the MAX even harder to move as the aircraft moves out of trim?
Same size trim wheel, same size horizontal stabilizer and elevator in both variants. Can't see any reason why manual trim forces would be significantly different.
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Old 15th Feb 2020, 11:08
  #223 (permalink)  
 
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Dave, similar forces but not necessarily the same. Consider the aerodynamic influences of wing tip changes, and the 'MCAS issues' of thrust, engine cowl and wing-pylon interface.

Whilst there should not be any mechanical increase, small but significant changes can arise from revised cable runs and pulleys, pressure bulkhead seals, etc.

If the NG was marginally acceptable, then a small change in the Max might not meet the certification requirements.
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Old 15th Feb 2020, 11:34
  #224 (permalink)  
 
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Originally Posted by Twitter View Post
What a lame response by B - “pulling out the wires risks chafing the other wires...”
Disconnect the wire, leave it in place and route a new wire externally to the bundle.
IIRC, not permitted. You don't leave non functional wiring in place.
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Old 15th Feb 2020, 12:16
  #225 (permalink)  
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Originally Posted by safetypee View Post
Dave, similar forces but not necessarily the same. Consider the aerodynamic influences of wing tip changes, and the 'MCAS issues' of thrust, engine cowl and wing-pylon interface.
If an improvement in tip losses occurs from the upper and lower wing tip devices, (which would be consistent with studies on sections such as flaps) then there is a slight increase in the effective aspect ratio, and the L/D curve would be slightly steeper. That effect doesn't affect to any significant extent the downwash that impinges on the horizontal stabiliser, but the engine geometry will. The effect would be for an increase in downwash to the tailplane, but disregarding the MCAS issue, that would be a constant differential to the forces acting at any time on the aircraft for a given cg/mach/AoA, for normal range AoA. For higher AoA, the effect of the nacelle interaction with the inner wing area, would be to increase downwash at higher AoA, which for a given stab setting would result in an increased resultant trim downforce giving a pitch up tendency. in itself, that is tending towards a higher pitch attitude and reduction in speed which reduces the load that would exist on the manual trim system. Yes, that would result in non linear elevator forces, which is undesirable to the certification for HQ, but the system itself washes out the stab forces so would not have been a problem to manual trim in the absence of MCAS. May sound odd, but thats how the forces would play out.

Originally Posted by safetypee View Post
Whilst there should not be any mechanical increase, small but significant changes can arise from revised cable runs and pulleys, pressure bulkhead seals, etc.
True, but there is apparently not much if any difference between the flavors considered here. Not sure that TBC has any drivers towards alteration of the control runs in the stab itself, or with the pressure bulkhead seals etc. Roll control architecture was altered in respect to the spoilers.

Originally Posted by safetypee View Post
If the NG was marginally acceptable, then a small change in the Max might not meet the certification requirements.
Maybe, but as far as the manual stab trim use goes, in the absence of MCAS, it probably was slightly better due to the slight changes in the wing downwash.

​​​​​​​
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Old 15th Feb 2020, 14:32
  #226 (permalink)  
 
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Originally Posted by ktcanuck View Post
IIRC, not permitted. You don't leave non functional wiring in place.
You don’t? Aircraft with uninstalled options for sure have the wiring pre incorporated in the loom - which is for the time being non functional.
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Old 15th Feb 2020, 21:54
  #227 (permalink)  
 
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What would the adverse weather be?

https://www.aeroinside.com/item/1246...ult-of-weather

Other interesting issues here, a few engines, the door and the stowaway.

https://www.aeroinside.com/incidents...ing-737-800max
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Old 16th Feb 2020, 01:21
  #228 (permalink)  
 
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Originally Posted by Twitter View Post
You don’t? Aircraft with uninstalled options for sure have the wiring pre incorporated in the loom - which is for the time being non functional.
On new build aircraft, the wiring for uninstalled options will often be deleted during build to save weight (wire bundles are not mass produced in the way that automotive wiring is). However it's not uncommon for wiring to be 'capped and stowed' when optional equipment is deactivated (often occurs when aircraft change hands and the new operator wants a standard configuration).
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Old 16th Feb 2020, 06:01
  #229 (permalink)  
 
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Originally Posted by Bend alot View Post
I don’t know, but icing would be a typical culprit for weather related engine vibrations.
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Old 16th Feb 2020, 07:01
  #230 (permalink)  
 
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Originally Posted by AerocatS2A View Post
I don’t know, but icing would be a typical culprit for weather related engine vibrations.
I would expect weather to be a common factor to both engines.
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Old 16th Feb 2020, 07:51
  #231 (permalink)  
 
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Originally Posted by tdracer View Post
On new build aircraft, the wiring for uninstalled options will often be deleted during build to save weight (wire bundles are not mass produced in the way that automotive wiring is). However it's not uncommon for wiring to be 'capped and stowed' when optional equipment is deactivated (often occurs when aircraft change hands and the new operator wants a standard configuration).
Thanks TD. So Boeing’s objection to the wiring change on the grounds of chafing while removing is an invalid one.
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Old 16th Feb 2020, 12:51
  #232 (permalink)  
 
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Originally Posted by Twitter View Post
Thanks TD. So Boeing’s objection to the wiring change on the grounds of chafing while removing is an invalid one.
What the FAA wants isn't to remove an individual wire but to remove and reconfigure multiple wire bundles; apparently by re-looming the wires into entirely new bundles.

It's tough enough to correctly fabricate and maintain bundles before installation with all the room of a factory floor - my experience is military ground vehicles up to 50 feet in length. Essentially remanufacturing the wiring post install in the confines of a fuselage is asking for nearly innumerable defects.

Running a wire all by itself alongside an existing bundle is a bad idea as it will easily move and chafe and fatigue or wear through, allowing short circuits or corrosion.
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Old 16th Feb 2020, 14:25
  #233 (permalink)  
 
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Originally Posted by MechEngr View Post
What the FAA wants isn't to remove an individual wire but to remove and reconfigure multiple wire bundles; apparently by re-looming the wires into entirely new bundles.

It's tough enough to correctly fabricate and maintain bundles before installation with all the room of a factory floor - my experience is military ground vehicles up to 50 feet in length. Essentially remanufacturing the wiring post install in the confines of a fuselage is asking for nearly innumerable defects.

Running a wire all by itself alongside an existing bundle is a bad idea as it will easily move and chafe and fatigue or wear through, allowing short circuits or corrosion.
Thanks for the insight Mech.
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Old 16th Feb 2020, 19:38
  #234 (permalink)  
 
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Issues like this one are clearly going to be met by harder looks and more rigid responses at the FAA than previously. Positioned between the US manufacturer and the other CAAs of the world is a less comfortable position that it once was. Boeing has significantly shaken the world's confidence in its trustworthiness and the consequences are already expensive and painful.
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Old 16th Feb 2020, 23:33
  #235 (permalink)  
 
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Not sure if you have seen this yet?

https://www.nakedcapitalism.com/2020...t-recover.html
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Old 17th Feb 2020, 00:23
  #236 (permalink)  
 
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Originally Posted by Chris2303 View Post
Not sure if you have seen this yet?

https://www.nakedcapitalism.com/2020...t-recover.html
Well. I guess few will accuse Travis of mincing words with this one.
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Old 17th Feb 2020, 05:50
  #237 (permalink)  
 
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Originally Posted by Chris2303 View Post
Not sure if you have seen this yet?

https://www.nakedcapitalism.com/2020...t-recover.html
WOW, WOW, WOW!

This article says things out loud which many of us suspected a year ago, and explains them in a way which is much clearer than some of the mainstream coverage. It also addresses several points about the B737 MAX and MCAS, which I have not seen, despite reading the many thousands of posts on this forum.
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Old 17th Feb 2020, 09:40
  #238 (permalink)  
 
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Originally Posted by GordonR_Cape View Post
WOW, WOW, WOW!

This article says things out loud which many of us suspected a year ago, and explains them in a way which is much clearer than some of the mainstream coverage. It also addresses several points about the B737 MAX and MCAS, which I have not seen, despite reading the many thousands of posts on this forum.
Quite a few of the astonishing items in that article are false. But it is written as a Gish Gallop, so an equally lengthy response is required to debunk them.
Example: That the 737 MAX was unstable and MCAS corrects that instability. So far, all facts point to False. The 737 Max is stable and MCAS is not needed to correct instability. There are many others, but since it starts off with misinformation, it is not a good sign.
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Old 17th Feb 2020, 11:08
  #239 (permalink)  
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Originally Posted by MechEngr View Post
Quite a few of the astonishing items in that article are false. But it is written as a Gish Gallop, so an equally lengthy response is required to debunk them.
Example: That the 737 MAX was unstable and MCAS corrects that instability. So far, all facts point to False. The 737 Max is stable and MCAS is not needed to correct instability. There are many others, but since it starts off with misinformation, it is not a good sign.
Pity that the conversation loses it's force in loose facts.

For the record, the strakes on the engine cowl are not fitted as an aid to stability, they make up for the decrement in CL at the higher AOA that arises from the interaction of the cowl flow and the wing with a close coupled cowl/wing design. The AOA that occurs at is high but all speeds for TO and landing are related to the stall speed, and therefore the decrement at stall impacts TO and landing requirements.

Indeed, as far as stability goes, they actually are slightly destabilising on a swept wing.... Why? Because... as AOA increases, the normal cowl will start to degrade flow conditions in the wake of the nacelle, (and a bit inboard...) and that lowers local CL. For the section it has a modest effect on Cm, but the overall geometry of losing CL inboard means that there is a shift of lift distribution span-wise towards the tip, and as the tips are swept... rearwards (makes the flutter stability nicerer) then there is an increase in nose down pitching moment as AOA increases. Yaay. That's nice. So. with the MAX-facktor, we get a biggerer effect from the interaction of the cowl, and the strakes were added... and that means we got a betterer CLmax, yaay, but it is destabilising. Fix MCAS, reset the strakes... add water and mix. Thats the aero fix, and you get a bit of a loss of performance for TO and LDG, which can be picked up with fun stuff on the TE of the flap, which also makes the wing work better in the cruise. Yet, here we are, 16 months into this debacle, awaiting a fix of a lousy software code and system architecture that could be removed completely with a hacksaw and some bondo. Now where did I put my bottle... its Miller time.

Simply put: for the restoration of CL that the strake give, you get rid of the natural negative Cm that occurs without them,... yet the program keeps them in place. Loopy $h[#.

[b]Happy pickky time:

Zhang, W., Chen, H., Zhang, Y., Fu, S., Chen, Y., Li, Y., and Zhou, T., “Numerical Research of the Nacelle Strake on a Civil Jet”, ICAS2012, 2012.










References cited in the above paper. The understanding on the effect of the strake goes back further than these to work in the mid 80's and early 90's. The improvement in CFD gives prettier pictures though. BTW, the same effect does occur on TP aircraft dependent on their cowl design, and a strake may improve CL at modest AOA, DLR has nice work on that recently giving a 10% increase in CL.
[1] Meredith P. T. Viscous Phenomena Affecting High Lift Systems and Suggestions for Future CFD Development. High-Lift Systems Aerodynamics. AGARD, CP 315, Sep. 1993, pp. 19-1~19-8.

[2] R. Rudnik. Stall Behaviour of the EUROLIFT High Lift Configurations. 46th AIAA Aerospace Sciences Meeting and Exhibit. AIAA Paper 2008-836, Reno, Nevada, January 2008.

[3] Harald Quix, Matthias Schulz and Jürgen Quest, et. al. Low Speed High Lift Validation Tests within the European Project EUROLIFT II. 25th AIAA Applied Aerodynamics Conference. AIAA Paper 2007-4298, Miami, FL, June 2007.

[4] H. Frhr. v. Geyr, N. Schade, J.W. v. d. Burg, et. al. CFD Prediction of Maximum Lift Effects on Realistic High Lift Commercial Aircraft Configurations within the European project EUROLIFT II . 25th AIAA Applied Aerodynamics Conference. AIAA Paper 2007-4299, Miami, FL, June 2007.

[5] Heinz Hansen, Peter Thiede, Frederic Moens, et. al. Overview about the European high lift research programme EUROLIFT. 42nd AIAA Aerospace Sciences Meeting and Exhibit. AIAA Paper 2004-767, Reno, Nevada, January 2004.

[6] R. Rudnik, H. Frhr. v. Geyr. The European High Lift Project EUROLIFT II –Objectives, Approach, and Structure. 25th AIAA Applied Aerodynamics Conference. AIAA Paper 2007-4296, Miami, FL, June 2007.

[7] Christopher L. Rumsey, Susan X. Ying. Prediction of high lift: review of present CFD capability. Progress in Aerospace Sciences. Vol. 38, pp 145-180, 2002.

[8] Jeffrey P. Slotnick, Judith A. Hannon, Mark Chaffin. Overview of the First AIAA CFD High Lift Prediction Workshop. 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. AIAA Paper 2011-862, Orlando, Florida, January 2011.

[9] HaiXin Chen, Song Fu, FengWei Li. Navier–Stokes Simulations for Transport Aircraft Wing/Body HighLift Configurations, JOURNAL OF AIRCRAFT, Vol. 40, No. 5,pp883-890, 2003.

[10] 1st AIAA CFD High Lift Prediction Workshop Gridding Guidelines, http://hiliftpw.larc.nasa.gov.

[11]Niko F. Bier, David Rohlmann, Ralf Rudnik. Numerical Maximum Lift Predictions of a Realistic Commercial Aircraft in Landing Configuration. 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. AIAA Paper 2012-279, Nashville, Tennessee, January 2012.

[12]Peter Eliasson, Pietro Catalano, Marie-Claire Le Pape, et al. Improved CFD Predictions for High Lift Flows in the European Project EUROLIFT II. 25th AIAA Applied Aerodynamics Conference. AIAA Paper 2007-4303, Miami, FL, June 2007.

[13]Masahiro Kanazaki, Yuzuru Yokokawa,Mitsuhiro Murayama,et al., Efficient Design Exploration of Nacelle Chine Installation in Wind Tunnel Testing. 46th AIAA Aerospace Sciences Meeting and Exhibit. AIAA Paper 2008-155, Reno, Nevada, January 2008.

[14]Yuzuru Yokokawa, Mitsuhiro Murayama, Masahiro Kanazaki, et al., Investigation and Improvement of High-lift Aerodynamic Performances in Lowspeed Wind Tunnel Testing. 46th AIAA Aerospace Sciences Meeting and Exhibit. AIAA Paper 2008-350, Reno, Nevada, January 2008.

[15]Yuzuru YOKOKAWA, Mitsuhiro MURAYAMA, Hiro-shi UCHIDA, et al., Aerodynamic Influence of a Half-Span Model Installation for High-Lift Configuration Experiment. 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. AIAA Paper 2010-684, Orlando, Florida, January 2010.

[16]Zhang Y., Chen H., Fu S., Improvement to Patched Grid Technique with High-Order Conservative Remapping Method, JOURNAL OF AIRCRAFT, Vol. 48, No. 3, pp. 884-893,2011.

[17]Zhang Yufei, Chen Haixin, Zhang Wensheng, et al., Wing/engine integrated optimization based on Navier-Stokes equations. 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. AIAA Paper 2012-1046, Nashville, Tennessee, January 2012.

[18]Zhang Yufei, Chen Haixin, Fu Song. A Karman Vortex Generator for Passive Separation Control in a Conical Diffuser. SCIENCE CHINA Physics, Mechanics & Astronomy, Vol.55, No. 5, pp. 828-836, 2012.


Last edited by fdr; 17th Feb 2020 at 11:24.
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Old 17th Feb 2020, 11:20
  #240 (permalink)  
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Yes, having read that, it rather coloured the rest of the article. (that was of course re #238 )
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