Civil Aviation Development & Discussion

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Austin
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Re: Civil Aviation Development & Discussion

Postby Austin » 03 Apr 2019 14:27

WSJ reports that Ethiopian Airline Pilot disabled MCAS system following Boeing procedure but was not able to level off the plane.

This is from preliminary reading of BB/FDR

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Re: Civil Aviation Development & Discussion

Postby chola » 03 Apr 2019 14:38

Austin wrote:WSJ reports that Ethiopian Airline Pilot disabled MCAS system following Boeing procedure but was not able to level off the plane.

This is from preliminary reading of BB/FDR


My god, this is frightening. Sounds like it went into an unrecoverable stall/spin. Something might be very wrong with the MAX's design now after mating the new engines and messing with the CoG of the classic 737.

They should have designed a new aircraft. Horrible.

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Re: Civil Aviation Development & Discussion

Postby Austin » 03 Apr 2019 15:18

Ethiopian Airlines Pilots Initially Followed Boeing’s Required Emergency Steps to Disable 737 MAX System

https://www.wsj.com/articles/ethiopian- ... 1554263276

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Re: Civil Aviation Development & Discussion

Postby chetak » 04 Apr 2019 01:22

twitter


Image

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Re: Civil Aviation Development & Discussion

Postby chetak » 04 Apr 2019 01:39

Austin wrote:WSJ reports that Ethiopian Airline Pilot disabled MCAS system following Boeing procedure but was not able to level off the plane.

This is from preliminary reading of BB/FDR


the MCAS software seems to have an evil mind of its own.

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Re: Civil Aviation Development & Discussion

Postby Austin » 04 Apr 2019 10:02

They call it AI for a reason :evil:

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Re: Civil Aviation Development & Discussion

Postby Austin » 04 Apr 2019 18:10

BBC: Ethiopian Airlines Boeing 737 pilots 'could not stop nosedive'

https://www.bbc.com/news/business-47812225

The Ethiopian Airlines plane that crashed last month nosedived several times before it hit the ground, a preliminary report has said.

Pilots "repeatedly" followed procedures recommended by Boeing before the crash, according to the first official report into the disaster.

Despite their efforts, pilots "were not able to control the aircraft", Transport Minister Dagmawit Moges said.


In a news conference in Addis Ababa, Ms Dagmawit said: "The crew performed all the procedures repeatedly [that were] provided by the manufacturer but were not able to control the aircraft."

The 737 Max family of aircraft was grounded following the Ethiopian Airlines crash, a move affecting more than 300 planes.

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Re: Civil Aviation Development & Discussion

Postby Austin » 04 Apr 2019 21:17

Don’t Let Boeing 737 Max 8 Jets Fly Until Fix Is Confirmed, Report Recommends


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Re: Civil Aviation Development & Discussion

Postby negi » 04 Apr 2019 21:21

Austin wrote:They call it AI for a reason :evil:
Not that AI is some magic wand but let's not blame something that was not even the issue here ; the problem at hand here does not need any AI based solutions , it's classic case of technical debt in core areas being offloaded to the software layer . The guy who must have come up with idea would have thought "sardar khus hoga sabaasi dega..... " (master will be elated and give a pat on the back) haaa thoo.


I have always maintained for things that move physically keep software to bare minimum just like cars after the 90s with layers of software they fail due to one reason or another .

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Re: Civil Aviation Development & Discussion

Postby Austin » 04 Apr 2019 21:55

Civil Aircraft has always been software driven since the time Airbus went with FBW for A320 and this then the software component has grown far greate r in aircraft ...Safety is one key requirement which drives it and that makes Civil Aircraft that fly today 99 % safe

My thinking is MAX has aerodynamics issue likely that also involves CG and not sufficiently tested and badly implemented Software in MCAS.

Boeing needs to thoroughly debug MAX Aerodynamics and MCAS along with its FBW even if it means loosing leadership position in narrow body market. Some quick fix MCAS patch recently tested may not completely solve this issue and will show up in different ways leading to more loss of life.

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Re: Civil Aviation Development & Discussion

Postby chetak » 05 Apr 2019 00:53

Austin wrote:Civil Aircraft has always been software driven since the time Airbus went with FBW for A320 and this then the software component has grown far greate r in aircraft ...Safety is one key requirement which drives it and that makes Civil Aircraft that fly today 99 % safe

My thinking is MAX has aerodynamics issue likely that also involves CG and not sufficiently tested and badly implemented Software in MCAS.

Boeing needs to thoroughly debug MAX Aerodynamics and MCAS along with its FBW even if it means loosing leadership position in narrow body market. Some quick fix MCAS patch recently tested may not completely solve this issue and will show up in different ways leading to more loss of life.


A few days ago while boarding the A320, I noticed that each engine cowling had one prominently downward slanted vane on the outboard side.

That would possibly reduce any unwanted lift produced by the engine cowling itself.

At higher AOAs, the max8's new and bigger engine cowling does produce considerable lift on its own, which possibly causes the MCAS to compensate that much more, thus complicating further an already complex situation.

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Re: Civil Aviation Development & Discussion

Postby Austin » 05 Apr 2019 10:58

chetak wrote:A few days ago while boarding the A320, I noticed that each engine cowling had one prominently downward slanted vane on the outboard side.

That would possibly reduce any unwanted lift produced by the engine cowling itself.



Can you show by any pics what you mean by this ......Sorry I dont get this. Visual rep may help to understand this

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Re: Civil Aviation Development & Discussion

Postby Austin » 05 Apr 2019 11:05

Boeing CEO 'sorry' for lives lost in 737 MAX accidents

https://edition.cnn.com/2019/04/04/worl ... index.html

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Re: Civil Aviation Development & Discussion

Postby chetak » 05 Apr 2019 11:08

Austin wrote:
chetak wrote:A few days ago while boarding the A320, I noticed that each engine cowling had one prominently downward slanted vane on the outboard side.

That would possibly reduce any unwanted lift produced by the engine cowling itself.



Can you show by any pics what you mean by this ......Sorry I dont get this. Visual rep may help to understand this



as a representation, this is on the embraer E190

Image

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Re: Civil Aviation Development & Discussion

Postby Sri » 05 Apr 2019 11:55

Austin wrote:Civil Aircraft has always been software driven since the time Airbus went with FBW for A320 and this then the software component has grown far greate r in aircraft ...Safety is one key requirement which drives it and that makes Civil Aircraft that fly today 99 % safe

My thinking is MAX has aerodynamics issue likely that also involves CG and not sufficiently tested and badly implemented Software in MCAS.

Boeing needs to thoroughly debug MAX Aerodynamics and MCAS along with its FBW even if it means loosing leadership position in narrow body market. Some quick fix MCAS patch recently tested may not completely solve this issue and will show up in different ways leading to more loss of life.


The issue is the height / ground clearance of the wings. New MAX aircraft needs more air intake in order to be efficient, just like Airbus Neo. Difference is the ground clearance of the wings. Since 737 is shorter the engineers had to bring the engine forward to accomodate for the larger diameter of the engine. This changed the Aerodynamics of the aircraft.

Since it was commercially important for Boeing to ensure that the pilots didn't have to retrain for the new 737 version, they introduced MCAS. System was designed to work at the background without the pilot feeling the difference in aerodynamic performance.

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Re: Civil Aviation Development & Discussion

Postby nachiket » 05 Apr 2019 13:00

Sri wrote:Since it was commercially important for Boeing to ensure that the pilots didn't have to retrain for the new 737 version, they introduced MCAS. System was designed to work at the background without the pilot feeling the difference in aerodynamic performance.

Yes that was discussed earlier in the thread. The MCAS system is basically a grade A jugaad solution that Boeing chose because they did not want to spend the time and money for a proper hardware fix. There are many other bits of Jugaad on the 737 like the exposed wheels due to lack of landing gear doors. This requires rubber seals for the wheel wells and a special hub cap that acts as a partial fairing to make the exposed wheels more aerodynamic. The flat bottomed triangular engine intakes on the Classic and NG series as well.

All of it done to keep making a 60's era airframe relevant in modern times. They would have been better off making a clean sheet design in the 2000's, but in the zest to compete with Airbus they took the easier way out.

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Re: Civil Aviation Development & Discussion

Postby Singha » 05 Apr 2019 14:06

2nd SW problem found in the FCS. FAA orders boeing to fix it.

ibnlive

Federal aviation regulators have ordered Boeing to fix a second problem with the flight-control system of its grounded 737 Max, the company acknowledged Thursday, as new details emerged that pilots of two planes could not counteract a malfunction of the system using the company's recommended procedures.
The pilots of Ethiopian Airlines Flight 302 performed all the procedures recommended by Boeing to save their 737 Max 8 aircraft but could not pull it out of a flight-system-induced dive, a preliminary report into the crash concluded Thursday.

In a brief summary of the much-anticipated preliminary report on the March 10 crash, Ethiopian Transport Minister Dagmawit Moges told reporters that the "aircraft flight-control system" contributed to the plane's difficulty in gaining altitude after it left Addis Ababa airport. It crashed six minutes later, killing all 157 on board.

She said the crew "performed all the procedures, repeatedly, provided by the manufacturer but was not able to control the aircraft."

As in the aftermath of a Boeing 737 Max 8 crash in Indonesia in October, attention in the Ethiopian Airlines crash has zeroed in on a flight-control system known as the Maneuvering Characteristics Augmentation System, or MCAS, which pushes the nose of the aircraft down to avoid a stall.

But later Thursday, Boeing confirmed to The Washington Post that it had found a second software problem that the Federal Aviation Administration has ordered fixed - separate from the anti-stall system under investigation in the two crashes, and that had led to the aircraft's worldwide grounding.

That additional problem pertains to software affecting flaps and other flight stabilization hardware and is therefore classified as critical to flight safety, said two officials who spoke on condition of anonymity to discuss the ongoing probe.

The realization of a second software problem explains why the timeline that Boeing projected publicly last week for getting hundreds of the aircraft airborne again has slipped, the officials said.

Boeing initially said it planned to submit fixes for its stall-prevention system to the FAA for review last week. On Monday, an FAA spokesman said the agency instead expected to receive the final package of software "over the coming weeks."

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Re: Civil Aviation Development & Discussion

Postby arvin » 05 Apr 2019 19:14

With bugs coming out like this, Looks like process was to directly transfer Jenkins build to factory floor completely bypassing QA.

Aviation equivalent of infamous medical therac 25 incident.

https://en.m.wikipedia.org/wiki/Therac-25

A commission concluded that the primary reason should be attributed to the bad software design and development practices, and not explicitly to several coding errors that were found. In particular, the software was designed so that it was realistically impossible to test it in a clean automated way.


Another similarity with what was done on the plane.

Previous models had hardware interlocks to prevent such faults, but the Therac-25 had removed them, instead on software checks for safety.

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Re: Civil Aviation Development & Discussion

Postby nachiket » 05 Apr 2019 23:31

Both Boeing and the FAA played with people's lives by not doing their due diligence. Unfortunately there are so many airlines with sunk costs on the Boeing 737 that Boeing will get away with it. It will be nearly impossible for most of them to cancel orders and switch to a different model.

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Re: Civil Aviation Development & Discussion

Postby nithish » 06 Apr 2019 02:00

Boeing will slow 737 production by one-fifth; no layoffs planned

The two recent fatal crashes and subsequent grounding of Boeing’s 737 MAX have prompted the jetmaker to sharply and quickly cut production in Renton from the current 52 airplanes per month to 42 per month, signalling that a return to flight isn’t expected soon.

Boeing said it does not plan any layoffs due to the rate reduction, which begins in about 10 days. Managers are informing employees of the Renton 737 factory at meetings on Friday.

“The 737 program will maintain current employment levels,” said Boeing spokesman Paul Bergman. “We’re adjusting the rate to accommodate the pause in deliveries. There’s no employment impact.”

---

So Boeing typically changes the rate only when it knows it can maintain the new production pace for at least a year or so. In this case, Boeing is calling the rate reduction “temporary,” its extent dependent on how long the MAXs are grounded — which is unpredictable.

However, the move suggests Boeing anticipates a prolonged grounding lasting months. Obstacles to resumption of flight include both technical fixes and regulatory approvals from a global community of aviation safety agencies that have grown more skeptical of both Boeing and the U.S. Federal Aviation Administration (FAA).


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Re: Civil Aviation Development & Discussion

Postby chetak » 06 Apr 2019 12:33

nachiket wrote:Both Boeing and the FAA played with people's lives by not doing their due diligence. Unfortunately there are so many airlines with sunk costs on the Boeing 737 that Boeing will get away with it. It will be nearly impossible for most of them to cancel orders and switch to a different model.


the competition just does not have the capacity, for many years to come, to absorb new aircraft orders that may flow to it if max8 boeing orders were to be canceled and changed over to equivalent single aisle airbus orders.

Sadly, the vice versa is also true, if for some reason airbus orders were to be canceled and changed to equivalent single aisle boeing orders.

There is a small possibility however that china/russia may possibility benefit if such a drastic situation did actually come about. They seem to have a somewhat similar single aisle chinese/russian made aircraft already flying.

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Re: Civil Aviation Development & Discussion

Postby arvin » 06 Apr 2019 15:51

nithish wrote:Boeing will slow 737 production by one-fifth; no layoffs planned

The two recent fatal crashes and subsequent grounding of Boeing’s 737 MAX have prompted the jetmaker to sharply and quickly cut production in Renton from the current 52 airplanes per month to 42 per month, signalling that a return to flight isn’t expected soon.

Boeing said it does not plan any layoffs due to the rate reduction, which begins in about 10 days. Managers are informing employees of the Renton 737 factory at meetings on Friday.



production cut means orders are getting cancelled. Customers will be either refunded or asked to take 737-800 or 900. Profits will be less relative to those operating Neo. Customers will start looking for russian or chinese alternatives.
Good thing for us is P8I was not offered on max8 :mrgreen: .
Just like we cleaned up our house on howitzers, missiles, fighter jets and radars with very little need to import in those spheres, now is the right time to launch a IGMDP for civil jet planes starting with 180 and 250 seater.

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Re: Civil Aviation Development & Discussion

Postby chetak » 06 Apr 2019 16:23

arvin wrote:


production cut means orders are getting cancelled. Customers will be either refunded or asked to take 737-800 or 900. Profits will be less relative to those operating Neo. Customers will start looking for russian or chinese alternatives.
Good thing for us is P8I was not offered on max8 :mrgreen: .
Just like we cleaned up our house on howitzers, missiles, fighter jets and radars with very little need to import in those spheres, now is the right time to launch a IGMDP for civil jet planes starting with 180 and 250 seater.



acceptance is getting delayed.

where will the customers keep these NPAs after acceptance??

Insurance, parking and maintenance charges will kick in and cost will be billed to the customer, no??

Best not to accept these duds until all MCAS issues are sorted out and the FAA gives the final OK to fly the max8 on revenue flights.

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Re: Civil Aviation Development & Discussion

Postby Austin » 06 Apr 2019 16:31

Sri wrote:
Austin wrote:Civil Aircraft has always been software driven since the time Airbus went with FBW for A320 and this then the software component has grown far greate r in aircraft ...Safety is one key requirement which drives it and that makes Civil Aircraft that fly today 99 % safe

My thinking is MAX has aerodynamics issue likely that also involves CG and not sufficiently tested and badly implemented Software in MCAS.

Boeing needs to thoroughly debug MAX Aerodynamics and MCAS along with its FBW even if it means loosing leadership position in narrow body market. Some quick fix MCAS patch recently tested may not completely solve this issue and will show up in different ways leading to more loss of life.


The issue is the height / ground clearance of the wings. New MAX aircraft needs more air intake in order to be efficient, just like Airbus Neo. Difference is the ground clearance of the wings. Since 737 is shorter the engineers had to bring the engine forward to accomodate for the larger diameter of the engine. This changed the Aerodynamics of the aircraft.

Since it was commercially important for Boeing to ensure that the pilots didn't have to retrain for the new 737 version, they introduced MCAS. System was designed to work at the background without the pilot feeling the difference in aerodynamic performance.


Yes and no one every disputed that.

The point is SW driven aircraft came into picture in mind 80's with A320 and since then many types have adopted it via FWB system and over period of time flying has become safer.

Boeing screw up is epic but that is boeings designer fault not the SW a faulty aerodynamic problem was offloaded to sw hope it would take care without pilot knowing about it.

Perhaps it is possible MAX SW would have taken care of many scenarios where accidents were possible and MCAS worked , May be but for the 2 occassion it didnt it crashed ......but in the end it was a epic disaster waiting to happen something MCAS would not have solved it.

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Re: Civil Aviation Development & Discussion

Postby chetak » 06 Apr 2019 17:30

Austin wrote:
Sri wrote:
The issue is the height / ground clearance of the wings. New MAX aircraft needs more air intake in order to be efficient, just like Airbus Neo. Difference is the ground clearance of the wings. Since 737 is shorter the engineers had to bring the engine forward to accomodate for the larger diameter of the engine. This changed the Aerodynamics of the aircraft.

Since it was commercially important for Boeing to ensure that the pilots didn't have to retrain for the new 737 version, they introduced MCAS. System was designed to work at the background without the pilot feeling the difference in aerodynamic performance.


Yes and no one every disputed that.

The point is SW driven aircraft came into picture in mind 80's with A320 and since then many types have adopted it via FWB system and over period of time flying has become safer.

Boeing screw up is epic but that is boeings designer fault not the SW a faulty aerodynamic problem was offloaded to sw hope it would take care without pilot knowing about it.

Perhaps it is possible MAX SW would have taken care of many scenarios where accidents were possible and MCAS worked , May be but for the 2 occassion it didnt it crashed ......but in the end it was a epic disaster waiting to happen something MCAS would not have solved it.


This is a foolishly precipitated crisis that was solely created by deliberately isolating the existing multiple sensor inputs and converting it to a single point failure system that ultimately involved inputs from only one AOA sensor, when actually two are fitted (pilot and copilot side AOA sensors).

This goes against all the norms of flight safety, against common or even garden variety of logic and and also against all the inviolable principles of design governing a software dependent, vital and flight critical subsystem that was illogically allowed far too much authority and was not really amenable to manual intervention because it kicked in repeatedly and most unexpectedly, even after being disabled or inhibited on multiple occasions.

If this single point failure was ABSOLUTELY the very first thing that struck me about the accident, a company like boeing and an aviation authority like the FAA with their many thousands/millions of man years of cumulative as well as accumulated design and regulatory expertise, have both failed miserably in the conduct of the very basic and fundamental processes of weighted risk and failure modes analyses and we will not even talk about the multiple and independent reviews that the software and the MCAS subsystem had to pass through before being installed on the max8, test flown by experienced test pilots prior to being released to ordinary commercial pilots for revenue flight.

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Re: Civil Aviation Development & Discussion

Postby chetak » 06 Apr 2019 19:01

twitter

This traveler almost was the number 150 victim after the Ethiopian plane crashed yesterday, and all 149 passengers died.
His name was Antonis from Greece, and he was only 2MIN late ,and he felt so angry and shouted at them to enter, but it flew without him, and he escaped death



Image

Image

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Re: Civil Aviation Development & Discussion

Postby chetak » 06 Apr 2019 19:10

the culinary future of a repurposed max8 engine??


twitter



Grilled chicken Burger comes out of the engine

Image

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Re: Civil Aviation Development & Discussion

Postby arvin » 06 Apr 2019 20:50

Austin wrote:...
Boeing screw up is epic but that is boeings designer fault not the SW a faulty aerodynamic problem was offloaded to sw hope it would take care without pilot knowing about it.

Perhaps it is possible MAX SW would have taken care of many scenarios where accidents were possible and MCAS worked , May be but for the 2 occassion it didnt it crashed ......but in the end it was a epic disaster waiting to happen something MCAS would not have solved it.


Its the owners and management and people who talk bottomline, profit, cost optimization thats responsible.
The designer's brief would have been No structural modification that would entail spending money on anything. No canards, no dead weight , no T tail like in 727. Nothing. Handle everything in software. Somebody was desperate for a promotion.

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Re: Civil Aviation Development & Discussion

Postby nachiket » 07 Apr 2019 15:00

arvin wrote:production cut means orders are getting cancelled. Customers will be either refunded or asked to take 737-800 or 900. Profits will be less relative to those operating Neo. Customers will start looking for russian or chinese alternatives.
Good thing for us is P8I was not offered on max8 :mrgreen: .
Just like we cleaned up our house on howitzers, missiles, fighter jets and radars with very little need to import in those spheres, now is the right time to launch a IGMDP for civil jet planes starting with 180 and 250 seater.

They have had one order cancellation, but this cut is more because they have no space to park the newly built planes. The previously built ones are all stranded there because they can't be delivered to the customers at the moment.

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Re: Civil Aviation Development & Discussion

Postby chola » 07 Apr 2019 16:54

Austin wrote:
The point is SW driven aircraft came into picture in mind 80's with A320 and since then many types have adopted it via FWB system and over period of time flying has become safer.

Boeing screw up is epic but that is boeings designer fault not the SW a faulty aerodynamic problem was offloaded to sw hope it would take care without pilot knowing about it.

Perhaps it is possible MAX SW would have taken care of many scenarios where accidents were possible and MCAS worked , May be but for the 2 occassion it didnt it crashed ......but in the end it was a epic disaster waiting to happen something MCAS would not have solved it.



From my layman's knowledge, FBW for civilian aircraft are to be an aid in flying an aircraft that is aerodynamically stable in design. When the AoA is pointing toward stall or when power is reduced or loss due to engine issues any pickup in speed when the plane is nose down should stabilize the plane in a glide.

Unlike the unstable design for fighters where without FBW the aircraft is simply uncontrollable, airliners should be able to be flown manually in nearly all normal regimes. It is a margin of error for planes carrying passengers not dogfighting.

But the Ethiopian evidence is telling us that the pilots cannot regain manual control even after following the Boeing steps in disabling the software.

So either:

1) MCAS or the software as a whole never gives up control despite what Boeing says,

or

2) the software does give up control but the aircraft was still not controllable because of the aerodynamics of the design.

The way Boeing decided to approach the software and training issues seems to be that they believe that the plane should never be allowed to go fully manual.

The 737 MAX might be an unstable design that will point down not matter what a pilot does unless FBW is working perfectly. So when the software is confused by a bad sensor there is no margin for error.

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Re: Civil Aviation Development & Discussion

Postby SriKumar » 08 Apr 2019 01:05

^^^ This is the key question I have.....is the new Boeing craft flyable at all without the MCAS. And does MCAS fully turn off when pilots hit that switch? Only Boeing knows the answer. One the face of it, BOeing has said how it can be disabled, and I suppose some pilots have done it and still flown it. But now the question arises as to are there any unstable flight regimes if the MCAS is turned off. This no pilot can find out, only Boeing knows.

I dont know who would want to be in that plane with 'software fixes' coming up one after the other. First, What hardware issues is the software hiding? And from the recent investigations, it seems like BOeing's control systems people dont really have a handle on how to design a fool-proof control system software. Lion Air had one AoA sensor-Boeing's standard offering, and that ended in a tragedy. Ethiopian Air had 2 AoA sensors...and the software could not handle that either.

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Re: Civil Aviation Development & Discussion

Postby chetak » 08 Apr 2019 01:23

SriKumar wrote:^^^ This is the key question I have.....is the new Boeing craft flyable at all without the MCAS. And does MCAS fully turn off when pilots hit that switch? Only Boeing knows the answer. One the face of it, BOeing has said how it can be disabled, and I suppose some pilots have done it and still flown it. But now the question arises as to are there any unstable flight regimes if the MCAS is turned off. This no pilot can find out, only Boeing knows.

I dont know who would want to be in that plane with 'software fixes' coming up one after the other. First, What hardware issues is the software hiding? And from the recent investigations, it seems like BOeing's control systems people dont really have a handle on how to design a fool-proof control system software. Lion Air had one AoA sensor-Boeing's standard offering, and that ended in a tragedy. Ethiopian Air had 2 AoA sensors...and the software could not handle that either.


this f***up took place because the bean counters took charge and pushed profit before safety.

Both Lion Air and Ethiopian Air Max8s had 2 AoA sensors but only one would work at any given time to provide AOA inputs to the MCAS.

The mistake was in not allowing the two AOA sensors to work together so that an AOA disagree warning could have been generated in case one of the sensors malfunctioned or failed.

In both cases, the pilots did not know that it was the AOA sensor malfunction that triggered the MCAS.

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Re: Civil Aviation Development & Discussion

Postby nachiket » 08 Apr 2019 01:47

chola wrote:From my layman's knowledge, FBW for civilian aircraft are to be an aid in flying an aircraft that is aerodynamically stable in design. When the AoA is pointing toward stall or when power is reduced or loss due to engine issues any pickup in speed when the plane is nose down should stabilize the plane in a glide.

Unlike the unstable design for fighters where without FBW the aircraft is simply uncontrollable, airliners should be able to be flown manually in nearly all normal regimes. It is a margin of error for planes carrying passengers not dogfighting.

But the Ethiopian evidence is telling us that the pilots cannot regain manual control even after following the Boeing steps in disabling the software.

So either:

1) MCAS or the software as a whole never gives up control despite what Boeing says,

or

2) the software does give up control but the aircraft was still not controllable because of the aerodynamics of the design.

The way Boeing decided to approach the software and training issues seems to be that they believe that the plane should never be allowed to go fully manual.

The 737 MAX might be an unstable design that will point down not matter what a pilot does unless FBW is working perfectly. So when the software is confused by a bad sensor there is no margin for error.


Guys, MCAS only turns on in rare cases. Most of the times it is off. The instability happens in certain cases only. So the aircraft is fully flyable manually.

So why were the Ethipian pilots unable to control it after cutting out MCAS? Here is how.

EDITED: Found a much better explanation of this than the one I posted earlier. This is from a commercial pilot reading the preliminary report and explaining every step.

Youtube URL (not embedding it here): https://youtu.be/HBqDcUqJ5_Q?t=904

So here's the sequence of events summarized in my words.

Since the flight was taking off in moderate hot and high conditions, the Thrust setting was set to 94%N1. They would need this thrust to climb as well.

However, because of the faulty sensor, the MCAS turned on and caused the aircraft to dive which, at such a high thrust setting, led to a very high airspeed (for that altitude) and caused overspeed warnings.

After attempting to recover for a while, they eventually realized that the Stabilizer Trim Cutout needed to be engaged to disconnect the MCAS system, which they did.

But the stabilizer trim was still stuck in nose down position and they needed to fix it. But with the stabilizer trim cutout, they could no longer use the electric switches on the control yoke to do it and it had to be done manually by moving the trim wheel.

Unfortunately, due to the high speed in the dense air at low altitude and constant back pressure on the control column to keep the nose up, they found it nearly impossible to move it manually. The pressure on the system was just too high.

In desperation, one of the crew reset the stabilizer trim cutout to get the electric switches working again. For an instant they were able to get the stabilizer trim back to normal as the electrical system was able to move it again. However, resetting the stabilizer trim cutout meant that the MCAS system was also operational again and that once again moved the trim in nose down position.

This doomed the flight. They just did not have any altitude to recover from that.

nachiket
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Re: Civil Aviation Development & Discussion

Postby nachiket » 08 Apr 2019 03:54

This proves that Boeing's original solution of just using the stabilizer trim cutout to disengage MCAS does not work in all circumstances, as recovery may still be impossible at low altitude.

All this could have been found during testing itself, if Boeing hadn't been rushing to get the aircraft into production and the FAA had not been letting Boeing run its own safety tests. Absolutely criminal behavior.

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Re: Civil Aviation Development & Discussion

Postby SriKumar » 08 Apr 2019 04:25

thanks nachiket. your posts are always informative.
If the craft can be flown with mcas off completely & no bad habits in the craft due to c.g., it still has a chance.

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Re: Civil Aviation Development & Discussion

Postby chetak » 08 Apr 2019 08:59

SriKumar wrote:thanks nachiket. your posts are always informative.
If the craft can be flown with mcas off completely & no bad habits in the craft due to c.g., it still has a chance.


Bad habits of the Max8 will start to surface if the AOA approaches the stall values set in the software along with thrust and airspeed values. The repositioned and larger engines, the engine nacelles producing additional lift at higher AOA when least required as this lift tended to raise the nose further, all of which interfered with or grossly complicated the aerodynamics and hence the stability of the Max8.

The Lion air and Ethiopian air pilots were unable to specifically recognize this because of other flight instruments not indicating the high AOA input that was erroneously being sent by the faulty AOA sensor and the MCAS reacting solely on the basis of this single faulty sensor input.

Some ameriki airlines, on payment, installed a boeing mod to indicate when there was an AOA disagree (which meant that both AOA sensors were working together at all times and their outputs were being continuously compared) and that is how they knew to disregard the AOA inputs, disable or inhibit the MCAS and fly on their normal flight instruments.

Other ameriki airlines did not install this paid mod but trained their pilots to go by other flight instruments and as part of a specific company checklist that told them to disable or inhibit the MCAS when such a situation arose.

Lion air and Ethiopian air pilots, unfortunately, did not have the benefit of such a mod or even the cursory training to recognize the real problem.

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Re: Civil Aviation Development & Discussion

Postby chetak » 08 Apr 2019 09:22

nachiket wrote:This proves that Boeing's original solution of just using the stabilizer trim cutout to disengage MCAS does not work in all circumstances, as recovery may still be impossible at low altitude.

All this could have been found during testing itself, if Boeing hadn't been rushing to get the aircraft into production and the FAA had not been letting Boeing run its own safety tests. Absolutely criminal behavior.


Sirji,

Testing WAS done prior to release but some specific aspects were not fully investigated and high AOA was a condition that was assumed to be completely correctable with the MCAS and so, it only had a cursory examination, with everyone carefully looking the other way. To place such overwhelming reliance on a single point of failure AOA sensor was not only insanely foolish but also criminal.

This was not a reliable aircraft but more of an accident looking for a place to happen. This was further complicated by not informing the flight crews about the implications of the MCAS and willfully abandoning them when help was most urgently needed.

Both Boeing and the FAA are culpable, jointly and severally and IMVHO, this is also a criminal act. In their rush to market the max8, with customer airlines subtly pushing for nil commercial impact on pilot training and recertification, Boeing ignored its own core competencies and brazenly prioritized profit over passenger and crew safety.

This speaks very badly of the design process, the stagewise design review process, the software development process, the S/W testing process, the failure modes analysis, the risk analysis and finally the weak regulatory oversight from the FAA that should have independently and thoroughly investigated all the test results and reviewed the entire design process, the design review process, the software development process, the S/W testing process, the failure modes analysis, the design and conduct of the all important flight tests and the risk analysis followed by similarly thorough oversight of the entire flight test process as well.

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Re: Civil Aviation Development & Discussion

Postby nachiket » 08 Apr 2019 09:53

chetak wrote:This speaks very badly of the design process, the stagewise design review process, the software development process, the S/W testing process, the failure modes analysis, the risk analysis and finally the weak regulatory oversight from the FAA that should have independently and thoroughly investigated all the test results and reviewed the entire design process, the design review process, the software development process, the S/W testing process, the failure modes analysis, the design and conduct of the all important flight tests and the risk analysis followed by similarly thorough oversight of the entire flight test process as well.

Chetak ji, I agree completely. But the malaise runs very deep. Everyone's hands are dirty, Boeing, FAA and even the US Congress which keeps encouraging the FAA to let aircraft manufacturers carry out more and more of their own safety certifications.

Basically the FAA's safety inspectors are designated Boeing employees who have been vetted and certified by the FAA to act as its own representatives. But they are still being paid by Boeing!! So the people certifying Boeing's aircraft as safe are Boeing's own employees but they can give them an FAA certificate. Huge conflict of interest here but this has gone on for decades and it keeps getting worse.

FAA's close ties to Boeing questioned after 2 deadly crashes

For more than six decades, the Federal Aviation Administration has relied on employees of airplane manufacturers to do government-required safety inspections as planes are being designed or assembled.

But critics say the system, dubbed the “designee program,” is too cozy as company employees do work for an agency charged with keeping the skies safe while being paid by an industry that the FAA is regulating.

“There is a potential conflict of interest,” said Todd Curtis, a former Boeing Co. safety engineer and creator of airsafe.com, a website that focuses on airline safety. “They (the FAA) don’t have the money to do all of the oversight. It’s a question of being practical.”


And now this has cost the lives of 340 people. It could have easily cost more, since this incestuous mechanism was questioned after the Boeing 787 battery fires as well, any of which could have caused a crash. No action was taken of course to remedy it.

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Re: Civil Aviation Development & Discussion

Postby Zynda » 08 Apr 2019 19:55

nachiket wrote:Basically the FAA's safety inspectors are designated Boeing employees who have been vetted and certified by the FAA to act as its own representatives. But they are still being paid by Boeing!! So the people certifying Boeing's aircraft as safe are Boeing's own employees but they can give them an FAA certificate. Huge conflict of interest here but this has gone on for decades and it keeps getting worse.

Per my experience, this mechanism was designed to avoid huge costs incurred during FAA inspection/certification services. AFAIK, the product company is responsible for covering the travel, per diem, lodging & transportation costs of the FAA inspector as long as required apart from the hourly fees charged by the individual/FAA. For many small companies, this leads to huge costs. The above was seen as a compromise. Further, from what I understand, the designee mechanism also can speed up product development pace. The FAA probably wants to or can hire only so much people and with so many companies wanting to certify different products, the wait list for next available FAA personal can be long and thus delaying product development. The designee can help in alleviating the above. Many companies only invite FAA inspectors/certification folks only during final process while using designee folks for checking for compliance during the early & intermediate design process.

In theory, like you mentioned, the loyalty of the Designee rests with FAA while he is paid by the employer. In one of my peecha company, I knew many such designees. Most of them would refuse to sign or put down their name if they were not satisfied with the process/outcome. One of such person (a fav of mine) would say that if his names comes up as the person who was responsible for signing a faulty design/document, then it would become an express ticket to jail. Many of the other employees, particularly, from different departments would see these designees as an annoyance and nuisance even though they acknowledged the spirit of the intent behind such designee.

But it is possible in bigger OEMs like Boeing, which may have the clout to threaten to disrupt a person's career if that individual does not pay heed to organizations bigger picture or whatever, the designee mechanism may not be accomplishing the required intent. Perhaps, the FAA can re-examine on how to involve FAA inspectors/certification folks early on during the design & testing process.

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Re: Civil Aviation Development & Discussion

Postby Austin » 08 Apr 2019 22:31

Simple Explanation by a Professor



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