Ethiopia crash

[threexgreen 3,139]

1 hour ago, charlie130 said:

So if you can't disable the computer sitting between your stick and throttle and the moving parts, you ( the pilot flying) don't have full control of the aircraft?  A silicon chip and some program has the final say?

That's just what FBW is. Most Airbusses and the 787 and any FBW aircraft I can't think of right now work exactly like this. The MAX, in fact, isn't even full FBW, it only has a FBW spoiler system so you still have mechanical linkage to the control surfaces.

[skelsey 765]

11 minutes ago, honanhal said:

This is true in ordinary trim runaway cases, but there appears to be some disagreement on whether those cutouts have any influence on MCAS-commanded trim operation, unfortunately.

For example, this gentleman believes it does not — and argues that the confusion resulting from flipping those switches and the nose-down trimming continuing would contribute to crew disorientation and poor decision making.

You're misunderstanding what's been written in the article.

As I said above, the pedestal cut-out switches (highlighted in Fr Bill's post) do indeed cut out the trim and would stop MCAS from trimming.

What does not stop MCAS is the microswitches installed in the control column mechanism which prevent you trimming against control column movement (i.e. if you pull the column back the microswitches will be tripped and it will not let you trim nose down and vice versa -- this is something which you can try out in the PMDG 737, for instance). As I explained above, this is for a logical design reason: the whole point of MCAS is to trim against the "pull" on the column to provide a nose-down force to pull against at high AoA.

To that extent I'm not sure really what the author of the article you linked is really trying to say. At one point he talks about how MCAS is fine and should have all the authority it needs, then says "but it should only trim once" (even if it needs more authority than that to meet the requirements?!?) and finally, having explained exactly why the control column cut out switches are bypassed, then says Boeing shouldn't have bypassed them. ?!?!

[IUBrian 151]

I found this article from the Seattle Times interesting. It talks about shortcuts in the FAA certification process and explains in simple to understand terms how a fault with MCAS would create a “hazardous” situation, one level below “catastrophic” - 

https://www.google.com/amp/s/www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/%3famp=1

 

 

[Bobsk8 12,732]

1 hour ago, IUBrian said:

I found this article from the Seattle Times interesting. It talks about shortcuts in the FAA certification process and explains in simple to understand terms how a fault with MCAS would create a “hazardous” situation, one level below “catastrophic” - 

https://www.google.com/amp/s/www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/%3famp=1

 

 

Just as I thought, a cover up by Boeing, and the FAA/White House on how  serious this issue was, because the powers to be realized that this would be a heavy hit in the US economy if this plane was grounded. Once Boeing and the White House/FAA  realized that the entire world was not buying this garbage, they had to buckle and finally ground the Max. I have been a Boeing fan for decades, in fact the NGX is my favorite sim aircraft to fly, but frankly I am disappointed in Boeing's behavior on this issue and it looks like the almighty dollar versus possible loss of life, the dollar wins with Boeing. Numerous calls between Boeing's President and the White House during this issue is another indication that something was not right. My guess is the Max will be grounded for quite awhile until they fix this design flaw. 

Edited March 17, 2019 by Bobsk8

[honanhal 1,420]

2 hours ago, skelsey said:

You're misunderstanding what's been written in the article.

Indeed I did, which I realized just after posting! Appreciate your very helpful explanation.

James

[Bobsk8 12,732]

Another explanation from a 737 Pilot.   

 

[threexgreen 3,139]

2 hours ago, Bobsk8 said:

Once Boeing and the White House/FAA  realized that the entire world was not buying this garbage, they had to buckle and finally ground the Max.

AFAIK, the FAA couldn't ground the plane earlier at the same time many other countries did because by legislation, they require actual data to be authorized to ground an entire fleet. When other countries stepped forward and grounded the plane that data wasn't available yet, which changed a couple of days later when investigators at the Ethiopian crash site found and reported clues showing similarities between the two accidents.

[IUBrian 151]

I too am a “Boeing guy”, but cannot help but be disappointed. As a lawyer, I can appreciate the “literally true” statement that Boeing followed FAA certification procedures while omitting that key parts of it were delegated to Boeing itself, like the fox guarding the henhouse. 

Like most engineering disasters, it appears that a series of relatively small events and decisions may have combined to create a critical flaw leading to catastrophic results. Another part of me wonders if Boeing has grown fat and complacent, relying on generous defense contracts and a “helpful” government as much or more than the  innovation it was known for to keep up with competitors. In that sense it reminds me of American auto manufacturers in terms of how well they reacted to foreign competition while their quality declined. 

I am a big fan of Boeing, but it appears to me there are two routes to take. One, a band-aid approach that masks real issues within the company that helps in the short term but will be marked as the beginning of a long decline. Or two, a recognition of serious internal issues that results in legitimate changes (including some people losing jobs) that restores worldwide faith and confidence in Boeing.

I don’t think I’m being too dramatic. My initial reaction when my daughter told me about the latest crash (we were actually just getting off a Southwest flight) was “it’s not a Boeing issue, probably just a shoddily maintained plane and ill-trained African airline crew - Boeing is awesome.” In the time since I’ve read a number of articles, one specifically relating how the new Pegasus tankers are being delivered to the Air Force “full of trash” that makes me really question their current culture.

https://www.google.com/amp/s/www.popularmechanics.com/military/aviation/amp26627917/air-force-kc-461-deliveries-trash-boeing/

 

[John_Cillis 2,406]

19 minutes ago, IUBrian said:

I too am a “Boeing guy”, but cannot help but be disappointed. As a lawyer, I can appreciate the “literally true” statement that Boeing followed FAA certification procedures while omitting that key parts of it were delegated to Boeing itself, like the fox guarding the henhouse. 

Like most engineering disasters, it appears that a series of relatively small events and decisions may have combined to create a critical flaw leading to catastrophic results. Another part of me wonders if Boeing has grown fat and complacent, relying on generous defense contracts and a “helpful” government as much or more than the  innovation it was known for to keep up with competitors. In that sense it reminds me of American auto manufacturers in terms of how well they reacted to foreign competition while their quality declined. 

I am a big fan of Boeing, but it appears to me there are two routes to take. One, a band-aid approach that masks real issues within the company that helps in the short term but will be marked as the beginning of a long decline. Or two, a recognition of serious internal issues that results in legitimate changes (including some people losing jobs) that restores worldwide faith and confidence in Boeing.

I don’t think I’m being too dramatic. My initial reaction when my daughter told me about the latest crash (we were actually just getting off a Southwest flight) was “it’s not a Boeing issue, probably just a shoddily maintained plane and ill-trained African airline crew - Boeing is awesome.” In the time since I’ve read a number of articles, one specifically relating how the new Pegasus tankers are being delivered to the Air Force “full of trash” that makes me really question their current culture.

https://www.google.com/amp/s/www.popularmechanics.com/military/aviation/amp26627917/air-force-kc-461-deliveries-trash-boeing/

 

TWA 800 was another example where us who love Boeing almost begged for that accident to have another cause than what was proven to be an explosive issue in the bowels of the fuel tanks.  That accident has saved many lives since and the MAX accidents, once the reasons for them are resolved, will save many lives.  One must remember the teething pains of the Comet, where hull breeches by the windows brought aircraft down, and a redesign was made and the fleet flew on, I found the Comet such a beautiful aircraft, especially the nose, the birth along with the 707 of civilian jet travel.  The B47 was the prophet that brought in the jet age, with its almost perfect shape, not to forget the ME262 w121hich I call a baby 737-200 with its low slung wing mounted engines.

Still the MAX accidents have surprised me and saddened me, not due to their maker, but that they happened at all.  I am beginning to agree that the 737 may be getting morphed into something it was not meant to be.  For me the 700/800 series, and the 600, all of which I have flown on, represent the heyday of the 737 family.  Just like my first and only trip on a 747-400 in 2017 to London and back from Phoenix.  Going home I felt a strange vibration on my flight, only to find a few weeks, or maybe a few months later that it had a bad engine and had to make an urgent landing after it was discovered in flight.

I have always been an engine whisperer, having built my first one along with my friend at age 12, his dune buggy, and at age five I watched and listened to another friend, sadly lost in Vietnam, tune his motorcycle engines.  My dad taught me to be one, my Dad almost bought a Cessna 337 (pushmepullu) but my Mom talked him out of it, we needed a bigger house for our big family of three boys, two parents, two dogs and some tropical fish.

I have never, ever bought a car, used or new, with a bum engine, thanks to my experience as a boy and my father, who let me participate even as a child in every car purchase and haggle session he ever had.  He insisted on the test drive, and that helped me buy vehicles until my last one, which I gave up because of my being run over recently by an SUV, my feet just do not have good car manners on the brake and throttle because of the accident, which is a bad omen for my future flight ambitions too, for rudder control.

My summary for this accident: they will find the cause, better aircraft will come out of it, and any flatlander like I am now will agree, it is still safer up there, than down here, angels protect us all in flight!

John

[HighBypass 2,339]

I'd like to consider an airliner in an ACTUAL stall, or during the onset of an actual stall, not an airliner which thinks it's in a stall but isn't, and not a TOTAL FBW airliner. Bear with me if you would.

This feature of the MCAS giving an artificial force in the column so that the pilot finds it hard to pull back on the stick... Why do we need that? What are the characteristics of an airliner stall? Is there not some airframe buffeting as the plane approaches stall speed? I know there's a stick shaker installed, but discounting that, how much can the crew "feel" - not necessarily through the control column?

IF an airliner is actually stalled wouldn't the crew notice a lack of elevator effectiveness by the plane not reacting in pitch? - The pilot pulls back on the column and nothing happens... Conversely, can excessive speed begin to overcome the boosted controls so that it requires more than normal force to pull the stick back (pulling out of a dive?)

I guess it's more obvious in a plane with direct linkages to the control surfaces rather than hydraulic boosting etc. An example if you would: With a glider approaching a stall for instance, not only do you get the buffeting, but you also get a reduction in elevator effectiveness. So much so that further into the stall you can pull and push the stick between its limits and the elevator does nothing. You can observe this directly by looking out of the canopy: No pitch change despite you wanging the stick forward and back. You also don't feel any aerodynamic resistance either, but that's moot I guess because airliner controls are all boosted in some way. I only mention this because in normal flight the airflow provides some resistance. On a winch launch there's even more! This is the only real world experience I have due to it being demonstrated to me and I've done it myself  (great couple of flights!)

Long story short - could the MCAS increase in back force on the column actually be counter to a pilot's prior experience, at least if the plane is actually stalling?

[Bobsk8 12,732]

1 hour ago, John_Cillis said:

TWA 800 was another example where us who love Boeing almost begged for that accident to have another cause than what was proven to be an explosive issue in the bowels of the fuel tanks.  That accident has saved many lives since and the MAX accidents, once the reasons for them are resolved, will save many lives.  One must remember the teething pains of the Comet, where hull breeches by the windows brought aircraft down, and a redesign was made and the fleet flew on, I found the Comet such a beautiful aircraft, especially the nose, the birth along with the 707 of civilian jet travel. 

They only made 70 Comets after it was fixed. 

[Bobsk8 12,732]

46 minutes ago, HighBypass said:

Long story short - could the MCAS increase in back force on the column actually be counter to a pilot's prior experience, at least if the plane is actually stalling?

I suggest you watch this video. 

 

Edited March 17, 2019 by n4gix
REMOVED EXCESSIVE QUOTE!!!

[skelsey 765]

1 hour ago, HighBypass said:

This feature of the MCAS giving an artificial force in the column so that the pilot finds it hard to pull back on the stick... Why do we need that?

The short answer is "because the rules say so".

To pass certification, the FAA requires that the aircraft must demonstrate positive static longitudinal stability. In simple terms, this means that the stick force/aft displacement must increase as airspeed reduces.

As I said earlier, think about a standard approach to stall in your glider. You achieve this from level flight by easing the stick back to reduce the airspeed. The slower the airspeed, the more aft the stick. Eventually you reach the point where the stick is fully aft, the stall occurs and the nose pitches down.

The problem, apparently, with the 737 Max is that when Boeing test flew it they would have done exactly this sort of thing. Unfortunately they found that instead of that stick force gradually increasing as the stall was approached, at certain AoA values the stick force reduced or may even have become negative.

Imagine that in your glider as you are practicing stalling -- you gradually ease the stick back and the nose up at a nice controlled rate and all of a sudden the nose starts leaping up faster and faster -- in fact you suddenly have to push forward to reduce the rate at which the nose is coming up and control the stall entry. So you could actually be pushing forward slightly but the nose is still rising in to the stall!

This is clearly an unpleasant (and potentially dangerous) handling characteristic and this is what MCAS is designed to counteract.

Edited March 17, 2019 by skelsey
clarity

[HighBypass 2,339]

Thank you Simon, although why would the stick force gradually increase as the stall was approached? Is that a feature of boosted controls?

9 minutes ago, skelsey said:

...Unfortunately they found that instead of that stick force gradually increasing as the stall was approached..

Thanks, Bob, but you didn't need to re-quote my entire post 😉

[skelsey 765]

3 minutes ago, HighBypass said:

why would the stick force gradually increase as the stall was approached? Is that a feature of boosted controls?

Stick force may be a confusing way of putting it - perhaps stick displacement is a better description (which implies a stronger pull -- increased backpressure is how I would patter it!).

So conventionally you would expect (and certification standards require) increasing aft stick displacement as you reduce speed in the approach to stall.

In the Max, the larger, higher and more forward-located engine nacelles create lift (like any other part of the airframe). At low angles of attack this is negligible (and designed to be so - the lift to drag ratio of an engine nacelle is pretty rubbish). But at higher angles of attack the lift from the nacelles is significant and it is this which results in the unstable pitch characteristics of the Max in the approach to stall. This is why it is different to the NG and older 737 models.