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Boeing 737 MAX+

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Boeing 737 MAX+

Postby Kikapu » Wed Mar 27, 2019 3:55 pm

Did Boeing tried too hard to add a "safety feature" into the B-737 max planes that would prevent another Air France 447 disaster, but instead, have become anything but?

AF447 flying from Brazil to France crashed into the Pacific Ocean with it's nose up attitude as the pilots got totally confused as the instruments stopped working correctly for a while due to the Pitot tubes freezing up, because the automated warning system commanded the pilot to "pull up, pull up", which the pilot complied, but the plane crashed anyway killing all aboard. What the pilot in command didn't realize, was that the plane's nose was up, but too much, which with full power, it was still coming down as the wings stalled and it was coming down in an almost 45% angle facing up while mushing through the air forward. Being in complete darkness, the pilots lost all awareness what the plane was doing, other than it was going to crash.

All pilots learn one thing very early in their training, that when the wings are stalling, is to add power and/or bring the nose of the aircraft down regardless how close one is to the ground, because maintaining status quo will result in a crash. The AF447 pilot only added power, but did not put the nose down. So, did Boeing wanted to make the plane put the nose down automatically if the pilots got confused? Sounds like a good safety feature to have, but it appears, the software is not done properly as it is normal for planes to have a high nose up attitude during takeoff and the need of the automated action by the plane to bring the nose down at such early in the flight wouldn't be necessary. But it seem, it is the reason of the two crashes of the B-737 Max's crashes so far as the pilots were not able to pull the nose up because the computer wouldn't allow it.
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Re: Boeing 737 MAX+

Postby Robin Hood » Wed Mar 27, 2019 5:30 pm

Although AF-447 was an A-330 Air Bus it would appear to be a very similar problem as with the 737 Max, where good intent turned into tragedy?

An animation based on the findings of the BEA Report into the AF-447 accident.

https://www.youtube.com/watch?v=JSTTnl8-_q8


Maybe in this modern age we rely too much upon computer based systems? I was told by my Chief Instructor, when I learned to fly in 1986, who was an older BA Senior Check pilot who came from the days of the Boeing Strato Cruiser and DC6 era, and eventually the Comet and the 707, that what I was doing in a Cessna 152 was flying ........ he was merely a systems manager sat in the front of an expensive electro-mechanical system, flown by electrons and he was there just in case anything went wrong! :roll:

With the Air Bus a similar thing happen at an air display? The aircraft did a low pass down the runway and when the pilot put the power on to climb out, you hear the engines spool-up...... nothing happened and he just crashed into a forest. Most on board survived that accident.

https://www.youtube.com/watch?v=sp64BnDpnPk

It is too easy to blame the system or even the pilot when something goes wrong but whatever we do there are often unintended consequences that occur in circumstances that are overlooked at the design stage. It is a human failing.

The computer systems in a passenger jet, as I understand it, are normally triplicated and it is a ‘two-out-of-three’ voting system. Each system is a different make and has different software, but all do the same thing. The theory being that you may get one computer fail, but the other two read the same so the system chooses the information from the two rather than the one. So in this case there should have been three measuring Pitot tubes not just one? This is how critical control systems work in industrial systems like refineries and chemical plants. On both the 737 Max incidents this seems not to have happened.

A thought: If the majority of aircraft accidents are due to pilot error then we are still better off relying on the electronics, than the pilot! Or is it a case of when they cannot find the cause they blame the pilot?

It is only the reluctance of passengers to fly without a human being ‘flying’ the aircraft that stops airliners being pilotless. In reality is IS the electronics that flies the aircraft and a lot of the computing capacity is designed to counter the pilot making a bad decision or incompatible data inputs. In the 737 Max crashes it seems to be the other way around as it also limits the human intervention to correct the computer problem.

What you are taught early on in flying is known as Spatial Disorientation! The instructor takes the controls ..... you shut your eyes...... he throws the aeroplane up and down, left and right ..... then stabilises and asks you (still with your eyes closed) ..... whether you are straight and level, climbing, descending or banked right/left. It is very difficult to do with no references ..... that is why you learn to rely on what your instruments tell you ..... not you senses! :wink:

I’m still here so I must have got it right! :)
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Re: Boeing 737 MAX+

Postby Pyrpolizer » Wed Mar 27, 2019 6:08 pm

Kikapu wrote:Did Boeing tried too hard to add a "safety feature" into the B-737 max planes that would prevent another Air France 447 disaster, but instead, have become anything but?

AF447 flying from Brazil to France crashed into the Pacific Ocean with it's nose up attitude as the pilots got totally confused as the instruments stopped working correctly for a while due to the Pitot tubes freezing up, because the automated warning system commanded the pilot to "pull up, pull up", which the pilot complied, but the plane crashed anyway killing all aboard. What the pilot in command didn't realize, was that the plane's nose was up, but too much, which with full power, it was still coming down as the wings stalled and it was coming down in an almost 45% angle facing up while mushing through the air forward. Being in complete darkness, the pilots lost all awareness what the plane was doing, other than it was going to crash.

All pilots learn one thing very early in their training, that when the wings are stalling, is to add power and/or bring the nose of the aircraft down regardless how close one is to the ground, because maintaining status quo will result in a crash. The AF447 pilot only added power, but did not put the nose down. So, did Boeing wanted to make the plane put the nose down automatically if the pilots got confused? Sounds like a good safety feature to have, but it appears, the software is not done properly as it is normal for planes to have a high nose up attitude during takeoff and the need of the automated action by the plane to bring the nose down at such early in the flight wouldn't be necessary. But it seem, it is the reason of the two crashes of the B-737 Max's crashes so far as the pilots were not able to pull the nose up because the computer wouldn't allow it.


Shhhh... Paphitis will freak out.
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Re: Boeing 737 MAX+

Postby Pyrpolizer » Wed Mar 27, 2019 7:00 pm

Robin Hood wrote:Although AF-447 was an A-330 Air Bus it would appear to be a very similar problem as with the 737 Max, where good intent turned into tragedy?

An animation based on the findings of the BEA Report into the AF-447 accident.

https://www.youtube.com/watch?v=JSTTnl8-_q8

.....


I watched the video and kept wondering how on earth they didn't know whether they were going with the nose up stalling the plane, when a simple spirit level could do the job...
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Re: Boeing 737 MAX+

Postby Robin Hood » Wed Mar 27, 2019 7:54 pm

Pyrpolizer:
I watched the video and kept wondering how on earth they didn't know whether they were going with the nose up stalling the plane, when a simple spirit level could do the job...

They actually have a sort of ‘spirit level’, it’s called a Bank-and-Turn coordinator.

https://www.youtube.com/watch?v=CZDEfq1Tdro

There is also the Artificial Horizon. The mechanical version I would think is the more reliable as it relies mechanically on the Laws of physics, including gravity. The electronic version needs electronic inputs to work and if a pitot tube is iced up then you have a false reading.

https://www.youtube.com/watch?v=nATAcpHD7E4

If the pilot has experience in flying light aircraft he would use both instruments when making a turn or a climb/descent when he had no ground reference. Plus of course the compass and the air speed indicator ..... this is why you ‘scan’ these instruments and why they are always grouped in the same physical layout.

In a modern jet the pilot would twiddle knobs in response to instructions by ATC, that give height (Flight Level) and heading (Degrees magnetic) and the electronics does the rest ..... he doesn’t even need to see out of the windscreen. So the reliance is 100% on the electronics.

I am sure that if I have it wrong Paphitis will correct me? :roll: :wink:
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Re: Boeing 737 MAX+

Postby Kikapu » Wed Mar 27, 2019 8:36 pm

Pyrpolizer wrote:
Robin Hood wrote:Although AF-447 was an A-330 Air Bus it would appear to be a very similar problem as with the 737 Max, where good intent turned into tragedy?

An animation based on the findings of the BEA Report into the AF-447 accident.

https://www.youtube.com/watch?v=JSTTnl8-_q8

.....


I watched the video and kept wondering how on earth they didn't know whether they were going with the nose up stalling the plane, when a simple spirit level could do the job...


The captain made few errors in the AF447.

1. He left the most junior with the least experience in command as he went for his rest.
2. Upon the captain returning back to the cockpit, he never asked who was flying the plane.
3. He didn’t take his seat to take over in flying the plane.

Fresh mind could have recovered the doomed plane, because the two officers left in the cockpit, at some point, they were both trying to fly the plane at the same time in opposite to each other.

The question stands. Was Boeing trying to prevent another AF447 disaster with the new designs for the 737 MAX and got it very wrong?
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Re: Boeing 737 MAX+

Postby Kikapu » Wed Mar 27, 2019 9:23 pm

More errors by the captain.

1. He didn't divert the plane when he knew there were thunderstorm s ahead.
2. Leaving the cockpit in the first place under those conditions.
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Re: Boeing 737 MAX+

Postby Paphitis » Thu Mar 28, 2019 1:25 am

Pyrpolizer wrote:
Kikapu wrote:Did Boeing tried too hard to add a "safety feature" into the B-737 max planes that would prevent another Air France 447 disaster, but instead, have become anything but?

AF447 flying from Brazil to France crashed into the Pacific Ocean with it's nose up attitude as the pilots got totally confused as the instruments stopped working correctly for a while due to the Pitot tubes freezing up, because the automated warning system commanded the pilot to "pull up, pull up", which the pilot complied, but the plane crashed anyway killing all aboard. What the pilot in command didn't realize, was that the plane's nose was up, but too much, which with full power, it was still coming down as the wings stalled and it was coming down in an almost 45% angle facing up while mushing through the air forward. Being in complete darkness, the pilots lost all awareness what the plane was doing, other than it was going to crash.

All pilots learn one thing very early in their training, that when the wings are stalling, is to add power and/or bring the nose of the aircraft down regardless how close one is to the ground, because maintaining status quo will result in a crash. The AF447 pilot only added power, but did not put the nose down. So, did Boeing wanted to make the plane put the nose down automatically if the pilots got confused? Sounds like a good safety feature to have, but it appears, the software is not done properly as it is normal for planes to have a high nose up attitude during takeoff and the need of the automated action by the plane to bring the nose down at such early in the flight wouldn't be necessary. But it seem, it is the reason of the two crashes of the B-737 Max's crashes so far as the pilots were not able to pull the nose up because the computer wouldn't allow it.


Shhhh... Paphitis will freak out.


Why would I freak out? Kikapu is asking some great questions.

I got no problem with Kikapu's post. What is evident to me once again is the fact that the media are creating a huge media storm against Boeing that is unwarranted. And most of what they are saying is nonsense. People take the bait and there is even talks of conspiracy and negligence. It's beyond Boeing's capability to eliminate stupidity when operating their aircraft. Their aircraft was not operated compliantly as Boeing intended it to be operated and this resulted in a crash. Also bear in mind that the B737 MAXI and its MCAS is certified in all jurisdictions around the world (America's, EU, Australia you name it) and in order to do this, the system has been tested for thousands of hours.

So far, the media are saying that because there were 2 crashes quite possibly with MCAS as a contributing factor, that it must be Boeing's fault and that the entire fleet should be grounded. This is NOT the case. The accident was caused because 2 pilots stalled the aircraft. This is the primary cause. This is a situation that is completely avoidable by proficient and experienced pilots. Pilots should never rely on Stall Avoidance. To me, this is unacceptable. Also, the grounding is precautionary. The MCAS is just a safety feature, not a replacement to good Airmanship.

Anyway it will all come out in due course. The B737 MAXI will also be flying within the next few days as well.

Rest assured, Boeing knows what it is doing. The B737 is probably the best built aircraft and most successful aircraft ever built.

This technology isn't new. Stall Avoidance Systems have been in commercial aircraft over 5700KGs in the Regular Public Transport category of operations since WW2.

Things like Stick Shakers and Stick Pushers are one such safety feature. The Maneuvering Characteristics Augmentation System (MCAS) fitted on the B737 MAXI is just a Fly By Wire electronic version of the more mechanical Stick Pusher and Stick Shaker system but a side affect is that the pilots have less control. That is the issue here. A problem that can be easily fixed with an upgrade to the software and better pilot training. There is definitely a training issue element in the Ethiopian Airlines Crash.

Stall Avoidance Systems are also not only triggered by a high Angle of Attack. It's also triggered by low airspeed. For instance, the most dangerous phase for Stall Avoidance is actually on the LANDING with a lower Angle of Attack than on the Take OFF with a high Angle of Attack. Airspeed on Rotation is about the same as Landing Airspeed at the Touch Down Markers (there is a small variance) but the aircraft accelerates fast to 180 knots to the acceleration altitude where the attitude is lowered to accelerate to 220 knots in the second segment of climb where it is safe from ground obstacles. This acceleration is achieved by lowering the attitude or Angle of Attack. Also, the power is reduced from Take of Power to Climb Power (an arbitrary setting dependent on Outside Air Temperature and Weight in order to achieve the right performance in the second segment, a legislated performance criteria that is in The Civil Aviation Orders Section 20.7.1b for high capacity RPT aircraft.

Boeing and Airbus have been building compliant aircraft to meet these requirements for decades. The issue is in the software and in pilot training. Sadly in Aviation, new technology quite often results in loss of life until the authorities can re-calibrate because its uncharted territory which will ultimately make aviation safer when everyone is across this capability. What I believe occurred is that the airline did not keep up with this technology in educating its pilots. There were hundreds of B737 MAXI aircraft flying around the world without incident.

Now, I stated that the most dangerous phase is landing. You have a lower Angle of Attack but a very low airspeed that is 1.2 Vstall. So you got a 20% margin above the stall on short finals below 500FT Above the Ground on an approach meeting the Stable Approach Criteria - Rate of Decent below 1000 Feet per minute, wings level, on the centreline, on the glide-slope and in tolerance (half scale deflection) and all landing checks complete. So you got your Vref which is what you should be as the aircraft touches down on the Markers. Vref is 1.2 Vstall.

When the airspeed reduces by 7 knots below Vstall - the Stall Avoidance activates. This is the start. Pilot intervention is easy. Plane is easily recovered.

When the airspeed reduces further by another 7 knots, a force is applied to the Control Column to lower the nose and increase airspeed. Imagine this on Short Final. This is the most likely time. This is a lot harder for pilot intervention, but the plane should NEVER get there and if it does the pilots have failed in their duties. You apply max power to accelerate the aircraft and execute a missed approach Go Around, where you rotate from a low Angle of Attack to a Climb Angle of Attack. This is a serious safety occurrence resulting in a safety Report.

The stall is entered by a further 7 knot reduction - aircraft stalls. Everyone dies.

This is what the MCAS is.

The problem with this accident I hate to say is mostly pilot error. The pilots should have never found themselves in this position.

I have had a SAS event (Stall Avoidance Event) only once in the last 12 months (in about 800 hours of flying) and that was a minor 7 knot deviation caused by wind shear when I was landing at Sydney Runway 34R on a stormy day. These events are rare because we are trained to follow procedures and maintain our speeds. Also, we add additives for gusty conditions and wind shear. In other words we add 50% of the wind gust component to our Vref in order to add an additional safety margin.
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Re: Boeing 737 MAX+

Postby Kikapu » Thu Mar 28, 2019 9:51 am

Paphitis,

The creation of the MCAS for the 737 MAX is not the problem to get the aircraft out of a stall if the pilot is careless by putting the aircraft into a stall, but the problem is when the aircraft is no longer in a stall. Once the nose is forced down by the MCAS to get out of the stall, it won‘t allow the pilot to resume normal flight to level the aircraft, but instead, retains nose down attitude to the ground without some problem solving first by the pilots, by going through the operator‘s manual, which time may not allow when so close to the ground soon after takeoff.
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Re: Boeing 737 MAX+

Postby Londonrake » Fri Mar 29, 2019 2:18 pm

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