Pilots offer insights on Boeing 737 crashes

Money quote is as the end, from a Max pilot:<p>“Tecce did not fault the FAA for taking a wait-and-see approach. “A lot of people throwing a lot of rocks at the FAA. Since 2010 we’ve had one aviation fatality” in the United States. “Our safety record is astonishing,” he said. “I don’t think there’s anything wrong with the airplane. If you talk to the pilots who fly them, they’ll tell you it’s not the airplane so much as whether or not the manual properly describes what’s going on.””<p>Seems more and more consensus is forming around this idea, that the MCAS system generally did what it was supposed to do, _and_ has an appropriate safety cutoff for the pilot if needed, but that Boeing did not focus a lot of attention on this new system in their training&#x2F;documentation when in fact they needed to.

It seems like there&#x27;s a never ending barrage of &#x27;news&#x27; around this. All of this is speculation at this point though. Investigation takes time, which is almost unusual in a time of minute by minute updates on absolutely everything.<p>I would not be surprised if the cause ends up being more complicated than the currently suggested causes. There&#x27;s definitely a lot to suggest that the cause of the Ethiopian and Lion Air crashes is the same, but the current explanation seems overly simplistic.<p>The failure modes in the leading theory for the Lion Air crash were a broken AOA sensor causing the MCAS to kick in erroneously, combined with the pilots not reacting properly to a runaway trim situation. From what I understand, while MCAS is new, the process for reacting to runaway trim is not new to the 737 Max. This is probably also why the FAA and airlines like Southwest were confident their pilots would handle this situation correctly.<p>For the cause of the Ethiopian crash to be the same, the pilots would also need to be unfamiliar with the runaway trim process. This seems unlikely though after the Lion Air crash since it put so much attention on that scenario. That suggests to me there might at least be other contributing factors to both these crashes. I think we just need to wait and see what the investigations of both these crashes find.

I was waiting to hear something like this. Generally speaking, Airline pilots who actually flew the plane are one of the best sources to consult when it comes to determining any possible safety malfunction of an aircraft.<p>One thing to note is the mention of a &quot;Runaway Trim Checklist&quot;. When piloting an airliner, there is a checklist for almost everything. Sometimes there are multiple checklists with branching paths. Most emergency&#x2F;malfunction checklists involve what are called &quot;memory items&quot;. These are checklist steps that the pilot must remember in order to react quickly to any possible problem. After the memory items are completed, the pilots will break out the checklist binder and follow the checklist procedure that comes after the memory items.<p>Every procedure the pilots undergo has passenger safety as it&#x27;s #1 concern. Pilots are free to make whatever decision they deem necessary to ensure the safety of their passengers, even at the detriment of the airline&#x27;s bottom line. They are free to make these decisions without question, even if the problem seems small.<p>I believe it&#x27;s important to note the above information whenever we look at these horrible accidents and try to reason about them. Often, pilots are the first line of defense against failures. Most aircraft have 2-3 redundant systems for almost every control and feature. Pilots need to understand and know how to work with and around these systems in order to react to emergency situations. That&#x27;s why I think the MCAS isn&#x27;t really to blame here as much as Boeing is to blame for not properly documenting it&#x27;s operation in their manuals.

It almost looks like if it was an error to call this plane 737 MAX instead of, let&#x27;s say, 738, to communicate that it&#x27;s quite a different plane because of aerodynamic differences and electronic systems to require a training for the pilots. Aircraft semaver.

How hard is it to flip through a binder while fighting against the trim system by putting significant force onto the stick and overriding the trim system every 10 seconds? Seems excessively challenging.

The important part of the article ----------<p>“When Boeing built the MAX, in order to increase fuel efficiency, they went with a different engine, explained Fred Tecce, a commercial aviation expert. “Because the 737 sits pretty low on its landing gear, [Boeing] had to move the engines up a little bit and move them forward a little bit” on the MAX versions. “In order to compensate, they extended the nose gear by eight to 12 inches&quot; and repositioned the engines which &quot;affected the airplane’s pitch characteristics and center of gravity.”<p>Tecce concurred that control inputs and the resulting pitch changes were challenges that had to be overcome in the latest version of the world’s best-selling aircraft.<p>“In order to compensate for what the engineers perceived to be an issue with respect to pitch, they added this MCAS system that operates when the autopilot is off and the angle of attack exceeds certain limitations and when the airplane is banked pretty steeply.” He said the technology runs the stabilizer pitch down for several seconds and it “reassesses and will start again until it believes the airplane has reached a safe angle of attack, and it operates without the pilots knowing [about it].”<p>Tecce noted that in the case of the Lion Air Boeing 737 MAX crash, “now the airplane is pitching down and actually moving the control wheel will not stop that system. If the pilot uses the trim system on the yoke, the [MCAS] system will stop&quot; but &quot;if the airplane isn’t in the proper attitude it will reactivate,” Tecce said, further forcing the aircraft downward if pilots fail to recognize the situation and take proper corrective action.<p>A pilot familiar with the system pointed out that recognizing this scenario was crucial to determine if there was a problem that warranted activating the trim cutoff switches. Additionally, if the autopilot is engaged, activating a yoke trim switch disconnects the autopilot and gives full control back to the pilot immediately.<p>Tecce did not fault the FAA for taking a wait-and-see approach. “A lot of people throwing a lot of rocks at the FAA. Since 2010 we’ve had one aviation fatality” in the United States. “Our safety record is astonishing,” he said. “I don’t think there’s anything wrong with the airplane. If you talk to the pilots who fly them, they’ll tell you it’s not the airplane so much as whether or not the manual properly describes what’s going on.”

There is some evidence that doesn&#x27;t fit with the faulty angle of attack sensor triggering MCAS hypothesis.<p>With the LionAir crash, they thought there was an a problem with the AoA sensor and replaced it but problems continued. On the flight before the fatal one and &quot;Passengers in the cabin reported heavy shaking and a smell of burnt rubber inside the cabin.&quot; (wikipedia) &quot; The plane floor is hot. During the flight, it&#x27;s never been like that&quot; (<a href="https:&#x2F;&#x2F;news.detik.com&#x2F;berita&#x2F;d-4278530&#x2F;kesaksian-penumpang-soal-masalah-di-lion-air-denpasar-jakarta" rel="nofollow">https:&#x2F;&#x2F;news.detik.com&#x2F;berita&#x2F;d-4278530&#x2F;kesaksian-penumpang-...</a>) also &quot;erroneous airspeed indications were still present&quot;<p>Then with the Ethiopian flight several witnesses reported smoke and a weird sound from the plane. Also the pilots were aware of the Lionair crash and MCAS issues.<p>I guess they&#x27;ll figure it eventually.

Refreshingly good analysis of the 737MAX from the pilot&#x27;s perspective.<p>Most are focusing on the flaws of the plane (which I&#x27;m not discounting) but pilot training is also a big part in recovering from unexpected situations, overriding MCAS or automation in general when things go south, and hand-flying the airplane.<p>The two crashes happened in developing countries, Indonesia and Ethiopia, with local crew. While I don&#x27;t know the specifics here, often times local airline pilots in developing countries (i.e. no pool of experienced general aviation or military pilots to recruit from) are trained ab initio to have a high reliance on automation, not so much hand-flying the jet. That&#x27;s how you get, e.g. a first officer with 200 hours.<p>I do believe that the US civil and military pilot training pipelines, flawed as they are, teach hand-flying and build up experience, and these crashes would be very unlikely to happen with a US carrier and crew.

Not in any discussion I&#x27;ve read so far: what is the stall behavior of 737NG compared to 737MAX <i>when MCAS is disabled</i> via STAB TRIM set to cutoff?<p>We don&#x27;t know, but will eventually find out, whether either plane was flying during the final descent to crash. By that I mean, was the wing producing any lift (dive to crash), or was the wing stalled (stall to crash) or some combination of both and in which order? And the stall behavior very well may become highly relevant.<p>It&#x27;s a whole lot of ifs, a lot of questions, and not many answers.