121pilot, a frequent commenter on this blog, is a U.S. commercial airline pilot. I asked him to address the safety of the Boeing 737 MAX and he graciously agreed. His thoughts are below.
There has been a great deal of concern within the aviation community after the recent crash of an Ethiopian 737 MAX, shortly after takeoff. Especially since this is the second fatal crash in five months of this relatively new type of aircraft. Based on the information we currently have, both crashes look eerily similar and leave many people wondering whether the 737 MAX is safe. Nine countries have grounded the MAX and several operators have voluntarily grounded its MAX sub-fleet until they can be assured that it is safe to continue operations.
I’m a professional pilot flying for a US major airline on the Airbus 320 series. While I’m not rated on the 737, like most people in my profession I follow accidents and their causes closely. Personally, I’m not at all concerned with the safety of the 737 MAX at present. Why?
The New York Times published an excellent article last month that looked at the Lion Air crash and its suspected root causes. When Boeing developed the MAX series a new system called the Maneuvering Characteristics Augmentation System (M.C.A.S) was added to the aircraft to meet certification requirements. This system senses the approach of a stall, and forces the nose of the aircraft down to prevent it. It does this through the use of the aircrafts trimmable horizontal stabilizer which along with the elevators controls the pitch (nose up and down) of the aircraft.
The Lion Air pilots faced what is akin to a run-away stabilizer trim scenario. M.C.A.S. reacted to faulty data from the aircraft’s sensors and activated using the horizontal stabilizer trim to force the nose of the aircraft down. While there are procedures to deal with this scenario, at the time of the Lion Air crash training materials on the MAX did not include the existence of M.C.A.S. Nor did they include that one of the methods of overriding the stabilizer trim system on previous models of the 737 no longer worked on the MAX.
I’ve been through run-away trim evolutions in the simulator on prior aircraft that I’ve flown and they are no joke. They can quickly produce control forces that you simply cannot overpower and lead to the loss of the airplane. Which is precisely why we train to deal with them. While M.C.A.S may have been unknown prior to Lion Air it generated enormous attention in the wake of that accident. Consequently, I would expect pilots flying the MAX today to be aware of the system and how to deal with potential faults.
On the Airbus we had something similar happen some time ago when an aircraft experienced an un-commanded nose down pitch movement that the pilots struggled to overcome. In that case, the crew was able to maintain control and land safely but obviously it was a matter of great concern. New procedures were created and we now have a memory item that, should it happen again, allows us to override the computers and regain control of the aircraft.
It’s important to keep in mind that we know very little right now about what caused the Ethiopian crash. The cause may be very similar to the Lion air incident or it may be completely unrelated. But at this point, I see no reason to think that there is a problem with the MAX making it unsafe to fly. Flying transport category jets requires a high degree of professionalism and knowledge of the aircraft systems. The MAX may present challenges that didn’t exist on previous versions but following proper procedures and checklists enables those flying the airplane to do so safely. At this point with the data we have available there is simply no good reason to think the MAX is unsafe.
image: Jeff Hitchcock / Wikimedia Commons
As a commerical pilot, what are your thoughts on FO having only 200 hours flight time? Can this be enough for someone to be a competent 737 pilot?
Unless Boeing demonstrates the contrary, 737 MAX is not fit to fly safely. We are not talking about near-misses, emergency landings or whatever… these are planes falling from the sky: 2 in the last 5 months.
The problem: political and commercial interests.
Unless Boeing demonstrates the opposite, 737 MAX is not fit to fly safely. We are not talking about near-misses, emergency landings or whatever… these are planes falling from the sky: 2 in the last 5 months.
The problem: political and commercial interests.
I appreciate your perspective.
However, I’m not comfortable with the idea expressed here, and by Boeing, the FAA, the airlines, etc… that we don’t know enough yet to know if there is a safety issue and that until proven otherwise, we assume it is safe.
I don’t get his point? He provides no evidence or logical argument other than let’s wait and see how the investigation turns out. How many crashes would it take before it is considered unsafe? What in the investigation would make him think the plane is safe or unsafe? Wouldn’t the Ethiopian pilots be aware of the new emergency procedures?
According to the Ethiopian CEO, they were aware of the new procedures. I can see the argument that US pilots have better training and more experience than anywhere else; that the FAA has more training and experience and is a better judge of safety than other agencies; perhaps that pilots have learned from the last incident…but the wait and see idea is not comforting.
Armchair quarterbacking, but I suspect the training or flight time as Dan pointed out in other countries could be a contributing factor. I always think twice before booking and don’t book in some cases based on the origin of the airline.
Can someone with 200 hours safely act as a First Officer? Yes. However…
A 200 hour pilot even one who has been trained to a very high standard is not going to have much in the way of experience to fall back on. My experience as a regional Captain years ago flying with very low time first officers was that most of them were great as long as things went according to plan. When things came off script is when they tended to struggle. It could (and sometimes did) lead to me essentially being single pilot as they tried to get their head around what was happening.
It’s why I fully support the US requirement of 1500 hours to be a pilot at a 121 operation. You simply cannot replace the experience that comes from time in the seat no matter how good the training is.
I’d also be interested in your perspective about how rare the situation is where MCAS should activate. Boeing stated, I believe, that they didn’t inform pilots of the change as pilots should never really be in a situation where MCAS should activate (high G load and near stall). Yet so far, it seems the system is responsible for at least one, and maybe 2, total losses. So a niche system with a very remote chance of saving lives has instead taken 150+ lives? Why not remove it entirely?
Nevermind – after reading the referenced NYT article, I suppose that if MCAS were to be removed, it would require simulator training. But, it does seem like the situations described in the NYT article: low speed, steep bank climbs, could be used to describe any number of take-off experiences I’ve had. I’m not sure what the parameters for the roll angle are, which probably makes all the difference, but the general description certainly doesn’t seem as rare as Boeing might maintain.
I appreciate his opinion but if you have a contributor who is a 737-8MAX pilot, I think we’d all appreciate hearing from him/her too.
@Josh and @Nathan Comsider that based on what we know about the Lion Air crash no grounding was required. Remember that in the case of that aircraft MCAS looks to have activated due to faulty data on earlier flights and those crews handled it without incident.
With respect to Ethiopian at this moment we have no solid information on the cause of the accident though given that the black boxes have been recovered we should expect that shortly.
I don’t view an accident in and of itself as a reason to ground a type. Before that happens there needs to be some evidence that the type isn’t safe to fly. Right now we just don’t have that information.
Should 767’s be grounded right now after what happened with Atlas? Frankly that incident scares me a good deal more than anything that has happened with the MAX to date.
@Dan in essence if your doing your job right MCAS should never come on because you should never get close to the stall. In the case of Lion Air it was bad sensor data that led MCAS to activate when in fact it shouldn’t have. With Ethiopian we just don’t know yet. It may have been some completely unrelated cause.
Thanks @121Pilot, appreciate the perspective!
In short, Boeing got a new techie but somehow forgot to teach people how to use it. After few hundred died, they simply said sorry and teach pilot about new tech. Then something similiar like the new techie incident happened.
Are we gonna wait for another simple sorry?
@James that’s not it at all. I would suggest reading the linked NYT article for a far more in depth explanation.
@121Pilot: there’s a reason I wrote, “in short…”
While there are procedures to deal with this scenario, at the time of the Lion Air crash training materials on the MAX did not include the existence of M.C.A.S. Nor did they include that one of the methods of overriding the stabilizer trim system on previous models of the 737 no longer worked on the MAX.
This!! This is what I find mind boggling and disturbing. Why do people shrug it off…
@Paula it hasn’t been shrugged off and in fact generated a good deal of outrage from those who fly the airplane when
It came out 5 months ago. Clearly it was a bad call on the part of Boeing and the regulatory authorities that signed off in it.
But the situation is different now and the entire community of MAX pilots knows or should know about these issues.
It seems to me like Boeing needs to add some redundancy. The impact of a single sensor failure is just too high. Add another sensor or two so that the probably of failure goes down to almost nothing.
@121Pilot. One thing I found interesting is that you mention how you have trained for these situations in simulators for the A320. I think what is missed here in your well written post is that there are currently only 4 737MAX simulators in the world. Southwest has the only one in the U.S. This because Boeing touted the idea that pilots can move from the NG to MAX seamlessly. With that, only 4 simulators exist in the world that allow pilots to simulate the issue with the MCAS so as to build “muscle memory.” This, as the NG simulators do not have it. Few pilots of the MAX have the same luxury as you in an A320 actually practicing this event.
This was, interestingly, recognized last year only by the Brazilian equivalent of the FAA which was the only world agency that required specific training on the MAX and refused to accept Boeing’s claim of seamless crossover between both variants.
Stuart to be clear the memory Item I mentioned is not something we’ve trained in the sim. A bulletin came out advising us of the issue and giving us a new procedure to deal with it should it arise. So I have a procedure I’ve been required to memeorize but not one I’ve practiced in the sim.
What I have trained on past aircraft (not the 320 series) is a trim run away where due to a fault the stab trim starts running uncommanded. Given how MCAS has been advertised to function the two scenarios should be quite similar in appearance.
I really appreciate your taking the time and addressing us here. It is refreshing to get a pilot’s perspective in this small community of people who, like you, rely on the safety of the system each and every day.
As an avid whitewater kayaker I opted for the term “muscle memory” in that when we learn new techniques and safer approaches to getting down a rapid, either because the design of the kayaks has changed/evolved or we as paddlers have, the key to learning this is always by doing it (simulating) vs just studying it. Not just once, but many times, until it is not just memorized visually but is a part of the core of our muscle memory. In essence where we could do it blindfolded if need be. In a few occasions this has been the difference for me in avoiding an injury or death in the past 20 years.
I guess my point being that from what I have read (and feel free to correct me if I am wrong) is that the MAX has a completely different and unique set of steps in which to counter a faulty MCAS reaction and to retake control of the aircraft. That is three buttons that must be pushed, two on the control panel and one near the throttle. It seems that while perfectly acceptable that a trained and practiced pilot in this should be able to press three buttons – in comparison to other aircraft these steps are actually, according to a pilot commenting on Aviation Herald, “Different from any other aircraft and are counter-intuitive, archaic, and absurd for pilots to perform under the stress of an emergency situation.”
Again, this is fantastic you are taking the time to explain things on a deeper level and I appreciate Matthew bringing you on for what I trust is intelligent conversation and better understanding.
Stuart my understanding (and remember I don’t fly the 737) is that because MCAS uses the stabilizer trim to push the nose down the counters are the same as for a trim runaway event. The most prominent of those counters (and there may be more than one) are the two stab trim cut out switches on the center console. Pull those and because stab trim is disabled MCAS is effectively disabled.
Muscle memory is a very apt term to what we do much of the time. Many of our normal “flows” are a sequence of events that we perform from memory and then backup with a checklist. Emergency situations much less so because the community has learned over time that long memorized emergency procedures tend to get forgotten or done wrong under stress. Hence the reason we have very few true memory items.
Does that address your question?
Yes, and again, thank you for spending time here. Though I wish it were under different circumstances as it is a fascinating subject overall to understand better.
Often though, just like in ww kayaking, it takes the unfortunate experience of accidents – and deaths – to help us determine that there actually was a “better way.” I have no doubt that the fine people investigating these two accidents will quickly figure out the answers and come up with solutions.
I don’t get it. Enlighten me. It would seem that an angle of attack sensor that gives false readings is potentially LETHAL. One would think that such an item would be carefully engineered and built so as to never, ever, ever, ever (or very, very, very rarely) give false readings that lead to an imminently-catastrophic situation. What the F is wrong with this sensor? They should never fail. And so — what — the latest crash is ALSO due to a failing angle of attack sensors? Are they buying these at Wal-Mart? I’m serious. YES, the pilots need to know exactly what to do when the computers are taking over and putting everyone in mortal danger. But how often should this be happening? GET REAL.
This is ridiculous.
When the cause of a plane crash that killed people is not known, the plane should be grounded for precautions instead of continuing to fly until the exact cause gets identified.
You should always pick the safer option when it comes to these unonown situations.
I cannot believe a pilot said this.
Please tell us what airline you work for and I will never fly that airline.
Tom,
Are you saying that everytime an airliner crashes that fleet should be grounded until the cause is definitively known? Should 767’s be grounded right now?
Fallacious argument 121 Pilot. You have introduced a classic red herrings into the discussion by changing the subject. Tom never talked about “an airliner” crashing nor 767 grounding. Instead he talked about two 737 Max crashes.
Let me remind you of the possible problems in the 737 Max. Its angle of attack characteristics have changed significantly. Some pilots are apparently are unaware of MCAS and few have trained with new system in a simulator or in the air.
I suggest you tell Tom and the forum who you fly for or promise to resign as a pilot. Why? Discussion as well as flight training require discipline and if you fly like you write you are not qualified to fly.
The 738Max has just been grounded in Europe until further notice.
@121pilot – I appreciate your perspective and expertise. While as a lay person who flies all the time, I understand what you are saying but at an absolute minimum Boeing should have their asses handed to them in the courts. To develop a plane with new functionalities rendering old sops void should at a minimum require extensive pilot training and education. It almost seems like they just sent off the planes with an instruction manual and wiped their hands.
While US based pilots might be semi more trained, I don’t agree that these pilots crashed because of being lion air he Ethiopian pilots. Until all max pilots are thouroughly trsined I still feel they should be grounded as a precautionary measure. While the plane might be safe to fly, pilots obviously need more training in how to do so with this aircraft.
Shawn,
We don’t know at this point whether or not training played a role in this accident. I will say in the industry when an event can be addressed by training the norm is not to ground the type until training occurs. You issue bulletins that pilots are required to read that address the issue and how to mitigate it. Then if hands on training is needed that gets done at the next normal cycle.
It’s worth bearing in mind that even well trained western pilots have made mistakes that led to hull losses. Air France 447 being just one example.
A lot of people are pointing to the fact that we have had two accidents in 5 months as a reason to ground the type. But what should be remembered right now is that the underlying causes of that first accident are pretty well understood and none of them point to an aircraft that is unsafe to fly. As for this most recent event while it is similar we just don’t know what has caused it right now.
@Tom – Thats just not realistic generally although I agree with you in this instance because we have had two crashes on a plane which has been around less than a year.
At a minimum ground them until all companies can provide x education in how to fly this plane.
There’s obviously something wrong. Planes just don’t see saw and fall from the sky because an Ethiopian pilot was st the helm. These people too are professionals more than able to fly a plane. Now whether they’ve had adequate training for the max….?
The problem is that if pilots aren’t properly trained to deal with this issue (and its completely absurd that pilots weren’t informed about the MCAS prior to the Lion Air crash) they may not be able to properly respond in the moment when it occurs mid-flight. Even then, while training is valuable, it can’t completely eliminate human error, especially in tense life/death situations where every second counts. Not to mention the fact that most 737 pilots are more used to other 737 variants that have a different autopilot system, which increases the risk of error in a stressful situation (they might know how to handle the MCAS, but if they briefly forget in the moment, that won’t matter).
While we don’t know precisely what happened in either incident, the similarities (and the relative rarity of plane crashes) suggest this issue caused both crashes. While there have only been two crashes so far, that is a relatively high number for the same airframe in such a short timeline given how safe air travel is in general and we have no idea how often the sensor issue has occurred or continues to occur. Emergency situations happen, there’s no controlling that, but there shouldn’t be an airframe flying thousands of flights per day that has a known issue that leads to emergency situations and potentially crashes if the pilots don’t respond properly.
Follow the money: Boeing has a product that will compete well against Airbus, but only if it can be marketing as requiring very little additional retraining of pilots , including simulator time. FAA is reported to be very reluctant to agree that no retraining is required but acquiesced following intense lobbying from Boeing. Boeing is then able to flog a large number of planes around the world, with only Brazil requiring the additional sim training.
Two similar crashes in a very short time, a frequency never seen before, including the DC10.
Much of the public commentary revolves around the fact that these were ‘third world’ crashes , consequently likely to be unrelated to the safety of the plane.
No doubt that the lobbying of the FAA by Boeing will come under intense scrutiny over the next few months ( already raised by the NYT in articles following Lion Air, prior to Ethiopian).
Question: If the MCAS system can be turned off while in flight using a three-step procedure, why can’t it be turned off before takeoff until the problem is resolved? Can you answer that 121pilot?
SF Ron I’m not sure the 3 step procedure you mention actually applies. Remember I’m not a 737 driver.
Regardless though pilots would want to leave MCAS on unless they were sure there was a related malfunction because it’s an esstential part of the aircraft’s certification.
@121Pilot – Dan again with just one further question on the MCAS (and realising it’s specific to the 737-MAX so you may not be familiar with it), but in both this case and the Lion air case, it seems the pilots reported trouble controlling the plane, with the Lion air case having more than two dozen downward pitch movements.
With the MCAS only supposed to provide control inputs in high banked turns approaching stall speed, if the pilots decreased roll and flew straight would the MCAS no longer provide control inputs? I’ve only flown a little recreationally (ultra-lights, flying boats, paragliding, and RC planes) but know the feeling of losing lift in a turn and it would seem like straightening the plane out would be at least one reaction on the table? Or would the MCAS keep nosing the plane down because of the AoA sensor fault (in the case of Lion Air)? Or are flight paths so packed at takeoff that this is just something one would never do for fear of hitting another plane? Again – total amateur here so not questioning anyone’s actions, but just wondering.
Dan,
My understanding of MCAS is that while the need for it was greatest at steep bank angles the system activates based on the Angle of Attack (The angle at which the airflow is hitting the wing) or AOA. So if MCAS senses that the aircraft is nearing the stall it activates to push the nose down regardless of bank angle. This is what we saw in the Lion Air Crash.
It occurs to me that it may be helpful to talk a bit about why MCAS is there in the first place. On aircraft like the 737 or A320 with underwing mounted engines those engines produce a nose up pitch force. At normal speeds you don’t really notice this as their is easily enough control authority to offset it. But at low speeds when the airflow over the control surfaces is diminished it can become quite pronounced. The force can be powerful enough that if your very close to the stall and go from Idle thrust to max power quickly that there is a good chance it will push the nose up regardless of control input and result in the aircraft stalling.
Based on the linked article it would seem that on the MAX this effect without MCAS was pronounced enough that the airplane wasn’t going to meet certification requirements. But with MCAS there to help push the nose down it did.
Now it bears mentioning that what I’m talking about is a art of the operating envelope that you should NEVER be in. So on any normal day of flying MCAS should never activate. It would only be after you’ve made some serious errors and allowed the aircraft to get near the stall that it would kick in.
Of course malfunctions of various systems (in the case of Lion Air a bad AOA vane) can cause it to activate when it shouldn’t. But there are established procedures that allow you to override the system and fly the airplane safely.
I hope that answers your question.
@121 Pilot – thanks, this is great and answers my question very well! I hadn’t realised the MCAS would activate regardless of the bank angle, which, at least to me, would increase the possibility that (and expand the realm of scenarios where) one might get MCAS activation based on false (or real) sensor input. Your explanation of why MCAS would be intended to activate regardless of bank angle also makes sense, of course, and was very helpful in explaining why it’s a crucial part of the airplane and can’t just be removed. Hopefully Boeing’s software fix to use both AoA sensors will reduce the possibility of it activating on false data.
Thanks again for taking the time to answer all these questions from lay people!
” Nor did they include that one of the methods of overriding the stabilizer trim system on previous models of the 737 no longer worked on the MAX.”
Boeing should be sued to the max for this. The way the c stock reached after first crash people didn’t expect there to be substantial payout. If the victims had been a bunch of white Republican males Boeing would have something to worry about.
how often is that sensor going to stall and have the MCAS activate without the pilot understanding how to operate it. Boeing said that it should rarely activate and that is why the pilots were not aware or trained. Don’t understand that, they should absolutely understand everything no matter what. There was a statement made by a US pilot that said that the manual and training was criminal. Why does this need to be a conversation. Figure it out, fix it, then resume. Why are we taking chances that more flights will crash. Senseless. I will not board one of these aircrafts and maybe not a 767. I was over the ocean in a 767 when we lost all electrical power. Terrifying…
Is the 737 Max the only Boeing that needs MCAS for stability? If yes, doesn’t this indicate that the design of this generation is inherently unstable? Did Boeing cut corners to save money instead of designing/ building a new aircraft that properly incorporated the new larger and heavier engines?
Previous 737s had no problems with stability and therefore the new design never should have been certified. The FAA is responsible for allowing /certifying a software fix to compensate for an inherently unstable aerodynamic design.
Beyond stupid.
@121pilot are you not on the below mentioned meeting?
https://www.straitstimes.com/world/united-states/pilot-complaints-raise-questions-over-boeings-response-to-lion-air-crash
Ups… Sorry… Just re-read that you fly airbus, not boeing (esp 737).
This video clip may give readers a sense of what it was like for Lion Air 601 and Ethiopian Airlines Flight 302 passengers and crew: