Pilots approach this angle of 17 degrees shortly after takeoff in order to gain altitude as quickly as possible. MCAS does not kick in until about one minute after takeoff. Even then, MCAS does not kick in until the AOA sensor(s) indicate that the angle of attack is above about 20 degrees. Using the current MCAS (before the new software fix), MCAS will automatically push up the tail about 2.5 degrees over a 10 second period. Due to the 8 to 1 lever arm effect, this will lower the nose about 20 degrees over 10 seconds. In short, the current version of MCAS is intended to bring the plane from a dangerous angle of 20 degrees back to a nearly level angle.
Calculating the Odds of a Crash with the current version of MCAS
Let’s assume that there were an average of 333 Boeing 737 max airplanes in service during the past year and that each one of them takes off and lands 3 times a day. That is about 1000 737 Max missions per day. Lets also assume that all of these planes were in service for about 500 days before they were grounded. This would mean that two disasters occurred in 500,000 missions. This would put the odds of a crash at 1 in 250,000.
Put this way, it looks like the 737 Max - even with the current MCAS settings - has been a pretty safe plane. But that is not how the public looks at plane crashes. The public wants the odds of them dying in a plane crash to be much less than one in a million. The safety record of the current 737 Max is therefore not acceptable to the flying public.
Calculating the Odds of a Crash with the new version of MCAS
Let’s assume that the FAA rubber stamps Boeing’s new “fixed” version of MCAS and that 737 Max planes start flying again on September 1, 2019. Let’s further assume that airline carriers are crazy enough to accept delivery on the 300 or so 737 Max planes that will be parked in airports all across Washington state and these new airplanes join the fleet of 387 current 737 Max planes. This would mean that nearly 700 737 Max planes will be making 3 trips a day by September 2019. If there was no change in risk between the new MCAS and the old MCAS, simply this 80% increase in the number of 737 Max planes would increase the risk of one of them crashing on any given day by 80%.
But let’s make two more assumptions. First, let’s assume that half of the problem was the reliance on a single sensor and that changing to two sensors fixes this half of the problem. One might assume that this would bring the risk factor back down to about one in 250,000 missions.
But we need to also make one more assumption. This is that the Boeing test engineers in 2016 knew something very important that we currently do not yet know – and these test engineers in 2016 - who changed MCAS from 0.6 degrees of change and no repeat to 2.5 degrees of change with a repeat function – were not idiots. They clearly believed in the summer of 2016 after getting the test results from the initial four 737 Max planes that the safest settings for MCAS was 2.5 degrees with a repeat function. They had concluded based on several test flights that the 737 Max had such a huge risk of the nose going up and causing a stall that it had to be prevented at all costs. That is the only reasonable explanation for why they made this change in the first place. Therefore, any new setting for MCAS (such as the current fix) that is less than 2.5 degrees and lacks a repeat function must be LESS SAFE than the current setting of MCAS! In short, while Boeing is making some changes that might reduce the hazard, they are making several other changes that are likely to increase the hazard of a crash.
These other changes that increase the hazard of a 737 Max crash include putting more a lot more 737 Max planes in the air and reducing the power of MCAS to prevent a stall. As Boeing will continue to deliver 50 737 Max planes per month after September 2019, there will be at least 1400 Boeing 737 Max Death Traps in the air every day by October 2020.
Table of 737 Max Planes Made Parked and Delivered
| Year/Month |
Monthly Rate |
Parked |
Delivered |
New Total |
| 2019-Jan |
52 |
0 |
52 |
382 |
| 2019-Feb |
52 |
47 |
5 |
387 |
| 2019-March |
42 |
89 |
0 |
387 |
| 2019-April |
42 |
131 |
0 |
387 |
| 2019-May |
42 |
173 |
0 |
387 |
| 2019-June |
42 |
215 |
0 |
387 |
| 2019-July |
42 |
257 |
0 |
387 |
| 2019-Aug |
42 |
299 |
0 |
387 |
| 2019-Sept |
52 |
52 |
299 |
686 |
| 2019-Oct |
52 |
0 |
104 |
790 |
| 2019-Nov |
52 |
0 |
52 |
842 |
| 2019-Dec |
52 |
0 |
52 |
894 |
| 2020-Jan |
52 |
0 |
52 |
946 |
| 2020-Feb |
52 |
0 |
52 |
998 |
| 2020-March |
52 |
0 |
52 |
1050 |
| 2020-April |
52 |
0 |
52 |
1102 |
| 2020-May |
52 |
0 |
52 |
1154 |
| 2020-June |
52 |
0 |
52 |
1206 |
| 2020-July |
52 |
0 |
52 |
1258 |
| 2020-Aug |
52 |
0 |
52 |
1310 |
| 2020-Sept |
52 |
0 |
52 |
1362 |
| 2020-Oct |
52 |
0 |
52 |
1414 |
The odds of one of these 1400 to 1500 737 Maxes crashing before the end of 2020 are extremely high – much greater than 50%. And the odds will only increase every month and every year after that as the number of dangerous Mad Maxes in the sky will only grow until one of them crashes. Keep in mind that the eventual plan is to put 5000 of them into the sky.
The only difference between the next crash and the two previous crashes will be that the next crash will be from the result of a stall caused by the nose up problem that MCAS was not able to stop - rather than a crash from the result of a a dive caused by an over-active MCAS. In previous versions of the 737, when you pull five pounds of force on the yoke, you get five degrees of pitch change, and when you pull 10 pounds, you get 10 degrees of pitch change. However, on the MAX, it only takes a 10-pound pull to get 15 degrees of pitch. This was why MCAS was needed. But instead of too much MCAS, the new 737 Max will have too little MCAS. This is the problem with a plane that is inherently unstable.
Here is an extremely important question that no one in the corporate media has ever asked: Why was the repeat function added to MCAS?
The current repeat function, which will not be present on the new “fixed” version of the 737 Max, was clearly intended to serve some purpose. It was not added by accident. The purpose is likely due to a “positive feedback loop” that only becomes apparent in the 737 Max when it is very close to a stall AOA of 20 to 25 degrees (the test required to pass FAA certification in 2016).
This positive feedback loop likely increases the nose angle very rapidly. We can assume this is true because first, the initial change of the current MCAS is also very rapid – a rate of 2 degrees per second for 10 seconds. We can also assume this is true because MCAS only waits 5 seconds before repeating the nose down action for 10 more seconds. Such a rapid change of 40 degrees over 25 seconds means that the 737 Max must have a tendency to go into a nose up stall position of 40 degrees in 25 seconds.
Removing the repeat function, on the surface, may seem to make the 737 Max safer. But it does nothing to change the aerodynamics of the 737 Max. Therefore, eliminating the repeat function may actually make the 737 Max less safe by increasing the odds of it going into a 40 degree nose up stall position.
Here is a good analogy published by the Observer on May 17 2017:
To give an example of what occurred, imagine a car company builds a new model that, due to the design, the front of the car points upward when driven faster than 30 miles per hour. To “fix” the problem, the car company increases the weight in the front of the car by 500 pounds. Technically, the car rides more level. However, due to an imbalance in weight between the front and rear of the car, the car can skid sideways when going around corners. No need to worry. The engineers at the auto company create software that forces the car to drive slower around corners eliminating the issue. Over a period of weeks and months, reports begin to surface that when the car is forced to drive slowly around corners, it’s nearly impossible to steer the car and keep it on the road. “That’s an easy fix,” proclaim the engineers, and software is developed to automatically steer the car around corners. For a while, all is well. Unfortunately, in a period of several days, multiple families are killed while driving the car, because for some unknown reason, the car decides to start steering itself without warning and multiple crashes occur. “Not to worry,” states the CEO, “we’ll quickly make improvements and when we are finished, the car will be the safest on the road.” And the victims? They’re buried and gone forever.
What should happen to the 737 Max? Nothing. The plane should permanently be grounded. No husband should ever allow his wife or family to fly on a 737 Max. No wife should allow her husband to fly on a 737 Max. No parents should ever allow their children to fly on a 737 Max. No one who cares about anyone should ever allow them to fly on a 737 Max. The families of the passengers killed in the two 737 Max crashes are in a nightmare that will never end. The desire of Boeing to get the 737 Max flying again doesn’t justify the risk of more crashes on a plane that should never have been certified to fly in the first place. https://observer.com/2019/05/boeing-737-max-software-fix-permanently-ground/
Factors that will increase the likelihood of the next crash
First, it is likely that the next crash will involve a less experienced pilot flying for a discount airline. A highly experienced pilot is not likely to ever crash a 737 Max because a highly experienced pilot will be very careful not to let a 737 Max get into a 20 degree AOA nose up position in the first place. An experienced pilot would never trigger MCAS and does not need MCAS and would likely turn it off the first time it was active.
Second, there likely will be some sort of front wind, cross wind or tail wind combined with vertical turbulence such as a thunder cloud associated with a Cold Front. There will likely be icing on the wings and icing on both AOA indicators. A flock of birds could also cause a problem for the AOA sensors.
Third, there will be limited visibility preventing the pilot from seeing that their Angle of Attack is too high. Clouds will likely be very thick all the way down to the airport.
Fourth, there will be some reason the plane needs more lift. One example is a plane that is over loaded with baggage and passengers. Another reason is that there is some mountain range in front of the airport the plane needs to climb over. Any several reasons could cause a pilot to want to gun the engine to the maximum. When this happens, torque will cause the nose to rise up very rapidly.
All four of the above factors will increase the odds that an inexperienced pilot will exceed the 20 degree maximum nose up position. When he or she does, a reduced power MCAS will not be enough to return the nose to a level position. This is especially true if the pilot has turned MCAS off due to erroneous sensor readings. The complete stall will occur in less than 25 seconds and the pilot and passengers will suffer the same fate as the two previous crashes – even though the actual cause will be from an extreme nose up event instead of an extreme nose down event.
There are some lessons here. First, either do not fly on a 737 Max or, if you do, do not fly with an inexperienced pilot on a discount carrier when the weather is bad and the wind is blowing. Also try to avoid migrating geese. Hopefully, you can now see why I am so certain that a 737 Max accident will occur somewhere in the world by the end of 2020.
But since there are more 737 Maxes in the US than in the rest of the world (see graph below), the odds of a crash are more likely in the US or Africa than in other parts of the world since a higher percentage of 737 Max planes are being sold in the US and Africa.
Now that we better understand how serious this problem is, let’s take a quick trip down memory lane to see how Boeing executives were lured into making such a terrible decision in the first place.