3 ms·

Doesn't handle well is not equivalent to "is uncontrollable", though.

phkahler 7y ago
If I recall, it made it more prone to stall in certain conditions. I'd like to call that hazardous, but without test pilot feedback I'm not sure how to classify it. My recollection from articles a few months ago is that they added MCAS not due to simple differences in handling, but due to a potentially hazardous difference in handling.
- darkpuma 7y ago
  Mentour Pilot on youtube, a 737 instructor, has a few videos about it. The gist is that in any plane when you're close to stall, you want to pitch down and increase airspeed over the wings. Depending on the precise circumstances you do this by pitching down and throttling up. However in the case of every 737 and in fact any aircraft with engines slung below the wings, the act of throttling up the engines causes the airplane to pitch up. The reason is because the engines are not in line with the center of mass. Imagine rowing a row boat with only a single oar. This is something all 737 pilots are trained for, so they have to balance that pitch up from the engines throttling up by pitching the plane down more than they would otherwise need to. The precise relationship between throttling up and pitching up was changed when the 737 was modified to create the 737 MAX. Namely, on the 737 MAX the pitch-up is more extreme. It is not so extreme that it makes the airplane a bad design, but it is extreme enough that pilots need to not expect the legacy 737 behavior. Had pilots been trained for the performance characteristics of the 737 MAX specifically, it would have been perfectly fine. But they weren't, and instead MCAS was meant to paper over the difference so pilots could be kept in the dark (which is cheaper but borderline homicidal...) To put this another way, in some hypothetical universe where the 737 MAX was the first 737 ever, it would have been introduced without MCAS and pilots would have said it handles like a dream. Then, when the 737 NG was introduced after the 737 MAX, there might have been a reverse-MCAS system implemented to make the NG handle like a MAX. That reverse-MCAS system may have then failed catastrophically.
  - chipsa 7y ago
    MCAS was not designed to make the 737 Max behave like the 737 NG or Classic. It was designed to make the 737 Max certifiable at all. The problem with the 737 Max is that the engine nacelles are further forward and larger than previously, so the lift that the nacelles make at high angle of attack is greater. This results in less stick force being necessary to maintain a high angle of attack than at lower angles of attack. This is uncertifiable behavior. Hence, MCAS, to augment the manuvering characteristics of the 737, to increase stick forces at high angles of attack. In a hypothetical universe where the Max was the first 737, it'd be fly by wire and all the stick forces would be synthetically generated anyway.

If I recall, it made it more prone to stall in certain conditions. I'd like to call that hazardous, but without test pilot feedback I'm not sure how to classify it. My recollection from articles a few months ago is that they added MCAS not due to simple differences in handling, but due to a potentially hazardous difference in handling.

darkpuma 7y ago
Mentour Pilot on youtube, a 737 instructor, has a few videos about it. The gist is that in any plane when you're close to stall, you want to pitch down and increase airspeed over the wings. Depending on the precise circumstances you do this by pitching down and throttling up. However in the case of every 737 and in fact any aircraft with engines slung below the wings, the act of throttling up the engines causes the airplane to pitch up. The reason is because the engines are not in line with the center of mass. Imagine rowing a row boat with only a single oar. This is something all 737 pilots are trained for, so they have to balance that pitch up from the engines throttling up by pitching the plane down more than they would otherwise need to. The precise relationship between throttling up and pitching up was changed when the 737 was modified to create the 737 MAX. Namely, on the 737 MAX the pitch-up is more extreme. It is not so extreme that it makes the airplane a bad design, but it is extreme enough that pilots need to not expect the legacy 737 behavior. Had pilots been trained for the performance characteristics of the 737 MAX specifically, it would have been perfectly fine. But they weren't, and instead MCAS was meant to paper over the difference so pilots could be kept in the dark (which is cheaper but borderline homicidal...) To put this another way, in some hypothetical universe where the 737 MAX was the first 737 ever, it would have been introduced without MCAS and pilots would have said it handles like a dream. Then, when the 737 NG was introduced after the 737 MAX, there might have been a reverse-MCAS system implemented to make the NG handle like a MAX. That reverse-MCAS system may have then failed catastrophically.
- chipsa 7y ago
  MCAS was not designed to make the 737 Max behave like the 737 NG or Classic. It was designed to make the 737 Max certifiable at all. The problem with the 737 Max is that the engine nacelles are further forward and larger than previously, so the lift that the nacelles make at high angle of attack is greater. This results in less stick force being necessary to maintain a high angle of attack than at lower angles of attack. This is uncertifiable behavior. Hence, MCAS, to augment the manuvering characteristics of the 737, to increase stick forces at high angles of attack. In a hypothetical universe where the Max was the first 737, it'd be fly by wire and all the stick forces would be synthetically generated anyway.