6 ms·

I made the prediction a month ago and I’ll make it again. MCAS won’t ever fly again. I think the plane will fly without MCAS with a new type rating, and where

by zaroth 8y ago

I made the prediction a month ago and I’ll make it again. MCAS won’t ever fly again. I think the plane will fly without MCAS with a new type rating, and where pilots specifically train on the stick feel during a power on stall. They needed the 737 with new engines to fly like the old 737 in order to maintain the type rating and avoid training. Now that they obviously have lost that and require substantial training, I don’t see any reason to keep the system. Some people think the plane is unflyable / inherently unstable without MCAS. I’ve only flown about 15 hours in my life, and a Cessna at that so I’m not qualified to offer an expert opinion. But my intuition is that if that were true, if MCAS was not just a bandaid to maintain a type rating, but rather a safety critical system essential for flightworthiness, it would never have shipped in its current form in the first place. Or rather, the 737 MAX would not have been viable to begin with. If it is the case that 737 MAX is not actually airworthy without a functioning MCAS then Boeing has fucked up an order of magnitude worse than even they appear to have at this point.

VBprogrammer 8y ago
Unflyable or unstable isn't nearly the same thing as uncertifiable. People have flown a whole lot of time in uncertifiable aircraft (see the whole experimental aircraft sector) but transport category aircraft are supposed to exhibit as full proof as possible behaviour. I bet you it flies again with MCAS. I'll also bet it flies with barely a few hours of conversion training and that there aren't any accidents directly related to the updated MCAS system.
- lutorm 8y ago
  This isn't true though, it seems perfectly possible to certificate transport-category airplanes with sketchy stall characteristics, since T-tail planes can end up in unrecoverable situations by blanketing the tail in a stall. Twin-engine planes also are not required to be recoverable from an engine failure at speeds below Vmc. I don't know what the certification requirements are, but it seems they rely on being able to guarantee that you never get below a certain speed since in multi-engine airplanes there's always a low power/high thrust regime that's potentially uncontrollable.
  - salawat 8y ago
    While the FAA has allowed it, not all aircraft have been certified to fly in all airspace without safety systems to prevent stalls. Give the D. P. Davies Interview, recorded by the Royal Aeronautics Society a listen, and you'll learn how the 727 was not allowed to be certified in the U.K. without a stick pusher equipped. I think it's this one. https://www.aerosociety.com/news/audio-the-d-p-davies-interview-on-testing-the-comets-boeing-707-britannia-brabazon/ https://www.aerosociety.com/news/audio-the-d-p-davies-interv... If not that one then this one. https://www.aerosociety.com/news/audio-the-d-p-davies-interview-on-the-boeing-747-the-trident-vc10-one-eleven-the-boeing-727/ https://www.aerosociety.com/news/audio-the-d-p-davies-interv... Edit: 2nd one I think is the one I'm remembering. Pumping the first one, because...well, it's just damn interesting.
deleted 8y ago
[deleted]
trimbo 8y ago
> I think the plane will fly without MCAS with a new type rating Without the 737 type rating, the value prop of the 737 MAX is lost. There would be no point in continuing the program (at least at anywhere near its current scale).
- andbberger 8y ago
  There's billions in capital sunk in the already existing 737 MAXs. They will fly again.
- VBprogrammer 8y ago
  Type ratings don't really work like that. 90% of the type rating is systems knowledge, emergency procedures etc. If a new type rating was needed there would be a conversion course from the existing type rating.
- janoc 8y ago
  That's a red herring, the MCAS issue has nothing to do with the type rating. MCAS is not something the crew was even supposed to be aware of, even less trained on, so no effect on type rating at all there. What it may cause problem with is the certification of the plane as such - MCAS was required to correct the behavior of the plane in high speeds/high thrust and high angle of attack situation where the new larger engines made it difficult to bring the nose down (and avoid stalling). However, that's not something that cannot be fixed. Airbuses fly full of similar augmentation systems and there is no problem with them, so it is certainly doable.
  - raverbashing 8y ago
    Yes but the 737 is not fly by wire, you don't have the same ways of "inserting yourself" into the loop as in a fbw plane
    - janoc 8y ago
      How do you "insert yourself in the loop" on a FBW plane when the computers conk out? There is manual reversion on an Airbus but it is very minimal - if you ever end up in a situation where that is needed you are having a very very bad day. On the other hand, 737 is actually fly-by-wire - literally, because actual steel wires are still connected between the cockpit controls and the control surfaces. So if the electronics dies and the hydraulics isn't working neither for whatever reason, the plane can still be controlled. These "magic boxes" are there to augment the control characteristics, such as the "feel" of the control column (which is normally lost due to the hydraulics driving the control surfaces). Or, in the case of MCAS, to help with an aerodynamic issue. Both are hardly unprecedented - the last large transport plane that didn't rely on any computers/electronics for controls was maybe the 707. The problem is the poor design of the MCAS software/system, not that it exists as such.
rpiguy 8y ago
It is a critical system. Part of the problem is that AOA sensors and MCAS were never considered critical before the software changes made for the 737 MAX and uprating them to critical was overlooked (which would have forced a lot more testing of them). There is no established requirement that says software can't be used to correct for pitch up on acceleration. The software just has to work properly.
- dylan604 8y ago
  > uprating them to critical was overlooked (which would have forced a lot more testing of them). Was this "overlooking" accidental or designed specifically to ignore the forced testing? This is the question that might be hardest to answer, but would justify criminal charges for the deaths in my mind.
  - rpiguy 8y ago
    True. Would be impossible to prove without a whistle blower. Boeing hasn't been charged with a crime so there won't be any subpoenas of e-mail records, etc. It is within the realm of possibility, but I certainly hope that was not the case. I lean very slightly toward thinking it was an accident as the whole program was rushed and give the engineers the benefit of the doubt (innocent until proven guilty) - however, it would not take much evidence to sway my mind.
snowwrestler 8y ago
Is there any indication that MCAS is a problem when it is provided with accurate AOA data? I don't think so, but I'm willing to be educated. My understanding is that MCAS only goes haywire when it gets haywire sensor data--specifically, data that indicate an AOA that is much higher than reality. So much depends on the investigations, which are currently in progress. But it seems possible that the technical solution could simply be: require 3 AOA sensors and require agreement between 2 out of 3 to activate MCAS. Of course, there are probably significant business and regulatory issues to consider/fix as well.
- raverbashing 8y ago
  It might be. I suppose the flight testing program tested MCAS on the situations where it would trigger and it has performed accordingly. Unfortunately the way things are, my supposition is anything but certain
- rconti 8y ago
  I'm not sure how easy it is to just bolt a third AoA sensor onto an existing airframe. OTOH, the MCAS system could at least be redesigned to take BOTH AoA sensors into account.
- dboreham 8y ago
  Yes, but there's also the problem of just how haywire it goes --- forcing the horizontal stabilizer in an unflyable position from which it can't be moved (the subject of this article).
janoc 8y ago
MCAS is not there because of maintaining pilot type rating. The plane's airworthiness certificate depends on certain behavior while approaching stall and the new larger and more forward engines on the MAX changed the behavior of the machine in such way that would make it very difficult for the crew to bring the nose down at high angles of attack and high thrust. The engines on the MAX are forward of the CoG, so they are pushing the nose up as you add thrust - exactly what you do not want when approach a stall. MCAS has been added to help with this - to help the crew push the nose down in such situation by using the stabilizer trim. The older NG doesn't have this issue because the engines are both smaller and more to the back, so the pitch-up moment is smaller, even though it is still present. This is an inherent issue with underslung engines, all planes with engines mounted under and ahead of the CoG have this issue. >If it is the case that 737 MAX is not actually airworthy without a functioning MCAS then Boeing has fucked up an order of magnitude worse than even they appear to have at this point. That's BS. By that logic no Airbus or any fly-by-wire plane could ever be certified - they actually require the computer augmentations to fly. Even the 737 NG has a similar trim system that automatically trims the plane depending on speed, angle of attack and what not.
- VBprogrammer 8y ago
  > The engines on the MAX are forward of the CoG It doesn't make much difference, most of what you've said is accurate to the best of my knowledge, however the thrust can be as far forwards of the CoG as it likes, that doesn't increase the pitch up moment. Having them lower may increase that moment and them having more power too. But the main issue on the Max is airodynamic lift generated by the nacelles at high AoA.
  - acqq 8y ago
    > the main issue on the Max is airodynamic lift generated by the nacelles at high AoA. This simplifies the physics so much that it's wrong. It is true that there are texts attributing everything just to the "nacelles", but the engineering doesn't work the way you argue: First, you can't put the engines on the plane without some casing for them (you have to have nacelles). Second, if you'd try to modify the casing of the engines (the said nacelles) to have other aerodynamic properties, you'd interfere with other design goals (e.g. you can increase the fuel consumption which was the most important design goal for the MAX). Third, the position of the engines definitely does matter for the behavior like "nose up" as long as the rest of the plane has some already determined form, which in this case is what has to be kept to have the plane being 737 and not something completely different. In short: the 737 MAX is Boeing's equivalent of VW's diesel cars. Its behavior was determined by the prescribed design goals (by those who sold the plane): Boeing simply directly lied, selling something that can't be achieved given the "sold" design characteristics. Just like the diesel cars can reduce nitrogen oxides production, but then they are less "efficient" than as they were sold (they need more refills, or use more fuel, i.e. cost more than advertised). Likewise, the 737 MAX-like plane could have been safer, but then Boeing could have not sold it as a plane for which there's "no need for pilot's re-certification and retraining." At the end, Feynman conclusion of his Shuttle investigation report holds: "For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." Note also: https://www.theguardian.com/business/2019/apr/15/former-head-of-volkswagen-could-face-10-years-in-prison https://www.theguardian.com/business/2019/apr/15/former-head... ("Former head of Volkswagen could face 10 years in prison -- Martin Winterkorn and other executives charged with fraud over emissions test cheating") I'm quite sure Boeing's "heads" won't even be charged. And no, the "nacelles" aren't the main issue. It's the fraudulent selling of the planes which can't deliver what they were sold for. Fraud. (P.S. It's "aerodynamic")
macspoofing 8y ago
>I think the plane will fly without MCAS with a new type rating, and where pilots specifically train on the stick feel during a power on stall. Maybe. Keep in mind MCAS was a system put in place to mitigate a catastrophic risk. If you remove it, you no longer have that mitigation - meaning you either have to argue that increased training can be a substitute (I would be skeptical of that if I was a regulator) or come up with something else. It's a shitshow.
- linuxftw 8y ago
  I think it all comes down to certifying bodies other than the FAA. FAA seems happy to go along with whatever Boeing wants (as evidenced by the 'self certification' efforts of the agency); it remains to be seen if the EU or another major market airspace will capitulate.
  - macspoofing 8y ago
    >FAA seems happy to go along with whatever Boeing wants (as evidenced by the 'self certification' efforts of the agency) I strongly suspect this is way overstated. I think there's a misinformed view of what a regulator is and the role they play. Regulations and regulators don't work within a system where there's a preponderance of cheating. This is why you can't go do a corrupt country and simply legislate corruption away (all corrupt countries have very good laws on the books). Regulators necessarily exist within a largely honest system. The FAA, and FDA and other regulatory agencies do not go around testing every claim made by every manufacturer - though they reserve the right to. If that was the case the economy would grind to a halt and no product would be released. This would be akin to the IRS auditing every tax return every year. The second point about regulations is that like security or marketing, there is no end-game. You can always have more regulations, just as you can invest in more security and more marketing - but at some point, you will have diminishing resulting leading to negative outcomes. In the specific case, Boeing put themselves under a certification process meant for certifying non-trivial but also non-major incremental upgrades (i.e. no fuselage and wing redesigns). The process is less onerous because the aircraft upgrades don't introduce new significant risks. This process does not apply to the 737Max8. Boeing was wrong to put the plane in that category and they will pay dearly for this and will serve as a cautionary tale moving forward, but let's not throw out the regulatory regime that resulted in making the airline industry incredibly safe, and the safest it has ever been in history.
bronco21016 8y ago
I’m not sure a type rating works that way. A Boeing 717 has the same type rating as a Douglas DC-9. The two aircraft have similar airframes and some common systems but are quite different as one was built decades later. What the FAA does in these cases is requires more training. A DC-9 rated pilot who has only flown DC-9s will not fly a B717 without several hours in a simulator. The MAX will certainly fly again. I suspect some form of a redesigned MCAS in addition to more training for pilots will be the end result. The airlines may have to spend some money training but they’ll still be left with B737 type rates pilots who can fly B737NG and B737MAX which is where the cost savings is derived.

by zaroth 8y ago

VBprogrammer 8y ago

Unflyable or unstable isn't nearly the same thing as uncertifiable. People have flown a whole lot of time in uncertifiable aircraft (see the whole experimental aircraft sector) but transport category aircraft are supposed to exhibit as full proof as possible behaviour. I bet you it flies again with MCAS. I'll also bet it flies with barely a few hours of conversion training and that there aren't any accidents directly related to the updated MCAS system.

lutorm 8y ago
This isn't true though, it seems perfectly possible to certificate transport-category airplanes with sketchy stall characteristics, since T-tail planes can end up in unrecoverable situations by blanketing the tail in a stall. Twin-engine planes also are not required to be recoverable from an engine failure at speeds below Vmc. I don't know what the certification requirements are, but it seems they rely on being able to guarantee that you never get below a certain speed since in multi-engine airplanes there's always a low power/high thrust regime that's potentially uncontrollable.
- salawat 8y ago
  While the FAA has allowed it, not all aircraft have been certified to fly in all airspace without safety systems to prevent stalls. Give the D. P. Davies Interview, recorded by the Royal Aeronautics Society a listen, and you'll learn how the 727 was not allowed to be certified in the U.K. without a stick pusher equipped. I think it's this one. https://www.aerosociety.com/news/audio-the-d-p-davies-interview-on-testing-the-comets-boeing-707-britannia-brabazon/ https://www.aerosociety.com/news/audio-the-d-p-davies-interv... If not that one then this one. https://www.aerosociety.com/news/audio-the-d-p-davies-interview-on-the-boeing-747-the-trident-vc10-one-eleven-the-boeing-727/ https://www.aerosociety.com/news/audio-the-d-p-davies-interv... Edit: 2nd one I think is the one I'm remembering. Pumping the first one, because...well, it's just damn interesting.

deleted 8y ago

[deleted]

trimbo 8y ago

> I think the plane will fly without MCAS with a new type rating Without the 737 type rating, the value prop of the 737 MAX is lost. There would be no point in continuing the program (at least at anywhere near its current scale).

andbberger 8y ago
There's billions in capital sunk in the already existing 737 MAXs. They will fly again.
VBprogrammer 8y ago
Type ratings don't really work like that. 90% of the type rating is systems knowledge, emergency procedures etc. If a new type rating was needed there would be a conversion course from the existing type rating.
janoc 8y ago
That's a red herring, the MCAS issue has nothing to do with the type rating. MCAS is not something the crew was even supposed to be aware of, even less trained on, so no effect on type rating at all there. What it may cause problem with is the certification of the plane as such - MCAS was required to correct the behavior of the plane in high speeds/high thrust and high angle of attack situation where the new larger engines made it difficult to bring the nose down (and avoid stalling). However, that's not something that cannot be fixed. Airbuses fly full of similar augmentation systems and there is no problem with them, so it is certainly doable.
- raverbashing 8y ago
  Yes but the 737 is not fly by wire, you don't have the same ways of "inserting yourself" into the loop as in a fbw plane
  - janoc 8y ago
    How do you "insert yourself in the loop" on a FBW plane when the computers conk out? There is manual reversion on an Airbus but it is very minimal - if you ever end up in a situation where that is needed you are having a very very bad day. On the other hand, 737 is actually fly-by-wire - literally, because actual steel wires are still connected between the cockpit controls and the control surfaces. So if the electronics dies and the hydraulics isn't working neither for whatever reason, the plane can still be controlled. These "magic boxes" are there to augment the control characteristics, such as the "feel" of the control column (which is normally lost due to the hydraulics driving the control surfaces). Or, in the case of MCAS, to help with an aerodynamic issue. Both are hardly unprecedented - the last large transport plane that didn't rely on any computers/electronics for controls was maybe the 707. The problem is the poor design of the MCAS software/system, not that it exists as such.

rpiguy 8y ago

It is a critical system. Part of the problem is that AOA sensors and MCAS were never considered critical before the software changes made for the 737 MAX and uprating them to critical was overlooked (which would have forced a lot more testing of them). There is no established requirement that says software can't be used to correct for pitch up on acceleration. The software just has to work properly.

dylan604 8y ago
> uprating them to critical was overlooked (which would have forced a lot more testing of them). Was this "overlooking" accidental or designed specifically to ignore the forced testing? This is the question that might be hardest to answer, but would justify criminal charges for the deaths in my mind.
- rpiguy 8y ago
  True. Would be impossible to prove without a whistle blower. Boeing hasn't been charged with a crime so there won't be any subpoenas of e-mail records, etc. It is within the realm of possibility, but I certainly hope that was not the case. I lean very slightly toward thinking it was an accident as the whole program was rushed and give the engineers the benefit of the doubt (innocent until proven guilty) - however, it would not take much evidence to sway my mind.

snowwrestler 8y ago

Is there any indication that MCAS is a problem when it is provided with accurate AOA data? I don't think so, but I'm willing to be educated. My understanding is that MCAS only goes haywire when it gets haywire sensor data--specifically, data that indicate an AOA that is much higher than reality. So much depends on the investigations, which are currently in progress. But it seems possible that the technical solution could simply be: require 3 AOA sensors and require agreement between 2 out of 3 to activate MCAS. Of course, there are probably significant business and regulatory issues to consider/fix as well.

raverbashing 8y ago
It might be. I suppose the flight testing program tested MCAS on the situations where it would trigger and it has performed accordingly. Unfortunately the way things are, my supposition is anything but certain
rconti 8y ago
I'm not sure how easy it is to just bolt a third AoA sensor onto an existing airframe. OTOH, the MCAS system could at least be redesigned to take BOTH AoA sensors into account.
dboreham 8y ago
Yes, but there's also the problem of just how haywire it goes --- forcing the horizontal stabilizer in an unflyable position from which it can't be moved (the subject of this article).

janoc 8y ago

MCAS is not there because of maintaining pilot type rating. The plane's airworthiness certificate depends on certain behavior while approaching stall and the new larger and more forward engines on the MAX changed the behavior of the machine in such way that would make it very difficult for the crew to bring the nose down at high angles of attack and high thrust. The engines on the MAX are forward of the CoG, so they are pushing the nose up as you add thrust - exactly what you do not want when approach a stall. MCAS has been added to help with this - to help the crew push the nose down in such situation by using the stabilizer trim. The older NG doesn't have this issue because the engines are both smaller and more to the back, so the pitch-up moment is smaller, even though it is still present. This is an inherent issue with underslung engines, all planes with engines mounted under and ahead of the CoG have this issue. >If it is the case that 737 MAX is not actually airworthy without a functioning MCAS then Boeing has fucked up an order of magnitude worse than even they appear to have at this point. That's BS. By that logic no Airbus or any fly-by-wire plane could ever be certified - they actually require the computer augmentations to fly. Even the 737 NG has a similar trim system that automatically trims the plane depending on speed, angle of attack and what not.

VBprogrammer 8y ago
> The engines on the MAX are forward of the CoG It doesn't make much difference, most of what you've said is accurate to the best of my knowledge, however the thrust can be as far forwards of the CoG as it likes, that doesn't increase the pitch up moment. Having them lower may increase that moment and them having more power too. But the main issue on the Max is airodynamic lift generated by the nacelles at high AoA.
- acqq 8y ago
  > the main issue on the Max is airodynamic lift generated by the nacelles at high AoA. This simplifies the physics so much that it's wrong. It is true that there are texts attributing everything just to the "nacelles", but the engineering doesn't work the way you argue: First, you can't put the engines on the plane without some casing for them (you have to have nacelles). Second, if you'd try to modify the casing of the engines (the said nacelles) to have other aerodynamic properties, you'd interfere with other design goals (e.g. you can increase the fuel consumption which was the most important design goal for the MAX). Third, the position of the engines definitely does matter for the behavior like "nose up" as long as the rest of the plane has some already determined form, which in this case is what has to be kept to have the plane being 737 and not something completely different. In short: the 737 MAX is Boeing's equivalent of VW's diesel cars. Its behavior was determined by the prescribed design goals (by those who sold the plane): Boeing simply directly lied, selling something that can't be achieved given the "sold" design characteristics. Just like the diesel cars can reduce nitrogen oxides production, but then they are less "efficient" than as they were sold (they need more refills, or use more fuel, i.e. cost more than advertised). Likewise, the 737 MAX-like plane could have been safer, but then Boeing could have not sold it as a plane for which there's "no need for pilot's re-certification and retraining." At the end, Feynman conclusion of his Shuttle investigation report holds: "For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." Note also: https://www.theguardian.com/business/2019/apr/15/former-head-of-volkswagen-could-face-10-years-in-prison https://www.theguardian.com/business/2019/apr/15/former-head... ("Former head of Volkswagen could face 10 years in prison -- Martin Winterkorn and other executives charged with fraud over emissions test cheating") I'm quite sure Boeing's "heads" won't even be charged. And no, the "nacelles" aren't the main issue. It's the fraudulent selling of the planes which can't deliver what they were sold for. Fraud. (P.S. It's "aerodynamic")

macspoofing 8y ago

>I think the plane will fly without MCAS with a new type rating, and where pilots specifically train on the stick feel during a power on stall. Maybe. Keep in mind MCAS was a system put in place to mitigate a catastrophic risk. If you remove it, you no longer have that mitigation - meaning you either have to argue that increased training can be a substitute (I would be skeptical of that if I was a regulator) or come up with something else. It's a shitshow.

linuxftw 8y ago
I think it all comes down to certifying bodies other than the FAA. FAA seems happy to go along with whatever Boeing wants (as evidenced by the 'self certification' efforts of the agency); it remains to be seen if the EU or another major market airspace will capitulate.
- macspoofing 8y ago
  >FAA seems happy to go along with whatever Boeing wants (as evidenced by the 'self certification' efforts of the agency) I strongly suspect this is way overstated. I think there's a misinformed view of what a regulator is and the role they play. Regulations and regulators don't work within a system where there's a preponderance of cheating. This is why you can't go do a corrupt country and simply legislate corruption away (all corrupt countries have very good laws on the books). Regulators necessarily exist within a largely honest system. The FAA, and FDA and other regulatory agencies do not go around testing every claim made by every manufacturer - though they reserve the right to. If that was the case the economy would grind to a halt and no product would be released. This would be akin to the IRS auditing every tax return every year. The second point about regulations is that like security or marketing, there is no end-game. You can always have more regulations, just as you can invest in more security and more marketing - but at some point, you will have diminishing resulting leading to negative outcomes. In the specific case, Boeing put themselves under a certification process meant for certifying non-trivial but also non-major incremental upgrades (i.e. no fuselage and wing redesigns). The process is less onerous because the aircraft upgrades don't introduce new significant risks. This process does not apply to the 737Max8. Boeing was wrong to put the plane in that category and they will pay dearly for this and will serve as a cautionary tale moving forward, but let's not throw out the regulatory regime that resulted in making the airline industry incredibly safe, and the safest it has ever been in history.

bronco21016 8y ago

I’m not sure a type rating works that way. A Boeing 717 has the same type rating as a Douglas DC-9. The two aircraft have similar airframes and some common systems but are quite different as one was built decades later. What the FAA does in these cases is requires more training. A DC-9 rated pilot who has only flown DC-9s will not fly a B717 without several hours in a simulator. The MAX will certainly fly again. I suspect some form of a redesigned MCAS in addition to more training for pilots will be the end result. The airlines may have to spend some money training but they’ll still be left with B737 type rates pilots who can fly B737NG and B737MAX which is where the cost savings is derived.