Cayman Airways Grounds 737-8 MAX Planes

[Dan]

Supposedly Boeing was already working on a software update for the 737-Max aircraft after the Indonesia crash, and regulatory approval of that update was delayed for 5 weeks by the federal shut down. So if the Ethiopia crash is determined to follow the same pattern of control glitches, it is likely that the software update will come through quickly and the aircraft hopefully won't be grounded long.

My understanding from reading comments from pilots who fly the Max aircraft on another site is that the larger and heavier engines on the Max planes sit further forward on the wing, and there was concern about stall risk increasing, so Boeing added an automated system that would force the nose down when the plane sensed a stall was imminent. The scuttlebutt was that they didn't try to train the pilots about this system because it was "too complicated" which probably forms part of the genesis of Trump's tweets about overly complex flight systems. Reportedly, the system can be turned off very easily, but many pilots were not aware of how to do it, and it is suspected that in both the Indonesia crash and the Ethiopia crash, the stall sensors were sending faulty info causing the plane to try to force the nose down. Presumably the pilots fought the system instead of disabling it and eventually the plane crashed.

I dove in Indonesia once to twice / year for the past 10 years and flew their domestic flights quite a few times (to Raja Ampat, Komodo, Alor, Lembeh, Ambon, Maratua Atoll, etc.) and noticed the Indonesian pilots tend to take off in more aggressive (steeper) angle to reach the cruising altitude quickly, in comparison to the American pilots. Perhaps the Max-8 heavier engine and more forward mounting on the wing design could be becoming less tolerant (getting closer to stalling situation) for such aggressive style of take off.

 

[FindingMenno]

Update from Cayman Airways
Welcome to Cayman Airways

 

[FindingMenno]

It sounds like Boeing wanted to use an existing airframe with a proven design and just slap newer engines on it. When that created signs of instability, they just added a new system to fix the instability instead of stepping back and changing the engine mounting or positioning to avoid creating it in the first place.

That is pretty much it in a nutshell. However, due to the basic design of the 737 (it first flew in 1967) there is no room to change the engine mounting. It was originally designed for much smaller engined than the CFM (LEAP) series that the current NG and MAX models use.
Boeing does not want to change the basic design of the 737, as a lot of it is grandfathered in the certification. A major redesign would mean a costly recertification process. For example, I'm in the understanding that the passenger door design would never pass under the current certification rules.

Next to that, they want the MAX to have the same type rating as the previous/current NG series. This allow pilots to fly both types with one rating, meaning more flexibility in assigning aircraft and pilots, and no costly extra training. As due to the newer engines on an older design the MAX handles slightly different, the MCAS system was introduces to 'patch' this difference and allow the single rating.

The presence of the system is not a real issue, the issue is that: a) this system was not properly documented in the manuals so pilots were unware of it, the functionality, and risks; b) the system was not designed with proper reduncancy, so a single sensor failure could make it malfunction.

Some more info:
737 MAX - MCAS
What is the Boeing 737 Max Maneuvering Characteristics Augmentation System?

 

[AggieDiver]

Yeah, that was the scuttlebutt I got from the conversation between a few pilots that I read. Doctorfish, this isn't a knock on the capabilities or morals of the Boeing engineers. In any engineering process, there are design tradeoffs that pit cost, safety, and ease of implementation against a more complete or robust design. As you said, we will need to wait to see the eventual cause, but the information currently being published about the flight paths of both planes sounds very much like they were fighting this system.

As FindingMenno pointed out, the easy engineering move would have been to redesign the engine mount. But that had tradeoffs against the requirement to upgrade other parts of the plane to obtain recertification of the airframe. Putting the MCAS system in to cover for that tradeoff was not a big deal...but publicizing this new system too much ran the risk of requiring pilots to recertify to be able to fly it, which would be seen as an increased cost of operation by new buyers. So they downplayed or perhaps even avoided training pilots about the system, and at least some appear to be unaware of how to disable it if it malfunctioned. Time will tell what Boeing will be asked to do to remedy those issues if they are determined to be a factor in the crashes...but now that the issues are out there, they will probably have to address them either way.

 

[Joneill]

Yeah, that was the scuttlebutt I got from the conversation between a few pilots that I read. Doctorfish, this isn't a knock on the capabilities or morals of the Boeing engineers. In any engineering process, there are design tradeoffs that pit cost, safety, and ease of implementation against a more complete or robust design. As you said, we will need to wait to see the eventual cause, but the information currently being published about the flight paths of both planes sounds very much like they were fighting this system.

As FindingMenno pointed out, the easy engineering move would have been to redesign the engine mount. But that had tradeoffs against the requirement to upgrade other parts of the plane to obtain recertification of the airframe. Putting the MCAS system in to cover for that tradeoff was not a big deal...but publicizing this new system too much ran the risk of requiring pilots to recertify to be able to fly it, which would be seen as an increased cost of operation by new buyers. So they downplayed or perhaps even avoided training pilots about the system, and at least some appear to be unaware of how to disable it if it malfunctioned. Time will tell what Boeing will be asked to do to remedy those issues if they are determined to be a factor in the crashes...but now that the issues are out there, they will probably have to address them either way.

Quite awful if 346 people have paid with their lives due to what amounted to cost avoidance measures - but it sure seems that is, at least, part of the cause here? Of course, we need to wait for the final results of the investigations - but, hopefully, the full truth comes out so this type of thing does not happen again!

 

[KathyV]

Here's a tongue-in-cheek comment by Caymanman (aka the Barefoot Man, George Nowak)

 

[Dan]

A bit of funny safety briefing presented by a flight attendant to help relieve some of the stress of flying

 

[KathyV]

A Southwest Boeing 737 Max malfunctioned after takeoff and made an emergency landing at Orlando. Only the Pilot and Co-Pilot were on board and they were supposed to move the plane from Florida to California for storage. I thought that they were grounded!

Southwest Boeing 737 Max makes emergency landing in Orlando

 

[Manatee Diver]

They are grounded for commercial service isn't the same as completely grounding the aircraft. As the aircraft still need to move to whichever MX base will perform the software upgrade.

 

[KathyV]

They are grounded for commercial service isn't the same as completely grounding the aircraft. As the aircraft still need to move to whichever MX base will perform the software upgrade.

I see, thanks! They are saying that this was an engine problem so that doesn't sound like the same problem suspected in the crashes.