Not an aircraft safety expert but I am curious if shifting the wires may not introduce more potential issues in existing planes, as the existing risk factor seems to be proven low (i.e. they are not requiring all 737-NG airframes to have the work)
I would imagine there is a non-trivial risk of a worker introducing a higher risk factor (drilling a little too far, creating metal shavings, putting too much weight on a support).
The rules were made for a reason, and Boeing should follow them. However I wonder if it would be safer to simply fine Boeing a similar cost to what the rectification would cost and grandfather it in for existing airframes.
I am just glad there are people more qualified to make this decision.
Boeing wants to have a quick and cheap fix (no fix) and get a pass on international aviation norms based on the argument it's not "too unsafe" and that fixing it would risk making the 737 MAX fleet non-flightworthy.
Well... It's not like it's flightworthy right now. If Boeing can't offer a fix that makes the plane flightworthy, then the airplanes should be scrapped. Remember we only are experiencing this because Boeing wanted a plane of the same type rating as the 737 NG and opted for that instead of a new design (that would be in accordance to all current safety norms, unlike the MAX) because it'd increase their profit.
Two planes fell from the sky, killing everyone on board, for no other reason than Boeing wanting to increase its profits.
IIRC, on a high AoA the lift generated by the larger engines moves the center of lift ahead of the center of gravity, making the plane unstable. This is what MCAS was arguably designed to prevent, forcing the plane behave like a 737 with smaller engines.
Without MCAS, this would be a crappy experience for the pilots, but, with proper training, they'd be able to fly it just like you and me can safely drive cars like a Reliant Robin (just never think about hitting the brakes in a curve). If you feel the plane wanting to point up a bit too enthusiastically, you can push the stick forward (or adjust the trim) and make it more cooperative.
It just turns out that, with MCAS, little training, and a defective AoA sensor, the experience was lethally crappy.
> Without MCAS, this would be a crappy experience for the pilots, but, with proper training, they'd be able to fly it just like you and me can safely drive cars like a Reliant Robin (just never think about hitting the brakes in a curve). If you feel the plane wanting to point up a bit too enthusiastically, you can push the stick forward (or adjust the trim) and make it more cooperative.
That's the worst part of this, the plane is perfectly flyable without MCAS but they applied it anyways because it would have required recertifying pilots because that difference is enough that it might have required a new type certificate for pilots to fly. So all this trouble and the deaths are because Boeing couldn't make an appealing aircraft with the old 737 body and handling so they took a shortcut to make few 100M more.
In the 737 Max, the engine nacelles themselves can, at high angles of attack, work as a wing and produce lift. And the lift they produce is well ahead of the wing’s center of lift, meaning the nacelles will cause the 737 Max at a high angle of attack to go to a higher angle of attack. This is aerodynamic malpractice of the worst kind.
That's just the with it feeling wrong near stall at high angle-of-attacks.
Theoretically yes, you can train pilots to deal with it. Hell, it would have been safer to just ignore the issue and not train pilots than the clusterfuck of the original MCAS implementation.
But it's not that it doesn't just feel wrong compared to the 737-NG. It feels wrong compared to every single certified aircraft.
The FAA has strict rules on how all aircraft must feel when approaching stall. You can't certify an aircraft without meeting this feel requirement. So the 737-MAX simply can't be certified without MCAS or some other fix.
The actual problem is Boeing made more changes from the 737 base and the checks for this changes were nod done properly because FAA didn't do it's job. Now if FAA and other international agencies check everything from scratch you will find all this hidden problems.
Now imagine you are hired to check the plane systems, would you sign on subsystem X because it worked fine in the old 737 or use your brain and experience andcx flag all potential issues you see.
I am also a non-expert, and am sympathetic to your argument, but I don’t think there’s any reason to believe that whatever fix is proposed wouldn’t account for the type of risks you are concerned about. All of the risks/concerns you mention would be relevant to any sort of mechanical work on an aircraft, and that is a field of engineering that on the whole has an impeccable record of safety and rigor. Again, not an expert, but from what I understand the issues with the 737 max were software/design related.
Mostly agree, however I think Boeing should be required to engineer an approved and deemed safe remedy by a panel of experts comprised of international regulatory engineering staff deemed to be experts in this field.
The cost would be the greater of the approved solution or the envisioned cost of correctly re-working existing airlines. (The cost savings might come from a factor of cost not considered here, Boeing's liability to airlines for downtime of units or inability to sell new planes.)
Part not talked about is the wires in question for the tail also offer redundancy. Boeing wanted to cut time on manufacturing ran them all along the same section of the tail.
Feeding an automated system (with authority to crash the plane) from a single sensor is also known to be wrong. Controls engineering has taught failure modes and redundancy since the '60s. That didn't stop Boeing.
> Not an aircraft safety expert but I am curious if shifting the wires may not introduce more potential issues in existing planes, as the existing risk factor seems to be proven low (i.e. they are not requiring all 737-NG airframes to have the work)
The 737-NG was introduced in 1997, one year before the new regulations went into effect so it's grandfathered in. Seeking to have the 737-NG retrofitted would be like requiring all cars without airbags to be retrofitted.
What Boeing did with the 737-Max through out it's certification process was argue that it was so similar to the 737-NG that it should be grandfathered into certifications as well. This is done in a lot of industries where certification or regulatory approval is costly and complex, regulators offer a Me-Too path to certification where you argue that your product is based upon or similar enough to an existing product that only the differences need scrutiny. By going this route, Boeing was able to avoid redesign and retooling for things like the wiring harnesses which saved cost and time to market.
Now that the 737-Max is having to be re-certified, AND Boeing's delegated authority to self-certify has been revoked, the FAA is going over everything. The wiring harnesses which were Me-Too'd, aren't in compliance with 1998 requirements. Boeing is trying to argue that the 737-NG has proven the design safe and thus the new requirements shouldn't apply.
This is definitely a concern. Having to undo so much of the wiring could introduce the risk of some of the insulator breaking on other wires, or accidental damage or something else.
But the FAA would definitely weigh this against the possible issues of high-voltage wires running in the same bundle as control wires.
I would imagine there is a non-trivial risk of a worker introducing a higher risk factor (drilling a little too far, creating metal shavings, putting too much weight on a support).
The rules were made for a reason, and Boeing should follow them. However I wonder if it would be safer to simply fine Boeing a similar cost to what the rectification would cost and grandfather it in for existing airframes.
I am just glad there are people more qualified to make this decision.