The upgrades have to be inplemented first on the MAX-10 and then rolled over. The MAX-10 can only be certified with the new flight controls.
So ASAP depends on how quick Boeing wants the MAX-10 in the air. Or how fast they can implemenent a non-botched version...
I think TFA describes things a bit differently:
Two sources familiar with the discussions said regulators want the permanent design changes done on a relatively tight timetable. “We are looking for this to be implemented at the latest by the time of the certification of the 737 MAX 10,” said one. The second source verified this as the target.
I think it will be hard to officially link the two.
How can you officially say -8 can fly without the improvements yet -10 cannot?
Yet unofficially I think such linkage will exist, and I think it is wise for EASA et al to make such a linkage while they have the leverage to do so.
To add a synthetic system to the MAX now would be costly. All its interactions with existing systems would have to be tested and certified, and Boeing will have to convince regulators the information it produces is as reliable or better than a physical sensor.
According to the person familiar with the FAA’s deliberations — who spoke on condition of anonymity because of the sensitivity of the ongoing discussions between the regulators — EASA’s demand for the equivalent of a three-sensor system arises from a fundamentally different design philosophy between Airbus and Boeing.
“For Airbus and EASA, three Angle of Attack sensors is just what you do,” said the person. “For Boeing and the FAA, it’s not necessary, because in addition to the two Angle of Attack sensors, you have that physical connection with the aircraft.”
Still, the FAA has told Boeing it must address EASA’s concern.
To me this seems like they are trying to get 737 to become a FBW one bug fix at a time, which is never a good approach.
It also puts into question any other two-sensor aircraft in revenue service.
And this should reawaken the poster who is sensitive to FAA ceding authority to EASA, TC, et al, for some pretty obvious reasons.
Yet this is all real politik, and if I were Boeing I would get out the drill for the hole for the 3rd AoA sensor and get on with it.
Every other option such as dicking around with synthetic airspeed to the point the regulators will accept it seems worse.
If the unofficial deadline is MAX-10 EIS, Boeing wants that end 2021 so you need a solution pretty much immediately.
Given how long it takes to get things done in aerospace, this very well could delay MAX-10 EIS.