MAX’s computer has reached its limit
This text was written following the a commentary from Normand Hamel:
“It is increasingly likely that the CSeries will enter the Air Canada fleet before the 737 MAX returns to service.
Especially as I understand the FAA would have discovered that the flight computer is unable to simultaneously process some data generated by the changes made to the software Max. It seems indeed that the processor of the flight computer is too slow and therefore it would saturate when the number of data to be analyzed is too important.
If proven, this problem seems to me particularly serious because the main cause would be attributable to the dilapidated chips used, a more powerful variant, probably made by Harris, the famous Intel 80286. The same processor is used without problem on the NG and the difficulty with the Max would come from the number of data to be processed that would be bigger on the latter.
The problem is that it is much easier to modify a software than to change a microprocessor because it would then completely redo the certification of the flight computer. Unless of course there is a computer tip that could alleviate this problem. “
In addition to the facts cited by Mr. Hamel, here is some more information about the Intel 80286 processor and the MAX.
The 80286 was launched in 1982, its maximum speed is 20 MHZ. It is always possible to increase the speed by reprogramming its internal clock but this considerably increases its instability. In addition, the 80286 tends to overheat a lot when it is overloaded and it slows down a lot. Everyone in the computer and electronics field we consulted was surprised to see that this processor was still being used on the MAX.
The last update of the MCAS programming would therefore tend to use the processor at its maximum capacity under normal conditions, which leaves no room in the event of a problem. Even if Boeing came up with a solution, it could not be implemented safely.
For us the question is not so much whether Boeing should replace the MAX’s flight computer, but rather how long will it take?
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