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Comment by ggm | Hacker News Reader

Root cause analysis: excessive pressure to keep type rating caused lax engineering to be considered acceptable.

Fix:let the FAA do it's job independently

On a technical level: personally I think that the root cause could be a lack of "integration" of the system (MCAS) with the rest.

Meaning that e.g.

1) if the pilots' yokes/sticks are being pulled and

2) if the altitude based on gps and/or air pressure and/or radar is decreasing and

3) if the speed registered by the airspeed probe is high respectively increasing and

4) if the fuel being used by the engines to keep or even increase the speed is very low and

5) if the G-force registered by <some sensor, if it exists?> is lower than usual (neutral or even negative?)

6) etc... (anything else excluding AoA?)

...then the airplane is mooost probably "going down", even if the AoA says the opposite.

As the MCAS auto-trim has apparently a big potential impact on how the airplane flies (surfaces on the tail are big and their angle can move a lot), it should therefore not rely on just 1 (or even 2 duplicate) lonely sensor(s) but on multiple types that provide multiple point-of-views of the aircraft's situation to then abstract/determine/confirm the current high-level situation (in this case "is the aircraft going up or down?") and only after such result to react/take countermeasures to save the aircraft respectively help the pilots and/or lower costs for the flight.

If this is not totally wrong, is this (the total integration of all sensors) how Airbus did it with their super-automated systems like e.g. their side-sticks/joysticks just telling the airplane what pilots "want"? (meaning, did they start already from scratch creating a totally integrated system, if they did create such an integrated system?) (not sure about how automated the new Boeing airplanes are, so I did not mention them...)

Angle of attack is not related to any of the items that you list. You could be approaching stall even while your altitude is increasing (2), while you are at a high speed (3), at less than 1 G (5) etc.

I'm not sure you quite understand what a stall is. A great resource I can recommend is a book called See How it Flies (http://www.av8n.com/how/).

I never mentioned "stall"... .

EDIT: expanding: I understand "stall" as an end-result, and AoA as one of the sensors that might be an indicator of a "stall"

EDIT2: thx for that URL => I'll have a look at it - looks very interesting.

Actually from the link you provided, airspeed is absolutely a quantitative indicator of a stall.

"The airspeed indicator provides quantitative information about angle of attack, when the airspeed is not too low. Correction factors must be applied to correct for nonstandard weight and/or load factors.3"

Absolutely quantitative except when airspeed is low, when weight is non-standard and when load factor is not 1.

I guess you and I disagree on the definition of "absolutely".

You miss my point. Root Cause typically does what you are doing, focusses on technology and in-the-moment behaviours and remediation.

I wanted to go above this to a higher layer: Had the regulatory environment the FAA has mandate to operate run better, then Boeing could not have asserted "same type" for such a huge change to the flight dynamics of the aircraft moving its CG with the new engine.

The "root cause" is not technological, its the compliance processes, and the desperate desire to artificially re-create a "level playing field" between Boeing and Airbus

Ok, I understand - thanks :)

Funny thing is, that sounds a lot like a certain Air France flight. Besides the airspeed probe, though, since it was inoperative. (And the AOA sensors agreed) But in that situation, pushing the nose down would have been the correct decision.

You're referring to this one?

https://en.wikipedia.org/wiki/Air_France_Flight_447

Fix: Make Engineers actually liable for the correct classification of systems and require signed justification for NOT defaulting to the highest possible standard.

...which demands a fully independent FAA. Not the one we seem to have which appears on the face of it, compromised by the consequences of embedded self assessment and 'same type' rules. Why was it in the national interest to have Boeing get 'same type' ? Because of the cost of competing with airbus.

The regulator was hamstrung in the interests of 'efficiency'

(I'm not an American and this is an argument i read which resonates. I'd welcome good rebuttal)

This also causes a lot of over engineering. ( Which maybe good for Boeing right about now)

I'd dispute it causes the over-engineering. Engineering principles cause safety margins, and regulators enforce safety margins. As the industry decides it can live with reduced safety margins they get reduced. When they get too close to a risk window, they get raised.

I know the over-engineering term exists, but I think it's based on flawed logic. Not having margins results in under-engineering, which is significantly worse in almost all cases. Its not a symmetric world out there. Some things are worse than others.

You hit the nail on the head with this.

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