[SystemSafety] "FAA chief '100% confident' of 737 MAX safety as flights to resume"

[Tom Ferrell]

Couple of quick thoughts on this:

Re the Max.  In general PBL, I agree that trying to overcome what is fundamentally a airframe design problem created by the introduction of larger engines was a VERY bad decision by Boeing and shows how economics pushed the very precepts of safe aircraft design aside.  Boeing needed to have retired the 737 many years ago in favor of a clean sheet design IMO.  There are many reasons for this not just the need to move to larger, more efficient engines.  As just one example, the equipment bay on the 737 is woefully undersized for all of the modern avionics that have been added over the years creating cabling challenges, equipment cooling challenges, etc.  All of this does not, however, change my basic point concerning the level of scrutiny applied to the MAX.

Re: Sioux City.  My understanding of that event is very different than what you noted in your brief post.  The first two events associated with the cargo door was a structures issue.  Explosive decompression leading to cabin floor collapse which in turn compromised multiple aircraft systems including the hydraulics.  As I understand it, that scrutiny included the routing of hydraulics throughout the airplane.  The hydraulics routing passed that scrutiny based on the best knowledge at the time.  The subsequent unconstrained rotor burst in the Sioux City created shrapnel patterns that far exceeded what the earlier analyses had assumed.  The idea that ALL the hydraulics were routed through the tail such that one event disabled all the systems is erroneous.  The hydraulics were compromised due to multiple impacts in at least two different locations, only one was the tail which disabled two of the three redundant systems.  Both industry and the FAA were surprised at the much wider distribution of the shrapnel and this led to significant updates in the corresponding regulations.  Sometimes, you just don't know what you don't know.  The accident occurred, lessons were learned, and the safety safeguards improved.  Highly recommend Samme Chittum's book, The Flight 981 Disaster, as a very readable account of the DC-10 crashes.

As Michael noted, there are plenty of opportunities to point out how ridiculous some of the statements made by Boeing, the FAA, and others have been throughout all of this.  My earlier comments were not intended to endorse or condone any of that. 

-----Original Message-----
From: systemsafety <systemsafety-bounces at lists.techfak.uni-bielefeld.de> On Behalf Of Peter Bernard Ladkin
Sent: Friday, November 20, 2020 5:44 AM
To: systemsafety at lists.techfak.uni-bielefeld.de
Subject: Re: [SystemSafety] "FAA chief '100% confident' of 737 MAX safety as flights to resume"

On 2020-11-20 14:26 , Michael Holloway wrote:
>  the criticism here is ridiculous.

Thanks, Mike. Might you have a technical, rather than an emotional, reaction to share?

> First, it is pedantry of an extreme sort to think that "100% 
> confident" means anything more than "as confident as it is possible 
> for me to be."

So you are suggesting that he is at least as confident that he won't die, flying in a MAX, as he is that 2+2=4 ? Or should that confidence be relativised somehow?

> Third, everything Tom wrote about the level of scrutiny the plane has undergone is correct. 

Yes. And that the defined procedures are not enough has been pointed out twice in reports.

After Ermenonville, the DC-10 became "the most scrutinized [sic] aircraft in the history of the commercial transport fleet." Then came Sioux City. Along with nobody noticing that you could lose structural integrity if you lost pressure in one half of the PV (which led to Ermenonville through a couple of other occurrences), nobody apparently noticed that they had routed all the control system hydraulics through one spot in the tail, which was duly sliced through by a shed blade. Many put that down to the overall design process of the airplane and worried about other oversights. Which ended up being, some say, why the DC-10 fleet converted to freighters, followed quite quickly by the MD-11.

PBL

Prof. Peter Bernard Ladkin, Bielefeld, Germany ClaireTheWhiteRabbit RIP
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de