Programmer: “Was that integer or floating point? Oh well, what difference will it make.”
https://www.wikijournalclub.org/wiki/SOAP_II
SOAP II
Clinical Question
Among patients with shock, how does dopamine compare to norepinephrine in decreasing mortality?
Bottom Line
In the treatment of shock, norepinephrine and dopamine compare similarly with respect to 28-day mortality, but dopamine is associated with an increased risk of arrhythmias.
You are projecting your western values on Asians with different value systems. I doubt the programmers are experience any moral or emotional concerns.
As for the American executives - they’ve already cashed their bonus checks for 2018.
Good pilots have and have had time to override the Horizontal Stab’s over comp.
https://www.aaaai.org/conditions-and-treatments/related-conditions/mcas
Mast Cell Activation Syndrome (MCAS)
The real issue is why the pilots couldn’t over ride the computer. That should be a hard disconnect and not dependent on code.
Southwest Airlines have some 80 737 aircraft with the MAX MCAS. Yet not one of them has crashed; and nor, as far as I am aware, have their pilots reported difficulties with managing the system. Perhaps Southwest takes crew training and aircraft safety more seriously than others.
MCAS makes the plane safer when there are competent pilots on board.
My Theory after reading much on this:
The 737 Max does not fly like a 737. The larger engines and forward position create very unique attributes in flight.
When a plane flies so differently from others, it usually gets its own type-rating....meaning pilots must be trained specifically on that type of aircraft.
That costs a lot of money for both Boeing and for the airlines. Pilot training and recurring training is expensive.
Boeing needed to get the 737 Max to market quickly to counter the Airbus 320 Neo.
But if the 737 Max was given a different type rating, it would be cost-prohibitive for the airlines to add them to their fleet.
The ideal would be to have the 737 Max share the same type rating with the rest of the 737 series so pilots trained on one can fly the other.
But because the 737 Max did not perform like other 737s, Boeing created the MCAS system so the FAA would rate the Max as the same as any other 737.
Now, there have been problems with the MCAS reported by several pilots. There was a complaint that Boeing did not disclose the system fully enough.
As the flight ascends, the MCAS, which only uses the input from one Angle of Attack sensor, gets flakey. Most airlines use three sensors for automated systems. When two sensors agree, the computer uses that data. But when you only use one sensor and you get erroneous data....computers just do what the strange data tells it to do. In this case, it pushes the nose of the plane down.
The pilot tries to correct and ends up fighting the MCAS. Realizing this, the pilot disconnects the MCAS and tries to fly manually.
But remember, the 737 Max does not behave like most 737s. In a difficult situation, close to the ground, the pilot who has been flying 737s for a long time will fall back on their experience and make corrections as if it was a 737-800, for example.
That would be like making manual corrections on a 747 that you would make with a Piper Cub. It can make the situation worse.
Maybe it’s how they wrote the requirements. Can be dicey with all those H1B Visas.
E.g.
Wife tells programmer husband “Pick up a loaf of bread on the way home from work and if they have eggs, get a dozen.”
The husband arrives at home with twelve loaves of bread.
So did they operate on relays. Or revolvers, resistors, capacitive tachometer potentiometers.
Thus my nightmare(s) about autonomous ground vehicles when the decision cycle deteriorates to what constitutes an acceptable choice of bad outcomes. Say vehicle is traveling at 45 mph when road ahead has tractor trailer jackknifing, and there is a school bus on the left and a group of bicyclists riding on a low-curb separated trail on right. What value-based selection comes into play at this 98% unlikely scenario?
Leeham News & Analysis
Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots
November 14, 2018
By Bjorn Fehrm
The automatic trim Boeing introduced on the 737 MAX, called MCAS, was news to us last week. Graver, it was news to the Pilots flying the MAX since 18 months as well.
Boeing and its oversight, the FAA, decided the Airlines and their Pilots had no need to know. The Lion Air accident can prove otherwise.
The background to Boeing’s 737 MAX automatic trim
The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System.
It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines.
The nacelles for the MAX are larger and placed higher and further forward of the wing, Figure 1.
(Figure 1. Boeing 737NG (left) and MAX (right) nacelles compared. Source: Boeing 737 MAX brochure.)
By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.
The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity (the line in Figure 2, around which the aircraft moves in pitch) will contribute to destabilize the aircraft in pitch.
(Figure 2. The 737-800 (yellow) overlaid on the 737 MAX 8 (purple), with the line denoting the CG in pitch. Source: Leeham Co. and 737 ACAP.)
The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft’s natural tendency to Dutch Roll = Wagging its tail).
Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described last week which assisted the pilot to exit the stall. But not in normal flight.
The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt.
The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings.
But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the manoeuvre has a high pitch ratio. The aircraft’s inertia can then provoke an over-swing into stall AOA.
To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.
It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.
It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.
How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.
They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.
Boeing designed a new aircraft that has stability issues due to placement of the engines (plane can accidentally go nose up and stall).
Rather than correcting the design, Boeing instead invents something called MCAS... sensors and a computer, which should correct the accidental nose-up situations caused by the badly balanced plane.
Being version 1 of the MCAS (software and sensors), it sometimes screws up and makes the plane go nose down and crash.
Boeing's response is: "Hey, RTFM. We told you it might go nuts and you can do this to shut it off...". But, if pilots turn off the MCAS, then they have no assistance to combat the problems MCAS was created to deal with. Right?
I can say ENIAC and IBM 360, but I am not familiar with the term SOAP II. Apparently, it’s an IBM application called Simple Object Access Protocol
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Boeing is finalizing its development of a previously-announced software update and pilot training revision
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So, Boeing is “finalizing” a for its software (presumably because they found an issue in the code’s logic?), but have no idea - or are unwilling to say - what the cause of the deadly crashes are?
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I assume nobody is reading this thread anymore but I thought I’d post this item. Looks like I might not be too far off. So the code written by somebody really may have contributed/caused to the failures.