Re: Boeing 737 and 737 MAX software

[robin.vowels@gmail.com]

On Monday, May 6, 2019 at 12:29:13 AM UTC+10, robin...@gmail.com wrote:
> On Saturday, April 6, 2019 at 8:16:22 AM UTC+11, Paul Rubin wrote:
> > Does anyone know anything about this?  It has been under some criticism
> > lately.
> > 
> > I have heard that the 777 software was almost entirely in Ada.  It also
> > sounds as if Boeing's software operation may have slipped in recent
> > years, not good news for the 737 MAX.
> 
> It seems that computers (and their computer programs) 
> are not really suitable to take command of aeroplanes. 
> 
> This week appeared a re-run of the (then new) A320 fatal crash on 
> a demonstration flight (Air Crash Investigations). 
> 
> In that case, the computer overrode the pilot, 
> even when the pilot called for full power and climbing. 
> Power was increased, but the computer failed to set 
> the ailerons to climb, so that the plane continued 
> flying horizontally at 30 feet and into trees at the end of the runway. 
> The pilot had made a gross error in flying too close to the ground 
> (30 feet), and the computer thought that the pilot wanted the 
> plane to land. 
> 
> Tonight was screened on TV a report on the two new Boeing 737 MAX 
> planes that crashed -- one in March this year and another in 
> October last year. 
> 
> In both cases, a sensor failed; it was the input to the stall 
> correction computer.  The computer sensed that the plane was 
> about to stall (it wasn't), and put the nose down.  But the 
> attitude of the planes was set to 60 degrees, which is an 
> awfully steep dive, and not merely a minor correction to help 
> the plane to avoid a stall. 
> 
> The pilot had five seconds to consult  a "check" list 
> (a thick manual) as to what to do.  Even if he had been 
> able to correct the problem (by adjusting the ailerons), 
> the computer applied the stall correction again for 
> 10 seconds (which resulted in another steep dive), 
> and the pilot had another 5 seconds to correct the 
> problem. This 5/10-second cycle repeated ad infinitum. 
> In one case, the plane was close to the ground, as it had 
> not long before taken off from the runway. Each steep dive 
> took the plane closer to the ground ... 
> 
> One major point of the TV report was that Boeing had never 
> made mention of this software feature in any manual, 
> so no pilots had been trained to deal with a situation 
> in which software took over flying the plane. 
> 
> Three questions: 
> 1. Whatever happened to the stick shaker? 
> 2. Why was the dive so ridiculously steep? 
> 3. Why did not the autopilot save the plane 
>    as it careered towards the ground? 
> 
> Usually the best operator of a plane is the pilot, 
> and he should always be able to take over from 
> any computer program (autopilot or stall correction) 
> and to fly the plane manually in the event that the 
> automatic equipment fails.

Recently was screened, for the first time, 
on Aircraft Crash Investigations [probably also in the USA] 
the report on the Airbus A330 Qantas that experienced 
loss of control of the aircraft when it suddenly dived 
at 10 degrees.  The controls failed to right the plane. 
Passengers and crew hit the ceiling, injuring themselves 
and breaking ceiling panels. 

The plane eventually responded to stick control. 

The same thing happened again, with angle of attack 10 degrees. 

Again, after a while, the plane responded to the pilot's control. 

Analysis showed that one of the units sends data (height and 
angle of attack) to the flight computer. 
The data is sent with a tag.  The unit got those tags mixed up: 
it sent one set of the height data with the angle-of-attack tag, 
and vice versa. 

That (apparently) appeared to be a programming error. 
The information was sent to Airbus. 

As to landing the plane, the pilots made an emergency landing, 
side-slipping the plane in order to lose height quickly, 
but also to gain speed in case the same thing happened again, 
which would give them more chance of recovering. The pilots 
realized that, if the plane misbehaved close to ground, 
with a normal slow descent, there would be no chance of recovery.