16 hours ago, Wink207 said:

Without insight into the engineering and program management organizations within Boeing, you can't really say "....Boeing have let themselves be driven too much by the pressure to keep up and, as a result, cut corners...."

What I'm alleging here is based on reports from Boeing as well as FAA engineers who spoke under anonymity about the speed of the design process of the aircraft (twice the normal speed) and its certification. They talked about pressure to get things done as fast as possible. Other reports have claimed that FAA managers signed papers themselves in haste without a chance for the engineers to review them. All to catch up with the competition which was ahead. If you want to read the articles, a quick Google search should give out plenty.

16 hours ago, Wink207 said:

a company such as Boeing (or Airbus) does not create another baseline like the 737 Max, or the 320 NEO, without extensive analysis, calculations, trade studies, model testing, simulation, and flight testing.

But it would be a mistake to think that Boeing made that decision only to sell aircraft, meet schedule, save money, or some such programmatic factor.

I think you missed the point I was making here. I was giving an answer to people who say the MAX shouldn't exist by pointing out that the aircraft program makes perfect sense from a business point of view and is a competitive airframe. Obviously, Boeing didn't just jump from the business conclusion straight to producing airframes, even if that is what some (many) people seem to believe.

16 hours ago, Wink207 said:

An alternative scenario for the existence of MAX MCAS could well be that the nonlinear aerodynamic lifting effect of the LEAP cowl in the location forward of the wing was not initially recognized conceptually, predicted computationally, or witnessed in wind tunnel testing, and was not experienced before the first full scale (flight) testing.

This is a good point. I never thought of that before.

16 hours ago, Wink207 said:

Why was that decision made?

A fault of MCAS/erroneous activation was put into the failure category of "hazardous" which only requires the system to rely on one AoA sensor. The next higher category ("catastrophic" as far as I recall, and, in fact, the highest) would have demanded it to use the second sensor as well which, in hindsight, would have been the correct category for an MCAS failure/erroneous activation in its inital iteration. I do believe the "hazardous" category was chosen because no one predicted that an erroneous activation of MCAS could have such a catastrophic outcome.

20 hours ago, n4gix said:

..I've been manually trimming ...

Pun possibly not intended, Fr.Bill 

2 hours ago, HighBypass said:

Pun possibly not intended, Fr.Bill 

Not intended for sure and certain, but quite serendipitous, n'est pas?

1 hour ago, n4gix said:

Not intended for sure and certain, but quite serendipitous, n'est pas?

Don't forget to turn off the auto-trim first!

On 4/16/2019 at 1:47 PM, Bert Pieke said:

I beg to differ..

Airbus crashed one of its earliest A320s because of computer systems overriding the pilot... They fixed the code, and went on from there.

Wrong example. The captain survived and lost his job. At any rate, he could have saved some tree top margin and nobody during the exhibition would have noticed the difference on the ground and the show would have gone on perfectly. Showmanship gone awry.

Cheers,

3 hours ago, mabe54 said:

Wrong example. The captain survived and lost his job. At any rate, he could have saved some tree top margin and nobody during the exhibition would have noticed the difference on the ground and the show would have gone on perfectly. Showmanship gone awry.

Still, the plane was supposed to avoid the trees by itself. That's why the pilot didn't do anything because everyone was sure the automation would kick in in time. Which it didn't. The parallel here to the MAX is that the software, which was thought to be properly designed, in fact wasn't. Lessons (very hard lessons in the case of the MAX with regard to the amount of lives lost, mind you) have been learned and led to a better, safe design.

This is the best post I have seen on this subject for at least 3 months.

https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa-207.html#post10450681

19 hours ago, threegreen said:

Still, the plane was supposed to avoid the trees by itself... 

I do not know what you got that from and I am sure Airbus wasn't selling that option that day and not even nowadays. So, I am done with this example.

Cheers,

One survived because a third member on the cockpit and during the landing phase. Two crashed during takeoff and first duties of the roasters early morning time. No ideal times.

Cheers,

 

3 hours ago, mabe54 said:

I do not know what you got that from

Sorry, disregard that.

Interesting article here by a software engineer and also a pilot: https://spectrum.ieee.org/aerospace/aviation/how-the-boeing-737-max-disaster-looks-to-a-software-developer

 

2 hours ago, honanhal said:

Interesting article here by a software engineer and also a pilot: https://spectrum.ieee.org/aerospace/aviation/how-the-boeing-737-max-disaster-looks-to-a-software-developer

 

Interesting article, but I am not sure that he is correctly describing the hardware systems (he is a software engineer..)

Based on what I have read, the MCAS system does not push the control column forward, but only operates on the stabilizer via the trim motors..

Edited April 20, 20197 yr by Bert Pieke

Hello,

I rather think that he does indeed know what he is writing about.

 

Quote

MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation.

 

46 minutes ago, Reader said:

Hello,

I rather think that he does indeed know what he is writing about.

What is being said in what you quoted is that MCAS pushes the nose down via automatic stab trim. From simming you will know that when the aircraft is out of trim with AND, you have to pull back hard on the yoke to keep the nose up. The trim pushing the nose down is the force you feel when pulling back. What the author of the article said is that MCAS actually pushes the yoke forward to create a force the pilot has to work against. This is not correct, however. Bert is right.

The author is also a bit off on the 737 MAX in terms of how the flight controls work and the overall amount of computer authority over the aircraft. It's possible that what he misunderstood is that the MAX has a FBW spoiler system. At certain flaps settings (15-30) and thrust close to idle, the spoilers will extend automatically to increase drag and thereby increase thrust above idle. It also helps to establish an adequate nose gear margin for touchdown by extending the spoilers slightly at flaps 30/40, reducing lift and requiring a higher AoA. But this is all FBW technology there is in the MAX. The flight controls are all still connected to the control column mechanically and assisted by hydraulic systems. Unlike in an Airbus, there is no computer in the MAX that ignores pilot input and refuses to move control surfaces when it senses the pilots are about to screw up. The hydraulic systems do take some of that 'feel' of moving the control surfaces away, but only because without their help no human could move the control surfaces more than a tiny bit compared to their actual range, let alone when the aircraft is flying and there is aerodynamic load on the control surfaces (think about trying to trim manually using the wheel at high speeds). It's not an artificial feel.

 

Edited April 20, 20197 yr by threegreen

Thanks.

Is the part about "give a steady increase in stick force as the stall is approached as required by regulation" incorrect?

Once again, I am the uninformed here but if the aircraft thinks it is stalling because the AoA reading is faulty, is there not

an indication to the pilot through the yoke, even though it is not stalling?