L
Lasse Langwadt Christense
Guest
mandag den 3. juni 2019 kl. 20.44.01 UTC+2 skrev tra...@optonline.net:
stick shaker and stick pusher is anti stall, MCAS is not
On Monday, June 3, 2019 at 1:56:19 PM UTC-4, Lasse Langwadt Christensen wrote:
mandag den 3. juni 2019 kl. 18.44.18 UTC+2 skrev tra...@optonline.net:
On Monday, June 3, 2019 at 10:19:38 AM UTC-4, Rick C wrote:
On Monday, June 3, 2019 at 10:10:34 AM UTC-4, tra...@optonline.net wrote:
On Sunday, June 2, 2019 at 9:34:34 PM UTC-4, bitrex wrote:
On 6/2/19 9:30 PM, bitrex wrote:
On 6/2/19 9:20 PM, bloggs.fredbloggs.fred@gmail.com wrote:
On Sunday, June 2, 2019 at 8:15:39 PM UTC-4, tra...@optonline.net wrote:
On Sunday, June 2, 2019 at 7:55:36 PM UTC-4, bitrex wrote:
On 6/2/19 4:37 PM, bloggs.fredbloggs.fred@gmail.com wrote:
On Sunday, June 2, 2019 at 9:18:59 AM UTC-4, Winfield Hill wrote:
Details of an error in engineering procedures
  and decision-making:
https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html
  The comments to the article are also interesting.
The airlines have a history of this kind of risk taking.
"According to the NTSB, a fuel tank explosion happens on average
every four and a half years. In May 1990, six years before TWA 800,
a center tank exploded on a Philippine Airlines 737 shortly before
take off, killing eight people. Four years and eight months after
TWA 800, the center tank of a Thai Airways jet exploded on the
ground, killing one person."
http://www.cnn.com/2006/US/07/14/twa.main/index.html
Up to the TWA flight 800 disaster, they were spending way more
money on their in-flight entertainment system than a fuel tank
oxygen removal system could ever cost.
As for the NYT article, they have the basic facts but as usual
their interpretation is pathetically naive.
The FAA is incapable of certifying a design as complex as the 737
MAX. They in fact handed the entire certification off to Boeing
with the certification reports being "reviewed" by semi-comatose
swivel chair operators with probably less than 10% (on the high
end) comprehension of what they were reading. And when NYT reports
Boeing delivered this or that information to FAA, it only means it
was part of a probably huge documentation package most of which was
simply glossed over by the FAA. As is typical of most politicized
bureaucracies, they're just not going to pay much attention to
anything that's not already a high visibility issue.
I agree with Boeing about the MCAS not being a single-thread
catastrophic failure mechanism because the pilot is always
available to pull the system out of MCAS control, and the MCAS was
relatively slow acting, taking 10 seconds to do anything. And you
can't implement a voting scheme with just two sensors. The only
good a second sensor would serve is if it was something the pilot
could switch in when/if the first sensor gave him trouble with the
MCAS.
The fault lies with the airlines for not properly training their
pilots.
Has anyone told Boeing there's no point to using two sensors? Cuz as
part of their fix to this issue, according to the article, using two
sensors continually seems to be central to the plan, not just a second
sensor that's switchable/optional.
The idea to two seems to be that if they disagree by a substantial
amount, then
MCAS will take no action, because something is wrong and the cure is
potentially far worse than the problem.
That's the least reliable option because you lose MCAS if either/or
the angle sensors fail. Maybe they think it's important to have MCAS,
making the switchable option the most reliable to that end.
In both crashes the sensor activated MCAS because it thought the angle
was too high and the aircraft was in danger of stalling. So it put the
nose down at a steep angle causing the crash. I don't know why it just
as easily could have sensed the nose was down too much and put the
nose up causing the plane to stall and crash. The basic problem is the
pilot doesn't have any wiggle room when he's coming in for a landing.
It only takes a few seconds of bad control to put the aircraft in a
bad spot it can't get out of. Maybe they should just shut the damn
thing off below a certain ground height and ground speed.
The way the article framed it was that there was feature-creep in the
design of the MCAS system. from an emergency system that would only
engage in exceptional circumstances to being just another part of the
normal flight controls that was always operating in the background to
make it a more comfortable aircraft to fly.
That is to say it might be expected it would also be operating at low
ground height/ground speed because it was operating in the other
regimes, also. Shut it down in that area and suddenly you're flying a
different plane. Which could also be pretty hazardous if you're not
expecting it.
Two things. First you also needed a dangerous angle of attack, nearing a
stall, which the plane would not see during normal operations. Second
at lower speeds and elevation, eg landing, as soon as flaps are activated,
MCAS is disabled.
I'm not certain, but I don't think the MCAS was installed to deal with impending stalls. It was added to improve the handling characteristics of the plane.
Well, you're wrong. MCAS was added specifically to counter the tendency
of the Max to increase nose up when approaching a stall because of the
placement of the new, larger engines.
MCAS is not an anti stall system, 737 pilots have repeated that numerous times
MCAS is there to make a 737-Max behave like a 737-NG
It most certainly is an anti-stall system. The Max when pushed to a high
level of attack will tend to push itself further nose up into a stall.
It's both an anti-stall system and to make the Max behave like other 737s
that don't exhibit that undesirable behavior. And also possibly because
they could not get it certified without it too.
stick shaker and stick pusher is anti stall, MCAS is not