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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 11th Mar 2019, 08:12
  #261 (permalink)  
 
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Early days but it does sound more like a pitot problem to me.
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Old 11th Mar 2019, 08:15
  #262 (permalink)  
 
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China has this morning grounded all B737-MAX8 being flown by Chinese airlines - some 97 airframes.

Ethiopian (perhaps with different motivation) have also withdrawn their MAX8 from service

tick tock FAA, tick tock
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Old 11th Mar 2019, 08:29
  #263 (permalink)  
 
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Originally Posted by BRE View Post
MCAS sounds a lot like Airbus Normal Law, specifically pitch control and alpha protection. How does the Boeing implementation differ?
Uh, they have nothing in common. Normal Law will ensure whatever you do with the stick, the airplane will remain inside the flight envelope. MCAS just trims the nose forward every 5s regardless of any other parameters.

Perhaps the bigger issue is the core design. Airbus, being FBW by design, has triple sensors. If one fails, the other 2 overrule the broken one. Boeing relies on 2 sensors, if one breaks all hell will broke loose.

Also, on a Bus, if things go south, the HAL will say "sorry, your plane", turn into degraded/direct law and let the pilot handle it (which does not always work, e.g. AF447). Mcas will fight the pilots and try to get its way unless it's manually shut down.

In short, mcas is probably going to be known as one of the biggest f***ups in modern aviation history (yeah, I'm jumping to conclusions fas here, but time will tell).
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Old 11th Mar 2019, 08:30
  #264 (permalink)  
 
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Originally Posted by BRE View Post
MCAS sounds a lot like Airbus Normal Law, specifically pitch control and alpha protection. How does the Boeing implementation differ?
In the Airbus, a faulty AOA or ADR causes the airplane to either:
1. Do nothing, or
2. Turn off Normal Law.
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Old 11th Mar 2019, 08:31
  #265 (permalink)  
 
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Originally Posted by BRE View Post
MCAS sounds a lot like Airbus Normal Law, specifically pitch control and alpha protection. How does the Boeing implementation differ?
MCAS is an add-on to an upgraded design.... Airbus on the other hand is designed in full around the centre of interest - FBW, hence Normal Law.
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Old 11th Mar 2019, 08:37
  #266 (permalink)  
BRE
 
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Originally Posted by derjodel View Post
Uh, they have nothing in common. Normal Law will ensure whatever you do with the stick, the airplane will remain inside the flight envelope. MCAS just trims the nose forward every 5s regardless of any other parameters.

Perhaps the bigger issue is the core design. Airbus, being FBW by design, has triple sensors. If one fails, the other 2 overrule the broken one. Boeing relies on 2 sensors, if one breaks all hell will broke loose.

Also, on a Bus, if things go south, the HAL will say "sorry, your plane", turn into degraded/direct law and let the pilot handle it (which does not always work, e.g. AF447). Mcas will fight the pilots and try to get its way unless it's manually shut down.

In short, mcas is probably going to be known as one of the biggest f***ups in modern aviation history (yeah, I'm jumping to conclusions fas here, but time will tell).
So what you are saying is that Boeing have kind of broken their former selling point of allowing the pilot to be in control at all times?
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Old 11th Mar 2019, 08:39
  #267 (permalink)  
 
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Originally Posted by Flap40 View Post
There is a comment on AVH that the Chinese authorities have grounded all Max8's. FR24 is not showing any airborne over China.

Edit: now on Reuters.
Presumably they mean all 737 Max aircraft, not just the Max 8. Although Chinese airlines don't yet have any of the latter, Thai Lion Air operate the Max 9 into Guangzhou, Chengdu and Jinan.
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Old 11th Mar 2019, 08:42
  #268 (permalink)  
 
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They should have just stick with a simple stick pusher, very transparent, easily recognized and overcome by the pilots
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Old 11th Mar 2019, 08:44
  #269 (permalink)  
 
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Originally Posted by derjodel View Post
Uh, they have nothing in common. Normal Law will ensure whatever you do with the stick, the airplane will remain inside the flight envelope. MCAS just trims the nose forward every 5s regardless of any other parameters.

Perhaps the bigger issue is the core design. Airbus, being FBW by design, has triple sensors. If one fails, the other 2 overrule the broken one. Boeing relies on 2 sensors, if one breaks all hell will broke loose.

Also, on a Bus, if things go south, the HAL will say "sorry, your plane", turn into degraded/direct law and let the pilot handle it (which does not always work, e.g. AF447). Mcas will fight the pilots and try to get its way unless it's manually shut down.

In short, mcas is probably going to be known as one of the biggest f***ups in modern aviation history (yeah, I'm jumping to conclusions fas here, but time will tell).
The only problem Airbus pilot have is, that “your plane” situation forces you to fly aircraft you don’t know (character of the flight controls and aircraft response on side stick is very sensitive). 99% of the time on the sim, we never fly Direct Law....

Last edited by zonak; 11th Mar 2019 at 09:28.
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Old 11th Mar 2019, 08:52
  #270 (permalink)  
 
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Had an AOA vain failure on a 737-800 many years ago. Aircraft was in a cruise climb at around 6000 feet, A/P and AT engaged, when my PFD lit up with multiple warnings, low speed displays etc and we got the stick shaker. It’s was CAVOK, the * pitch and power settings were clearly normal * for the phase of flight we were in and the F/O’s instruments reflected this. Handed control to F/O, ran the checklists and told ATC we were coming back.

No real drama, but had it been a MAX with MCAS kicking in it may well have been more challenging ....

Last edited by Aldente; 11th Mar 2019 at 09:13.
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Old 11th Mar 2019, 08:52
  #271 (permalink)  
 
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Originally Posted by BRE

MCAS sounds a lot like Airbus Normal Law, specifically pitch control and alpha protection. How does the Boeing implementation differ?
Sorry mate, this is like comparing apples with oranges; as others have stated above, Airbus design is a full FBW aircraft with full flight control computers and triple redudancy; while this kind of arrangement is not fail proof, unfortunately, it provides a far better design resilience and robustiness as compared to that incorporated in the B 737 MAX. The less sophisticated Airbus FBW design is the A 320, but also on this aircraft if you lose one system, nothing happens; if you lose two systems of the same kind, the aircraft goes in a degraded flight control law (normally alternate law, in few cases directly in direct law). Flying the two degraded flight controls laws it is not a big handling problem: problems arise from the kind of failures affecting the flights (i.e. degradeg flight controls). For example, losing two radioaltimeters bring the aircraft to revert in direct law from normal law at landing gear extension but, providing that a full approach briefing covering the penalties and performances issues has been done, to fly the aircraft it is a piece of cake..
Very sad for this accident and for the lives lost, and my thinking goes to the professional fellows pilots involved: we, as professional pilots, know very well that we are paid for the increasing flight safety that our skills can provide to the system.
Happy landings.
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Old 11th Mar 2019, 08:52
  #272 (permalink)  
 
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[QUOTE=ironbutt57;10413275]
Originally Posted by porch monkey View Post
Sorry George, you'll never fit in around here with an attitude like that...........[/QUOTE

gotta love the self-appointed attitude police who turn up....
gotta love the interweb, where people don't get irony and jokes go over heads at mach .78.
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Old 11th Mar 2019, 08:56
  #273 (permalink)  
 
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Originally Posted by hikoushi View Post


In the Airbus, a faulty AOA or ADR causes the airplane to either:
1. Do nothing, or
2. Turn off Normal Law.
Abnormal Valpha Prot? Pitches down the aircraft and cannot be stopped with sidestick?

Granted, it's been fixed already.
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Old 11th Mar 2019, 08:56
  #274 (permalink)  
 
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[QUOTE=tprop;10413287]
Originally Posted by ironbutt57 View Post
[left]

gotta love the interweb, where people don't get irony and jokes go over heads at mach .78.
That's always been the drawback of the written word.
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Old 11th Mar 2019, 08:58
  #275 (permalink)  
 
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Originally Posted by phylosocopter View Post
google coffin corner
More pertinent here is flight with reduced static pitch stability. Basically, reducing static stability margin (flying with the CofG and centre of pressure closer together) means you need less downforce on the horizontal stab to counter the nose-down pitching moment. This means lower trim drag AND less lift required from the rest of the airframe to counteract the horizontal stab downforce. Less drag = less fuel burn = more efficient. Less induced drag from needing less lift to counter the horizontal stab = less fuel burn = more efficient.

The design challenge is to minimise cruise trim forces on the horizontal stab whilst maintaining JUST enough static stability margin. Works fine until you stick two new ruddy great big engines (with more wetted surface area) forward of the normal centre of pressure...
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Old 11th Mar 2019, 08:59
  #276 (permalink)  
 
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Originally Posted by mryan75 View Post

Not to mention the fact that the guys flying the Lion Air plane the day before (UK captain) had the same problem as the accident flight, hit the STAB TRIM CUTOUT switches and went on about their day. Even if this is MCAS, again, and even if it was the same for Lion Air, I still believe 100% that a US or European crew wouldn't have had any problem at all. A new captain and a 200-hour wonder is the absolute worst possible combination here... just saying.
Good to know that all we need is US crews or maybe European ones. That nuance seems to have passed me by. Could you clarify if an hispanic (but US) crew or a crew of colour would qualify in this respect as it seems the president your countrymen & women elected doesn't rate them too highly. Good of you to keep us informed
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Old 11th Mar 2019, 09:02
  #277 (permalink)  
 
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Originally Posted by BRE View Post
So what you are saying is that Boeing have kind of broken their former selling point of allowing the pilot to be in control at all times?
But B737 pilots are not always in control, e.g. the B737 has been doing things automatically (i.e. without pilot input) ever since the introduction of the Speed Trim System (STS).

For those not in the know wrt B737 systems, the speed trim system (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft centre of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabiliser in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabiliser using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed. STS operates most frequently during takeoffs, climb and go-arounds.

So, STS is a bit like MCAS (albeit for slightly different regimes of flight) in that it operates automatically and moves the stabiliser.

Last edited by Old King Coal; 11th Mar 2019 at 09:15.
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Old 11th Mar 2019, 09:16
  #278 (permalink)  
 
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I've plenty of time on Boeings, but not on this one. What is MCAS?
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Old 11th Mar 2019, 09:23
  #279 (permalink)  
 
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Originally Posted by Sailvi767 View Post


The pilot has complete control. In the event of a trim runaway you simple disconnect the trim via the provided switch, trim manually and continue the flight. The 737 provides far better indications of a trim issue than any current airliner via the trim wheels.
There is quite a difference between a trim runaway and what seems to happen here.

How do you recognise a trim runaway?
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Old 11th Mar 2019, 09:23
  #280 (permalink)  
 
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From what I understand one condition for the MCAS to work is manual flight. My question is, if the the MCAS starts to trim the nose down, can the AP be still engaged and save the situation?
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