Boeing Max.

This forum has been developed to discuss aviation related topics.

Moderators: ahramin, sky's the limit, sepia, Sulako, lilfssister, North Shore, I WAS Birddog

C.W.E.
Rank (9)
Rank (9)
Posts: 1200
Joined: Mon Dec 18, 2017 2:22 pm

Re: Boeing Max.

Post by C.W.E. » Thu Aug 29, 2019 12:24 pm

How many airline category airplanes require a computer driven ( load alleviation ) device to stop a pitch excursion caused by the engine thrust needed to take off and climb that is so powerful it can cause the airplane to crash if it is handled improperly?
---------- ADS -----------
  

imcool
Rank 1
Rank 1
Posts: 20
Joined: Mon Aug 26, 2019 7:43 pm

Re: Boeing Max.

Post by imcool » Thu Aug 29, 2019 12:26 pm

https://www.bloomberg.com/news/articles ... -engineers

This also make me nervous. More I read about malpractices more I get nervous for this Max plane.
---------- ADS -----------
  

C.W.E.
Rank (9)
Rank (9)
Posts: 1200
Joined: Mon Dec 18, 2017 2:22 pm

Re: Boeing Max.

Post by C.W.E. » Thu Aug 29, 2019 12:34 pm

“Boeing has many decades of experience working with supplier/partners around the world,” a company spokesman said. “Our primary focus is on always ensuring that our products and services are safe, of the highest quality and comply with all applicable regulations.”
Ahhhh, now I feel better about this Boeing Max issue.

It is not Boeing that is responsible for these crashes it is the pilots just were not capable of figuring out what it was doing and sort of got a little behind what it was doing.
---------- ADS -----------
  

GoinVertical
Rank 2
Rank 2
Posts: 54
Joined: Sat Jan 19, 2019 1:12 pm

Re: Boeing Max.

Post by GoinVertical » Thu Aug 29, 2019 2:06 pm

C.W.E. wrote:
Thu Aug 29, 2019 12:24 pm
How many airline category airplanes require a computer driven ( load alleviation ) device to stop a pitch excursion caused by the engine thrust needed to take off and climb that is so powerful it can cause the airplane to crash if it is handled improperly?
How many transport category aircraft have any form of automation that effects primary flight controls without redundant input? Stick pusher that takes data from only one source? Even the stab trim switches need redundant input to function.

Whoever designed the MCAS system to take information from only on AOA sensor and not compare to the other should be taken out behind the barn, as far as I'm concerned.

Oh, and then let's not tell pilots that the system exists, let alone how poorly it's designed.
---------- ADS -----------
  

imcool
Rank 1
Rank 1
Posts: 20
Joined: Mon Aug 26, 2019 7:43 pm

Re: Boeing Max.

Post by imcool » Thu Aug 29, 2019 3:38 pm

GoinVertical wrote:
Thu Aug 29, 2019 2:06 pm
C.W.E. wrote:
Thu Aug 29, 2019 12:24 pm
How many airline category airplanes require a computer driven ( load alleviation ) device to stop a pitch excursion caused by the engine thrust needed to take off and climb that is so powerful it can cause the airplane to crash if it is handled improperly?
How many transport category aircraft have any form of automation that effects primary flight controls without redundant input? Stick pusher that takes data from only one source? Even the stab trim switches need redundant input to function.

Whoever designed the MCAS system to take information from only on AOA sensor and not compare to the other should be taken out behind the barn, as far as I'm concerned.

Oh, and then let's not tell pilots that the system exists, let alone how poorly it's designed.
that too programmed by 9$ per hour programmers to save the cost :/
---------- ADS -----------
  

boeingboy
Rank (9)
Rank (9)
Posts: 1078
Joined: Wed Mar 03, 2004 2:57 pm
Location: West coast

Re: Boeing Max.

Post by boeingboy » Thu Aug 29, 2019 8:10 pm

How many airline category airplanes require a computer driven ( load alleviation ) device to stop a pitch excursion caused by the engine thrust needed to take off and climb that is so powerful it can cause the airplane to crash if it is handled improperly?
There is so much wrong with this statement - it makes me wonder if you understand anything of the actual problem
---------- ADS -----------
  

boeingboy
Rank (9)
Rank (9)
Posts: 1078
Joined: Wed Mar 03, 2004 2:57 pm
Location: West coast

Re: Boeing Max.

Post by boeingboy » Thu Aug 29, 2019 8:25 pm

The on-again off-again aspect of MCAS seems unusual. Stick pushers, stick feel adjustment systems, load alleviation systems - isn't it unusual for them to run for 5 seconds, then shut down for 10 seconds, then magically start up again? Wouldn't they be either active at a given point in the flight envelope or inactive? Anyone know?
Generally speaking - A stick pusher/stall warning will remain active until the stall has been counteracted. In the case of the max - As it only had one AOA input and the vane was damaged by a bird (Ethiopian) the AOA told the plane he was at 74 degrees nose up. The system operated as designed, except that the AOA input to the computer never changed so the plane thought it was still stalled.

The on again off again that you refer to is due to the fact that Boeing - in addition to being able to turn it off altogether - basically said if the pilot wants to over ride the system - he can with the electric pitch trim, which is what the pilots of both flights were doing. Although I still cant figure for the life of me why they just didn't trim the plane back to level flight. Theywould only trim for 2 or 3 seconds after the system trimmed for much longer than that
---------- ADS -----------
  

Eric Janson
Rank 8
Rank 8
Posts: 816
Joined: Thu Feb 08, 2007 10:44 am

Re: Boeing Max.

Post by Eric Janson » Fri Aug 30, 2019 9:38 am

boeingboy wrote:
Thu Aug 29, 2019 8:25 pm
Although I still cant figure for the life of me why they just didn't trim the plane back to level flight. They would only trim for 2 or 3 seconds after the system trimmed for much longer than that.
This is one possible explanation:-

It's apparent that both crews had to apply increasing force on the yoke in an effort to maintain level flight. If you really need to exert maximum force on the yoke then your hands will need to move down slightly from their normal position. That is just enough to make accessing the trim switches difficult.
---------- ADS -----------
  
Always fly a stable approach - it's the only stability you'll find in this business

FICU
Rank (9)
Rank (9)
Posts: 1237
Joined: Sun Dec 23, 2007 2:37 am

Re: Boeing Max.

Post by FICU » Fri Aug 30, 2019 10:10 am

The Ethiopian Captain used control wheel force to bring the nose up rather than the nicely placed electric trim switches by his thumb. He forgot about controlling the thrust and then he got tired. In the Lion Air crash the pilot used the electric trim switches many, many times to bring the nose up and it worked it would seem until he handed control over to search the checklists.
---------- ADS -----------
  

fish4life
Rank (9)
Rank (9)
Posts: 1692
Joined: Sun Jun 27, 2010 6:32 am

Re: Boeing Max.

Post by fish4life » Fri Aug 30, 2019 5:55 pm

The craziest part is the Ethiopian crew had it fixed but instead of manually trimming the airplane after turning off the electric trim they turned it back on causing the MCAS to run again.
---------- ADS -----------
  

mijbil
Rank 1
Rank 1
Posts: 23
Joined: Mon Jun 10, 2013 8:06 pm
Location: Rain Coast

Re: Boeing Max.

Post by mijbil » Sat Aug 31, 2019 10:08 pm

Hey F4L, From reading the initial crash investigation report I think that they did try to trim it manually but the force from the CA hauling back on the elevators to try and counteract the Aircraft Nose Down commanded by the stab was too much for the manual trim wheel to overcome. The analogy I was told was that it's like having a really big fish on a line that you can't reel in (trim manually) The only way to trim manually is to release back pressure momentarily, trim like mad manually, haul back on the yoke again and repeat as necessary. It's similar to lowering the rod tip while reeling in the fishing line and then hauling up the rod again.
Here is a brief excerpt from the Ethiopian crash report : At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working."
And from the Boeing FCTM : Excessive air loads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases, it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.
What isn't mentioned is that you might need a fair bit of altitude to relieve that airload.
The link posted by Flying Low written by an engineer is the best explanation so far that I have seen of the MCAS system.
---------- ADS -----------
  

boeingboy
Rank (9)
Rank (9)
Posts: 1078
Joined: Wed Mar 03, 2004 2:57 pm
Location: West coast

Re: Boeing Max.

Post by boeingboy » Sun Sep 01, 2019 1:58 am

The link posted by Flying Low written by an engineer is the best explanation so far that I have seen of the MCAS system.
Oh please - it's his own opinion and works for Airbus.....half of what he states is a crock.
---------- ADS -----------
  

User avatar
Flying Low
Rank 8
Rank 8
Posts: 925
Joined: Sun Feb 15, 2004 7:22 pm
Location: Northern Ontario...why change now?

Re: Boeing Max.

Post by Flying Low » Sun Sep 01, 2019 3:22 am

Oh please - it's his own opinion and works for Airbus.....half of what he states is a crock.
Fair enough. Now what is incorrect in the article?
---------- ADS -----------
  
"The ability to ditch an airplane in the Hudson does not qualify a pilot for a pay raise. The ability to get the pilots, with this ability, to work for 30% or 40% pay cuts qualifies those in management for millions in bonuses."

DH82EH
Rank 1
Rank 1
Posts: 30
Joined: Tue Oct 17, 2017 5:51 pm

Re: Boeing Max.

Post by DH82EH » Wed Sep 04, 2019 3:26 pm

boeingboy wrote:
Thu Aug 29, 2019 8:10 pm
How many airline category airplanes require a computer driven ( load alleviation ) device to stop a pitch excursion caused by the engine thrust needed to take off and climb that is so powerful it can cause the airplane to crash if it is handled improperly?
There is so much wrong with this statement - it makes me wonder if you understand anything of the actual problem
The answer is simple. One, although it is not currently in service.
---------- ADS -----------
  

lostaviator
Rank 5
Rank 5
Posts: 300
Joined: Fri Jul 20, 2012 12:42 pm

Re: Boeing Max.

Post by lostaviator » Wed Sep 04, 2019 3:45 pm

Once you get yourself into the situation of having that much nose down trim, at such a low altitude, you are done.

The manual trim wheel won’t move with the opposing forces applied. The only way to trim is to release all force and let the nose fall. If you don’t have a few thousand feet, it’s all over.
---------- ADS -----------
  

User avatar
pilotbzh
Rank 7
Rank 7
Posts: 576
Joined: Sat Jan 15, 2005 7:33 am
Location: yyz

Re: Boeing Max.

Post by pilotbzh » Wed Sep 04, 2019 4:09 pm

lostaviator wrote:
Wed Sep 04, 2019 3:45 pm
Once you get yourself into the situation of having that much nose down trim, at such a low altitude, you are done.

The manual trim wheel won’t move with the opposing forces applied. The only way to trim is to release all force and let the nose fall. If you don’t have a few thousand feet, it’s all over.
Not true, first pull hard to bring the nose up respecting the stall warning, then release pressure to manually trim nose up, no need to loose altitude.... as long as you control the speed, it won't work if you let the speed go 350+Kts
---------- ADS -----------
  

GoinVertical
Rank 2
Rank 2
Posts: 54
Joined: Sat Jan 19, 2019 1:12 pm

Re: Boeing Max.

Post by GoinVertical » Wed Sep 04, 2019 4:58 pm

pilotbzh wrote:
Wed Sep 04, 2019 4:09 pm
lostaviator wrote:
Wed Sep 04, 2019 3:45 pm
Once you get yourself into the situation of having that much nose down trim, at such a low altitude, you are done.

The manual trim wheel won’t move with the opposing forces applied. The only way to trim is to release all force and let the nose fall. If you don’t have a few thousand feet, it’s all over.
Not true, first pull hard to bring the nose up respecting the stall warning, then release pressure to manually trim nose up, no need to loose altitude.... as long as you control the speed, it won't work if you let the speed go 350+Kts
What if the stab is trimmed so nose - down that full up elevator only gives you level flight or just slightly better?
---------- ADS -----------
  

User avatar
confusedalot
Rank 8
Rank 8
Posts: 906
Joined: Fri Jul 03, 2009 9:08 pm
Location: location, location, is what matters

Re: Boeing Max.

Post by confusedalot » Wed Sep 04, 2019 5:53 pm

With all respect to all, yer all missing the point. And the point is.....you still need to know how to fly a plane. These machines are now so dummy proof that pretty much any driver can operate them. Good, bad, does not matter, if you have a quarter of a brain of the average human, you can't get hurt. YET, they still crash.

Reminds me of the toyota incident where the lady had a gas pedal runaway but could not figure out that all she needed to do was push on the brakes. She was smart enough to call her husband though while all of this was going on, telling him how terrified she was.......go figure......So all toyotas have a convoluted kill system now.
Flew the ng only, not the max, but pretty much the same plane. Did max sim though.
You could kill the whole system with a flick of a switch, but that was not done. That includes the mcas. But then......you need to fly the plane.
Sure, there was an engineering lapse/mistake. How far do we need to go?
Remember air france who could not figure a out a deep stall in an airbus and flat stalled into the south atlantic?
And of course there is the media, they conviently forget to tell the whole story for a quick and lucrative story.

Cheers.
---------- ADS -----------
  
Attempting to understand the world. I have not succeeded.

veni, vidi,...... vici non fecit.

:?

User avatar
pilotbzh
Rank 7
Rank 7
Posts: 576
Joined: Sat Jan 15, 2005 7:33 am
Location: yyz

Re: Boeing Max.

Post by pilotbzh » Wed Sep 04, 2019 7:19 pm

GoinVertical wrote:
Wed Sep 04, 2019 4:58 pm
pilotbzh wrote:
Wed Sep 04, 2019 4:09 pm
lostaviator wrote:
Wed Sep 04, 2019 3:45 pm
Once you get yourself into the situation of having that much nose down trim, at such a low altitude, you are done.

The manual trim wheel won’t move with the opposing forces applied. The only way to trim is to release all force and let the nose fall. If you don’t have a few thousand feet, it’s all over.
Not true, first pull hard to bring the nose up respecting the stall warning, then release pressure to manually trim nose up, no need to loose altitude.... as long as you control the speed, it won't work if you let the speed go 350+Kts
What if the stab is trimmed so nose - down that full up elevator only gives you level flight or just slightly better?

With full nose down trim, you still have full authority on the elevators to pull that nose up but the force required to do so increases with speed. The trim only adjust the horizontal stab... and juste like railing a fish you don’t have to give back any line as you lower the rod to rail or descent at all to manually re-trim a mis-trim situation, but speed control is crucial...
---------- ADS -----------
  

lostaviator
Rank 5
Rank 5
Posts: 300
Joined: Fri Jul 20, 2012 12:42 pm

Re: Boeing Max.

Post by lostaviator » Thu Sep 05, 2019 4:52 am

pilotbzh wrote:
Wed Sep 04, 2019 7:19 pm
GoinVertical wrote:
Wed Sep 04, 2019 4:58 pm
pilotbzh wrote:
Wed Sep 04, 2019 4:09 pm


Not true, first pull hard to bring the nose up respecting the stall warning, then release pressure to manually trim nose up, no need to loose altitude.... as long as you control the speed, it won't work if you let the speed go 350+Kts
What if the stab is trimmed so nose - down that full up elevator only gives you level flight or just slightly better?

With full nose down trim, you still have full authority on the elevators to pull that nose up but the force required to do so increases with speed. The trim only adjust the horizontal stab... and juste like railing a fish you don’t have to give back any line as you lower the rod to rail or descent at all to manually re-trim a mis-trim situation, but speed control is crucial...
I don’t want to start an argument, but where did you get that information? Every conversation I’ve had with training pilots has been that the elevator can JUST keep the plane level with full nose down trim.

The shortage of max sims, and... the fact that Boeing doesn’t even know how the max handles, makes this a hard discussion to find real answers too.
---------- ADS -----------
  

User avatar
pilotbzh
Rank 7
Rank 7
Posts: 576
Joined: Sat Jan 15, 2005 7:33 am
Location: yyz

Re: Boeing Max.

Post by pilotbzh » Thu Sep 05, 2019 5:44 am

Did it in the max Sim.... Have 14000h TT just 400h on Max...
---------- ADS -----------
  

J31
Rank (9)
Rank (9)
Posts: 1043
Joined: Thu Feb 26, 2004 7:21 am

Re: Boeing Max.

Post by J31 » Thu Sep 05, 2019 3:59 pm

The sim will only simulate what is programmed. Boeing provided the parameters to the sim manufactures and originally never included the MCAS programming. Many of the world regulators have little faith in the simulator programming to accurately portray the extreme corners of the MAX flight flight envelope.

I know from experience that the manual trim forces in the simulator do not accurately represent the Boeing 737-200. The aircraft took much more strength to manually turn the trim wheel in flight.

I would not put a lot of faith in a MAX sim to accurately simulate the ability to climb with full nose down trim at this point in time.

Boeing is going to have to prove both in the sim and the aircraft that the trim forces do not need super strength or split second reaction to keep the MAX from becoming a lawn dart.
---------- ADS -----------
  

User avatar
iflyforpie
Top Poster
Top Poster
Posts: 7776
Joined: Tue Apr 15, 2008 12:25 pm
Location: Winterfell...

Re: Boeing Max.

Post by iflyforpie » Thu Sep 05, 2019 5:12 pm

The stab doesn’t just trim the stabilizer. It also trims the elevators via the feel and centering unit and the PCUs. So nose down, you have to overcome a lot more spring pressure than when it’s neutral... and have to deflect the elevator much more relative the to neutral set by the feel and centering unit to counter what the stab is doing. Add some speed in there and now you’re fighting hydraulic pressure from the feel system as well.
---------- ADS -----------
  
Geez did I say that....? Or just think it....?

User avatar
Flying Low
Rank 8
Rank 8
Posts: 925
Joined: Sun Feb 15, 2004 7:22 pm
Location: Northern Ontario...why change now?

Re: Boeing Max.

Post by Flying Low » Thu Sep 05, 2019 10:28 pm

Boeing is going to have to prove both in the sim and the aircraft that the trim forces do not need super strength or split second reaction to keep the MAX from becoming a lawn dart.
Well....the Lion Air crew flew the airplane for around 9 minutes using the electric trim repeatedly and the Ethiopian crew flew for 6 minutes using brute force. Even if you say it's 3 minutes to get the flaps up (when the MCAS kicks in) that's 6 and 3 minutes respectively for each crew flying with the MCAS forcing the nose down. I think we can fairly say split second reaction time is not necessary and considering the electric trim works neither is super human strength. Please don't get me wrong...I'm not excusing Boeing from a badly designed system...I still do not understand how either crew lost the airplane.
---------- ADS -----------
  
"The ability to ditch an airplane in the Hudson does not qualify a pilot for a pay raise. The ability to get the pilots, with this ability, to work for 30% or 40% pay cuts qualifies those in management for millions in bonuses."

mixturerich
Rank 3
Rank 3
Posts: 180
Joined: Mon Apr 13, 2015 7:04 pm

Re: Boeing Max.

Post by mixturerich » Fri Sep 06, 2019 1:38 am

Flying Low wrote:
Thu Sep 05, 2019 10:28 pm
...I still do not understand how either crew lost the airplane.
What are you implying? That they were incompetent??
---------- ADS -----------
  

Post Reply

Return to “General Comments”