Ethiopian ET302 Crash.

[Exhaustgases]

So what does MCAS and an airbag have in common?
Improper design.

The quick fix ? Get rid of them, meaning REMOVE THEM.

It seems the real fixes are too difficult for the nowadays engineers to figure out.

 

[fdcg27]

Well, it tried to kill me once but I caught it in time.
Let's give it another shot!
In fairness to the pilot and the flight attendant qualified passenger occupying the right seat, the trim wheels would have been very hard to turn at the speed they were operating, but the trim switches on the yoke would have been effective with stab trim motor power had they been used.
Power could have then been cut before the erroneously invoked MCAS had been allowed to trim nose down.

 

[Astro14]

Several posts ago, I commented on the wisdom of troubleshooting in the air...

Originally Posted by Astro14
I think we talked a bit about the 737 MAX flight control system in the Lion Air thread.

Too early to tell anything, but I will say this: if faced with a flight control problem, I'm not troubleshooting in the air. I will do what I need to get the airplane in a safe configuration to land and NO MORE.

I'm going to land it and let maintenance figure it out.

Back in the days when I had an ejection seat, I would fiddle with stuff in the air and give our guys all the data points and analysis they needed to fix the airplane the first time.

These days, I don't do that.

Lion Air pilots did that...they fiddled with the MACS over and over to try and get it to work. The previous flight, the mishap airplane had a problem, and the crew did some in flight troubleshooting and continued on to destination.

Crazy.

I think that in the course of investigation and cause, that we, of BITOG, will cover a lot of the same concepts we did in the Lion Air thread:

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4908879/1

Limits of flight control authority, ability to over-ride systems, systems engineering philosophy, training, startle response, judgement...

 

[Tom NJ]

Originally Posted by Astro14


Now, that integration takes place in the computers that power glass displays, which present everything at once. The autopilot and flight management computer provide the situational awareness.

I see a kid with 1,500 hours applying for an airline job, and wonder, how many hours were flown without all the aids? without autopilot? without even a flight director?

The point is: every minute of those flight hours was spent in actual control of the airplane.


It's like people driving cars into a canal in Amsterdam while following the GPS. Four times driving in Europe my GPS tried to steer me down the wrong way on a one-way street. Fortunately with 50 years of manual driving experience I caught it each time.

I bought a new fully loaded 2019 Altima last week and the electronics are amazing. Cruise control that maintains a pre-set distance from the car in front of you (even stopping if they do), vibrating steering wheel if you cross a line, steering assist that keeps you in your lane, beeping sounds if you are going more than a pre-set speed over the speed limit, pedestrian detection, blind spot warning lights, rear view camera, rear sonar that looks to the sides as well as back, voice commanded phone calls and texts through the car's bluetooth, etc. On top of this you have an 8" display full of entertainment and menus. Today I drove 20 miles on curvy and hilly roads without once touching the gas pedal or brakes.

While all of this is intended to improve safety (and mostly does), it can also be quite distracting with lights flashing and beeping sounds. I figure with another 20 hours in the owner's manual I'll qualify for my junior pilots license! Fortunately I can shut off most of the automation and still drive in manual mode, which I mostly do to avoid becoming dependent on the computer and drive into a canal.

 

[PimTac]

Originally Posted by Tom NJ
Originally Posted by Astro14


Now, that integration takes place in the computers that power glass displays, which present everything at once. The autopilot and flight management computer provide the situational awareness.

I see a kid with 1,500 hours applying for an airline job, and wonder, how many hours were flown without all the aids? without autopilot? without even a flight director?

The point is: every minute of those flight hours was spent in actual control of the airplane.


It's like people driving cars into a canal in Amsterdam while following the GPS. Four times driving in Europe my GPS tried to steer me down the wrong way on a one-way street. Fortunately with 50 years of manual driving experience I caught it each time.

I bought a new fully loaded 2019 Altima last week and the electronics are amazing. Cruise control that maintains a pre-set distance from the car in front of you (even stopping if they do), vibrating steering wheel if you cross a line, steering assist that keeps you in your lane, beeping sounds if you are going more than a pre-set speed over the speed limit, pedestrian detection, blind spot warning lights, rear view camera, rear sonar that looks to the sides as well as back, voice commanded phone calls and texts through the car's bluetooth, etc. On top of this you have an 8" display full of entertainment and menus. Today I drove 20 miles on curvy and hilly roads without once touching the gas pedal or brakes.

While all of this is intended to improve safety (and mostly does), it can also be quite distracting with lights flashing and beeping sounds. I figure with another 20 hours in the owner's manual I'll qualify for my junior pilots license! Fortunately I can shut off most of the automation and still drive in manual mode, which I mostly do to avoid becoming dependent on the computer and drive into a canal.







The big question is, if something happens will you react quickly on your own or wait for a split second or more to allow the computers to react for you? This is the conundrum we face on these systems.

Don't get me wrong, I like the technology as well but I like to be in command of the car, not the other way around.

It's a new paradigm for sure.

 

[BusyLittleShop]

Pilots are still the wild and variable component in the system whereas
Auto is the tame and constant component...

 

[oil_film_movies]

Originally Posted by Astro14
I said to the crew, "Am I the only one who feels low?" The FO, who was flying, said, "the glideslope shows us right on." I said, "I know, I can see that, but we're three miles out and only 600 feet above the field, that's wrong. We ARE too low."....The data presented was wrong because the ground station was providing faulty data.
I'm shocked the Captain didn't cross check other parameters and see it first. ..... Actually the glideslope was reset by bad guys on the ground, and we have them on video:

which is a silly movie adaptation.

Really it appears the glideslope transmitter became misaligned, having too low of an inclination due to some impact or something that moved it.

We always thought our HGS (HUD) enhanced Situational Awareness by keeping pilots from fixating on numbers and pretty symbols head-down too much. I had fun creating vector graphics on the HGS, good times for an avionics engineer I guess! Showing the Flight Path symbol on the HGS's pitch (horizon) scales helped.

 

[ZeeOSix]

Crash report summary.

 

[thescreensavers]

https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html

 

[oil_film_movies]

Originally Posted by thescreensavers
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html
Complicated, isn't it?
Not sure why the Ethiopian crew forgot to throttle down from the initial high take-off thrust. Panic and workload I guess. Then it couldn't be manually trimmed out a little later when over-speeding.

 

[DoubleWasp]

Sounds like there was a LOT more going on than the newspapers are revealing. Doesn't sound like Being procedure was followed to the letter at all.

Sounds like pilots were potentially so distracted by trim issues that they forgot to throttle back?

 

[PimTac]

We have to consider the time frame here as well. These pilots didn't have a whole lot of time to figure things out. Workload, situational awareness, and time all came together here.

I've been in a similar situation a long time ago as a coxswain of a Coast Guard 44 foot lifeboat running a search for a vessel in distress on a bar with sloppy conditions at night and in pouring down rain plus poor equipment . When that moment hit that we were off position a quick reaction saved our bacon.

We had a excellent debriefing afterwards. These folks won't have that opportunity.

 

[ZeeOSix]

Originally Posted by thescreensavers
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html


From the article:
"With the 737NG cutout switches, MCAS runaway is stopped by just throwing the autopilot cutout switch, leaving electric trim fully operable.

With the 737MAX cutout switches, MCAS runaway is stopped by throwing both switches, losing electric trim altogether. In this case, the flight crew must rely on manual trim via turning the trim wheel/crank. As discussed above, the manual crank can bind up, making flying much more difficult."

This is a very bad design and is ultimately what probably made it so the pilots could not recover flight in a manual mode. The airspeed was too high for them to manually crank the stab trim in time to recover. IMO, you still want to have manual control of the jack screws through the electric motors so there is enough force to make quick stabilizer manual adjustment. The last thing you want pilots to do is manually try to crank in stabilizer adjustments when the force to do so with the hand crank is insanely high, all the while trying to recover from an emergency situation.

 

[ZeeOSix]

Crash report document link (PDF).

LINK

 

[oil_film_movies]

Originally Posted by ZeeOSix
Originally Posted by thescreensavers
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html
From the article:[color:#3366FF]"With the 737NG cutout switches, MCAS runaway is stopped by just throwing the autopilot cutout switch, leaving electric trim fully operable.
Bad wording. 737NG does not have MCAS, its got STS via the autopilot. Only other aircraft with MCAS is the AirForce 767 Tanker: "The KC-46 has a two-sensor MCAS system, which "compares the two readings," the Air Force said. Moreover, while the MAX 8 MCAS will reset and come back on automatically, the KC-46's system is "disengaged if the pilot makes a stick input," according to the Air Force. "The KC-46 has protections that ensure pilot manual inputs have override priority.""

 

[SEMI_287]

Originally Posted by ZeeOSix
Originally Posted by thescreensavers
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html


From the article:
"With the 737NG cutout switches, MCAS runaway is stopped by just throwing the autopilot cutout switch, leaving electric trim fully operable.

With the 737MAX cutout switches, MCAS runaway is stopped by throwing both switches, losing electric trim altogether. In this case, the flight crew must rely on manual trim via turning the trim wheel/crank. As discussed above, the manual crank can bind up, making flying much more difficult."

This is a very bad design and is ultimately what probably made it so the pilots could not recover flight in a manual mode. The airspeed was too high for them to manually crank the stab trim in time to recover. IMO, you still want to have manual control of the jack screws through the electric motors so there is enough force to make quick stabilizer manual adjustment. The last thing you want pilots to do is manually try to crank in stabilizer adjustments when the force to do so with the hand crank is insanely high, all the while trying to recover from an emergency situation.



Yes, it's an antiquated design but it works. Unloading the controls does make this much easier to manually trim at high air speeds. But you will lose some altitude, which these poor guys didn't have. When I say unload the controls I mean relieve some of the aft pressure on the yoke.

 

[fdcg27]

umm, the NG doesn't have MCAS. Only the MAX does.
Maybe not a very well informed writer of this article.

 

[oil_film_movies]

Originally Posted by oil_film_movies
Originally Posted by ZeeOSix
Originally Posted by thescreensavers
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html
From the article:[color:#3366FF]"With the 737NG cutout switches, MCAS runaway is stopped by just throwing the autopilot cutout switch, leaving electric trim fully operable.
Bad wording. 737NG does not have MCAS, its got STS via the autopilot. Only other aircraft with MCAS is the AirForce 767 Tanker: "The KC-46 has a two-sensor MCAS system, which "compares the two readings," the Air Force said. Moreover, while the MAX 8 MCAS will reset and come back on automatically, the KC-46's system is "disengaged if the pilot makes a stick input," according to the Air Force. "The KC-46 has protections that ensure pilot manual inputs have override priority.""
Originally Posted by fdcg27
umm, the NG doesn't have MCAS. Only the MAX does. Maybe not a very well informed writer of this article.

That was already pointed out above, although he meant "autotrim" instead of saying MCAS, and his point is correct about losing yoke electric trim when the MCAS is disabled.
BTW, the KC-46 has MCAS too, not just the 737 Max.

 

[ZeeOSix]

Originally Posted by oil_film_movies
That was already pointed out above, although he meant "autotrim" instead of saying MCAS, and his point is correct about losing yoke electric trim when the MCAS is disabled. BTW, the KC-46 has MCAS too, not just the 737 Max.


Yep, I figured the writer meant some kind of stab trim system since MCAS is only on the 737 Max models. Sure seems to me that only having "hand power" on a couple of manual trim adjustment wheels in an emergency situation isn't a good thing to be in.

I'm sure it would be easy enough to make MCAS disabled and still retain the full electrical stab trim functionality that could be adjusted by the pilot with a manual switch like they would normally do. The "hand wheels" stab trim adjustment with hand power should be an absolute last resort when all other electrical systems are dead for some reason (ie, not talking about purposely switched off by a pilot, but disabled due to an electrical failure or malfunction).

 

[DoubleWasp]

Ok, so this manual trim wheel is literally a mechanical connection of some sort dependent on sheer mechanical force to operate?

With the KC-46, does that mean that a pilot who had to "fight" the MCAS would automatically and permanently lock out the system just by grabbing the yoke and giving input?

Possible the ET302 crew put the switches back on to try to recover with electric trim realizing they weren't going to win against resistance using the mechanical trim? Situation looked even worse, so try turning the system back on to recover before MCAS cuts in, and then shut it back off soon as it tries?

Uneducated hypothetical: Would opening the flaps and speedbrakes have arrested their over speed issue and locked out MCAS while giving them back electric trim, or would that have just opened a whole other can of worms?