Ethiopian 737 - same as Indonesia ?

[cagarini]

Same 737 Max 8 model :-/

[Jeroen Hoppenbrouwers]

Nobody has any idea yet, but the grounding of MAX aircraft has started. Boeing postponed the commercial presentation of the 777X which is technically of course totally unrelated but not psychologically.

Hoppie

[andrej]

We need to get to the bottom of this, why both accidents have occurred. What was the cause? Was it preventable, rather than a major flaw with the airplane itself (that could open a new Pandora's Box for Boeing and regulators).

However, it is very intriguing that both, relatively very young air-frames, have crashed just a  few minutes after the takeoff. I thought that after the reported issue with sensors and/or MCAS following the LionAir crash, Boeing/airlines/regulators would be more prudent in enlightening airlines/pilots/crews in differences between NGs and MAXs systems. I hope that lessons learned from both accidents, will benefit the flying public.

Call me crazy, but this is a first time in my life, that I question, whether to fly MAX or not. Is it paranoid or just precautionary feeling, I don't know.

On a side note, this crash is little more personal. My brother's former colleague, who became a public figure, has lost his wife, daughter, and son. My friend lost a friend on that flight. This is 4 people from Slovakia that have died. It is quite strange and somber feeling. Words can not express my grief for all souls lost, but this one is a little more "special". 

In regards the postponement of the commercial presentation of the 777X it makes sense. The timing is not right now. Boeing needs to mitigate current risk, that is 737MAX. I was looking forward to this presentation though.

[ahaka]

How reliable is the FlightRadar data? According to that the aircraft's vertical speed  was very unstable (going up and down) while the speed keeps increasing up to about 380 knots. Isn't this indication at least somewhat similar to the Lion Air crash?

[kryten]

I wonder if they will ever introduce cameras into the cockpit. There have been accidents where it would show important evidence not recorded (or difficult to deduce) on the CVR or FDS.

[Will]

One thing that comes from the flight radar tracking websites is that even though some airlines have grounded the 737 Max 8, there are still dozens in the air at any given time.

[Chris Kilroy]

I wonder if they will ever introduce cameras into the cockpit. There have been accidents where it would show important evidence not recorded (or difficult to deduce) on the CVR or FDS.

The pilot unions, at least stateside, will never allow that.

[Jeroen Hoppenbrouwers]

How reliable is the FlightRadar data?

FlightRadar and other tracking sites store and reproduce data received by a network of ground-based ADS-B IN receivers. Just as with personal weather stations, you can buy one of these and put it on your roof and feed into their network to get some perks. Enthusiasts like it. So the data is as reliable as what the ADS-B squitters spit out. If the data shows wild fluctuations, the aircraft spit out wildly fluctuating data.

The networks also have other data input sources, but the vast majority is ADS-B receivers.

Hoppie

https://flightaware.com/adsb/flightfeeder/

[Steve Hose]

Nobody has any idea yet, but the grounding of MAX aircraft has started. Boeing postponed the commercial presentation of the 777X which is technically of course totally unrelated but not psychologically.

Hoppie

Australia has just joined the list of countries banning the MAX from its airspace.

"This is a temporary suspension while we wait for more information to review the safety risks of continued operations of the Boeing 737 MAX to and from Australia." CASA chief executive and director of aviation safety, Shane Carmody, said.

"CASA regrets any inconvenience to passengers but believes it is important to always put safety first."
CASA's announcement comes after Singapore's aviation regulator today completely banned the use of the MAX aircraft in the country's airspace.

It joined China, Indonesia, South Korea and Mongolia in grounding the jets.

Ethiopian Airlines, Cayman Airways, Singapore Airlines' subsidiary SilkAir and carriers across China and Indonesia have grounded all MAX 8 planes in response to the fatal Ethiopian Airlines crash at the weekend.

Southwest, Air Canada and American Airlines are several carriers who continue to use the aircraft."

Australian media story here:

https://www.news.com.au/travel/travel-updates/incidents/virgin-pilot-body-says-it-has-utmost-confidence-in-boeing-max-8/news-story/2680f4379969f1a73b5351f51f17c0e6

[ahaka]

How reliable is the FlightRadar data?

FlightRadar and other tracking sites store and reproduce data received by a network of ground-based ADS-B IN receivers. Just as with personal weather stations, you can buy one of these and put it on your roof and feed into their network to get some perks. Enthusiasts like it. So the data is as reliable as what the ADS-B squitters spit out. If the data shows wild fluctuations, the aircraft spit out wildly fluctuating data.

Thanks for the info. So I assume this data comes from the same source as the one recorded by the FDR, but perhaps at a slightly different rate (Hz). However if FlightRadar interpolates for gaps (missing data) then it might not be as accurate.

[Markus Vitzethum]

For the sake of completeness, note that e.g. FR24 also utilizes other methods to acquire data.

The two other important methods are MLAT (Multi Lateration), basically using many receivers and monitoring the time differences between arrival of Mode-S signals (at individual receivers) to interpolate a position, and, particularly in Germany/Europe, FLARM, which is a custom-made ADS-B system designed for gliders and light aircraft (taking into account e. g. circling in thermals for collision prediction + avoidance).

And of course, North Atlantic / Pacific data from the FAA (at least: used to).

Typically, the more modern and/or large airliners transmit ADS-B, older/smaller regional jets / turbo probs (or 737 classics, for that matter), are tracked via Mode-S MLAT, and some of the light aircraft via ADS-B or FLARM.

Markus

[Jeroen D]

Thanks for the info. So I assume this data comes from the same source as the one recorded by the FDR, but perhaps at a slightly different rate (Hz). However if FlightRadar interpolates for gaps (missing data) then it might not be as accurate.

I am not sure how it does it, but FlightRadar does some weird tricks. If you look at the take off profile of this flight, it starts at 0 feet MSL. Then in the space of less then a minute, where you see the ground speed accelerating from zero upwards, it jumps from 0 to 8000 feet. I believe the airport elevation was somewhere around 7200 feet. Somehow during the take off run, flightradar records 0 feet and then jumps up to a more realistic altitude.

No idea what the sampling time is and how it deals with connecting the dots.

Jeroen

[farrokh747]

https://www.ndtv.com/india-news/boeing-737-max-aircraft-grounded-by-civil-aviation-watchdog-dgca-2006656?pfrom=home-topscroll

[torrence]

The item I find most unnerving about this at the moment is Boeing's announcement they are preparing a modification of the MCAS software.  Given the uncertainty about what role the current MCAS has played in these crashes, I find it hard to believe that they could test and verify new flight software adequately, while the investigation is just starting.

Cheers
Torrence

[Jeroen Hoppenbrouwers]

My theory: already before the Lionair crash, somebody pointed at MCAS as working fine unless one of the sensors failed, after which MCAS would not have the logic to quit. Much like the single faulty radio altimeter that made Turkish flare in midair near Schiphol. This is not a software fault, as it works perfectly as designed, but a design safety flaw that should have been caught by the system safety assessment. It's possible that this was considered a point of improvement and work had been started. Lionair may have pushed it forward, but such a change in a safety-critical system isn't easy to hasten. Ethiopian most definitely did not have an effect, it's way too recent.

Still all my theory. I'm not at all even near this system.


Hoppie

Edit: it seems that this point of work start was August 2018, after reading more stuff down below.

[United744]

My theory: already before the Lionair crash, somebody pointed at MCAS as working fine unless one of the sensors failed, after which MCAS would not have the logic to quit. Much like the single faulty radio altimeter that made Turkish flare in midair near Schiphol. This is not a software fault, as it works perfectly as designed, but a design safety flaw that should have been caught by the system safety assessment. It's possible that this was considered a point of improvement and work had been started. Lionair may have pushed it forward, but such a change in a safety-critical system isn't easy to hasten. Ethiopian most definitely did not have an effect, it's way too recent.

Still all my theory. I'm not at all even near this system.


Hoppie

+1.

It **SEEMS** to have NO redundancy, NO cross-checking of data, NO ability to fault, and instead, just works regardless if it is correct or not.

Someone said something VERY interesting this evening about MCAS: it adjusts the slats to maintain a constant pitch attitude to minimize drag. This is a very curious comment.

[John H Watson]

Someone said something VERY interesting this evening about MCAS: it adjusts the slats to maintain a constant pitch attitude to minimize drag. This is a very curious comment.

I think that someone is confusing MCAS with something else.

From PPRuNe:

While there is not yet sufficient information to draw a clear link between the ET accident that is the subject of this thread and MCAS I am deeply troubled by the amount of misinformation regarding MCAS that is being spread here. Reluctantly I offer the explanation below without any suggestion that this system contributed to the tragedy in Ethiopia this last weekend. The truth will be revealed by the recorder data and the full investigation. I strongly implore those who do not know MCAS details to stop providing incorrect information here or anywhere else. Posing questions is fine, but please do not state as fact that about which you are not sufficiently knowledgeable.

MCAS Operation Clarification

MCAS is triggered when all of the following are true:
A. Sensed AOA exceeds a flight condition based activation threshold
B. Flaps are fully retracted (i.e., up)
C. Autopilot is not engaged

When triggered, MCAS commands nose down stabilizer as a function of how much AOA has exceeded the activation threshold and the current Mach number. For large exceedence of the MCAS activation AOA threshold, MCAS will command 2.5 degrees of stabilizer at low Mach number but less than 1/3rd of that at cruise Mach number (gradual Mach number based schedule between). For a lesser exceedence of the MCAS activation AOA threshold the size of the stabilizer increment will be proportionally less. MCAS stabilizer command will be stopped immediately upon pilot activation of pitch trim. (Pilot trim input also serves as MCAS reset - see next paragraph.)

Once MCAS has commanded one increment of stabilizer motion, it will not command more until it has been reset. MCAS is reset if any of the following occur:
1. Pilot makes a manual trim command. (MCAS will not re-activate until there have been 5 continuous seconds without pilot trim command.)
2. AOA drops below MCAS activation threshold and MCAS has run stabilizer in the airplane nose up direction taking out the increment of airplane nose down command it inserted earlier.
3. Autopilot is engaged and then disengaged.

Without pilot trim input, MCAS will not run the stab more than one increment (up to 2.5 degrees) unless MCAS is reset via either 2 or 3 above.

Talk of MCAS running the stabilizer for 10 seconds, pausing for 5 seconds, and then running it again repeatedly without pilot trim input are patently incorrect.

[United744]

I would have been surprised if such a system existed.

I was very surprised at the very specific suggestion due to the apparently shifted CoG due to the engines being further forward than normal.

Using an aerodynamic approach rather than adding ballast was at the very least intriguing.

I was also considering the fact that both accidents occurred shortly after takeoff, where configuration changes involving the slats seems reasonable, changing AoA and possibly upsetting the MCAS.

[Hardy Heinlin]

I was very surprised at the very specific suggestion due to the apparently shifted CoG due to the engines being further forward than normal.

My understanding is that there is no CG shift on the 737 MAX even though these big pods sit more forward. I rather think the pitch momentum is greater because the engines are higher. The "pendulum" is shorter.

Imagine a clock with a pendulum that is 2 feet long.

Move its lower tip sideways by 1 inch. The pendulum will turn by an angle of one degree or so.

Imagine a clock with a pendulum that is 1 inch long.

Move its lower tip sideways by 1 inch. The pendulum will turn by more than 30 degrees.

The shorter the pendulum arm, the greater the rotation when the tip is moved sideways by 1 inch.

The motion sideways in this illustration is analog to the thrust vector. The pendulum length is analog to the distance between wing and engine. And the pendulum angle is analog to the aircraft pitch momentum.

The engines sit higher, the pendulum is shorter, the effect of a thrust increase on the nose-up momentum is greater. So the stab-trim-nose-down feature will compensate it.

If the aircraft was nose heavy, why should MCAS make it even more nose heavy?

[tango4]

I might be wrong here because I do not have all the necessary knowledge, but here is what I understood from various articles about the Indonesia accident.
In order to fit these new big engines on the 737, which was never designed for those, they had indeed to move them to a rather awkward position... Which moved, the CG, but also the center of thrust.
I read a few topics here about the speed trim system on the 747. Actually, if I am correct, the 737NG also has a speed trim system, to correct minor deficiencies of the aerodynamics of the aircraft, as for the 747 and this is not a problem. MCAS is something different (although the MCAS acronym might include the speed trim functions on the MAX, I don't know that for sure).
From what I got, the MCAS system is there because they feared that if the pilot found itself at high AOA, and suddenly increased thrust to get out of this situation, the forward center of thrust could generate of big nose up momentum which would in turn amplify the high AOA situation. MCAS was supposed to alleviate this.
I feel Boeing was a bit on the edge here as it looks like an economic decision. After deciding not to launch a replacement to the 737, Airbus announced the NEO which sold very well. So Boeing was a bit forced to react and launched the MAX. Unfortunately, the 737 is despite all its qualities an old design, and it feels they found themselves with a problem rather difficult to solve, and did it the quick and dirty way.
This is just my personal understanding of it. I am by no means an Airbus fanboy.


Charles