Ethiopian Airlines Crash/ B737MAX grounding

Jeff2 · 30-03-2019 03:00AM

Hotblack Desiato wrote: »

It's not to do with engine thrust.

You could say that any modern engine 'pulls from the front' as the fan will generate most of the thrust.

Rarther than the after burn from the back.?

billy few mates · 30-03-2019 06:10AM

Jeff2 wrote: »

Rarther than the after burn from the back.?

Yes

smurfjed · 30-03-2019 06:44AM

Measure the difference in pressure between the two holes and you have your angle

can you explain this again in greater detail?

smurfjed · 30-03-2019 06:46AM

In the US I’m sure you can sue anyone but wonder about elsewhere.

I understand that the families of the disappeared Malaysian aircraft are presently trying to sue in the USA and the courts rejected their case due to jurisdiction, however in this case due to the very transparent blame on Boeing, I doubt that a court could reject such a case.

Gaoth Laidir · 30-03-2019 08:45AM

PCros wrote: »

It typically adds $800,000 to $2M to the price of an aircraft.

It was $80,000.

billy few mates · 30-03-2019 08:53AM

smurfjed wrote: »

Generally during negotiations, each manufacturer will offer various OPTIONS, these can be simple like HF radio.
If BOEING didn’t explain the MCAS to flightcrew then I seriously doubt that their sales team explained it or the implications of not having it.
However this shouldn’t allow Boeing to pass the blame to individual airlines. They seriously fecked up with this system from the design, certification and implementation.
Having lost a colleague in Ethiopia, I seriously hope that his family take them to the cleaners !

Normally flight operations will spec the level of technology they require to be installed for their particular operation but the cost of having any of these features will vary from customer to customer and will be a closely guarded commercial secret.
There's a minimum equipment fit every aircraft must have but if you're prepared to pay the price you can pretty much have any amount of additional equipment you want and the manufacturer will make it happen.
Large customers like major airlines would have more buying power and leverage and more might end up paying very little for certain additional extras, particularly if it were a case that their flight operations department insisted on these features and there was a chance a rival manufacturer might be able to provide it for free.
Leasing companies would also have similar buying power but might not over-spec the aircraft because some of the operators who might lease those aircraft might not want these additional features so would not be prepared to pay extra for them.
Some operators may have turned down this option for commonality rather than cost, ie to keep it as similar as possible to other aircraft in the fleet that don't have it. Six months ago it would have been viewed as a 'nice to have' not a 'need to have' feature...

Widdensushi · 30-03-2019 09:28AM

Gaoth Laidir wrote: »

It was $80,000.

That even seems high for something that just tells you a sensor is not working correctly or have I misunderstood what this is ?

smurfjed · 30-03-2019 09:32AM

That even seems high

welcome to aviation.

lintdrummer · 30-03-2019 09:46AM

Jeff2 wrote: »

From what I read the new bigger engines pulled from the front rather than pushed from the back of the engine.
Different engine design.
That would mean with engines that were moved forward and could have more of a push up than the last ones.

That is why this system of MCAS was in place.

That's not accurate really. Older jets (1950's '60's) had pure turbojet engines in which all of the air sucked in the front went through the core of the engine, through the combustion chamber and the hot gas blown out the exhaust provided all the thrust.
Low bypass engines were then developed in which c. 20% of the intake air was blown through a duct on the outside of the engine, never going through the combustion chamber.
What we have now are called High Bypass Turbofans. These days more than 80% of the air sucked in the front is blown straight out the back. The core of the engine only serves to power the big fan at the front that produces most of the thrust.
Look at it this way: in old jet engines, relatively small quantities of air were pushed backwards at relatively high velocities. These days relatively large quantities of air are pushed backwards at relatively slow speeds but the net effect is the same in terms of thrust produced. It's more efficient and it's quieter.
That's why the new generation of engines are getting bigger. The bigger you can make the fan (and thus increase the bypass ratio) the more efficient the engine is.
In the case of the Max, it's not that the engine produced thrust in a different way, it's that the bigger size necessitated moving the engine further forward and up because ground clearance became a problem. This changed the fundamental relationship between the centre of thrust and the centre of gravity. All forces acting on an aeroplane act around the C of G. Moving the point where the thrust is coming from has a big effect on the stability of the aircraft. The further forward the thrust moment is from the centre of gravity, the more nose up movement you get as you apply thrust. Think of it as a lever, the longer the lever, the greater the force.
That's why MCAS is necessary, if you were in a fairly high AOA already and you apply a gob of thrust, the nose is going to rise even higher and put you into potential stall territory.
I've also heard that the engine nacelles on the Max were generating a bit of lift themselves, compounding the issue, but I haven't seen that verified anywhere.

Bob24 · 30-03-2019 11:11AM

Widdensushi wrote: »

That even seems high for something that just tells you a sensor is not working correctly or have I misunderstood what this is ?

Yes - My view is that optionally charging for a malfunction indicator is not acceptable no matter the price. Even 1 Euro would be too high.

Don’t get me wrong, Boeing can charge whatever they want for their aircrafts. They could have included it in the base price and increased it accordingly, or told customers that it is charged separately but a mandatory purchase. The issue for me is not how much it costa, but rather to make a malfunction indicator optional for marketing reasons and then to in a way blackmail airlines letting them decide if they wan to pay for a safety feature (which has now been proven to be potentially life saving).

billy few mates · 30-03-2019 11:32AM

Bob24 wrote: »

Yes - My view is that optionally charging for a malfunction indicator is not acceptable no matter the price. Even 1 Euro would be too high.

Don’t get me wrong, Boeing can charge whatever they want for their aircrafts. They could have included it in the base price and increased it accordingly, or told customers that it is charged separately but a mandatory purchase. The issue for me is not how much it costa, but rather to make a malfunction indicator optional for marketing reasons and then to in a way blackmail airlines letting them decide if they wan to pay for a safety feature (which has now been proven to be potentially life saving).

Yes but remember up until these incidents it was considered nothing more than a 'nice to have'. With hindsight it absolutely should have been mandatory as should the dual AOA sensor input and comparison warning system but you can be pretty sure it will be a FOC SB when it's issued.

Hotblack Desiato · 30-03-2019 11:34AM

lintdrummer wrote: »

The further forward the thrust moment is from the centre of gravity, the more nose up movement you get as you apply thrust. Think of it as a lever, the longer the lever, the greater the force.

You'll get a pitch-up tendency on pretty much any low-wing aircraft with underwing engines, I would think? I've not heard anything anywhere about MCAS having any relationship to throttle position.

I've also heard that the engine nacelles on the Max were generating a bit of lift themselves, compounding the issue, but I haven't seen that verified anywhere.

http://www.b737.org.uk/mcas.htm

MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift of the LEAP-1B engine nacelles and give a steady increase in stick force as AoA increases. The LEAP engines are both larger and relocated slightly up and forward from the previous NG CFM56-7 engines to accommodate their larger fan diameter. This new location and size of the nacelle cause the vortex flow off the nacelle body to produce lift at high AoA; as the nacelle is ahead of the CofG this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to further increase the back pressure on the yoke and send the aircraft closer towards the stall. This non-linear/reducing stick force is not allowable under FAR §25.173 "Static longitudinal stability". MCAS was therefore introduced to give an automatic nose down stabilizer input during steep turns with elevated load factors (high AoA) and during flaps up flight at airspeeds approaching stall.

STB. · 30-03-2019 11:43AM

billy few mates wrote: »

Yes but remember up until these incidents it was considered nothing more than a 'nice to have'. With hindsight it absolutely should have been mandatory as should the dual AOA sensor input and comparison warning system but you can be pretty sure it will be a FOC SB when it's issued.

Of course it should have been mandatory. As should have training.

The whole reason MCAS was put in, was because of the new design and weight placement of the large engines, and to avoid having to certify and train for a new type jet and sell it as much the same as what you have already been trained on.

Pilots had 40 seconds, by all accounts, to avert total nosedive and loss of control by something not tied back to the console display, that could be isolated. I hope Boeing and the FAA are taken for every penny they have.

Safety was clearly second to sales and profits.

Bob24 · 30-03-2019 11:50AM

billy few mates wrote: »

Yes but remember up until these incidents it was considered nothing more than a 'nice to have'. With hindsight it absolutely should have been mandatory as should the dual AOA sensor input and comparison warning system but you can be pretty sure it will be a FOC SB when it's issued.

Maybe nice to have for the general public who had no idea about it yes.

But for the Boeing engineers who worked on this and knew the alert was reporting the malfunction of a device driving a system which could aggressively change the trajectory of the airplane?

I mean if Boeing marketed it as a nice to have extra shiny dashboard in the the cockpit with no real safety implication - there is a serious lack of professionalism/expertise they need to answer for. And if they marketed it as a optional safety feature, then they need to explain how they came to think safety could come as an option. Doesn’t look good for them either way.

STB. · 30-03-2019 11:59AM

Bob24 wrote: »

But for the Boeing engineers who worked on this and knew the alert was reporting the malfunction of a device driving a system which could aggressively change the trajectory of the airplane?

More so Bob, did they actually test the system with incorrect data to see how it would react ?

According to reports in the media, the system deployed, that pilots apparently didn't need to know about, took control of the plane and reset itself and repeatedly took further action, every time the pilot took reactionary evasive action, until that snowballed to a situation that couldn't be corrected until you were buried in the ground

odyssey06 · 30-03-2019 01:00PM

Damien360 wrote: »

When manufacturers produce a manual for any airplane, particularly a new version, do they produce it in many languages other than English. I remember a pilot in here say that although English is the language of the skies, many non-english speaking pilots just know aircraft speak and couldn't order a pint.

The reason I ask, is the flight just before the doomed Ethiopian airlines one, a off duty pilot knew to disable the MCAS system and save the flight. Was this done due to his/her ability to actually read and understand the manual. What was their first language ?

I thought I read somewhere it wasnt explained in the flight manual carried on board. But could be wrong on that.

Damien360 · 30-03-2019 01:03PM

odyssey06 wrote: »

I thought I read somewhere it wasnt explained in the flight manual carried on board. But could be wrong on that.

But an off duty pilot on flight knew about it and was able to prevent disaster on a previous flight. This is why I asked, what was his first language. Is it a translation issue in part ?

odyssey06 · 30-03-2019 01:37PM

Damien360 wrote: »

But an off duty pilot on flight knew about it and was able to prevent disaster on a previous flight. This is why I asked, what was his first language. Is it a translation issue in part ?

I dont know how he knew but it wasnt from the flight manual based on this ...single reference in list of abbreviations.
https://www.google.com/amp/s/www.cbc.ca/amp/1.5065842

Boeing issued a safety bulletin after first crash so if that was issued in english that could be a factor in why second crew were unaware.

lintdrummer · 30-03-2019 02:45PM

Hotblack Desiato wrote: »

You'll get a pitch-up tendency on pretty much any low-wing aircraft with underwing engines, I would think? I've not heard anything anywhere about MCAS having any relationship to throttle position.

You misunderstood me there I think, I'm talking about the law of the lever, as in leverage. It has nothing to do with throttle position, just that if you increase thrust on a Max, the pitch up effect would be more pronounced than in a 737NG or Classic because of the forward position of the engines.

Hotblack Desiato wrote: »

http://www.b737.org.uk/mcas.htm

Thanks, that confirms it so.

lintdrummer · 30-03-2019 02:50PM

Damien360 wrote: »

But an off duty pilot on flight knew about it and was able to prevent disaster on a previous flight. This is why I asked, what was his first language. Is it a translation issue in part ?

I think the off duty pilot was a stroke of luck for that crew, not because of his language skills but because of where he was sitting. He would have been behind and in the middle of the two operating pilots, looking directly at the throttle quadrant and so it would have been very obvious to him that the trim wheel was spinning away while the other two pilots were likely distracted by the stick shaker and the unreliable airspeed.

Man Vs ManUre · 30-03-2019 03:12PM

lintdrummer wrote: »

I think the off duty pilot was a stroke of luck for that crew, not because of his language skills but because of where he was sitting. He would have been behind and in the middle of the two operating pilots, looking directly at the throttle quadrant and so it would have been very obvious to him that the trim wheel was spinning away while the other two pilots were likely distracted by the stick shaker and the unreliable airspeed.

Was it the very next take-off of that Lion air plane that crashed?? Why would there not have been some form of communication/handover that this serious malfunction had happened?? Especially if it was rare and lucky that a 3rd person would be sitting in the cockpit and was that person who resolved it.

billy few mates · 30-03-2019 03:30PM

Damien360 wrote: »

But an off duty pilot on flight knew about it and was able to prevent disaster on a previous flight. This is why I asked, what was his first language. Is it a translation issue in part ?

It's quite possible he mis-identified the MCAS operation of the stab trim as stabiliser runaway.
This is a memory item rather than a QRH checklist item, the response to to a runaway stab is to turn off the power to the two stab trim servos using the override switches on the P3 centre pedestal. Sitting in the jump seat these two switches would be directly in front of you.
They may have been extremely lucky because even if you never heard of MCAS the response to a runaway stab would also have the effect of cancelling the MCAS input.

https://www.theairlinepilots.com/forumarchive/b737/b737memoryitems.php

Brennus335 · 30-03-2019 04:55PM

smurfjed wrote: »

can you explain this again in greater detail?

Have to say I've never heard of this either. Hasn't been a feature of any of the 7 commercial types I've flown.

The only thing I could find with a Google search was a NASA document from 1958.
The link I've tried to paste doesn't work. It's direct to a downloadable PDF.

Brennus335 · 30-03-2019 05:07PM

Widdensushi wrote: »

That even seems high for something that just tells you a sensor is not working correctly or have I misunderstood what this is ?

You have to remember this is an industry where a wiper blade costs $5,000, a cockpit 8" LCD screen costs $40,000, and a pilots seat $90,000.

Aviation is an expensive business. The general public seems to be oblivious to this when they demand €20 return to Costa del Skobie for their holidays

Hotblack Desiato · 30-03-2019 06:49PM

lintdrummer wrote: »

You misunderstood me there I think, I'm talking about the law of the lever, as in leverage. It has nothing to do with throttle position, just that if you increase thrust on a Max, the pitch up effect would be more pronounced than in a 737NG or Classic because of the forward position of the engines.

Forward position of the engines affects lift, not thrust.

Thanks, that confirms it so.

Confirms that it's not to do with pitch-up on applying power. Just that a high angle of attack (even on a steady power setting) causes the MAX nacelles to produce lift - because they are ahead of the wing this moves the centre of lift forwards - causing a pitch-up tendency.

The MAX is unusual because the nacelles are pretty much level with the top of the wing. The airflow over the nacelle goes directly over the upper surface of the wing, so has a big influence on lift.

lintdrummer · 30-03-2019 07:50PM

Hotblack Desiato wrote: »

Forward position of the engines affects lift, not thrust.

Again, you're misunderstanding what I'm saying. It doesn't affect thrust, it affects the thrust moment. It has nothing to do with lift.

Hotblack Desiato wrote: »

Confirms that it's not to do with pitch-up on applying power.

When I said "that confirms it", I meant that what I had heard about the nacelles generating lift was true. I agree with you!

But there is also a more pronounced pitch up moment when power is applied than in previous 737 generations, due to the aforementioned thrust moment change.

Hotblack Desiato · 30-03-2019 08:04PM

lintdrummer wrote: »

Again, you're misunderstanding what I'm saying. It doesn't affect thrust, it affects the thrust moment. It has nothing to do with lift.

Is the thrust centreline on a MAX that different from an NG though? The top of the MAX nacelle is higher, but the fan is larger, the engine axis relatively lower, so the thrust centreline might not be very different.

When I said "that confirms it", I meant that what I had heard about the nacelles generating lift was true. I agree with you!

OK, I misread that

But there is also a more pronounced pitch up moment when power is applied than in previous 737 generations, due to the aforementioned thrust moment change.

I've not seen any reference for adverse pitch-up on power application on the MAX compared to the NG, if you have one please share.

lintdrummer · 30-03-2019 08:57PM

You know I'm sure I read it somewhere just after the Ethiopian crash in all the analysis but I can't find a reference to it...

I suppose it depends on whether the movement of the engine was totally offset by the larger diameter, the impression I got was that it wasn't and that the thrust moment had changed. I could be totally making that up though :eek:

jimmycrackcorm · 31-03-2019 12:38AM

Brennus335 wrote:

You have to remember this is an industry where a wiper blade costs $5,000, a cockpit 8" LCD screen costs $40,000, and a pilots seat $90,000.

Brennus335 wrote:

Aviation is an expensive business. The general public seems to be oblivious to this when they demand â‚¬20 return to Costa del Skobie for their holidays

Perhaps it's time the general public asked why a seat costs 90k out the same screen on an android tablet is a fraction of the price.

I work in IT and I remember a former boss taking me a story about an IBM mainframe that his company paid to upgrade in the early 80's to double the processing speed. They paid IBM $4.5m dollars. IBM sent out an engineer who just soldered two wires together. Hey presto, speed doubled.

smurfjed · 31-03-2019 05:58AM

android tablet is a fraction of the price.

The research and development costs for a Samsung screen are recouped through millions of device sales. The R&D costs for a device that needs to meet the regulatory requirements for installation in an aircraft can only be recouped through somewhat limited sales and that needs to be combined with the insurance costs associated with such a device. So you really aren't comparing apples with apples

Ethiopian Airlines Crash/ B737MAX grounding

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