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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

Old 17th Apr 2019, 20:22
  #681 (permalink)  
 
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Originally Posted by ATC Watcher View Post
I have read somewhere that there were only a handful ( even on one hand ) of MAX sims in the world, more will be delivered later this year but not enough to train everyone in a short time right after the "fix " is released. .Or will the training be possible on a normal NG sim ?
If they want to train the non normal (AoA duff) case, I guess the Max sims will be doing good business. Unless they put out a switchable mod for the NG sim...
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Old 17th Apr 2019, 20:32
  #682 (permalink)  
 
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While everyone is focused on addressing the problems with MCAS, I'm not sure enough attention is being given to the fact that there are other significant differences with the MAX and other unique failure modes that would best be demonstrated in a sim.
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Old 17th Apr 2019, 21:16
  #683 (permalink)  
 
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The major problem that the 'train in the simulator' group will face is that the failure mode of the Lion Air and Ethiopia crashes no longer exists. If a single AOA vane fails it will not cause MCAS to operate. If MCAS operates it will be for a legitimate high AOA and it will only operate once not repeatedly. So there is no failure mode that can exist with the new software where MCAS will operate as it did before. I would imagine that 737 pilots would be able to cope with a single nose down trim when they are legitimately at high AOA as it will keep the stick back pressure linear. Once the aircraft returns to normal AOA everything is back to normal.

So everyone goes out and buys new simulators to find that there is no MCAS failure mode to simulate. Simulator salesmen will like it - the beancounters not so much - the regulators will be holding the stable door firmly shut despite there being no horse
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Old 17th Apr 2019, 21:49
  #684 (permalink)  
 
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airlines can maintain lists of which pilots have had MAX sim training, and roster accordingly to MAX and other 737. Not a separate type rating but a bit of a nightmare though..... Although presumably there must have been a tracking system of who had/had not completed ipad MAX training before they flew a MAX?

G
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Old 17th Apr 2019, 22:13
  #685 (permalink)  
 
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Originally Posted by Ian W View Post
The major problem that the 'train in the simulator' group will face is that the failure mode of the Lion Air and Ethiopia crashes no longer exists. If a single AOA vane fails it will not cause MCAS to operate. If MCAS operates it will be for a legitimate high AOA and it will only operate once not repeatedly. So there is no failure mode that can exist with the new software where MCAS will operate as it did before. I would imagine that 737 pilots would be able to cope with a single nose down trim when they are legitimately at high AOA as it will keep the stick back pressure linear. Once the aircraft returns to normal AOA everything is back to normal.

So everyone goes out and buys new simulators to find that there is no MCAS failure mode to simulate. Simulator salesmen will like it - the beancounters not so much - the regulators will be holding the stable door firmly shut despite there being no horse
The root cause problem has not been eliminated, the hope is that it has been made less likely. We do not know why three sensors so far have failed at least Boeing is not telling us. We cannot assume that the failures are random and independent. If for example some console maintenance procedure happens to offset the AOA sensor by exactly twenty degrees then Murphy’s law dictates that at some time that procedure will be performed on both left and right consoles and you will still get a bogus high AoA that both sensors will agree upon.
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Old 17th Apr 2019, 22:18
  #686 (permalink)  
 
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it is shocking to read (or not to read) that nobody insists on improved AOA sensors.
Those "vane" sensors became obsolete somewhere in the late 70's.

The arrival of pressure AOA sensors was one of the "major improvements" that came when the F-16 replaced the F-104.
Again, this was in late 70's.

And how many accidents with how many lives have these obsolete vane style sensors cost us since then?
I am deeply saddened that nobody INSISTS on better and fool proof sensors.

Cdt Tony Vilters
Belgian Air Force
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Old 17th Apr 2019, 22:32
  #687 (permalink)  
 
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Originally Posted by Ian W View Post
(...) If MCAS operates it will be for a legitimate high AOA and it will only operate once not repeatedly.
Dual AOA failure may still trigger MCAS, depending on the failure scenario. And we've seen dual AOA failures (both failing the same way) on real flights several times already.

Having said that, assuming MCAS will only operate once, then IMHO it's no worse than a runaway stab trim. So I don't believe additional sim training will be made mandatory, unless the current runaway stab trim training is also deemed not sufficient (presumably covering both NG and MAX types).
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Old 18th Apr 2019, 00:00
  #688 (permalink)  
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Vilters, If I had to stab an an answer, it would be that the vane is a better instrument, in all that means in science. The output is infinitely variable, and, at least until it reaches an analogue to digital black box, fairly hard to corrupt. Okay, so why the more modern detection?

It would probably have a lot to do with the bearings and cogs technology being unsuitable for frequent high g forces. Once we get into the realms of 9 g, gut feeling is, it becomes an entirely unsuitable mechanism.
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Old 18th Apr 2019, 00:13
  #689 (permalink)  
 
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Also for fighters with probe and drogue refueling (eg F/A18) the basket can catch and rip out a blade/vane AoA sensor - less likely with a pressure sensor.
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Old 18th Apr 2019, 00:49
  #690 (permalink)  
 
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Originally Posted by Vilters View Post
it is shocking to read (or not to read) that nobody insists on improved AOA sensors.
Those "vane" sensors became obsolete somewhere in the late 70's.

The arrival of pressure AOA sensors was one of the "major improvements" that came when the F-16 replaced the F-104.
Again, this was in late 70's.

And how many accidents with how many lives have these obsolete vane style sensors cost us since then?
I am deeply saddened that nobody INSISTS on better and fool proof sensors.

Cdt Tony Vilters
Belgian Air Force
Retired
Any sensor -can- have issues, the B2 that crashed on takeoff in Guam was brought down by multiple failing pressure sensors with a common failure mode combined with a dose of human error/oversights.

What would be a significant improvement is to use multiple technologies such as vanes and pressure sensors, to provide better true redundancy.

That should apply to air speed as well, as was discussed (at great length!) in the AF477 thread(s) there are alternatives to pitot air speed sensors.

.
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Old 18th Apr 2019, 02:01
  #691 (permalink)  
 
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A video update on the new software from Boeing CEO Dennis Muilenburg:

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Old 18th Apr 2019, 08:19
  #692 (permalink)  
 
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Originally Posted by Vilters View Post
I don't understand why they keep using these "obsolete" AOA vane sensors with so many alternatives available.
As I wrote from the start; You can NOT fix a HARDWARE issue with a SOFTWARE update.

There are so many other AOA sensors systems available. => Drop those stupid 1950-1960 era vanes.
Ey dude, wake up, it‘s 2019 out there, YOU CAN FIX ANYTHING WITH SOFTWARE...
especialy when your competitor is flooding the market with a good new product and you got nothing in comparison.

And concerning AOA sensors, we are talking about 737, everything must be cheap as sh..., you cant rip off taxpayers like on a military program.

This is really a Frankenstein A/C, built in a hurry with a lot of old dead rotting parts mixed with some new stuff that would not fit but was bound together with questionable software.

And there is more to come, let’s wait for the first Landing Attitude Modifier screw ups...
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Old 18th Apr 2019, 11:51
  #693 (permalink)  
 
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Originally Posted by Loose rivets View Post
Vilters, If I had to stab an an answer, it would be that the vane is a better instrument, in all that means in science. The output is infinitely variable, and, at least until it reaches an analogue to digital black box, fairly hard to corrupt. Okay, so why the more modern detection?

It would probably have a lot to do with the bearings and cogs technology being unsuitable for frequent high g forces. Once we get into the realms of 9 g, gut feeling is, it becomes an entirely unsuitable mechanism.
OK, here we go.
AOA sensors with a vane can be bend, touched by ground equipment, torn off by birdstrikes or other FOD, freeze due to the vane sticking to the fuselage (very little space between vane and fuselage), and so on.

Pressure AOA probes don't have any of these issues.
We are 2019, and even the (in late 70's new F-15 / F-16) are becoming obsolete FAST.
Does the F-22 or F-35 have any of these? No they don't any more and they need a far more accurate AOA input then commercial airframes.

How many more funerals before we replace these 50 year old technology vane AOA sensors in our 2019 airplanes?
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Old 18th Apr 2019, 14:55
  #694 (permalink)  
 
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From The Wall Street Journal:

United States-Canada Rift Widens Over Training for Boeing 737 MAX Pilots: Canadian official calls for simulator training for pilots flying the jet; Federal Aviation Administration decided against mandating such instruction

The Wall Street Journal
By Kim Mackrael and Andy Pasztor
April 18, 2019 5:30 a.m. ET

A rift between the U.S. and Canada is growing over how to ensure the safety of Boeing Co.’s grounded 737 MAX planes, as Ottawa’s focus on additional pilot training could lead to a delay in getting the jet back in the air.

Canada’s transport minister has signaled that his government could require additional simulator training for pilots of the 737 MAX. That threatens to widen the gap between plans being developed by U.S. authorities to put the planes into service and those of other countries, according to industry officials and others participating in or tracking the process.

“Simulators are the very best way from a training point of view to go over exactly what could happen in a real way and to react properly to it,” Canadian Transport Minister Marc Garneau said Wednesday. “It’s not going to be a question of pulling out an iPad and spending an hour on it.”

The U.S. Federal Aviation Administration has tentatively decided against mandating additional simulator instruction as part of a package that is anticipated within weeks and includes a software fix for a flight-control system implicated in two fatal 737 MAX crashes in less than five months. Industry officials said that could change based on input from foreign regulators, as well as responses from domestic pilot unions and other groups during a public comment period ending April 30.

Aviation regulators in Canada, Europe, China and Brazil previously indicated they would conduct their own safety reviews of the software fix to the automated flight-control system—known as MCAS—instead of accepting the FAA’s analysis and decision to require only interactive and self-instructional training on laptops or other electronic devices.

However, Mr. Garneau’s remarks are the first explicit break with the U.S. by a foreign regulator and could mean months of additional delays in other countries while extra simulator time is reserved and new training scenarios are developed.

A spokeswoman for Mr. Garneau said no formal decision has been made about requiring simulator training. She said Mr. Garneau would wait to see what Boeing says and speak with experts before making a final decision.

An FAA spokesman didn’t have any comment. Previously, agency officials have said they welcome recommendations from foreign regulators but stressed that the U.S. will act independently based on its review of data and safety considerations.

A Boeing spokesman said the plane maker is working with global regulators and airlines “as they determine training requirements in their home markets.”

European regulators previously signaled it could take months for them to assess the FAA’s software fix and training requirements, according to industry and government officials on both sides of the Atlantic Ocean.

The situation marks a sharp departure from tradition—stretching back many decades—when major safety decisions from the FAA affecting American-built aircraft tended to be routinely embraced by foreign counterparts. Trust and cooperation have frayed following the 737 MAX groundings, which have roiled the global aerospace industry.

The FAA has set up a high-level international advisory panel, which includes Canadian representatives, to analyze the software fix and related training issues. FAA officials hope such strategies will help shore up international support among regulators and passengers. Brazilian and European regulators previously raised questions about certain MAX flight-control features during the initial FAA certification of the plane.

Canada has required additional training for domestic airlines in the past. After a Lion Air jet crashed off the coast of Indonesia last year, pilots with Canadian airlines that operate the Boeing 737 MAX 8 and 9 aircraft received training that Mr. Garneau has said went beyond what was mandated in the U.S.

The FAA’s preliminary training decision also has been shelved by one large U.S. carrier, American Airlines Group Inc. which is devising its own additional simulator sessions focusing on maneuvers similar to those that resulted from the misfiring of the suspect flight-control feature. Ground simulators specifically designed to mimic the 737 MAX won’t become widely available until autumn or later.

Chicago-based Boeing has been devising a software fix for the jet’s flight-control system that is expected to rely on two sensors that measure the angle of the plane’s nose—instead of one currently—and be less aggressive and more easily controllable by pilots.

The FAA originally approved the MAX by requiring minimal additional training for pilots who were transitioning from flying earlier 737 models. In developing the new model, Boeing aimed to keep additional training requirements at a minimum so pilots and airlines could avoid expensive simulator time.

United Continental Holdings Inc., one of three MAX operators in the U.S., said it had no plans to add simulator training unless federal authorities required it. Chief Operating Officer Greg Hart said Wednesday during an earnings conference call that even without specific training on the MAX’s stall-prevention system, United pilots already receive training on the type of situation pilots faced on both the Lion Air flight and the Ethiopian Airlines flight which crashed last month.
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Old 18th Apr 2019, 16:13
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Simulator training

Besides the procedures for recognizing and handling an AoA disagree/failed MCAS, will any emphasis be placed on the need for the flight crew to handle the 737X's unique stall characteristics? It is my understanding that this is why MCAS was invented in the first place. And once it is inop, pilots will be responsible for keeping the aircraft out of the stall regions of the performance envelope.

Asking as an SLF/engineer.
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Old 18th Apr 2019, 17:51
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The FAAs position on simulator training could be justified if based on the re-run Flight Ops review (was this the same team which overlooked MCAS first time round?).

However, if alternative views on training requirements for the 737 Max reconsider what is known, what has been learnt from these accidents, then simulation must be considered, even mandated. In particular for the recognition and timely action for trim runaway (trim moves, is this normal STS, or normal MCAS, or failed trim - 5 sec observation to differentiate). MCAS adds a further dimension to the evaluation process; a longer time period for recognition could generate more out of trim before its inhibited. Also the relevance of speed management - trim forces, requires hands on training.

Probably the most important aspect is to appreciate the feel of a mis-trimmed aircraft, switch selection, and the difficulty with manual (wheel) trim operation, particularly if starting with larger out of trim conditions. Also practicing the procedure required to regain control (Boeing advice on "aerodynamically relieving airloads" using manual stabilizer trim); is this really the same as in previous aircraft? Is it acceptable now?

MCAS is required to meet certification requirements, but the need for that reflects a difference between NG and Max, which is not necessarily adjusted through out the flight envelope (where MCAS is not programmed to operate). Is the Max the same, or just good enough to be called the same; what pilot compensation is assumed in this.
A further thought is if the Max pitch characteristics change the nose-up trim runaway case. Does the engine/ nacelle nose-up pitching moment aid nose up failures? Also, there has been little said about the engine/nacelle affecting downwash.

If the Canadian position reflects these aspects, then perhaps other certification authorities will ask similar questions relating to the overall safety case, not just that relevant to MCAS mods.
What were the Flight Ops review terms or reference?
Who will review the overall safety scene for the Max based on the findings of the accident investigations, and when.
What was the initiating factor in these accidents; vane, vane output, software conversation / corruption; a random effect, Murphy, Sod, or calculable probability?

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Old 18th Apr 2019, 20:16
  #697 (permalink)  
 
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Originally Posted by Vilters View Post
OK, here we go.
AOA sensors with a vane can be bend, touched by ground equipment, torn off by birdstrikes or other FOD, freeze due to the vane sticking to the fuselage (very little space between vane and fuselage), and so on.

Pressure AOA probes don't have any of these issues.
We are 2019, and even the (in late 70's new F-15 / F-16) are becoming obsolete FAST.
Does the F-22 or F-35 have any of these? No they don't any more and they need a far more accurate AOA input then commercial airframes.
A cobra probe (for example: the Rosemont/Goodrich/UTC/Collins/whoever-they-are-this-week Smartprobe, see page 11: https://www.faa.gov/air_traffic/sepa...n_for_RVSM.pdf) is also vulnerable to damage from GSE, birdstrike, and FOD. It can still fail due to either freezing external moisture or trapped internal liquid, and some of those failure conditions can be latent and undetectable until the aircraft changes altitude, and your AOA starts behaving as an altimeter.

As noted, this is not a new technology. Here's Rosemont trying to sell them in 1986: https://www.flightglobal.com/FlightP...20-%202855.PDFBut it does come with it's own set of failure conditions which also need to be assessed. For example, a B-2 bomber equipped with a completely flush-mounted air data system crashed and was destroyed due to water trapped in the static system - so eliminating excrescences like Pitot tubes and AOA vanes is not a panacea for faulty air data.

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Old 18th Apr 2019, 22:37
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Originally Posted by safetypee View Post

Probably the most important aspect is to appreciate the feel of a mis-trimmed aircraft
Is this really something that needs to be trained in qualified 737 pilots? And the most important aspect too?
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Old 18th Apr 2019, 23:46
  #699 (permalink)  
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Very interesting links, thank you both.

Given that it's Rosemont that's still involved, and that the vane is substantially mechanical, I conclude that the vane is the more expensive to produce. ergo, they wouldn't fit them if they weren't the best measuring instrument.

The errors in one of those new tec links left me taken-aback. And more, it left me thinking, 'how would I do it?' Not like that, that's for sure.

It's always been how I think. I was squirting water onto plate glass in my hobby shop, when one of my kids shouted, hey, Dad, look what's on tomorrow's world. Sure enough, a prototype rain detector - which didn't work as well as mine - which wasn't very good.

It is notoriously difficult to measure air molecules. Air after all, contains water, and in differing forms. Looking at those varied droplets I found very, very hard back then. That good old vane would follow a hail of 5mm droplets with ease. And come to that, real hail - all without coming asunder.

It's a bit of kit that's stuck around, not because it's cheap, but because it's a good measuring device.
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Old 19th Apr 2019, 05:31
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Here is another you tube video on the 737 NG. It is scary.


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