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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 22nd Mar 2019, 06:20
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Originally Posted by BrandonSoMD
Well, for most pilots in a commercial setting, AOA by itself means nothing.

For a military or airshow pilot who maneuvers to rather excessive AOAs regularly, or uses AOA as a primary reference for carrier landing, it makes a lot of sense to show some flavor of AOA. For example, nearly all Navy carrier aircraft are standardized to show something like15 units AOA in a properly configured approach, and something around 30 units AOA at stall. But there is no consistent units-to-degrees mapping, because the pilot doesn't care about absolutes; he just wants to know how close he is to some practical limit.

But for commercial pilots, AOA is relatively meaningless. In fact, it generally introduces needless concerns. What AOA is correct in a given setting: that's hugely dependent on a ton of factors. Which one (left or right) are you showing? How soon during takeoff roll should they come alive; with zero airspeed they can be at crazy values without any concern. They can be slightly different for various valid aerodynamic reasons (sideslip or roll rate). The only time you really care about AOA is when the two (or three or whatever) sensors dramatically disagree, or when they remain at excessive (very low or very high) values when they should not. That's all fairly easy to automatically check, if the FMC is programmed to do so.

WHY the FMC wasn't programmed to do so is a useful discussion. But showing the AOA to most pilots won't make things any better or safer. Principle #1 of human interface: only show what is important.
Well, for most pilots, and in a normal flying mode you are correct. But we are talking about when somethings going haywire.When you are not sure what the aircraft is doing, you might not be sure if you actually are stalling, you might not be sure about your airspeed. And we could go one step further for the more competent pilots, you wonder why just ONE stick shaker has activated, you wonder what the heck is the reason for the stabilizer trimming like crazy all the time, you wonder what is the reason for the IA showing different values on the left vs right display, and possibly reasons for other fault messages/warnings.

In such a scenario a displayed value of the AoA would in my opinion be VERY helpfull for the pilots in order to figure out what is really going on with the aircraft and what it's performance is.

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Old 22nd Mar 2019, 06:41
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Reuters latest on Boeing cancelled orders

JAKARTA (Reuters) - National carrier Garuda Indonesia has sent a letter to Boeing Co asking to cancel an order for 49 737 MAX 8 narrowbody jets, Garuda Chief Financial Officer Fuad Rizal said on Friday.

The airline could switch the order, valued at $6 billion at list prices, to other Boeing models, Rizal told Reuters. He said negotiations with Boeing were ongoing and Airbus SE jets were not under consideration.

Garuda is the first airline to publicly confirm plans to cancel an order for the troubled jets after the second crash of a 737 MAX 8, which killed 157 people in Ethiopia last week.

Indonesian rival Lion Air has been reconsidering its orders since one of its 737 MAX jets crashed in October.

Garuda CEO Ari Askhara told Reuters on Friday that customers had lost trust in the 737 MAX 8.

The airline has only one in its fleet at present.

“They have been relooking at their fleet plan anyway so this is an opportunity to make some changes that otherwise may be difficult to do,” CAPA Center for Aviation Chief Analyst Brendan Sobie said.

Askhara said last week it was possible it would cancel the order for 20 of the jets, with a final decision depending on what the U.S. Federal Aviation Administration does after the Ethiopian crash.

He told Reuters before the crash that the airline had decided to reduce the Boeing 737 MAX order from 49 by swapping some to widebody Boeing models.

Boeing declined to comment on customer discussions.


Last edited by Mike Flynn; 22nd Mar 2019 at 06:52. Reason: typo
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Old 22nd Mar 2019, 07:04
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Minimum flap retraction altitude for B737 is 400 ft so possible MCAS-activation at low altitude.
This.
  1. High AOA (sensor fault) is the first condition
  2. Manual flight (is the second condition)
Taught to clean up and find altitude, clear the MSA is what all pilots are taught to do.
Induce another failure, like an engine failure at V1, at 400' commence the drills, up go the flaps.

3. Flaps are up (Third condition is met)

MCAS activates. Now things get sporting. Quite possibly a procedure trained for by pilots worldwide was just complicated and made more difficult by doing what all pilots do with a sub system bought into the mix that has a single point of failure a solitary AOA sensor.
That is bad process.
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Old 22nd Mar 2019, 07:53
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Originally Posted by Mike Flynn
Reuters latest on Boeing cancelled orders
Lion Air are very displeased with Boeing and they have another 187 to come.

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Old 22nd Mar 2019, 07:56
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Originally Posted by dinbangkok
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
And then make alarms an "optional extra"!
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Old 22nd Mar 2019, 08:21
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Originally Posted by BobM2
Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
Do we know when the fault in the AoA system occured?
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Old 22nd Mar 2019, 08:27
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Originally Posted by dinbangkok
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
There are several exhibits of this out in the market: 777, 787, and soon to come 777X. These models all have full FBW systems that enable the bare airframe to have aerodynamic characteristics that with out any control system functionality at all would not be certifiable. The motivation is that these models have been able to design in improved performance because they have been able to take advantage of control system functions to yield certifiable handling qualities. The key, of course, is that the availability and reliability including any failure mode effects must be acceptable. Certification requirements cover all aspects of this.
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Old 22nd Mar 2019, 08:34
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Chilling reading by Bjørn at Leeham explaining that the elevator blow back problem - which our excellent Fceng84 explained in details a few pages ago - might have been a significant contributory cause for both of these crashes.

I know all about blowback problems of elevators. It was the most dangerous shortcoming of the fighter I flew, the SAAB J35 Draken. Even more dangerous than its famous “Super stall”, a Pugachev Cobra like deep stall behavior the aircraft would only exit from if you “rock it out” of the stall (more on this some other time). While “Super stall” is scary, Blowback is deadly.

What could have been done?
The only remedy to the blowback induced dive would have been a full nose up trim application, for a long time (throttles to idle and air brake would also have helped). But the reaction to trim is slow and the aircraft was now heading for earth. The reflex is not to trim but to pull for all there is, by both pilots, you have seconds to stop the dive. It didn’t help. If this is confirmed as the scenario for the end of both JT610 and ET302 I wonder why the danger of flying to fast at low altitude, while sorting out a raiding MCAS, was not communicated when the MCAS Airworthiness Directive was released after the JT610 crash. MCAS forcing the stabilator to full nose down should not have doomed JT610 or ET302. Their applied speed margins did. The JT610 crew knew nothing about MCAS and a potential blowback problem. The ET302 crew knew about the MCAS problem but not about the danger of flying to fast while sorting MCAS.

I have checked with longtime pilots of the 737. They have not heard of a Blowback problem when flying at elevated speeds at low altitude.

And before MCAS there was no reason to, it was beyond normal flying practice. But the JT610 investigators saw what can happen when you run into the MCAS rodeo. Why didn’t they warn to keep speeds within normal speed range?
Bjørn at Leeham

Last edited by SteinarN; 22nd Mar 2019 at 08:52.
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Old 22nd Mar 2019, 08:35
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Originally Posted by Chesty Morgan
Do we know when the fault in the AoA system occured?
When, see FDR analysis. Stick shake a function of WoW or Ralt.
But where did the fault occur, and why did the AoA value ‘fail’ up .
Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

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Old 22nd Mar 2019, 09:08
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Ethiopian pilots raised safety concerns years before fatal crash, records show

Washington Post reporting on FAA complaints years ago about allegedly flawed training programs and poor safety procedures at Ethiopian Airlines.

Ethiopian pilots raised safety concerns years before fatal crash, records show

One pilot said the airline didn’t “have the infrastructure” to support the fleet of Boeing and Airbus jets it ordered, and alleged the airline had a “fear-based” management culture in which “safety is being sacrificed for expansion and profit margin.” The pilot also accused the airline of failing to update pilot manuals and leaving out certain checklists designed to help pilots respond to “non-normal” situations. Another pilot criticized Ethiopian regulators for maintaining lax standards with respect to crew flight and rest time. The FAA’s data does not identify the pilots by name.
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Old 22nd Mar 2019, 09:10
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Do I get it correctly that "blowback" of the elevator would be a situation when the actuators for the elevator are not powerful enough to overcome the aerodynamic forces on the elevator, due to high speed (and perhaps an already high angle)?

Is there any indication that a 737 elevator (with nominally working actuators) can be in this situation in some flight regime?
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Old 22nd Mar 2019, 09:50
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Originally Posted by fgrieu
Do I get it correctly that "blowback" of the elevator would be a situation when the actuators for the elevator are not powerful enough to overcome the aerodynamic forces on the elevator, due to high speed (and perhaps an already high angle)?
Is there any indication that a 737 elevator (with nominally working actuators) can be in this situation in some flight regime?
See, related: Boeing advice on "aerodynamically relieving airloads" using manual stabilizer trim

and B737 RUNAWAY STABILIZER NNC
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Old 22nd Mar 2019, 10:07
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Originally Posted by Smythe
.

[It is amazing the amount of Boeing bashing on this forum. Boeing has made tens of thousands of safe & efficient airliners for more than half a century & that's why there are more Boeings than anything else.]

They pushed the MAX too far, a quick band aid to counter the neo.

A software fix to counter an unstable platform...

tale of the tape...why is MCAS required for certification?
In my humble opinion, they should have started again with the 73 about the time of the -300/-400 and completely redesigned it. As it stands, they seem to have cobbled together systems as they became available or desirable and bolted them where they could find space. (The “computer fuel summing unit” - can’t remember its exact name - is fixed outboard above the F/Os head - why not in the avionics bay?). The F/Os seat cannot be moved vary far back because of the C/B rack behind it. The elevator feel unit has its own pitot probes each side of the fin.

I only have experience of the -300/-400, but that aircraft is a mish-mash of mechanical and electronic devices, seemingly not properly integrated, but just about working. The ‘Classic’ autopilot does not trim ailerons or rudder, so when you take out the autopliot you often have to spend a mile or so on short finals getting the thing trimmed. The Cockpits of the -300/-400 look as if they were “designed” by firing a shotgun at a blank panel, and fitting the instruments and indicators whereever there was a handy hole. Generators have to be manually switched on to the buses. Later models without the round generator dials, still use the old panels with the cut-outs for the round dials rather than making a new panel....how cheap is that?

It seems to me that as each new requirement or problem came along, instead of doing a redesign, Boeing developed a standalone fix or widgit to solve the problem - but they don’t appear to have always thought it through in terms of the way the whole aircraft works, or how the pilots would interface with it.

As to why the 73 is so popular, I think South West have a lot to do with that, (they are also indirectly partly responsible for the arrested development of the 73). I have been told that Boeing also have some very creative fleet purchasing schemes for airlines.

As to MCAS, instead of affecting the THS trim, why not simply have it modify the elevator feel at hiigh AoA - which is, after all, the problem caused by the engine nacelles. Or insert a gentle down input to the elevators? But not the trim. Secondly, why have only one AoA probe, or even two? For such a critical device, why not have five?











Last edited by Uplinker; 22nd Mar 2019 at 11:01.
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Old 22nd Mar 2019, 10:11
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Originally Posted by BrandonSoMD
the stall AOA varies with configuration and weight and other things...
I agree stall AoA varies with configuration, Mach # and others however, I don’t think that, given all other values constant, weight changes AoA. Ie, a wing stops being a wing at the stall AoA, regardless of how much lift is demanded..

I also agree that simply introducing an AoA indication in the cockpit of an airliner will not benefit crews without some education. However, AoA is a fundamental parameter, if it is displayed and obviously in error (deduced by crew education) then it could assist in fault finding. One of the key parts of UPRT (being introduced as mandatory in Europe for all new CommerciL licence training from Dec 2019) is AoA & G awareness. I believe it would be of huge benefit if commercial aircraft had AoA displayed and pilots were educated in its interpretation from day 1 of flying training. P

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Old 22nd Mar 2019, 10:40
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Originally Posted by Ian W
There needs to be something like an Failure Modes Effects Analysis that flags up that at this point there are multiple separate warnings being displayed in various ways that will consume the entire cognitive resource of the pilot and not allow his primary AVIATE task any resource.
There needs to be an FMEA which understands the Pilot as being part of the system !
There is extensive FMEA/SSA work done for development and certification of aircraft, but it focusses on the physical systems and makes some simplistic/philosophical assumptions for the pilots. We need to better understand the Pilot as one System out of many which need to work together in an aircraft, which can fail in various ways, can recieve wrong data, can misinterpret things, can follow an inappropriate algorithm (=SOP) etc. Just because the system "pilot" may react sometimes in an unpredictable way is no reason to not include it in the analysis.

We have learned a lot about human factors in the last 20 years, but aircraft design still uses the same man-machine-interfaces like 50 years ago. Some >30 year old design (Airbus A320) is "modern" compared to many other aircraft still being built...
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Old 22nd Mar 2019, 11:02
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I've just done a search on pprune for MCAS and the first mention of the phrase at all was December 2018 when news of the Lion Air crash investigation got out. So for a group of several thousand professional fairly nosey/inquisitive bunch of pilots worldwide there hadn't been a sniff of anybody coming across MCAS in some obscure manual and asking what is was. Says it all really.

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Old 22nd Mar 2019, 11:07
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Originally Posted by dinbangkok
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
By the same reasoning why it was ok in earlier (think 707) models to include an analogue electronic device that does almost exactly the same thing, to bring the 707 in line with the same certification requirement.

Why would it not be ok? All fly-by-wire airliners, i. e. practically all that were developed since the late 1980s, cannot demonstrate unassisted control forces, because it is all artificial. That is even true for fully conventionally controlled aircraft such as the 747. Even the Comet (which predates the 707) had no aerodynamically created control forces, but fully powered flight control surfaces and only a spring-loaded artificial feel system.

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Old 22nd Mar 2019, 12:05
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Originally Posted by edmundronald
Ok, so we're supposed to believe that the speeded-up certification process of the Max just let ONE bug through.
Or rather, the industry agrees that the best way to search for more bugs is to pull the grounding order, put pilots and SLF in a bunch of planes, and fix whatever happens next.

No wonder the rich refuse to fly commercial.

Edmund
Actually, the rich may not fly commercial but they fly the same aircraft both A and B sell versions of their airliners that have been fitted out as business jets. See Boeing Business Jets



From wikipedia
I have no doubt that there are already 737Max Business Jets.
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Old 22nd Mar 2019, 12:09
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Originally Posted by bsieker
By the same reasoning why it was ok in earlier (think 707) models to include an analogue electronic device that does almost exactly the same thing, to bring the 707 in line with the same certification requirement.

Why would it not be ok? All fly-by-wire airliners, i. e. practically all that were developed since the late 1980s, cannot demonstrate unassisted control forces, because it is all artificial. That is even true for fully conventionally controlled aircraft such as the 747. Even the Comet (which predates the 707) had no aerodynamically created control forces, but fully powered flight control surfaces and only a spring-loaded artificial feel system.

Bernd
Nobody is saying FBW is bad, it works fine for Airbus! But if a plane is FBW it should be certified as FBW, which means the failure modes of necessary sensors, control algorithms and servos get carefully analysed by a third party for design weaknesses like a single point sensor failure. Which is where the US process failed with the Max 8 failed egregiously.


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Old 22nd Mar 2019, 12:20
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Originally Posted by dinbangkok
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
I was trained to fly over 50 years ago. That involved the Trident. It had a yaw damper - a computer system to counter the basic instability of the aeroplane. Aircraft that require computers are nothing new.

Several people have implied it's perfectly OK for fighters to be unstable but not airliners. I simply can't see the logic in this.

The ironic thing is Airbus take the opposite view - for the most part they take the model that the computers should be involved in all manoeuvring actions. As we know, a similar clash between computers and pilots on an A320 ( XL888T) caused a crash but everybody seems to accuse Boeing of inventing this kind of scenario.

It's a curious situation. There are lots of dodgy things about the Lion crash. The Ethiopian event has not yet - to my knowledge - been definitely attributed to an MCAS malfunction. I think we can all agree it would have been better if pilots had briefed about the potential failure behaviour of MCAS but this might simply have been an oversight on the part of Boeing rather than something cynical.
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