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Boeing to warn 737 MAX operators of a potential instrument failure that could cause the jet to nose-dive

Last week's Lion Air crash in Indonesia has prompted Boeing to issue a safety warning to all airlines operating the 737 MAX, instructing pilots in what to do if a specific sensor failure arises. ( More...

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erisajd 4
The real question is why can’t you turn OFF the damn automated systems and be a pilot and fly the darn airplane?

If the automation clauses Uncommanded actions it needs to be marked inop until the cause is found. Do not throw parts at it. And why didn’t the pilots simply turn off the system?

Automation is literally going to be the death of us all.
erisajd 3
As I am seeing pilot training develop you see people who simply take off and land and leave cruise to button pushing. And most airlines have rules AGAINST hand flying until the very end or beginning of a flight.

You need to understand what you are seeing and act on it. Once you know. It’s triage. A sudden uncommanded descent means act now. Thinking is not called for. Which means be a good aviator not a pilot.

If the pilots did not have their belts fastened the uncommanded descent pulls them out of their seats knocking them unconscious which is fatal for everyone. Given the nonchalant attitude I see in aviation everywhere these days . . . Those five point harnesses are uncomfortable for a 10 hour day.

Look. No one knows anything yet. But those airplanes can and do phone home. The maintenance of the aircraft was known by Boeing.
btweston -1
You know. You were there.
john kilcher 6
Perhaps the rush to market mentality very prevalent in the auto industry, with only 2 a/c manufacturers trying to vie for the most booked orders, Boeing has a design deficiency. Add to that, the demand for qualified pilots of which may be an issue as well... then there are the pitot tubes which may be sadly overlooked on the pre-flight inspection. One has to wonder about the possibilities of any of these hiccups, but, the fact remains, 189 people perished.
Shenghao Han 1
Boeing pushed Max as a very passive and rushed response to the successful A320neo...
Lion Air suddenly booked because budget air travel in and around south east Asia is underdeveloped and they want swiftly to have a large market share...
And we all know, when you rush something...
jthyland 2
From Boeing: The AOA is used to drive stall warning, stick shaker, stall margin info on airspeed indicators, pitch limit indicator.

It comes from this: (this file wont take photos). Anyway, an AOA Vane on the side of the A/C, just behind that is a transducer which changes analog movement to a to an electrical signal. That signal is fed to both Air Data Computers which drives all the above.

Failure of this unit (transducer) would create extremely dangerous conditions; stick shaker, stall horn (very loud), erratic airspeed, climb and dive, etc. Daytime VFR would be demanding (probably the source of the previous write-ups). Night IMC would most likely be fatal.

That A/C required a maintenance check flight.
bbabis 2
I'm no expert, but I believe that the AOA system can put various information over an airspeed indicator but cannot change the indicated airspeed or vertical speed information. AOA sending unit or transducer failure could cause horns, lights, shakers, and such that would confuse a pilot but good speed and climb/descent information would still be available along with attitude information and thrust settings. Hopefully a system expert will chime in.

R U there sparkie?
Maybe they should just fix the damn sensors!
patrick baker 5
so easy to assume Lion air is to blame, given their checkered past- poor training, poor maintence.
Uncomfortable to imagine that Boeing put deffective aircraft into a defficient airline. Grround the planes, find and fix the problem. How much is the speed-up in monthly/quartely deliveries to blame for all of this?
Steven Morley 7
Stuff breaks all the time. The procedure to deal with a faulty airspeed indicator (or angle of attack indicator) is clearly outlined in their training manuals and should have been trained. This SB is simply to say "Make sure you are familiar with this procedure". Boeing did not put a defective aircraft anywhere. It's a great aircraft that had a failure of a key component that was not caught by this airline's maintenance, nor was it dealt with appropriately via the appropriate checklists/memory items by the crew. It points to deficiencies in this part of the world and is an ongoing issue.
Wayne Arnold 2
I agree 100 percent with your comment about the plane.the plane had the same problem 2 day's before and they flew it without correcting the problem. It was a brand-new plane and they still managed to crash it
btweston 1
Did you find the missing CVR?
Ed Merriam 0
"swiss cheese" model
Highflyer1950 3
Hey Boeing experts! Do the AOA inputs not come from independent sources and require agreement in order to activate any pusher type system, especialy in the case of false, spurious signals?
sparkie624 5
Yes, they are totally separated and do not even share the same battery source. The only time that they can come together is in the case of a total AC power failure on board the a/c and at that point they share the 28 VDC Battery Buss
sparkie624 3
But at that point in time you are concerned about a lot more stuff than where your AOA Vane is sharing :)
Highflyer1950 1
Thanks for the info.
But wouldn't the AP disconnect when there's a disagreement? And if so then who's diving/pitching the plane? The pilot?
Shenghao Han 1
I thought it was the auto-trim pitching the plane down through trim adjustments. But I thought that should automatically disengage invent of air data, AoA, and attitude divergence...
sparkie624 1
It depends on the mode the A/P is in... If you are in CWS it may not disconnect, but if it is in full autopilot mode then it would probably disconnect! F/D would stay in engaged.
bbabis 1
I don't want to open a bag of worms here BUT, has a system added to any airplane that can push the nose down without the pilot's consent saved any more flights than they've caused to crash? Are we seeing more accidents as planes are designed to protect themselves from poor pilots that cause poor pilots to have even more problems?

I had a similar incident in the mid 80s flying a much less sophisticated Swearingen SA227. It had an SAS (Stability Augmentation System) that could pull the control column forward with 50+ pounds of force. On one takeoff, just after positive rate and calling gear up, the system erroneously fired and almost pulled the controls from my hands. Thank God we flew two pilots and I had both hands on the controls. It pulled until we disengaged it. The computer that controlled it was replaced and as far as I know it never happened again. I say that because, even though the AFM said the system must be on at all times, it was never on when I flew it again.
Shenghao Han 1
The stick pusher was added because pilots used to be over occupied during approach and take off especially during emergency, then lost their situational awareness and stalled the plane. But as far as I can remember this is the frist time it might contributed to a crash.

In the article it also mentioned auto-trim, but I thought the system would or at least should automatically disengage when air data, altimeter and AoA data diverge...

And yes you are exactly correct on the poor pilots vs poorly designed system to help poor pilots.

Poor pilots tend to over rely on automation, which contradicts why we put pilots in the cockpits in the first place, to safeguard automation. Sadly this issue wasn't news either, there was a crash caused by a pilot who over-relied on Airbus's auto-land caused him to overshot the runway in bad weather. It is very similar to the driver killed himself when he over relied on Tesla's "autopilot" and crashed into a stopped semi truck on the highway...
Bill Gratzl 1
Hand flew the BE1900 C/D for 5 years back in the 90's for Mesa Airlines. +/- 100 feet, all wx, 6 to 8 legs a day in the midwest great lakes region. You became comfortable and proficient with raw data. Pilots should be comfortable with disconnecting the AP and hand flying when automation fails to do what it is intended to do...
I am surprised this plane isn't being grounded...what if this plane was on a ILS 300 feet above the ground leaving no chances of recovery, or am I missing something here? Reminds me of the BA A320 where there was a Total Air Temperature (TAT) disagreement between the airframe and the EEC sensors resulting in incorrect Variable Stator Vane positioning, leading to a surge. It only happened a a select few...but I think some more testing needs to be done
Greg77FA 1
With the demand for more flights, complexity of systems, and more pilots needed, I see this happening again. More procedures just adds to complexity. They should fix and thoroughly TEST the manufactured equipment/hardware, and make sure there are simple procedures and alerts. Too many almost caused the crash of the A380 that had an engine malfunction. Humans can only absorb do much, and each reacts differently in time of crisis.
bbabis 1
This was a simple erroneous indication. The crew turned it into a crisis. I'm not familiar with the 737 but I imagine there is a button on the control wheel that gives control to the pilot. Put the attitude where you want it, put the power where you want it, and fly the plane. It didn't take super-pilot to fly this airplane or AF447 for that matter. Pay no attention to the sounds, flashing lights, or the man behind the curtain. Set an attitude and power setting that you know the plane will fly at and then work the problem. Job one is aviate.
Flew 121 for 37 years. Handling failure of one or more instruments is much easier than dealing with all instruments functioning, but one or more of those instruments are giving you FALSE information. Not sure if this happened here, but the cockpit gets very busy and confusing in those situations. Will be interested to see how this all shakes out.
gerardo godoy 1
Great mention of the correction procedure!!
Shenghao Han 1
This is never just one thing broken to cause a plane crash.
But poor maintenance and poor pilot training will always be the one to blame, simply because engineering can't design a perfect machine that will never break down. (I am not saying Boeing is innocent in this crash, but a programmer working for Boeing might not necessary know anything about flying.)

To me this crash is looking awfully similar to Air France 447. Something broken on the airplane, poorly trained/inexperienced pilots lost situational awareness, plane crashed into ocean. (On AF447 one of the less experienced relief pilot got so confused, he blindly followed GPWS's "sink rate, pull up" command, and kept pulling up, even after the Captain realized what went wrong, asked for control back and tried to push his side stick down to regain airspeed. Sadly Airbus's side stick isn't connected and computer averaged the two control inputs resulted the plane doing nothing)
But on the contrary at least AF447 had an excuse, they were flying in a storm, at night, at high altitude, but this one I am not sure why they still managed to get so confused they lost complete situational awareness...
Rick Hunt 1
From the very beginning instrument pilots are trained to scan and review data from multiple sources/instruments to both determine the situation of the aircraft and to cross reference instruments to determine which if any are defective. If a plane is at a level flight attitude with a few hundred knots of airspeed at a nearly constant altitude and the engines running a with significant amount of power the software should be able to determine that even it the angle of attack indicator is reading 40 degrees positive the aircraft is not in a stall condition. Where does Boeing get these software code writers? To detect a high angle of attack indication and immediately lower the attitude based only on that is absurd.
Mike Mohle 0
Not grounded till a positive identification of the fault is determined and a correction is made for the fleet or at least S/N block that is affected?
Shenghao Han 0
Grounding planes costs millions to an airline, it is a very tough decision to the governing body especially when multiple airlines will be affected. An airline won't volunteery do so for the same reason, especially if they don't have replacement aircraft to fly the same route.
They won't just press the red button because of one plane crashed, usually it takes two similar incidents to ground the whole fleet the 787 lithium battery smoke/fire incident is a classic example.
bashdan 0
(Duplicate Squawk Submitted)

Boeing Warns of False Angle of Attack Readings on 737 Max

Boeing on Tuesday issued an operations manual bulletin (OMB) directing 737 Max operators to follow existing procedures to address circumstances of false input from the airplane’s angle of attack (AOA) sensors.
Alan Hume 0
Unbelievable! This amounts to criminal negligence! Pilots should ALWAYS be able to override automated systems, no matter what.
Mike Herberts 1
You can..they are called Stab Trim Cutout switches and have a procedure in the QRH, for the Action and for the cause.
(Duplicate Squawk Submitted)

Boeing Close to Issuing Safety Warning on 737 Max

Boeing Co. is preparing to send a safety warning to operators of its new 737 Max jets in response to the investigation of last week’s fatal crash off the coast of Indonesia that left 189 dead, said a person familiar with the matter.
(Duplicate Squawk Submitted)

Boeing issues warning on potential instrument malfunction after Indonesia crash

Airplane manufacturer Boeing said Wednesday that it has issued a bulletin to airlines worldwide warning of erroneous readings from flight-control software on its planes, after an almost-new Lion Air jetliner crashed into the sea soon after takeoff, killing the 189 people on board.
MH370 -5
(Duplicate Squawk Submitted)

The Boeing 737 Max Jets Will Automatically Try To Push Down The Nose...

JUST IN: Boeing is preparing to send a bulletin to operators of its new 737 Max models warning that erroneous readings from a flight-monitoring system can cause the planes to aggressively dive - Lion Air Crash


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