What was that about AoA again?

Article states:

“Max jets will automatically try to push down the nose if they detect that an aerodynamic stall is possible, the person said.”

as if that’s unique to the Max.
 
There has to be more to that story. What is the root cause that leads the system to detect a stall and activate the stick pusher? That's what I want to know... and is it actually any different than anything else?
 
The press is using just a little hyperbole in reporting this. :rolleyes:

The bulletin from Boeing will alert airlines that erroneous readings from a flight-monitoring system can cause the planes to abruptly dive, said the person, who asked not to be named discussing details of the manufacturer’s plans.

The Seattle Times is even more dramatic...

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

Another source, this time a blog...

Just over one week after Lion Air Flight 610, a Boeing 737 MAX aircraft, crashed off the coast of Indonesia, Boeing is expected to send a bulletin to operators of the aircraft that incorrect readings from its flight-monitoring system can cause the planes to aggressively dive, a person familiar with the matter told Bloomberg.

While I've never even come close to piloting a 737 and don't know squat about the stick pusher system, I find it hard to believe the automation will put the aircraft in a terrifying dive if the alpha protection system engages as the news stories suggest.
 
3393RP said:
The press is using just a little hyperbole in reporting this. :rolleyes:

The bulletin from Boeing will alert airlines that erroneous readings from a flight-monitoring system can cause the planes to abruptly dive, said the person, who asked not to be named discussing details of the manufacturer’s plans.

The Seattle Times is even more dramatic...

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

Another source, this time a blog...

Just over one week after Lion Air Flight 610, a Boeing 737 MAX aircraft, crashed off the coast of Indonesia, Boeing is expected to send a bulletin to operators of the aircraft that incorrect readings from its flight-monitoring system can cause the planes to aggressively dive, a person familiar with the matter told Bloomberg.

While I've never even come close to piloting a 737 and don't know squat about the stick pusher system, I find it hard to believe the automation will put the aircraft in a terrifying dive if the alpha protection system engages as the news stories suggest.
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In the CRJ, the stick pusher is somewhat aggressive. Keep in mind, you want it to be agressive especially if you encounter a high altitude stall. You can’t just fire wall the thrust levers and power out of a stall. There’s not much excess thrust available at 35000ft. Expect to lose 4-6K feet. The FAA has changed their philosophy with stall recovery. It used to be lose as little altitude as possible. Now it’s just do whatever you need to do to break the stall. So yea, you’ll feel an agresisve nose dive when the pusher goes off and you’re trying to recover.
 
There are other reports saying the airspeed indicators were reported to be faulty on the last 4 flights. How is that not being fixed a Boeing problem?

I’m not a big plane pilot, so maybe that’s normal. From an outsider’s perspective, however, it leads to questions about the airline’s maintenance practices. Can any of you “real” pilots comment on how a typical airline would respond to reports of a faulty airspeed indicator.
 
skier said:
There are other reports saying the airspeed indicators were reported to be faulty on the last 4 flights. How is that not being fixed a Boeing problem?
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Partially because the airplane was only two months old.
 
midwestpa24 said:
Partially because the airplane was only two months old.
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It’s not Boeing’s fault that the operator failed to reject the aircraft and continued to operate it.

This discussion is timely to me. I’ve got a student who just got their airplane out of the shop after major panel work was completed and the airspeed indicators are indicating slow. I’ve declined to provide additional training until it is fixed, for obvious reasons. Had I not been flying with him and mentioned it I wouldn’t be surprised if the owner just kept flying it as is. Doing so could have had some very costly consequences.
 
skier said:
There are other reports saying the airspeed indicators were reported to be faulty on the last 4 flights. How is that not being fixed a Boeing problem?

I’m not a big plane pilot, so maybe that’s normal. From an outsider’s perspective, however, it leads to questions about the airline’s maintenance practices. Can any of you “real” pilots comment on how a typical airline would respond to reports of a faulty airspeed indicator.
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Our unreliable airspeed checklist is about 8 pages. Basically, disengage the AP, switch to the air data computer that has reliable information, and use N1/pitch degree chart to achieve level flight.
 
jordane93 said:
In the CRJ, the stick pusher is somewhat aggressive. Keep in mind, you want it to be agressive especially if you encounter a high altitude stall. You can’t just fire wall the thrust levers and power out of a stall. There’s not much excess thrust available at 35000ft. Expect to lose 4-6K feet. The FAA has changed their philosophy with stall recovery. It used to be lose as little altitude as possible. Now it’s just do whatever you need to do to break the stall. So yea, you’ll feel an agresisve nose dive when the pusher goes off and you’re trying to recover.
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My inexperience thinks that running the electric pitch trim for ten seconds would indeed lead to a very significant nose down situation.

https://theaircurrent.com/aviation-...bulletin-on-aoa-warning-after-lion-air-crash/
 
jordane93 said:
In the CRJ, the stick pusher is somewhat aggressive.
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The F/A 18's have a similar system to pitch the nose down if the AoA is out of whack. Fun fact, the back of a carrier is full of turbulent air and when you fly into that, the AoA thinks 'hmmm...we have a problem so let's just dump the nose down a few degrees'...like right at the fan tail. From what I hear, they lost a couple of Rhinos and crew until they figured out how to respond quickly to the nose down. Software...gotta love it.

Edit:
I had a conversation with an F/A 18 F WSO 10 or 15 years ago. The conversation predates my certification as a pilot by the same number of years. This is my recollection of that conversation. Based on feedback to my post, I think there are 3 possible readings for this post.
1. I accurately recall the conversation and the facts are correct.
2. I accurately recall the conversation and the WSO was exaggerating the phenomenon.
3. My recall of the conversation is faulty

1 is possible. 2 is not 3 is certainly possible as my memory is far from perfect.

Until I can speak with this aviator again (he's currently deployed and I have no intention of bugging him about this), let's just go with 3.
 
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Doug F said:
The F/A 18's have a similar system to pitch the nose down if the AoA is out of whack. Fun fact, the back of a carrier is full of turbulent air and when you fly into that, the AoA thinks 'hmmm...we have a problem so let's just dump the nose down a few degrees'...like right at the fan tail. From what I hear, they lost a couple of Rhinos and crew until they figured out how to respond quickly to the nose down. Software...gotta love it.
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Whoever told you this stuff has no idea what they are talking about.....not true at all. I will say that there is occasionally a "burble" behind the boat (the turbulence you spoke of), but there is nothing inherent in the jet's software that would create an unexpected response from the aircraft. You need to make some small power corrections to account for it, but that is no different than any other jet in the history of angled flight decks.
 
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Doug F said:
From what I hear, they lost a couple of Rhinos and crew until they figured out how to respond quickly to the nose down.
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Many years ago there was an issue with legacy Hornets and failed probe(s) off the front of the boat, but nothing like you talked about on approach, burble or no.

Doug F said:
Software...gotta love it.
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:rolleyes:

Nauga,
and his boarding rate
 
35 AoA said:
Whoever told you this stuff has no idea what they are talking about.....not true at all. I will say that there is occasionally a "burble" behind the boat (the turbulence you spoke of), but there is nothing inherent in the jet's software that would create an unexpected response from the aircraft. You need to make some small power corrections to account for it, but that is no different than any other jet in the history of angled flight decks.
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I got it from a Rhino aviator. I guess he didn't know what he was talking about even though it happened to him on one landing.
 
Doug F said:
I got it from a Rhino aviator. I guess he didn't know what he was talking about even though it happened to him on one landing.
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Sounds like it to me. I don't know anything about this Rhino you are speaking of but I can tell you it is not that uncommon to meet pilots flying complex aircraft that think they understand something when they might as well be talking about where the Christmas elf was that morning when they woke up.
 
Doug F said:
I got it from a Rhino aviator. I guess he didn't know what he was talking about even though it happened to him on one landing.
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I'm also a Super Hornet pilot. My guess is that some of the info got lost in translation, because none of that information about the Super Hornet is true. There is no AoA limiter, no stick pusher, nothing like that. You can absolutely depart the jet in the landing configuration, much like any other aircraft. People have done that before. You can also get yourself in trouble behind the boat flying auto throttles. For some very nerdy reasons that probably exceed the level of interest on here, auto throttle response in the Super Hornet is not as smooth as that of the Hornet, especially when you get into the situation where you have to make a big glideslope correction....better to just click out of autos and make the correction manually in that case. My guess is that the aviator you talked to had an issue with auto throttles......I'll just say that I do not fly auto (throttle) passes at the boat for this reason.
 
NBC is reporting there is an AD out this morning to force training on the crews on proper procedures... Wasn't very clear, but they are blaming the right AOA vane for giving an eronious output, and pitch trim driving full nose down to compensate. But I would guess the trim was driving nose down because the pilot was hauling back on the yoke. Anyway, I am suspicious as to why the single AOA vane had so much weight. Redundancy on critical flight control/air data systems usually votes a single bad signal source out.
 
35 AoA said:
I'm also a Super Hornet pilot. My guess is that some of the info got lost in translation, because none of that information about the Super Hornet is true. There is no AoA limiter, no stick pusher, nothing like that. You can absolutely depart the jet in the landing configuration, much like any other aircraft. People have done that before. You can also get yourself in trouble behind the boat flying auto throttles. For some very nerdy reasons that probably exceed the level of interest on here, auto throttle response in the Super Hornet is not as smooth as that of the Hornet, especially when you get into the situation where you have to make a big glideslope correction....better to just click out of autos and make the correction manually in that case. My guess is that the aviator you talked to had an issue with auto throttles......I'll just say that I do not fly auto (throttle) passes at the boat for this reason.
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I amended my post. Option 3 it is. I'll try and get with him after he'd done with his deployment to see if he recalls the conversation and clarify what he was trying to tell me.
 
Tarheelpilot said:
Sounds like it to me. I don't know anything about this Rhino you are speaking of but I can tell you it is not that uncommon to meet pilots flying complex aircraft that think they understand something when they might as well be talking about where the Christmas elf was that morning when they woke up.
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Rhino = Super Bug = Super Hornet = F/A 18 E/F.
I updated my initial post so let's go with option 3 of my update.
 
Doug F said:
I amended my post. Option 3 it is. I'll try and get with him after he'd done with his deployment to see if he recalls the conversation and clarify what he was trying to tell me.
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Once I thought about it, I am fairly certain the guy was probably talking about the auto throttles on the Rhino.....it takes getting used to if you were an auto guy in the Hornet (I wasn't, but so I've been told), and more than a few people have scared themselves. It relates to the other part you mentioned about the burble in a way, because if you are needing to make a large power correction (as you might need to with a strong burble), it is better to click out and just fly the rest of the pass manual. It has trouble keeping up with large power on or off corrections. That all being said, it is entirely possible said WSO just was confused about what he was talking about (option #2 I guess?). While many are highly knowledgeable about the airplane and all are expected to be highly knowledgeable about tactics, the stick and rudder/flying the plane stuff generally isn't their area of expertise. I'm guessing if I polled a room of Rhino WSOs, few, if any could explain to me such esoteric pilot stuff. That's not a dig at WSO's, I just wouldn't expect many to know, or even need to know stuff like this.
 
35 AoA said:
Once I thought about it, I am fairly certain the guy was probably talking about the auto throttles on the Rhino.....it takes getting used to if you were an auto guy in the Hornet (I wasn't, but so I've been told), and more than a few people have scared themselves. It relates to the other part you mentioned about the burble in a way, because if you are needing to make a large power correction (as you might need to with a strong burble), it is better to click out and just fly the rest of the pass manual. It has trouble keeping up with large power on or off corrections. That all being said, it is entirely possible said WSO just was confused about what he was talking about (option #2 I guess?). While many are highly knowledgeable about the airplane and all are expected to be highly knowledgeable about tactics, the stick and rudder/flying the plane stuff generally isn't their area of expertise. I'm guessing if I polled a room of Rhino WSOs, few, if any could explain to me such esoteric pilot stuff. That's not a dig at WSO's, I just wouldn't expect many to know, or even need to know stuff like this.
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I never waved the Rhino, but the Hornet/Tomcat autothrottles performed well on the bottom side of GS. Getting high is where they got people in trouble, especially when from an overcorrection for a settle in the burble.
It’s possible someone in the backseat could mistake poor auto throttle technique/function for trim.
 
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Cooter said:
I never waved the Rhino, but the Hornet/Tomcat autothrottles performed well on the bottom side of GS. Getting high is where they got people in trouble, especially when from an overcorrection for a settle in the burble.
It’s possible someone in the backseat could mistake poor auto throttle technique/function for trim.
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Second sentence is the root of the problem....autos or not. Scariest passes I've ever seen followed a common trend.....settle in the middle, power call, overcorrected, got full tall, then tried to recenter high ball in close (violated rules to live by). Cheap ticket to a long bolter, a scary 1 wire, or an in flight. As you know, and possibly counterintuitively to most of our readers, being mega high is probably more dangerous than being mega low......at least in the latter, you are probably already making a power on correction, and you're just gonna get pickled if it continues anyway, rather than in the former, guys doing unpredictable power off dumb corrections inside the 100' WO window that paddles don't have enough time to respond to. As an aside, now that we have PLM, new rules to live by include "DO recenter a high ball in close" as well as "Lead the low" (I'm not kidding)........take THAT paddles :)
 
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35 AoA said:
As an aside, now that we have PLM, new rules to live by include "DO recenter a high ball in close" as well as "Lead the low" (I'm not kidding)........take THAT paddles :)
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That’s enough to make a paddles head explode!

On my first cruise, we lost our lens for a little while on deployment. I don’t remember why, but MOVLAS was also down or wasn’t being used for some reason. So, we had to do paddles talkdowns. It was strange because you had nothing else to look at besides staring right at the wires. I remember realizing that despite paddles dire warnings, you can get pretty good at spotting the deck.
I was always slightly a contrarian, I never taught the three point power correction. But the leading a low can definitely be a killer, or I guess I should say, used to be a killer.
 
I don't know a thing about Naval aviation, but I imagine the island creates pretty significant turbulence. It seems this coupled with the angled flight deck could make the conditions at the fantail a bit sporty.

My hat's off to you guys.
 
3393RP said:
I don't know a thing about Naval aviation, but I imagine the island creates pretty significant turbulence. It seems this coupled with the angled flight deck could make the conditions at the fantail a bit sporty.
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The biggest difference (IMO) between a top tier ball flyer and someone at the bottom of the greenie board is the ability to anticipate and correct for the conditions. Looking at the wake, listening to winds call, listening to Paddles calls, etc. help to determine what will be needed and what type of pass it will be. The guys who do that the most consistently won’t be caught off guard by a burble or rooster tail from high winds, and better avoid the scary passes. Though no one is totally immune.
 
So here’s an excerpt from a high priority bulletin I got today:

“As a result of preliminary investigation of Lion Air flight 610, Boeing has determined an erroneous AOA input can cause uncommanded nose down stabilizer trim movement in increments lasting up to 10 seconds. It is important to note this can only occur with the flaps in the up position and during manual flight only. Boeing guidance to stabilize this condition is to execute the Runaway Stabilizer QRC/QRH procedure. With the erroneous AOA condition, opposing the trim with the control column force will not stop electric trimming, but the step to move both STAB TRIM CUTOUT switches per procedure will stabilize the system. Boeing also states the use of the electric stabilizer trim switches can be used to neutralize the control column until the STAB TRIM CUTOFF switches are activated. This information is located in the fleet briefing bulletin.”

So if one of my AOA probes ***ts the bed while I’m clean and hand flying, the MAX might respond with a nose down trim runaway.

That’s f***ing great Boeing. Thanks for that.
 
Your condemnation is a little premature, don't you think? Right now, there's no way of knowing if this is an isolated incident due to damage, a maintenance error, or other external cause.

The fact that the UAS condition in this particular aircraft was reported by crews and apparently didn't result in the attention it deserved is a consideration, along with the absent knowledge of how the event unfolded and the actions of the crew in response.
 
Perhaps, but it seems to me that Boeing is admitting that an erroneous AOA can cause an uncommanded stab trim runaway. Regardless of the mx or crew response - if that’s true, it’s a problem, IMO.
 
Is it not possible to man muscle and over power this system? I would think the pilot should be able to over ride any system in the plane via brute force if needed

**Also, ironic that Airbus tends to get the judgement for being overly automated, but haven't there been other 737 crashes as a result of some safety feature? I seem to recall a RyannAir or some other landing short a few years ago that was loosely related to some automated system as well
 
kayoh190 said:
Perhaps, but it seems to me that Boeing is admitting that an erroneous AOA can cause an uncommanded stab trim runaway. Regardless of the mx or crew response - if that’s true, it’s a problem, IMO.
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No bigger than any other runaway stabilizer trim event and it is handled no different.

The MCAS will trim nose-down, at half-speed, in ten-second intervals separated by five-second pauses until the activating condition is corrected. In this case, the activating condition was a fault so the process would continue from the time the flaps were retracted until the steps from the runaway stabilizer trim checklist were completed. The 'half-speed' part is important because the trim switches on the pilot yoke's operate at full-speed and will overpower a half-speed runaway.

The runaway stabilizer trim checklist has not changed on the 737 for decades. The only thing that the new MCAS adds is a new way that a runaway can be triggered.

An MCAS activation will only occur when the airplane is being hand-flown and the flaps are retracted. According to the preliminary DFDR readout, the MCAS activation began on the accident flight at flap retraction. The accident flight experienced 26 MCAS nose-down trim events. 25 times the flying-pilot overrode the input. On the 26th occurrence, he did not. The crew never completed the following steps on the runaway stabilizer checklist which would have included disabling the stab trim with the trim cutout switches located below, and to the right of, the throttles on the center console.

The preliminary report from the DFDR also indicated that the same thing (invalid MCAS activation) happened on the airplane's previous flight. That crew followed the applicable checklist, disabled the electric stabilizer trim, and completed the flight using manual stabilizer trim. I have not seen anything yet which suggests that the accident crew could not have done the same but we won't know about that until the final report is out. I also haven't seen anything to indicate why the fault wasn't repaired after the MCAS activation on the previous flight.
 
Larry in TN said:
I also haven't seen anything to indicate why the fault wasn't repaired after the MCAS activation on the previous flight.
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The maintenance log summary on pages 7, 8, and 9 of the preliminary report (13 Megabyte pdf link in my post above) shows multiple attempts by maintainers to troubleshoot several problems on flights beginning on October 26. Although they performed check Onboard Maintenance Function numerous times, reset breakers, cleaned connector contacts, and replaced the AoA sensor, etc., there is no mention of MCAS in the log which makes me wonder if the maintenance crew even knew it existed.

Preliminary Report said:
1.6.3 Aircraft Flight and Maintenance Log

The Aircraft Flight Maintenance Log (AFML) recorded that since 26 October 2018 until the occurrence date several problems occurred related to airspeed and altitude flag appeared on Captain (left) Primary Flight Display (PFD) three times, SPEED TRIM FAIL light illumination and MACH TRIM FAIL light illumination two times and IAS (Indicated Airspeed) and ALT (Altitude) Disagree shown on the flight Denpasar to Jakarta the day before the accident flight.
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Here are the significant FDR parameters from Flight JT610. It must have been terrifying for the crew and passengers.

PK-LQP%20Boeing%20737-MAX8%20FDR%20Major%20Parameters_zpsrf7oua7h.jpg
 
Stan Cooper said:
there is no mention of MCAS in the log which makes me wonder if the maintenance crew even knew it existed.
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They don't troubleshoot and repair based on personal systems knowledge. They follow the procedures in the aircraft maintenance manual. If those manuals were lacking it will come out in the investigation.
 
Larry in TN said:
They don't troubleshoot and repair based on personal systems knowledge. They follow the procedures in the aircraft maintenance manual. If those manuals were lacking it will come out in the investigation.
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That's sort of what I was implying.
 
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