[IanMan]

Originally Posted by Herdalum

How would rudder control cause a sudden drop in altitude? I don’t get that. I could see how it could cause a crash trying to land, or a spin maybe, but not just suddenly going straight down.

Going full lock at an angle????

[Captain Blood]

Originally Posted by IanMan

Going full lock at an angle????

Considering that this plane had 3 flights with problems before the crash, any guess is a good one. 4 problem flights in a row? I don't see myself boarding a Lion air flight, ever!

[IanMan]

Originally Posted by Real Dodger

Considering that this plane had 3 flights with problems before the crash, any guess is a good one. 4 problem flights in a row? I don't see myself boarding a Lion air flight, ever!

The problem is that this airline is too big to fail and an event like this likely won't put a damper on anything or make them any safer.

[CTinline-six]

Originally Posted by Real Dodger

Considering that this plane had 3 flights with problems before the crash, any guess is a good one. 4 problem flights in a row? I don't see myself boarding a Lion air flight, ever!

+1

That's like walking up to your BMW, seeing a puddle of coolant on the ground and deciding to drive it anyway.

[DDD31]

Originally Posted by IanMan

There is a common flaw associated with the 737 and that is a rudder reversal defect which leads to a single point of failure. It likely contributed to this crash. More info here:

http://airlinesafety.com/faq/B-737Ru...h0dyFgVqMnj-hc

That problem was identified and solved in the late 90’s. The 737 rudder system was redesigned after the investigation and with the advent of the 737 NG’s (which the MAX 8 is a new derivative of the NG) the 737 hasn’t had that issue since, so stop with the wild speculation.

If you want to read about the investigation:

https://en.m.wikipedia.org/wiki/Boei..._rudder_issues

[dmatre]

Originally Posted by IanMan

There is a common flaw associated with the 737 and that is a rudder reversal defect which leads to a single point of failure. It likely contributed to this crash. More info here:

http://airlinesafety.com/faq/B-737Ru...h0dyFgVqMnj-hc

You realize that the newest update to the info you posted is 16 years old, right? And airlines had 6 years to implement updates. Means all 737s have been flying revised rudder control since 2008.

This issue possibly led to 2 crashes (theorized - not proven) but I've not seen any reference to this occurring to an aircraft with the updated pieces.

Got any current info?

[IanMan]

I admit to being mislead and not informed about the subject. Thank you for spreading light on the matter.

[Captain Blood]

Originally Posted by dmatre

You realize that the newest update to the info you posted is 16 years old, right? And airlines had 6 years to implement updates. Means all 737s have been flying revised rudder control since 2008.

This issue possibly led to 2 crashes (theorized - not proven) but I've not seen any reference to this occurring to an aircraft with the updated pieces.

Got any current info?

Of course, there is the stripped thread on a jackscrew on the MD 80 rudder, caused a horrible crash, but it not befuddle a drunk Denzel Washington in the movie "Flight".

[lemetier]

Boeing issuing Alert S.B. and FAA issuing Emergency AD regarding erroneous Alpha Vane (AoA Probe) signals causing sudden pitch over and limited elevator control authority.

[eluded]

Maybe bad tubes that indicated incorrect air speed? Plane was probably not under manual control at the time. This causes bad things to happen when automation relies on correct air speed. If you're not trained properly you won't notice until bad things start to happen and then it will be too late.

[Dang3r]

Originally Posted by Real Dodger

Of course, there is the stripped thread on a jackscrew on the MD 80 rudder, caused a horrible crash, but it not befuddle a drunk Denzel Washington in the movie "Flight".

That was incorrect maintenance, they hadnt greased the jackscrew and the final electrical movement of the jammed pressure-off brake led to the rapid
stripping of the threads. And this wasnt the rudder but the vertical stabilizers.

[lemetier]

Originally Posted by eluded

Maybe bad tubes that indicated incorrect air speed? Plane was probably not under manual control at the time. This causes bad things to happen when automation relies on correct air speed. If you're not trained properly you won't notice until bad things start to happen and then it will be too late.

This wasn't a "Pitot Tube" issue and the plane was being hand flown. I suspected an AoA problem early on and this was released overnight:


The Boeing Company

Flight Crew Operations Manual Bulletin

Number: TBC-19

Issue Date: November 6, 2018

Airplane Effectivity: 737-8 / -9

Subject: Uncommanded Nose Down Stabilizer Trim Due to Erroneous Angle of Attack (AOA) During Manual Flight Only

Reason: To Emphasize the Procedures Provided in the Runaway Stabilizer Non-Normal Checklist (NNC).

The Indonesian National Transportation Safety Committee has indicated that Lion Air flight 610 experienced erroneous AOA data. Boeing would like to call attention to an AOA failure condition that can occur during manual flight only.

This bulletin directs flight crews to existing procedures to address this condition. In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.

Additionally, pilots are reminded that an erroneous AOA can cause some or all of the following indications and effects:

- Continuous or intermittent stick shaker on the affected side only.
- Minimum speed bar (red and black) on the affected side only.
- Increasing nose down control forces.
- Inability to engage autopilot.
- Automatic disengagement of autopilot.
- [COLOR="DarkRed"]IAS DISAGREE alert[/COLOR].
- [COLOR="DarkRed"]ALT DISAGREE alert[/COLOR].
- AOA DISAGREE alert (if the AOA indicator option is installed)
- [COLOR="DarkRed"]FEEL DIFF PRESS light[/COLOR].

In the event an uncommanded nose down stabilizer trim is experienced on the 737-8 /-9, in conjunction with one or more of the above indications or effects, do the Runaway Stabilizer NNC ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT [COLOR="DarkRed"]and stay in the CUTOUT position for the remainder of the flight.[/COLOR]

[Dang3r]

This sounds like a reason to ground the affected fleet immediately, if this happens direct after T/O, lets say below of 5000ft you have less that few seconds to respond. How often was this reported actually and how to fix that issue?
At my next scheduled simulator session I'll try to head to the 737-colleages and ask how about a simulation of this.

[Captain Blood]

Originally Posted by Dang3r

This sounds like a reason to ground the affected fleet immediately, if this happens direct after T/O, lets say below of 5000ft you have less that few seconds to respond. How often was this reported actually and how to fix that issue?
At my next scheduled simulator session I'll try to head to the 737-colleages and ask how about a simulation of this.

I've heard there are 0 incidents of this type reported in the US so far. But I'll drive with my umbrella up, next time I'm driving past DFW and a 737 tries to land on me (on Hwy 121).

[DDD31]

Originally Posted by Dang3r

This sounds like a reason to ground the affected fleet immediately, if this happens direct after T/O, lets say below of 5000ft you have less that few seconds to respond. How often was this reported actually and how to fix that issue?
At my next scheduled simulator session I'll try to head to the 737-colleages and ask how about a simulation of this.

I don’t think Boeing needs to go that far since the procedure they recommend in this instance is the stab trim runaway procedure. Having this happen after takeoff would definitely ruin your day but can be counteracted by pilot intervention if recognized quickly and appropriate stab trim runaway procedure followed (see post above for procedure). We practice this scenario in the simulator and the stab trim runaway needs to be caught quickly or it can rapidly get out of hand. Dealing with an instrumentation error at the same time would just compound the problem.

It’s possible the pilots in this instance were more fixated on the instrumentation errors and didn’t notice the aircraft rapidly trimming the nose down.

[Captain Blood]

Lion Air: Sensor was replaced day before crash but problems persisted https://www.cnn.com/2018/11/08/asia/...ntl/index.html

[******]

Sounds like a Fetzer valve problem.

[GiofromNJ]

Originally Posted by Herdalum

Sounds like a Fetzer valve problem.

it's all ball bearings these days

[******]

Originally Posted by GiofromNJ

it's all ball bearings these days

Exactly, Gordo!

[GiofromNJ]

Originally Posted by Herdalum

Exactly, Gordo!

just charge it to the Underhills...

[******]

Originally Posted by GiofromNJ

just charge it to the Underhills...

Is that spelled with two B’s?

[Captain Blood]

Originally Posted by GiofromNJ

just charge it to the Underhills...

Hey, those are my lines......