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Old 12th March 2019, 01:42   #31
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

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Originally Posted by sun_king View Post
Have to disagree here, the graph shows an almost linear acceleration up to about 400 knots, while I am not familiar with the B737 MAX' flight controls, I can boldly say that no aircraft is going to climb past 300 knots with flaps extended. I work for a company that makes FMS and on the platforms I work on, the FMS commanded speeds are way lower (in the range of V2+ 15 to 25) when flaps are deployed. The data suggests a clean up well before 250 knots.
Yes, but you need to look at the Flightradar24 data a little more closely and look at it in the context of where and how this happened.

It looks like the two graphs display altitude above Mean Sea Level and GPS or ground speed. But this particular aircraft took off from an airport at around 7500-8000 feet altitude. Also, GPS speed is not relevant for an aircraft in terms of developing lifts, or rather loss of it and stall. That is down to airspeed.

At the altitude of the airfield, with some wind factor thrown in, GPS (ground speed) versus air speed could differ substantially. At that altitude, if fully loaded, take off speed would have been likely to have been over 175 knots, if not more? If it was sunny and warm, that would have added to the take speed.

Also, note the data from Flightradar is far from perfect, especially in areas with few receivers. What we could probably tell from the graph is that the plane accelerated and probably got airborne around the 5.39.30 mark. I am not so familiar with Flightradar but I believe that the altitude readings until actually airborne, are just not accurate. Just check that blue line. It takes one minute from 5.38.30 to 5.39.30 to climb 7500 feet?? That is more fighter type of performance, not a civilian jetliner climbing away from a high altitude airport. So this is just Flight Radar data inaccuracies I believe. Would be good if someone with real in-depth knowledge on Flightradar data could elaborate how it all works.

If what I say is correct you see an airliner taking off from a high altitude airport (which negatively affects performance to start with) and is struggling to climb, let alone maintain altitude. Would you retract flaps in such a scenario? You would like to retract flaps as soon as possible. But only when you have sufficient vertical speed and horizontal speed. Would you start messing with the aircraft configuration so close to the ground?

I am not familiar with the 737 MAX climb performance and what configuration would give you the best vertical climb rate over distance. (You want to achieve maximum vertical climb at minimum horizontal speed)

Check out the terrain on google map. It’s mountainous out there!

Not sure what it all means, but several sources are now reporting having seen smoke coming from the aircraft whilst still in the air, and also peculiar noises, not persistent with typical jet engine sounds. We will see, but my money is on this being something different from the Lion incident.

But we need to wait and see. One thing I am sure off, you can not take FlightRadar data at face value. It needs thinking through and adding the actual environment into which the aircraft found itself at the time. When you start doing that, a very different picture starts emerging, from what speed and data on its own are telling.

Jeroen

Last edited by Jeroen : 12th March 2019 at 02:05.
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Old 12th March 2019, 02:24   #32
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Just came across this interesting read:

https://thepointsguy.com/news/southw...ion-air-crash/

Remarkably, lots of jet airliners have AoA (angle of Attack) sensors. They play an important role/input to the overall flight control system.

But few have the capability to actually display the actual angle of attack. It is all handled by clever software in the computer and you primary flight display could show dozens of parameters, but not AoA. On my little planes, AoA is a little more common and dedicated AoA sensors/read outs are often more and more provided as standard in the cockpit of General Aviation planes.

Jeroen
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Old 12th March 2019, 08:54   #33
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Quote:
Originally Posted by Jeroen View Post
Yes, but you need to look at the Flightradar24 data a little more closely and look at it in the context of where and how this happened.

Check out the terrain on google map. Itís mountainous out there!

But we need to wait and see. One thing I am sure off, you can not take FlightRadar data at face value. It needs thinking through and adding the actual environment into which the aircraft found itself at the time. When you start doing that, a very different picture starts emerging, from what speed and data on its own are telling.
Thank you Jeroen. Very well said.

All,
Emphasis in bold is mine. For all the genuine enthusiasts on the forum Jeroen speaks wise words about flightradar24 data. To that I will add clear air turbulence to add to the real context the pilot & aircraft are coping with. And we are not yet talking about what was happening to the machinery of the aircraft. In my opinion, mind you this just one retired man's view, the DGCA and several other regulators have done right by not announcing a knee jerk blanket grounding. The data from the fatal Ethiopian will be known fairly soon for the better. I am sure many passengers will disagree and clamour for a world wide grounding which is what social media has brought to us.
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Old 12th March 2019, 09:13   #34
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Default re: Boeing 737 Max crashes and grounding

Mod Note: All posts related to the recent crash have been moved to a new thread.
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Old 12th March 2019, 11:28   #35
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Quote:
Originally Posted by Jeroen View Post
But few have the capability to actually display the actual angle of attack.
This sounds a bit scary. You as a pilot, are relying on certain information reported by a sensor, which you are sure to be right and it isn't. We now have a solution where it reports if the sensor is relaying wrong information so we can act upon it which is all good.

It now feels like, wherever a sensor is located and feeding the pilot and co pilot critical information about the plane, there needs to be another check point to confirm that the information being sent is right or wrong. Sounds like a bit of re engineering or re visiting software code, now that everything runs on software that governs hardware.

In a situation where you as a pilot are dealing with a plane falling out of the sky, several lives at stake, your brain already in panic mode wondering what to do, you now have to question the instrument you rely on. Boeing better sort this out soon.
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Old 12th March 2019, 12:09   #36
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

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Originally Posted by sandeepmohan View Post
This sounds a bit scary. You as a pilot, are relying on certain information reported by a sensor, which you are sure to be right and it isn't. We now have a solution where it reports if the sensor is relaying wrong information so we can act upon it which is all good.

It now feels like, wherever a sensor is located and feeding the pilot and co pilot critical information about the plane, there needs to be another check point to confirm that the information being sent is right or wrong. Sounds like a bit of re engineering or re visiting software code, now that everything runs on software that governs hardware.

In a situation where you as a pilot are dealing with a plane falling out of the sky, several lives at stake, your brain already in panic mode wondering what to do, you now have to question the instrument you rely on. Boeing better sort this out soon.
Many sensors on airplanes are duplicated. And the computers verify signals and outputs and in many cases figure out which sensor data to use/trust.

So the emphasis is standardising trouble shooting through specific routines, or NNC non normal check list. If a certain condition occurs, you run through the NNC, check and perform accordingly, mend the problem or stabilise the situation so you can continue.

Putting this in the context of this discussion:

Quote:
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.
- IAS DISAGREE alert.
- ALT DISAGREE alert.
- AOA DISAGREE alert (if the AOA indicator option is installed)
- FEEL DIFF PRESS light.

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 and stay in the CUTOUT position for the remainder of the flight.
So if a pilot encounters the above indications/effects, he/she must execute the runaway Stabilizer NNC. That would ensure the system gets disabled properly. That the MCAS system and the AoA were at the heart of it is really that not relevant.

Fact is that with a faulty sensor, just about any sensor, you will either get an alarm annunciation or some other tell tale something is wrong. You get your NNC out and start working the check list. Nothing else, flying and especially troubleshooting whilst in flight is primary running the appropriate NNC. The thinking of what such an alarm annunciation really means, what caused it, has already been done on the ground by the designers.

Irrespective of the sensor being faulty or not, you still need to act prudent. Which means running the NNC, verifying the problem is gone, or contained and move on if it has not. But once you have an alarm, you can never assume it is just the sensor. You need to establish/verify that first. You have to act as if the sensor is ok.

A good example are the various switches and sensors that provide signals to the pilot about the gear being down and locked in place. You get three green lights in the cockpit if it is down and locked as it is a called. On a modern jet there is actually a whole lot of sensors/switches and software logic involved, even though all that is visible to the pilot are three lights, going from amber to green.

It is not uncommon for some of these switches/sensors to break (they are out there in the open, so they lead a hard life, wind, rain, snow etc).

If the pilot doesnít get three green lights during approach, he/she will go around, execute the NNC (which involves different checks and different methods of lowering the gear). If he/she still doesnít get the three green lights, they will land, but take all the precaution as if the gear isnít properly down and locked. They will probably talk to the tower and make a few low passes so observers can have a look at the gear. But that would just be a visual clue. If they canít get the lights to go green, they will need to land as if the gear is not probably down and locked. Another procedure for that.

If they are lucky it is, and it becomes just another routine landing. With lots of fire engines in high pursuit thundering along the runway. Maybe foam on the runway. If there was a problem with the gear, everything possible to ensure the best outcome will have been done.

So the NNC are designed to verify/mend/disable/bypass any component, be it a sensor (e.g. AoA) or a system (e.g. MCAS).

Obviously, it is not fool proof. Nothing is.

As I mentioned earlier, it will be interesting to see if Boeing in the end does decide to amend their Operating manual, training, certification etc.

Jeroen
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Old 12th March 2019, 12:49   #37
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Default re: Boeing 737 Max crashes and grounding

The angle of attack sensors seem to be a faulty lot and need recall and replacement with all deliveries.

At the moment when the wrong angle of attack data goes and a stall warning appears all pilots must immediately disengage the two stablizer trim switches to off position, they are located just ahead of the fire check switches and disengage auto pilot.

Such situations are being faced in simulator situations too. Not only by 737 MAX crew but by a casual A 320 commanders too changing aircraft type for practise. They all suggest kill the stablizer trim switches and shift to manual.

Last edited by desertfox : 12th March 2019 at 12:53.
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Old 12th March 2019, 13:00   #38
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Default re: Boeing 737 Max crashes and grounding

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Originally Posted by desertfox View Post
The angle of attack sensors seem to be a faulty lot and need recall and replacement with all deliveries.
Not sure on what data you base that? With respect to the Lion Air crash, has it been determined conclusively what the problem with the AoA was exactly. It could have been a product issues, a mechanical issue, a wiring issue in the sensor or in the wiring loom in the plane, an installation issue, a maintenance issue, a test instruction issue, a software issue etc.

Maybe somebody has insights as to the root cause of the AoA problem on the Lion Air?

Back t your point, how many other airplanes have had identical problems with the AoA sensor?

Without knowing the exact root cause, you can not determine an appropiate action I would think?


Quote:
Originally Posted by desertfox View Post
At the moment when the wrong angle of attack data goes and a stall warning appears all pilots must immediately disengage the two stablizer trim switches to off position, they are located just ahead of the fire check switches and disengage auto pilot.
There is no wrong AoA data warning as such. There is no alarm that says AoA data faulty or AoA sensor not working.
See my earlier and other posts. There are indicators and certain effects a pilot can observe. In which case he/she needs to execute the appropiate NNC. Which is a bit more elaborate than throwing a switch in this particular case. figuring out which NNC to apply in case of multiple failures and problems might be a challenge in itself.

Pilots work along different routines and procedures. Certain routines are called memory items. Which mean, upon a certain observation/occurrence you immediately start executing, without referring to a check list or procedure.

In all other case, a pilot will always refer to the aircraft documentation, in this case the NNC (non normal checklist). Pilots do not start throwing switches and or disabling system immediately. There is a thought process and procedure/NNC that needs to be followed.

Part of being a pilot is being able to remain calm under all, sometimes very stressful situations and still be able to execute these routines/procedures meticulously. Flicking switches randomly in the cockpit and think it will help solve a problem tends to be very risky!

Jeroen

Last edited by Jeroen : 12th March 2019 at 13:12.
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Old 12th March 2019, 13:13   #39
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Default re: Boeing 737 Max crashes and grounding

Boeing has issued the following release in relation to the ET 302 crash. The release seems more of a PR exercise to calm down investor nerves.

Statements like "designed to make an already safe aircraft even safer" clearly show that there is something amiss which needs to be addressed by a software upgrade. Two brand new planes crashing with four months of each other is no small coincidence. It is time Boeing finishes the investigation and the relevant fixes before more innocent lives are lost.

Quote:
Boeing issued following release with respect to MCAS, Lion Air Flight 610 and Ethiopian flight 302:

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.

...

The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.

It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.

A pitch augmentation control law (MCAS) was implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack. It was put through flight testing as part of the certification process prior to the airplane entering service. MCAS does not control the airplane in normal flight; it improves the behavior of the airplane in a non-normal part of the operating envelope.

Boeingís 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018.

...

A Boeing technical team is at the crash site to provide technical assistance under the direction of the Ethiopia Accident Investigation Bureau and U.S. National Transportation Safety Board. It is still early in the investigation, as we seek to understand the cause of the accident.
Source
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Old 12th March 2019, 13:21   #40
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Default re: Boeing 737 Max crashes and grounding

The Boeing 737 Max-8 has had 2 crashes in close succession, both apparently caused by the MCAS/AoA sensor and subsequent inability of pilots to handle the situation.

Airlines in China and Indonesia, and airlines like Ethiopian, Cayman, and AeroMexico, have grounded their B737 Max-8 fleets. Regulators in other countries have issued directives that basically advise caution and impose additional checks on operators.

But, the biggest operators of this aircraft type are Southwest (31), American (22), Air Canada (20). Other major carriers operating this type are WestJet, FlyDubai, Norwegian Air Shuttle, and TUI. From what I can read online about this particular aircraft type, these operators aren't particularly concerned about safety.

I am very curious - why would this be? Could it be because they know more than others? Or do they have better pilot training programs? More stringent company-specific SOPs that are more proactively updated? Do they have better, more pro-active maintenance?

As an average fare-paying passenger, it would be highly reassuring if, say, SpiceJet were to inform passengers that flying in their 737 Max-8 is safe because they have taken xyz precautions until the FAA mandated updates are made to the aircraft.

Last edited by KiloAlpha : 12th March 2019 at 13:22.
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Old 12th March 2019, 13:35   #41
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Default re: Boeing 737 Max crashes and grounding

Quote:
Originally Posted by KiloAlpha View Post
As an average fare-paying passenger, it would be highly reassuring if, say, SpiceJet were to inform passengers that flying in their 737 Max-8 is safe because they have taken xyz precautions until the FAA mandated updates are made to the aircraft.
My spouse in transit on her second SpiceJet Max 8 flight this morning . Talk about scary coincidence - Obsessing over FR24.

DGCA has issued detailed and clear guidance though:

A) Engineering and Maintenance:
To advise Engineers and Maintenance control:
1. No MEL release for following items:
a. Dual Autopilot Inoperative
b. Yaw Damper system Inoperative
c. Spoiler system faults
2. During extended transit inspection,
a. check the following systems for any stored maintenance messages and
carry out necessary corrective action prior to release of aircraft for line
operation:
i. Autopilot system
ii. Stall Management and Yaw damper system
b. Ensure null position of Angle of attack (AOA) sensor by BITE check.

B) Flight Operations to ensure:
1. Crew operating B737 Max aircraft have undergone training as advised in the
directive issued by DGCA dated 3rd December 2018.
2. The minimum experience level of crew operating B737 Max aircraft to fly as PIC is
1000 hours and co-pilot is 500 hours on Boeing 737 NG aircraft type.

http://dgca.nic.in/public_notice/PN_...x(Mar2019).pdf
Attached Files
File Type: pdf PN_Boeing737Max(Mar2019).pdf (429.9 KB, 32 views)

Last edited by itwasntme : 12th March 2019 at 13:39.
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Old 12th March 2019, 15:46   #42
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Default re: Boeing 737 Max crashes and grounding

As of now, many countries have banned 737 MAX in their airspace or have grounded them. These include airlines from Singapore, Australia, China, Cayman islands, Indonesia, Mongolia, South Korea, Ethiopia and Mexico . The pilot body of Argentina has refused to fly B737 MAXs.

https://m.timesofindia.com/business/...www.google.com
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Old 12th March 2019, 16:41   #43
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Default re: Boeing 737 Max crashes and grounding

Was just looking at data on fatal hull losses for various aircraft. At 2, the 737 Max is now equal to the 777, which has been operating for a couple of decades now. One incident could have been pilot error, two seems like a design problem. I hope they get to the bottom of this soon - but am clear, I would not travel by 737 Maxes until this is resolved.
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Old 12th March 2019, 18:38   #44
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Default re: Boeing 737 Max crashes and grounding

Just came across this link. Appears to be providing quite the in-depth view as to how the MCAS system work on the 737 Max.

https://www.satcom.guru/2018/11/737-...n-command.html

About the earlier discussion on whether pilots should have been aware that there was such a MCAS system in the first place.

Well, I just found out that on my beloved 747-400 there is also a fully automated speed trim feature.

Quote:
While the speed trim of the 737 MAX pushes the nose down when the thrust is increasing, the 744 speed trim pushes the nose up when the airspeed is increasing because the 744's natural speed stability needs a little "electric help" under certain conditions.
Never came across that before. Some guys claim it is (well hidden) in the AOM (Aircraft Operating Manual) but I can not find it in mine.

You can not really compare the two systems perse. But both automatically, without pilot interference and without the pilots knowing or providing any indication will adjust trim.

As with the 737 on the 747 if certain conditions affecting the flight regime would occur, the pilots will execute a NNC that will effectively close down the auto trim including this special speed trim feature.

I thought I would mention it to show that on jet liners there are system operating with little or no knowledge by the pilots. This 747 stuff is probably decades old as it is.

Whether Boeing’s design philosophy on what pilots need to know, need to train for etc will be updated after all of this remains to be seen. My main concern would be that under public outcry, they might feel compelled. That is never a good basis for such decision. In fact it could be very counterproductive for aviation safety when the public at large weighs in on these very complex processes and decisions. This is of course one of the challenges in our society. Everything needs to be transparent, which means lots of opinions, but not necessarily lots of expertise

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Old 12th March 2019, 18:59   #45
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Says wrong air speed indication.
Saw on you tube and not sure of the authenticity.
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