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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 2nd Dec 2018, 17:50
  #1921 (permalink)  
 
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CVR pinger designed to transmit for 90 days

Originally Posted by phil gollin
.
Anyone know what the nominal pinger life is on the cockpit voice recorder ?
To which @patplan stated: “…It was designed to last 30 days give and take….”

Not true. The correct answer is 90 days. Otherwise patplan's comments (post #1923) are worth pondering.

FWIW, from sleuthing around the web I present these findings, which now are pretty much inconsequential in the scheme of things:

Choice of recorder manufacturers seems to be a customer option.
The DFDR recovered from PK-LQP appears identical to the FA2100 model manufactured by L3 Aviation Products.
Obviously the complete assembly was not recovered. Photographs released by investigators (example here) show that divers retrieved only the armour encased memory unit with its attached beacon.
The pinger specs on this model conform to the new regulatory requirements which from the beginning of 2020 require all underwater acoustic beacons to transmit for 90 days. Recorder manufacturers will produce upgrades for A/C fitted with older 30-day units (off topic).

Logically the CVR fitted in the accident A/C would most likely have been L3 Aviation's sister product.

Here we are 35 days since the crash, and although the missing CVR's pinger unit should theoretically transmit for 90-days, investigators reported 12 days ago that they can no longer detect the signal.

Quote from the above article:
" 'We're still putting in all our efforts to find the CVR [cockpit voice recorder],' National Transportation Safety Committee (KNKT) chief Soerjanto Tjahjono told the House of Representatives [on November 22]. The search team was targeting an area with a radius of 300 meters using sonar and dredging mud from the sea floor, even though a signal initially heard from the recorder was now no longer being detected, he said."
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Old 3rd Dec 2018, 10:21
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Just a tad of update on the CVR search from 3 days ago, according to the Indonesia Times. The NTSC are bringing in a new vessel, which has - as I understand it - enhanced capacity to remain accurately positioned even in awkward seas.

NTSC will still conduct a CVR search using more sophisticated tools from Johor, Malaysia. Ony explained that ships that are imported do not need to use anchors and are equipped with 'dynamic positioning' facilities. "If the boat is rocked to the left, if you want to stay at the location, it will come back again, so you don't need to anchor," he said.....The Head of the NTSC Aviation Committee Sub Nurcahyo Utomo added that currently the ship is still in Singapore and must take equipment in Johor, Malaysia."We have submitted a licensing process in the form of underwater operations and closure of the area at the search location. We prepare these two things hopefully in the near future everything will happen and the search will begin," he said ..
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Old 3rd Dec 2018, 11:12
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Originally Posted by Bergerie1
silverstrata,

MCAS is not an anti-stall device. It neither detects the stall nor acts as a kind of stick pusher. It is there to maintain the correct longitudinal stability in order to meet the certification requirements.
Sorry, MCAS has little or nothing to do with longitudinal stability, and everything to do with stall avoidance. That is why it monitors AoA, and operates at high AoA angles (ie: at the stall). The Boeing info on MCAS says:

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during ... flaps up flight at airspeeds approaching the stall.

Is that clear enough for you?

Silver

P.S. Goneforgotten - read my post again. It matters not what the control surfaces on the Trident are - you still have a choice, whether to put a stall avoidance system on the control column or on the trimmer. Most aircraft choose the control column, while Boeing chose the trimmer. But as I said in my post above, there are potentially grave problems with choosing the trim system. Read what I said.

.

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Old 3rd Dec 2018, 11:18
  #1924 (permalink)  
 
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They needed all the force so they picked the stronger stab trim not the elevator to get the nose down, when accelerating out of very slow speed.
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Old 3rd Dec 2018, 12:00
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Originally Posted by silverstrata


Sorry, MCAS has little or nothing to do with longitudinal stability, and everything to do with stall avoidance. That is why it monitors AoA, and operates at high AoA angles (ie: at the stall). The Boeing info on MCAS says:

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during ... flaps up flight at airspeeds approaching the stall.

Is that clear enough for you?

Silver

P.S. Goneforgotten - read my post again. It matters not what the control surfaces on the Trident are - you still have a choice, whether to put a stall avoidance system on the control column or on the trimmer. Most aircraft choose the control column, while Boeing chose the trimmer. But as I said in my post above, there are potentially grave problems with choosing the trim system. Read what I said.

.

Really interesting, can the aircraft be stalled with the MCAS operating?
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Old 3rd Dec 2018, 12:19
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Apparently the 737 MAX (without MCAS) does not have acceptable pitch characteristics with flaps UP at airspeeds approaching the stall. Therefore ...

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during ... flaps up flight at airspeeds approaching the stall.
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Old 3rd Dec 2018, 12:35
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Originally Posted by zzuf
Really interesting, can the aircraft be stalled with the MCAS operating?
It may be impossible to maintain the airplane in a stalled condition with the MCAS operating, without manual trim inputs.
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Old 3rd Dec 2018, 13:21
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Originally Posted by FCeng84
Adding a stick pusher would have been a lot more complicated and would have involved new hardware.
So why is it being discussed? Boeing designed the MAX with MCAS and then decided not to tell anyone about it. Obviously they wanted a quick fix and stick pusher does not meet that criteria. From the data and report we know the previous crew actioned the Runaway Stabilizer NNC and the accident crew most likely did not. We do not yet know why.
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Old 3rd Dec 2018, 17:04
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I am not and never was a 737 pilot, neither was I a test pilot, however I did do many CofA air tests on VC10s, 707s and 747 aircraft, all of which involved stall tests. So may I try to disentangle some of the issues that have been brought up on this thread.

First of all, STS and MCAS are entirely different systems, although they do meet similar needs. STS is not an auto trim system. Indeed, it normally functions opposite to trim. And it is not designed to "prevent a stall condition." It is there to ensure adequate longitudinal stability before the stall. The Boeing 737 MAX FCOM states:-

The Speed Trim System (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabilizer in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabilizer using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed.

This is also well described here in the PPRuNe Tech Log by FCeng84:-

B-737 Speed Trim System

For the stall, the basic requirements (in laymans’ language) are that the aircraft should have acceptable flight characteristics before, at and after the stall. By this I mean it has (a) acceptable longitudinal stability as the speed decays before the stall; (b) adequate stall warning (either from natural aerodynamic buffet or artificial devices such as a stick shaker); (c) clear identification of the stall itself (either by the nose dropping at the break point or, in the absence of this, a stick pusher); and (d) no unusual or undesirable characteristics at or immediately after the stall such as a pitch-up, a severe wing drop or entry into a spin.

In the case of T-tail aircraft, where it is possible to become locked into a deep stall, it is essential that the stick pusher functions at or before the stall and has a phase advance which makes it push early in a dynamic situation - sufficiently early to prevent an ‘over-swing’ of pitch to too high an AoA.

When Boeing designed the 737 MAX with the bigger diameter LEAP engines it was necessary to position the nacelles further forward than before. Unfortunately, when at high AoAs, the nacelles generate a certain amount of aerodynamic lift which degrades the longitudinal stability. Thus, it was decided to incorporate the MCAS. It is separate from the STS and fulfils a similar but different function by running the stabliser nose down to ensure adequate longitudinal stability at high AoAs. Unfortunately a description of this system was not included in any of the Boeing manuals available to pilots. There is a good description here:-

https://leehamnews.com/2018/11/14/bo...to-the-pilots/

Silverstrata has quoted part of the note below in response to an earlier post by me:-

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control computer using input data from sensors and other airplane systems.

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.

I emphasise again, the MCAS is not an anti-stall device. It neither detects the stall nor acts as any kind of stick pusher. It is there to maintain the correct longitudinal stability before the stall in order to meet the certification requirements.

FAA Part 25 regulations require that there be a minimum stick force per knot when speed is changed from the trim condition. The MCAS is a design solution (a software fix?) applied to the automatics to increase the required force, giving a degree of "artificial stability" by trimming the stabiliser nose down when hand flying. The paragraphs on longitudinal stability are 5.2.2.1.2, 7.2.1.1.4 and 7.2.2.2.3. See here:-

https://www.faa.gov/documentLibrary/...r/AC_25-7D.pdf

The relevant point in para 7.2.1.1.4 says (and I quote):- The average gradient of the stick force versus speed curves for each test configuration may not be less than 1 lb for each 6 knots for the appropriate speed ranges specified in § 25.175. Therefore, after each curve is drawn, draw a straight line from the intersection of the curve and the required maximum speed to the trim point. Then draw a straight line from the intersection of the curve and the required minimum speed to the trim point. The slope of these lines must be at least 1 lb for each 6 knots. The local slope of the curve must remain stable for this range.

It contains a diagram which is similar to this one in Fig 1 in this Boeing document:-

https://www.boeing.com/commercial/ae...y/fo01txt.html

Finally, if anyone wants to know more about trimming, may I recommend this article by Captain Alex Fisher:-

https://www.skybrary.aero/bookshelf/books/2627.pdf

I apologise for the length of this post. If any of you think I am talking Bollux, please feel free to fire a suitable broadside! As I said at the beginning, I never flew 737s and, as you will see from my age, I am now somewhat out-of-date.
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Old 3rd Dec 2018, 17:51
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Reuters -

Exclusive: Lion Air ponders canceling Boeing jets in row over crash - sources
More at the above link.

WORLD NEWS
DECEMBER 3, 2018 / 10:36 AM / UPDATED 2 HOURS AGO
Exclusive: Lion Air ponders canceling Boeing jets in row over crash - sources
Tim Hepher, Cindy Silviana

PARIS/JAKARTA (Reuters) - Indonesia’s Lion Air is reviewing airplane purchases from Boeing Co and has not ruled out canceling orders as relations worsen in a spat over responsibility for a 737 jetliner crash that killed 189 people in late October.

Co-founder Rusdi Kirana is furious over what he regards as attempts by Boeing to deflect attention from recent design changes and blame Lion Air for the crash, while the airline faces scrutiny over its maintenance record and pilots’ actions.

Kirana is examining the possibility of canceling remaining orders of Boeing jets “from the next delivery,” according to a person familiar with his thinking. Another source close to the airline said it was looking at canceling orders.

No final decision has been made, but discussion over the fate of $22 billion of remaining orders highlights the stakes surrounding an investigation involving Boeing’s fastest-ever selling jet, the 737 MAX, which entered service last year.

Lion Air has 190 Boeing jets worth $22 billion at list prices waiting to be delivered, on top of 197 already taken, making it one of the largest U.S. export customers.

Any request to cancel could be designed to put pressure on Boeing and would likely trigger extensive negotiations. Many airlines defer orders, but industry sources say aerospace suppliers rarely allow much scope for unilateral cancellations...
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Old 3rd Dec 2018, 18:26
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Originally Posted by Zeffy
That article is disturbing to me from a corporate culture reason. It seems to be about blame deflection, and not about problem solving.
There seems to be a significant number of holes in quite a few slices of cheese.
Put differently, if we examine how many sectors their Lion Air 737 MAX hulls have flown since the first one arrived ...
How many of them had to be hand flown due to such a problem? Was this a first?
How many pilots knew about this work around that worked for one crew while the maintainers tried to figure out what needed to be fixed?
One, or more than one? Or was this a first time for everyone?
On Boeing's side, how many reports from all customers have come in regarding that kind of behavior since first passenger carrying flight flew? Any? If more than zero, how did that information get disseminated to the people flying the aircraft?
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Old 3rd Dec 2018, 18:38
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Bergerie1; Silverstrata,

I heard it is Part25.203a that 737 Max is having issue with, and MCAS to meet requirements
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Old 3rd Dec 2018, 20:13
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Originally Posted by Zeffy
Exclusive: Lion Air ponders canceling Boeing jets in row over crash - sources

Lion Air has 190 Boeing jets worth $22 billion at list prices waiting to be delivered, on top of 197 already taken, making it one of the largest U.S. export customers.
Lion Air has nowhere close to 197 Boeings in its current fleet.
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Old 3rd Dec 2018, 21:12
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I'm not afraid to say there's plenty of blame to go around here. And I'm not afraid to say that the 737 MAX has never generated enthusiasm anywhere but the C-suites. And I'm sure that Lion Air wants to negotiate a price cut - what company wouldn't? But let's consider the circumstances. This is a company that can't afford the suggestion that they are ruthless in cutting costs, regardless of the human price to be paid. To suggest that they'd take such a crass route after a tragedy like this one shocks the conscience. I mean, do they realize how much of a civil settlement on a US court they are flushing down the toilet ? So, not trustworthy news, unless Boeing signed a launch deal with a bunch of incompetents.
​​​
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Old 3rd Dec 2018, 21:34
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There have been several posts relating to training and the need for MCAS in training simulators. But what would the training consist of, to what purpose ?

The need to demonstrate the normal MCAS trim movement would not be essential based on the experience of pilots and operators of the large number of aircraft already in service. Who of them questioned that the trim was moving ‘in the wrong’ direction, who asked Boeing, checked manuals, questioned Pprune, etc. Apparently none.

The MCAS trim is the system’s visible output, which ‘fails’ due to input errors (AoA, speed, thrust ?) or switching logic (flap, WoW ?). In this accident, trim movement was consequential to flap retraction, before that all indications related to stick-shake, air-data (IAS, ALT) disagree, low speed awareness, and a FEEL DIFF PRESS alert.
The immediate flight task requires establishing a reliable speed indication - cross check and compare with standby speed, and the validity of the stick-shake. ‘Is there a speed error or is the aircraft approaching stall’.
Only thereafter, and depending on what was concluded above, the crew would have to inhibit the trim before retracting flaps. The cue for this is the particular combination of alerts, low speed awareness, and continuing stick-shake, i.e. an AoA vane problem, which in the MAX can affect MCAS. This discounts any effect of false AoA on speed correction / computation - (more info required)?

Thus the training task for AoA input errors with flaps down is primarily understanding the situation; air-data and low speed, or air-data, AoA, stick-shake. Fly the aircraft via the most reliable data, and use manual (mechanical trim).

MCAS trim only comes into play in situations with with flap up. If the AoA is a sudden onset, then all of the air-data issues and stick-shake as above still apply, together with the need to determine instrument accuracy vice real stall - fly the aircraft. Only subsequently would MCAS issues appear.
MCAS trim like STS and Mach TRIM, is un-commanded and intermittent. Only the PF has knowledge of aircraft feel and its relationship to manual electric trim.
In parallel with these effects the crew could have autopilot disengagement, or need to manage external contributions associated with the AoA problem, e.g. bird-strike, icing. There could be many simultaneous demands on mental resource and continuing stick-shake distraction.

The description of the ‘runaway stabiliser’ emergency drill could help understand the situation, but this first requires determining that the trim has ‘runaway’. The drill title is misleading if related to MCAS, trim movement is not continuous, and in order to differentiate between the various un-commanded trim inputs it might be necessary to observe the trim for up to 30 sec; two cycles of MCAS, give or take manual inputs - establishing trim control or not.
Whatever situation is established, or even if uncertain, inhibiting trim is either required or is an acceptable precaution. Thereafter the aircraft is flown with manual (mechanical trim).

Thus the training need is to establish and understand the situation, where the same or similar indications will relate to, or can be misinterpreted as other situations, e.g. independent air-data failure, UAS, or approaching a “real’ stall.
It may be necessary to demonstrate several situations in order to clearly differentiate between the critical one and choose an appropriate drill.
Depending on the situational context then MCAS might not be the most urgent concern, e.g. stick-shake after rotate, unreliable airspeed, and distractions with several simultaneous alerts.

Most if not all of these apply to previous versions of the 737, thus should be understood; in addition the key points do not require MCAS to be installed to replicated accurately except for demonstrating the difficulties in understanding the situation. The need to inhibit the trim in the presence of other alerts and indications is only a MAX problem, and once a correct understanding is achieved the action is simple.
Add to that some practice in manual flying without electric trim, and need to manage surprise, control of attention, and fly the aircraft.
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Old 3rd Dec 2018, 21:48
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Originally Posted by DaveReidUK
Lion Air has nowhere close to 197 Boeings in its current fleet.
Dave - I think they meant the Lion Air group, which also includes Batik Indonesia, Batik Malaysia, Thai Lion Air and Malindo. I tried to add them all up and got 242, but believe that includes some double counting, possibly due to my uncertainty over the apparent rebranding of Malindo to Batik Malaysia. Either way, it is a substantial fleet.
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Old 3rd Dec 2018, 23:17
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Originally Posted by AGBagb
Just a tad of update on the CVR search from 3 days ago, according to the Indonesia Times. The NTSC are bringing in a new vessel, which has - as I understand it - enhanced capacity to remain accurately positioned even in awkward seas.

NTSC will still conduct a CVR search using more sophisticated tools from Johor, Malaysia. Ony explained that ships that are imported do not need to use anchors and are equipped with 'dynamic positioning' facilities. "If the boat is rocked to the left, if you want to stay at the location, it will come back again, so you don't need to anchor," he said.....The Head of the NTSC Aviation Committee Sub Nurcahyo Utomo added that currently the ship is still in Singapore and must take equipment in Johor, Malaysia."We have submitted a licensing process in the form of underwater operations and closure of the area at the search location. We prepare these two things hopefully in the near future everything will happen and the search will begin," he said ..
Just think how useful a streamed copy of the CVR would have been. How much money would have been saved. How much contentious discussion.
But no - stay with an antediluvian approach that almost never works when it is really needed as in this and other cases when the unfortunate crew are not available to give evidence.
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Old 4th Dec 2018, 02:49
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Just think how useful a streamed copy of the CVR would have been. How much money would have been saved. How much contentious discussion.
The cost of a charter boat and rescue team pales into insignificance against the cost of implementing what you are suggesting. The data expense alone would be to much to bear for most airlines. Additional to cost you have no guarantee it would even work when you need it. Murphy's Law seems to magically prove itself in aviation time after time.
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Old 4th Dec 2018, 06:56
  #1939 (permalink)  
 
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MCAS functionality

It is surprising to me that the details of the MCAS functionality have not come to full focus here within PPRUNE yet. MCAS inserts airplane nose down stabilizer as a function of Mach number and how far beyond a trigger AOA value (a function of flight condition) the airplane has gone. When AOA reduces to below the MCAS sctivation threshold MCAS runs the stabilizer airplane nose up the same amount so that it is back where it started. If the pilot commands manual electric trim while MCAS is active, MCAS is “reset” based on the assumption that the pilot has taken over responsibility for pitch trim and will bring the stabilizer to the proper trimmed position.

The only way to get MCAS to insert more than one increment of airplane nose down trim is for all of the following to occur:
1. High AOA is detected leading to one MCAS increment of stabilizer
2. Manual pilot electric trim command is detected thus causing a reset of MCAS
3. Pilot does not fully command stabilizer to its trimmed position
4. High AOA is once again detected leading to another MCAS increment of stabilizer
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Old 4th Dec 2018, 07:21
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Originally Posted by FCeng84
When AOA reduces to below the MCAS sctivation threshold MCAS runs the stabilizer airplane nose up the same amount so that it is back where it started.
Does it?! Can I ask where you got that information from please. I can't recall having seen anything saying that MCAS provides nose up trim commands under any circumstances.

Originally Posted by FCeng84
The only way to get MCAS to insert more than one increment of airplane nose down trim is for all of the following to occur:
1. High AOA is detected leading to one MCAS increment of stabilizer.
2. Manual pilot electric trim command is detected thus causing a reset of MCAS
3. Pilot does not fully command stabilizer to its trimmed position
4. High AOA is once again detected leading to another MCAS increment of stabilizer
Are you sure about that? The Boeing Multi Operator Message SUBJECT: Information - Multi-Model Stall Warning and Pitch Augmentation Operation of 10 November stated:

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.
My reading of that is that MCAS will command more than one increment of nose down trim 'If the original elevated AOA condition persists.' That is, if after having commanded one increment of nose down trim the sensed Angle of Attack still exceeds the Angle of Attack threshold, MCAS will command another increment of nose down trim. That should be entirely independent of any manual trim interventions.

Last edited by MickG0105; 4th Dec 2018 at 07:22. Reason: Spelling
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