Indonesian aircraft missing off Jakarta
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737 Max does not have elevator authority issue
Some on this thread have suggested that MCAS May have been added to compensate for an elevator authority shortfall. That is not the case. This function was added to address a pitching moment vs AOA issue. With autopilot control of stabilizer to address a speed stability issue (aka STS) already in place on earlier 737 models, adding MCAS was relatively simple. Adding a stick pusher would have been a lot more complicated and would have involved new hardware.
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Both flight JT33 JT43 have delayed flight more than 120 min.
I correct all data based on confirmed the JT43 pax. The story JT33 pax is removed.
Last edited by Realbabilu; 2nd Dec 2018 at 18:04. Reason: Correct all info
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The Trident was a rear engined, "T" tail design which is subject to deep stalling, where the tailplane and engines can have their airflow blanketed by the wings, resulting in loss of elevator authority, rudder authority and engine flame out. Much higher levels of stall prevention would obviously need to be applied at the design and certification stage.
The 737 has a large nose up moment from underslung engines.
They each have a design issue at the stall that requires an anti-stall augmentation device (as do most large aircraft). Hawker Sidley went for a stick push, while Boeing went for a trim push. But which is best? The fact is, when a stick-push finally relents, you are still in trim and can easily pull out of the dive. When a trim-push finally relents you are left with full forward trim and cannot pull out of the dive.
Which system is best?
Silver
P.S. Obviously we are talking about old-fashioned cable-controlled aircraft here, as the 737 flight control system not computer controlled. The Airbus is more sophistcated, but must still choose between elevator stall augmentation and stabiliser stall augmentation. Judging by the AF447 incident, when in manual law there is no anti-stall augmentation device, as the crew held the aircraft nose up using elevators for some considerable time.
.
S
Last edited by silverstrata; 2nd Dec 2018 at 08:53.
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All the Pilots I have flown with instinctively trimmed their aircraft, they did not have to work out or analyse why it was needed; in the B737 Stab system, even if they could not hear it above the other noises, they would know it was moving, it is next to their knees and, as I understand, it was not just creeping around with the MCAS input.
Something more dramatic went wrong to cause the steep dive, be it health related or a mechanical failure.
If only to keep the options open for discussion, as the elevator input cables are designed to take full manual input loads, when there has been A&B hydraulic failure they are unlikely to have broken during this flight but what if?
Something more dramatic went wrong to cause the steep dive, be it health related or a mechanical failure.
If only to keep the options open for discussion, as the elevator input cables are designed to take full manual input loads, when there has been A&B hydraulic failure they are unlikely to have broken during this flight but what if?
Last edited by DaveReidUK; 2nd Dec 2018 at 10:06.
Some on this thread have suggested that MCAS May have been added to compensate for an elevator authority shortfall. That is not the case. This function was added to address a pitching moment vs AOA issue. With autopilot control of stabilizer to address a speed stability issue (aka STS) already in place on earlier 737 models, adding MCAS was relatively simple. Adding a stick pusher would have been a lot more complicated and would have involved new hardware.
My guess is that the slope of the curve is already very low, so a four times control force increase may be very low compared with that required to overcome the instability (that force could also be fairly low).
Makes me think that this increase in force applied by the EFS is actually just another stability augmentation system which has reach the limit of authority in at least one area with the 737 MAX hence the MCAS. Funny if this capability of the EFS was just a stick nudger in disguise.
Perhaps you or Seattle contacts could make an authoritative comment! Thanks.
Last edited by zzuf; 2nd Dec 2018 at 10:22.
Wiedehopf # 189, “Knowing you have an AoA problem means you might more easily disregard a stick shaker when it doesn't make sense. Also on takeoff crosschecking speeds AND AoA seems like a sensible idea”.
You appear to have overlooked the main points about comparison in a dual system, which can detect a difference, but not which one of the sensors is incorrect; hence the stick-shake could be real.
Whilst the converse could be true, it is fail safe; see discussion on 737 stick-shake in Tech Log.
An optimum design with a dual systems ‘disagree’ is to remove ambiguity particularly when there is no alternative display to cross check. e.g. AoA disagree, low speed awareness remove; IAS disagree, annunciate and check best 2 out of 3 displays for continued use.
zzuf, I would agree with the view in # 1902 that MCAS is more related to stability than stall.
For those who continue to focus on stall, consider that forward trim might be applied at any time over a wide speed range - at or below Vref down to Vss. MCAS appears to involve a continuous assessment involving speed, AoA, and thrust; pitch and pitching moment, not as a result of a specific AoA as in stall warning / identification.
Also, for elevator effectiveness, there is a significant difference between the low speed stall situations, and nose-down trim at high speed.
piratepete # 1907, and MickG0105 # 1909, re un airworthy.
As discussed previously, how might an operator determine ‘un airworthy’ in this instance.
What is the industry norm ?
Resetting maintenance logs might be a function of BITE, which was run (report page 17) and concluded ‘no faults’, i.e. a serviceable system.
Depending on functionality, BITE might only be able to check the integrity of the connection to each AoA vane but not identify an offset fault.
Underlying these operational problems is the complexity of the overall control, flight guidance, display and alerting systems. ‘Intractable and close coupled.’
The overall ‘system’ is difficult, impossible to describe at the sharp-end. The level of knowledge required is insufficient to relate all interconnections, implications, and consequences of sensor interactions over the complete operational envelope. Thus neither pilots nor maintenance can be expected to deal with difficult failures without accurate descriptive guidance and checklists.
Another thought, is that the manufacturer was similarly ‘unable’ to describe, or have awareness of the overall system; e.g. flight control /aerodynamics use AoA input (dual) to overcome a stability issue, but with a viewpoint of a redundant (triple) system - AFCS / trim. Such a situation can arise from ‘egg-box’ like organisations or extremely large, complex, and interacting subsystems; in these cases then there should always be some one in design, airworthiness, or certification who can ask ‘the question’, but what is the question, who asked, when. Similarly for the FAA.
You appear to have overlooked the main points about comparison in a dual system, which can detect a difference, but not which one of the sensors is incorrect; hence the stick-shake could be real.
Whilst the converse could be true, it is fail safe; see discussion on 737 stick-shake in Tech Log.
An optimum design with a dual systems ‘disagree’ is to remove ambiguity particularly when there is no alternative display to cross check. e.g. AoA disagree, low speed awareness remove; IAS disagree, annunciate and check best 2 out of 3 displays for continued use.
zzuf, I would agree with the view in # 1902 that MCAS is more related to stability than stall.
For those who continue to focus on stall, consider that forward trim might be applied at any time over a wide speed range - at or below Vref down to Vss. MCAS appears to involve a continuous assessment involving speed, AoA, and thrust; pitch and pitching moment, not as a result of a specific AoA as in stall warning / identification.
Also, for elevator effectiveness, there is a significant difference between the low speed stall situations, and nose-down trim at high speed.
piratepete # 1907, and MickG0105 # 1909, re un airworthy.
As discussed previously, how might an operator determine ‘un airworthy’ in this instance.
What is the industry norm ?
Resetting maintenance logs might be a function of BITE, which was run (report page 17) and concluded ‘no faults’, i.e. a serviceable system.
Depending on functionality, BITE might only be able to check the integrity of the connection to each AoA vane but not identify an offset fault.
Underlying these operational problems is the complexity of the overall control, flight guidance, display and alerting systems. ‘Intractable and close coupled.’
The overall ‘system’ is difficult, impossible to describe at the sharp-end. The level of knowledge required is insufficient to relate all interconnections, implications, and consequences of sensor interactions over the complete operational envelope. Thus neither pilots nor maintenance can be expected to deal with difficult failures without accurate descriptive guidance and checklists.
Another thought, is that the manufacturer was similarly ‘unable’ to describe, or have awareness of the overall system; e.g. flight control /aerodynamics use AoA input (dual) to overcome a stability issue, but with a viewpoint of a redundant (triple) system - AFCS / trim. Such a situation can arise from ‘egg-box’ like organisations or extremely large, complex, and interacting subsystems; in these cases then there should always be some one in design, airworthiness, or certification who can ask ‘the question’, but what is the question, who asked, when. Similarly for the FAA.
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The Trident in fact had an all flying tail, the column commanded the whole tailplane and what appears to be an elevator was in fact a geared tab, albeit quite a large one. So the pitch trim did not use an independent surface, unlike most subsequent CAT designs, and the distinction between a stick pusher and a MCAS-like device didn't arise. Hope that's clear
Another thought, is that the manufacturer was similarly ‘unable’ to describe, or have awareness of the overall system; e.g. flight control /aerodynamics use AoA input (dual) to overcome a stability issue, but with a viewpoint of a redundant (triple) system - AFCS / trim. Such a situation can arise from ‘egg-box’ like organisations or extremely large, complex, and interacting subsystems; in these cases then there should always be some one in design, airworthiness, or certification who can ask ‘the question’, but what is the question, who asked, when. Similarly for the FAA.
Many years ago at Boeing Seattle on B734 we had to do a test point which required input of false flight condition information to the autothrottle. I don't remember the detail but it required a comprehensive preflight briefing on the system.
A meeting room with 12 Boeing engineers - from the TOGA button specialist to the fuel control output specialist and 2 hours to give us brief rundown on how it all worked. The only specialist who had a reasonable overall understanding were the Boeing TP's. The others had a very detailed understanding of their part in the "egg box". There was no one "go to" person who understood the entire system to the level of detail we required.
Sorry about the subject drift.
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A friend emailed me this. Makes me thinking. Why not require a MAX simulator? Seems to me practicing MAX landings in non MAX simulators is disingenuous. What about the different placement of the larger MAX engines and the downward winglet? Not in normal conditions, but at crosswind limits and even gusty winds. I know when I got my 767 rating we had to make a night visual landing at crosswind limits. Spent a lot of sim time nailing that down.
American Air pilots seek more training on Boeing 737 MAX after Lion Air crash
Originally published November 29, 2018 at 3:54 pm Updated November 29, 2018 at 4:04 pm
The president of the Southwest Airlines Pilots Association said Boeing is proposing solutions and fixes for the anti-stall device on the MAX jet that should be in place before the end of the year.
By Mary Schlangenstein
Bloomberg News
American Airlines Group pilots want the carrier to offer more training on Boeing’s 737 MAX to better understand new anti-stall software, after a preliminary report on an Indonesia plane crash suggested that aircraft malfunctions left aviators overwhelmed.
The Allied Pilots Association (APA) made the request after what the union said was an unprecedented meeting with Boeing officials this week. The manufacturer also met with Southwest Airlines’ pilots union. Both carriers fly the MAX, Boeing’s latest iteration of the popular 737 jetliner. The new model replaced an older version called the next generation, or NG.
The APA is asking American “to consider additional days of training for these significant differences in the NG and the MAX,” said Dennis Tajer, a spokesman for the union and a 737 captain at the airline.
Boeing is working to bolster confidence in its systems after pilots from American and Southwest said they weren’t informed about a flight-control system on the MAX that can pitch the aircraft’s nose downward if it suspects the plane is losing lift under its wings. That change was an early focus of the investigation into what caused the Lion Air jet to crash into the Java Sea last month, killing 189 people.
Boeing didn’t immediately respond to a request for comment.
American said its approach to safety is based on “open communication and collaboration with manufacturers, regulators and the unions.” Southwest said it’s working closely with its pilots union and Boeing. The United Continental Holdings chapter of another union, the Air Line Pilots Association, had no immediate comment about any meetings with Boeing. United also operates the MAX.
American pilots flying the NG version of Boeing’s single-aisle workhorse, the 737-700 and 737-800, took about an hour of online training on operating the MAX. They also received training in a flight simulator for the older model on crosswind landings because of the MAX’s larger engines and lower wing tips. American and Southwest don’t have MAX simulators. (emphasis mine)
“We were told that not much else is different,” Tajer said in an interview Thursday. “Now we know there is. We’d like to revisit the training that pilots on the line have received now and going forward.”
Boeing reassured the Southwest Airlines Pilots Association that the company is “extremely confident there will be no more surprises” with the MAX after a thorough review, Jon Weaks, president of the union and a captain at the airline, told members in a message. Southwest, which has an all-737 fleet, uses NG simulators to help train pilots for the MAX, an airline spokesman has said.
The lack of disclosure about the anti-stall device known as the Maneuvering Characteristics Augmentation System (MCAS) “is still very disconcerting,” Weaks said. “Boeing is proposing solutions and fixes for the MCAS system which should be in place before the end of the year.”
A preliminary report released Wednesday by Indonesian regulators didn’t give a cause of the accident, but suggested poor safety procedures and a struggle by the pilots to control a repeatedly malfunctioning airplane may have contributed to the crash.
Regulators detailed steps taken to address malfunctions reported on the plane the previous night and difficulties that aviators on both flights had figuring out basic information such as speed and altitude.
The pilots on the flight the night before the accident were able to disable the system pushing down the nose. They landed safely. In bulletins to airlines, Boeing has reminded carriers that a longstanding emergency procedure — which pilots must memorize — enables them to handle such malfunctions.
With assistance from Alan Levin, Justin Bachman and Julie Johnsson
Originally published November 29, 2018 at 3:54 pm Updated November 29, 2018 at 4:04 pm
The president of the Southwest Airlines Pilots Association said Boeing is proposing solutions and fixes for the anti-stall device on the MAX jet that should be in place before the end of the year.
By Mary Schlangenstein
Bloomberg News
American Airlines Group pilots want the carrier to offer more training on Boeing’s 737 MAX to better understand new anti-stall software, after a preliminary report on an Indonesia plane crash suggested that aircraft malfunctions left aviators overwhelmed.
The Allied Pilots Association (APA) made the request after what the union said was an unprecedented meeting with Boeing officials this week. The manufacturer also met with Southwest Airlines’ pilots union. Both carriers fly the MAX, Boeing’s latest iteration of the popular 737 jetliner. The new model replaced an older version called the next generation, or NG.
The APA is asking American “to consider additional days of training for these significant differences in the NG and the MAX,” said Dennis Tajer, a spokesman for the union and a 737 captain at the airline.
Boeing is working to bolster confidence in its systems after pilots from American and Southwest said they weren’t informed about a flight-control system on the MAX that can pitch the aircraft’s nose downward if it suspects the plane is losing lift under its wings. That change was an early focus of the investigation into what caused the Lion Air jet to crash into the Java Sea last month, killing 189 people.
Boeing didn’t immediately respond to a request for comment.
American said its approach to safety is based on “open communication and collaboration with manufacturers, regulators and the unions.” Southwest said it’s working closely with its pilots union and Boeing. The United Continental Holdings chapter of another union, the Air Line Pilots Association, had no immediate comment about any meetings with Boeing. United also operates the MAX.
American pilots flying the NG version of Boeing’s single-aisle workhorse, the 737-700 and 737-800, took about an hour of online training on operating the MAX. They also received training in a flight simulator for the older model on crosswind landings because of the MAX’s larger engines and lower wing tips. American and Southwest don’t have MAX simulators. (emphasis mine)
“We were told that not much else is different,” Tajer said in an interview Thursday. “Now we know there is. We’d like to revisit the training that pilots on the line have received now and going forward.”
Boeing reassured the Southwest Airlines Pilots Association that the company is “extremely confident there will be no more surprises” with the MAX after a thorough review, Jon Weaks, president of the union and a captain at the airline, told members in a message. Southwest, which has an all-737 fleet, uses NG simulators to help train pilots for the MAX, an airline spokesman has said.
The lack of disclosure about the anti-stall device known as the Maneuvering Characteristics Augmentation System (MCAS) “is still very disconcerting,” Weaks said. “Boeing is proposing solutions and fixes for the MCAS system which should be in place before the end of the year.”
A preliminary report released Wednesday by Indonesian regulators didn’t give a cause of the accident, but suggested poor safety procedures and a struggle by the pilots to control a repeatedly malfunctioning airplane may have contributed to the crash.
Regulators detailed steps taken to address malfunctions reported on the plane the previous night and difficulties that aviators on both flights had figuring out basic information such as speed and altitude.
The pilots on the flight the night before the accident were able to disable the system pushing down the nose. They landed safely. In bulletins to airlines, Boeing has reminded carriers that a longstanding emergency procedure — which pilots must memorize — enables them to handle such malfunctions.
With assistance from Alan Levin, Justin Bachman and Julie Johnsson
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The Trident in fact had an all flying tail, the column commanded the whole tailplane and what appears to be an elevator was in fact a geared tab, albeit quite a large one. So the pitch trim did not use an independent surface, unlike most subsequent CAT designs, and the distinction between a stick pusher and a MCAS-like device didn't arise. Hope that's clear
Do you fit the anti-stall aumentation system to the control column, or to the trimmer..? The diferrence being that the control column (usually) gives an instantaneous response, while the trimmer (usually) gives a slow response. So when in the recovering dive, after an incipient stall event, the stick-push will relent immediately, while the trimmer may take 10 or 20 seconds to get back to neutral.
So tell me, how long did it take for the Trident to get from full trim forward, to neutral? The 737 takes about 20 seconds, which will probably make a recovery from the dive difficult or impossible.
The Rostov incident appears to have demonstrated this problem very well. Even with the trim set to 1.5 units (instead of the normal 5 or 6 units), the FlyDubai aircraft plunged to the ground almost vertically. But MCAS does not trim to 1.5 units, it can apparently trim to 0 units. So what chance is there for a recovery, with the stab-trim at 0 units (full forward) ? I would suggest little or none....
Silver
Can't vouch for MAX but on -800 it's possible to have AOA DISAGREE without AOA indication. NNC items are: 1. Airspeed errors and IAS DISAGREE alert may occur 2. Altimeter errors and ALT DISAGREE alert may occur. That's it.
Clandestino, … on -800 it's possible to have AOA DISAGREE without AOA indication.
Does this imply that with the EFIS AoA display modification, the AoA displays are removed with a disagree alert ?
Or if without the EFIS display mod, the alert is given because AoA is used in other systems apart from stall warning ?
Thus IAS and ALT disagree alerts may be given simultaneously (with speed/alt errors), a consequence of AoA disagree, like the MAX ?
Does this imply that with the EFIS AoA display modification, the AoA displays are removed with a disagree alert ?
Or if without the EFIS display mod, the alert is given because AoA is used in other systems apart from stall warning ?
Thus IAS and ALT disagree alerts may be given simultaneously (with speed/alt errors), a consequence of AoA disagree, like the MAX ?
Ask the pilot who flies it, he knows how to make it safe, else he wouldn't fly it
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, see link below:-
https://www.boeing.com/commercial/ae...y/fo01txt.html
Boeing 747s on the British register were fitted with a stick nudger that activated in the clean configuration when the stick shaker started. It gave a gentle 16lb push and was a rough and ready way of satisying the pre-stall longitudinal stability requirement. As far as I know MCAS was a more sophisticated way of achieving the same end. Whether or not it was the right solution we will await to see.
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, see link below:-
https://www.boeing.com/commercial/ae...y/fo01txt.html
Boeing 747s on the British register were fitted with a stick nudger that activated in the clean configuration when the stick shaker started. It gave a gentle 16lb push and was a rough and ready way of satisying the pre-stall longitudinal stability requirement. As far as I know MCAS was a more sophisticated way of achieving the same end. Whether or not it was the right solution we will await to see.
Last edited by Bergerie1; 2nd Dec 2018 at 17:05.
I've never understood why AOA indication has never gained any traction as a pilot aid on civilian aircraft? It presents a very useful cross check on ASI information at low speeds.
Dunno, I have never seen AoA display on the PFD and there is nothing about it in my FCOM, so there is good chance my company has not taken that option but AOA DISAGREE has been in our QRHs for quite a few years, with list of tail numbers it is applicable to, so there are some planes that don't have alpha comparator. All I'm saying that even AOA DISAGREE alert is a customer option not necessarily packed together with alpha display.
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It matters not if that rear surface on the Trident is an elevator, a balance-tab, or a servo-tab - the same choice applies.
Do you fit the anti-stall aumentation system to the control column, or to the trimmer..? The diferrence being that the control column (usually) gives an instantaneous response, while the trimmer (usually) gives a slow response. So when in the recovering dive, after an incipient stall event, the stick-push will relent immediately, while the trimmer may take 10 or 20 seconds to get back to neutral.
So tell me, how long did it take for the Trident to get from full trim forward, to neutral? The 737 takes about 20 seconds, which will probably make a recovery from the dive difficult or impossible.
The Rostov incident appears to have demonstrated this problem very well. Even with the trim set to 1.5 units (instead of the normal 5 or 6 units), the FlyDubai aircraft plunged to the ground almost vertically. But MCAS does not trim to 1.5 units, it can apparently trim to 0 units. So what chance is there for a recovery, with the stab-trim at 0 units (full forward) ? I would suggest little or none....
Silver
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But MCAS does not trim to 1.5 units, it can apparently trim to 0 units. So what chance is there for a recovery, with the stab-trim at 0 units (full forward) ? I would suggest little or none....