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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 11th Apr 2019, 21:36
  #3881 (permalink)  
 
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Originally Posted by L39 Guy View Post
If one rolls down the runway with both engines providing the advertised thrust (94%), the airspeed cross check at 80 indicates no disparity, and the aircraft is rotated normally at Vr with both airspeed indicators working normally then rotated to a climb attitude and the engines continue to turn and burn, then any erroneous stall warning has to be ignored and treated as such.
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Really?

You rotate and get a stall warning, and because your engines are "turning and burning", then you just ignore the stall warning? Has it not occurred to you that you may have your high lift devices incorrectly set, and that the fault was the takeoff config system (Spanair)? Or you have been loaded incorrectly? Or you have an engine indication issue (Air Florida)? Just because your engines are "turning and burning" does not mean that any stall detection on rotation is erroneous. Obviously.
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Old 11th Apr 2019, 22:08
  #3882 (permalink)  
 
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Originally Posted by maxxer View Post
All 3 sensors on the left side mess up at the same time , just not as bad as the AOA senser and also in the flip between 05:43:15 and 05:43:30 there is a influence on altitude speed and AOA so it seems the problem is not just with the one sensor but with the wiring or the adiru.
AoA data is used to adjust airspeed and altitude, so errorneous AoA signal will affect both of these.

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Old 11th Apr 2019, 22:29
  #3883 (permalink)  
 
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This is from the Bloomberg article, seems that pressing on with a stick shaker is not unheard of. SInce this was in Nasa safet database unlikely to be a 'third world crew', correct me if I am wrong on that.

As soon as the plane got airborne, the captain, seated on the left side, got the loud thumping noise and vibrating control column warning that the plane was about to stall, according to the NASA report. The captain’s airspeed and altitude displays disagreed with the copilot’s, indicating an error and setting off additional alerts. All of those symptoms occurred on the two recent Max crashes.

The pilots opted to continue onto their destination in spite of the multiple failures. Both the captain and the copilot said that they regretted continuing the flight and didn’t realize that they had violated their airline’s procedures by disabling the stall warning.

“A return, while considered, should have been accomplished,” said the captain.

Only after they landed did they realize that the captain’s angle-of-attack vane was bent for unknown reasons.
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Old 11th Apr 2019, 22:46
  #3884 (permalink)  
 
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Originally Posted by MurphyWasRight View Post
This is from the Bloomberg article, seems that pressing on with a stick shaker is not unheard of. Since this was in Nasa safety database unlikely to be a 'third world crew', correct me if I am wrong on that.
Correct. US carrier.
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Old 11th Apr 2019, 23:45
  #3885 (permalink)  
 
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Not sure whether this has been posted previously...

https://seekingalpha.com/instablog/3...se-pilot-error
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Old 12th Apr 2019, 00:11
  #3886 (permalink)  
 
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Originally Posted by L39 Guy View Post
If one rolls down the runway with both engines providing the advertised thrust (94%), the airspeed cross check at 80 indicates no disparity, and the aircraft is rotated normally at Vr with both airspeed indicators working normally then rotated to a climb attitude and the engines continue to turn and burn, then any erroneous stall warning has to be ignored and treated as such. That is why manufacturers provide nominal pitch/power settings to insure a stall free climb or cruise while it gets sorted out. In fact, I had the same stick shaker after take-off many years ago on the 737-200 after lift-off; yes, it gets your attention but if the attitude of the aircraft is ok and the engines are running fine then it cannot be a bona fide stall but an erroneous indication.
If the crew thought it was a stall, then the stall recovery should have been implemented - it was not and in fact they (Ethiopian) tried to engage the autopilot, a definite no-no in a stall.
So even setting aside the MCAS issue later, sadly this all points to training and experience to handle a pretty basic emergency. And that points back to the airline and the CAA who are responsible for that.
Maybe you should read about the background a little bit?

ADD, Addis Ababa Bole Airport, 2334 meter [7625 ft] elevation/ASL.
DIA, Denver International Airport, 1655 meter [5431 ft] elevation/ASL.

ADD is more than 2200 feet higher than DIA. It is among the top for the list of notoriously "HOT AND HIGH" airports in the world.

It goes without saying that the aircraft there will have a different TO routine, notably requiring a higher thrust and a longer run, plus high terrain avoidance.

We have to also remember the MCAS "deadly potion" as well: AOA False high & Autopilot Off & FLAP Zero.

105 seconds into their flight, the AOA was already gone mad [IAS disagree, ALT unreliable, stick shaker], but they MUST go FLAP ZERO ASAP to gain Altitude at this higher elevation. And, they needed all the thrust.

They knew they had to play around with the flap and/or the Autopilot to keep MCAS at bay- at least one of these had to be ON to hold off the MCAS "deadly potion".

So, these are their only choices:
1. Going with with Flap On|Autopilot Off.
2. Going with Flap Off|Autopilot On.
3. Going with Flap On|Autopilot On.

Obviously going with Flap On (i.e. [1] and [3]) would go against their effort to gain altitude. That would leave them with (2). So, they turned on the AP, not because they wanted the AP, but it was because their circumstance FORCED them to turn AP on.

When the AP was turned on, they bought themselves about 60 seconds [actually only about 20 "clean" seconds because during FLAP ZERO] to continue gaining the altitude but they were still only about 300-500 feet off the ground [8000+ ft - 7626]...

In other words, the MCAS "deadly potion" constraint made their already difficult TO situation [a high elevation TO, a long run, a stick shaker, an IAS disagree, an ALT unreliable, other warnings] much much worse.
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Old 12th Apr 2019, 00:45
  #3887 (permalink)  
 
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Originally Posted by Ace McKool View Post
Not sure whether this has been posted previously...

https://seekingalpha.com/instablog/3...se-pilot-error
Thanks for the link. That is an EXCELLENT read.

Summary

The pilots (crew) mismanaged engine thrust and airspeed.

Excessive airspeed rendered manual trim ineffective.

The crew deviated from the emergency procedure.

Crew experience and competency a major contributing factor.

CONCLUSION

Examining both accidents separately provides valuable insights—it’s easy to understand how these unrelated airlines and crew may have responded in similar ways—but the overall conclusion in our previous article, “Boeing’s Grounding: Catastrophic Crashes, and Questions About Boeing’s Liability And 737 MAX Aircraft Viability,” still stands—the major contributing factor to these accidents was pilot error.

After a more comprehensive analysis of each of the two accidents, especially Lion Air Flight 610, we are persuaded more than ever that the case for pilot error—as well as inadequate training—are the dominant contributing factors in both accidents, not the only ones but the most serious factors.

The LA 610 accident is somewhat excusable since the pilots were not privy to MCAS and its challenges. Even so, there were surprising pilot practices and judgment shortfalls as well as concerns with appropriate MAX training. The Ethiopian accident, however, is more confounding since it was verified by the airline that the pilots were trained in accordance with Boeing (and FAA) recommendations. Perhaps the company’s training verification should be scrutinized.

As we have highlighted, the ET 302 pilots did follow the runaway trim procedure, at least initially. However, questions remain as to why the pilots mismanaged the airspeed and deviated from company and Boeing procedures. These actions led to an unrecoverable dive resulting in the loss of crew and passengers. We believe that the final accident report will (or should) reflect this finding.

Last edited by Lost in Saigon; 12th Apr 2019 at 01:16.
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Old 12th Apr 2019, 01:06
  #3888 (permalink)  
 
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Aviation Daily: Ethiopian Crash Data Analysis Points To Vane Detachment

Ethiopian Crash Data Analysis Points To Vane Detachment

Ethiopian Crash Data Analysis Points To Vane Detachment

Guy Norris Aviation Daily Apr 10, 2019

LOS ANGELES—As the investigation continues into the causes of the Mar. 10 Ethiopian Airlines Boeing 737 MAX accident, sources close to the probe say flight data recorder (FDR) data firmly supports the supposition that the aircraft’s left angle-of-attack (AOA) sensor vane detached seconds after take-off and that, contrary to statements from the airline, suggests the crew did not follow all the steps for the correct procedure for a runaway stabilizer.

Detailed analysis of the FDR trace data shows that approximately six seconds after liftoff was signaled by the weight-on-wheels switch data, the data indicate the divergence in angle-of-attack (AOA) and the onset of the captain’s stick-shaker, or stall warning. Almost simultaneously, data shows the AOA sensor vane pivoted to an extreme nose-high position.

This, says one source, is a clear indication that the AOA’s external vane was sheared off—most likely by a bird impact. The vane is counter-balanced by a weight located inside the AOA sensor mounting unit, and without aerodynamic forces acting on the vane, the counterweight drops down. The AOA sensor, however, interpreted the position of the alpha vane balance as being at an extreme nose-high angle-of-attack.

With the stick shaker active, the trace indicates the crew pushed forward on the column to counteract what they believed were indications of potential approach to stall. The aircraft, now in level flight, also accelerated rapidly as its power setting remained at 94% N1 thrust used for take-off. This was followed by some manual trim inputs using the thumb switches on the control column.

Seconds after speed advisories were heard, the crew raised the flaps. With the autopilot turned off, flaps up and erroneous AOA data being fed to the flight control computer (FCC), the stage was set for the MAX’s maneuvering characteristics augmentation system (MCAS) to activate. This is indicated by approximately 8-sec of nose-down stabilizer movement, which was followed by the use of manual trim on the control column. However, with the MCAS having moved the stabilizer trim by 2.5 units, the amount of manual nose-up trim applied to counteract the movement was around 0.5 units, or roughly only 20% of the amount required to correctly re-trim the aircraft.

Because of the way the aircraft’s flight control computer P11.1 software worked, the use of manual trim also reset the MCAS timer, and 5 sec. later, its logic having not sensed any correction to an appropriate AOA, the MCAS activated again. The second input was enough to put in the full nose-down trim amount. The crew again manually counteracted with nose-up trim, this time offsetting the full amount of mis-trim applied by the latest MCAS activation.

By then, some 80% of the initial MCAS-applied nose down trim was still in place, leaving the aircraft incorrectly trimmed. The crew then activated the stabilizer trim cutoff switches, a fact the flight data recorder indicates by showing that, despite the MCAS issuing a further command, there was no corresponding stabilizer motion. The aircraft was flying at about 2,000 ft. above ground level, and climbing.

The crew apparently attempted to manually trim the aircraft, using the center-console mounted control trim wheels, but could not. The cut-out switches were then turned back on, and manual trim briefly applied twice in quick succession. This reset the MCAS and resulted in the triggering of a third nose-down trim activation lasting around 6 sec.

The source says the residual forces from the mis-trim would be locked into the control system when the stabilizer cut-off switches were thrown. This would have resulted in column forces of up to around 50 lb. when the system was switched back on.

Although this could have been reduced by manually trimming the aircraft, this did not occur, and the third MCAS activation placed the aircraft in a steep nose-down attitude. This occurred with the aircraft near its peak altitude on the flight—about 6,000 ft. The engines remained at full take-off power throughout the flight, imposing high aerodynamic loads on the elevators as the crew attempted to pull back on the columns.

Vertical acceleration data also indicates momentary negative g during which the AOA sensor on the left side unwinds. This is seen as further validation of the theory that the external part of the alpha vane was detached as the apparent change in angle indication could only be explained by the effect of negative g on the counterbalance weight, forcing it to float up inside the sensor housing. In addition, the captain’s stick shaker also comes off twice in this final phase, further reinforcing the severed vane notion.

The source indicates the crew appeared to be overwhelmed and, in a high workload environment, may not have followed the recommended procedures for re-trimming. Boeing’s stabilizer runaway checklist’s second step directs pilots to “control aircraft pitch attitude manually with control column and main electric trim as needed,” according to one U.S. airline’s manual reviewed by Aviation Week. If the runaway condition persists, the cut-out switches should be toggled, the checklist says.
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Old 12th Apr 2019, 01:18
  #3889 (permalink)  
 
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Aviation Week: Pilots Say MAX MCAS Software Updates Prove Effective In Simulator Demo

Pilots Say MAX MCAS Software Updates Prove Effective In Simulator Demo

Pilots Say MAX MCAS Software Updates Prove Effective In Simulator Demo

Fred George Aviation Week & Space Technology Apr 11, 2019

Boeing has demonstrated the old and new versions of the MAX’s Maneuvering Characteristics Augmentation System (MCAS) to pilots and regulators in its 737 MAX engineering cab simulator in Seattle. The MCAS is a new flight-control-computer (FCC) function added to the MAX to enable it to meet longitudinal stability requirements for certification.

However, the system is only needed to enhance stability with slats and flaps retracted at very light weights and full aft center of gravity (CG). The aircraft exhibits sufficient natural longitudinal stability in all other parts of the flight envelope without the MCAS to meet the rules. Boeing emphasizes that the MCAS is not an anti-stall or stall-prevention system, as it often has been portrayed in news reports.

The new software load [P12.1] has triple-redundant filters that prevent one or both angle-of-attack (AOA) systems from sending erroneous data to the FCCs that could falsely trigger the MCAS. It also has design protections that prevent runaway horizontal stabilizer trim from ever overpowering the elevators. Boeing showed pilots that they can always retain positive pitch control with the elevators, even if they don’t use the left and right manual trim wheels on the sides of the center console to trim out control pressures after turning off the trim cut-out switches.

Most important, the MCAS now uses both left and right AOA sensors for redundancy, instead of relying on just one. The FCC P12.1’s triple AOA validity checks include an average value reasonability filter, a catastrophic failure low-to-high transition filter and a left versus right AOA deviation filter. If any of these abnormal conditions are detected, the MCAS is inhibited.

Three secondary protections are built into the new software load. First, the MCAS cannot trim the stabilizer so that it overpowers elevator pitch control authority. The MCAS nose-down stab trim is limited so that the elevator always can provide at least 1.2g of nose-up pitch authority to enable the flight crew to recover from a nose-low attitude. Second, if the pilots make electric pitch trim inputs to counter the MCAS, it won’t reset after 5 sec. and repeat subsequent nose-down stab trim commands. And third, if the MCAS nose-down stab trim input exceeds limits programmed into the new FCC software, it triggers a maintenance message in the onboard diagnostics system.

According to a pilot who was shown the changes in a simulator session, the demonstration begins with the original MCAS software load. During a normal takeoff, at rotation, the left AOA indication moves to its maximum reading—as seen from the flight data recorder in the Ethiopian Airlines accident. Pilots currently do not experience this during initial or recurrent simulator training. The stickshaker fires continuously, using loud sound and control wheel vibration to focus the pilot’s attention on the critically high AOA indication. The erroneous AOA reading also creates large-scale indicated airspeed (IAS) and altitude errors on the primary flight display (PFD) which can be both distracting and disorienting.

AOA is used by the aircraft’s air data computers to correct pitot and static pressure variations induced by changes in nose attitude in relation to the relative wind. Large errors in AOA can cause 20-40-kt. errors in IAS and 200-400-ft. errors in indicated altitude. This is accompanied by the illumination of annunciators on both PFDs that warn of disparities in the IAS and altitude between the left and right displays. As part of the MCAS redesign, Boeing also is upgrading the MAX with AOA dial indicator displays and AOA disagree warning annunciators on the PFDs.

After the high-AOA indication, pilots then follow the checklist for “airspeed unreliable,” which assures that auto-pilot, auto-throttles and flight directors are turned off. They then pull back power to 80% fan speed, set 10-deg. nose-up pitch attitude and climb to 1,000 ft. above ground level. At that point, they lower the nose, start accelerating and begin retracting slats and flaps at 210 kt. indicated airspeed. When the slats and flaps are fully retracted—the MCAS kicks in.

“It’s a good thing we knew what to expect. Otherwise tunnel vision from the ‘airspeed unreliable’ event could have blinded us to the subsequent MCAS nose-down trim input. When I noticed the trim wheels racing, I grabbed the left wheel. It was easy to stop the trim with hand pressure, but I knew in advance what was happening,” says the pilot flying. “We followed the checklist for runaway stabilizer, checking again for auto-pilot off and auto-throttle off. We turned off both trim cut-out switches and cranked the ‘frisbees’ [manual trim wheels on both sides of the center console] to relieve control pressures. We used manual trim for the remainder of the flight to landing touchdown and rollout. That was quite an eye-opener, as I had never been exposed to that during sim training,” he notes.

It is critical to follow the checklist memory items: Pull back thrust to 75% after retracting slats and flaps and set attitude at 4 deg., nose up. If speed builds up beyond 220-250 kt., controllability becomes increasingly difficult, he adds.

Pilots for three U.S. air carriers tell Aviation Week that during their sim training they had never been exposed to extreme and continuous AOA indication errors, they’ve not experienced AOA induced airspeed and altitude deviations on PFDs and have not had to deal with continuous stall-warning stickshaker distractions. They also note that they have never been required to fly the aircraft from the point at which a runaway stab trim incident occurred all the way to landing using only the manual trim wheels. “We’re just checking boxes for the FAA,” says one Seattle-based pilot.

A full aerodynamic stall with the MCAS inoperative is another exercise pilots experience in the MAX engineering cab simulator. “We reduced thrust at 5,000 ft. and slowed the aircraft at about 1 kt. per sec. We were at a midrange cg [center of gravity] with gear, slats and flats up. We trimmed until we reached 30% above stall speed and then just continued to ease back on the control wheel,” one of the pilots says.

“Pitch feel was natural, progressively increasing as airspeed decayed. Somewhere between the audible low airspeed warning and stickshaker, I felt the slightest lightening on control pressure in my fingertips. Quite candidly, if I had not been watching for it, I don’t think I would have noticed any difference between the MAX and the Next Gen [NG] models. I kept pulling back through stickshaker, then buffet, then elevator feel shift [a function that doubles the artificial control feel forces near stall] and finally until the yoke was buried in my lap. The nose just flopped down gently at the stall, and I initiated recovery as I would in most other airplanes I’ve flown,” he adds.

During design of the MAX, Boeing added two more leading-edge vortilons [generating vortices over the top of the wing at high AOA] in 2018, for a total of six per side and also lengthened and raised the inboard leading-edge stall strips to assure stall behavior would be as docile as that of the NG.

Repeating many of the same maneuvers in the engineering cab simulator with the new software load would have been academic at best, as the triple-redundant AOA validity checks all but assure that the MCAS will not be triggered by erroneous AOA inputs in the future. But, FCC P12.1 changes do not protect against erroneous AOA causing stickshaker or large-scale distortions in indicated airspeed and altitude values. Those malfunctions still can cause distraction and disorientation, especially when flying at night and/or in instrument conditions.

The new MCAS protections built into the P12.1 software load preserve its essential role in enhancing the MAX’s longitudinal stability, while virtually guaranteeing that it won’t be triggered by erroneous AOA. And when it does activate, its nose-down stabilizer trim command authority will be limited to assure the pilots always can control aircraft pitch with the elevators.

However, the FCC software upgrades are not the only critical changes needed to boost safety margins for operators. Pilots who underwent the demonstration also say the sessions underscored the need for additional simulator training for dealing with compound emergencies involving AOA and runaway trim failures.
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Old 12th Apr 2019, 02:32
  #3890 (permalink)  
 
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Max not suitable for Hot/High?

An article on Bloomberg:
‘Not Suitable’ for Certain Airports

...‘Challenging Airports’

Boeing stated in a brief filed in the trade case that the “737 Max 7 has greater performance capabilities at challenging airports. In particular, the 737 Max 7 can serve certain ‘high/hot’ airports and has a greater range operating out of constrained airfields.” The brief then cites a number of such airports -- the names of which are redacted -- that the Max 7 can fly into that “the 8, 9 and 10 cannot."

“Larger 737 variants cannot be used at what are referred to has ‘high/hot’ airports,” the brief stated. Certain U.S. airports are unsuitable for the Max 8 “due to a combination of short runway lengths, elevation, temperature, humidity and other environmental conditions."...
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Old 12th Apr 2019, 05:03
  #3891 (permalink)  
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Ace's link is well written, but they don't cut the pilots enough slack. Boeing think crews should have their tiny brains protected from a simple program like MCAS, yet should be able to put up with the chaos of the two fatal flights. Even gums has said words to the effect, 'I don't suppose I would have known what was going on in those first minutes.'


Just what let them allow the wheels to spin for as long as they did? And why the taps open for the entire flight? So odd.

This is from airman1900 long link - the testing by invited pilots to try the new software. The started off with the original software. This shouts that the corrective drills and handling is not a free lunch.

Pilots for three U.S. air carriers tell Aviation Week that during their sim training they had never been exposed to extreme and continuous AOA indication errors, they’ve not experienced AOA induced airspeed and altitude deviations on PFDs and have not had to deal with continuous stall-warning stickshaker distractions. They also note that they have never been required to fly the aircraft from the point at which a runaway stab trim incident occurred all the way to landing using only the manual trim wheels. “We’re just checking boxes for the FAA,” says one Seattle-based pilot.

Back to Gordon's graph of the flight and the probability of three vanes failing. On the ET 302 I am persuaded that there's a high probability that there were two separate kinds of fault, if not three, counting the previous day to the Lion air. Years of electronics fault-finding has me trying to make some connection to all three, but it does sound like the first two could be electronic, and the ET 302 a vane detachment. Yes, the heater current is a strong argument.

What is puzzling is the push on the columns near the end. Yes, there's a negative g reading and its at the moment the left AoA vane or inner workings, spins to a new point. Bad negative g after that, poor souls. But if it's a sharp push forward on the controls ~ 1 g through 0 to ~ - 3 or more, g and AoA follows sharply and the shaker turns off with the pulse of g. A very good indicator that the vane unit is still rotating and sending signals. But why that particular shove on the poles? They were not gifted with much altitude.

Another bee in my bonnet is the burst of Fuel Flow on the Lion Air. It's unprecedented since the takeoff. There's one other large burst, but not like the last moments before the sudden sawing and then diving.

What were they trying to achieve with that? Could it possibly be connected as to why the PF in the 302 had a lot of power on. Could it have been keeping the nose up? Or at least making him think it was? It's these little things that are nagging at me.. Certainly, on the Lion Air, the nose went skyward.
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Last edited by Loose rivets; 12th Apr 2019 at 05:18.
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Old 12th Apr 2019, 05:18
  #3892 (permalink)  
 
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Originally Posted by Loose Rivets
And why the taps open for the entire flight? So odd.
Easy answer to that: overload. How often do/did those crews fly around manually using the trim with their other hand on the throttles? If you're not used to doing something, you're hardly going to do it when you need to. Not their fault, I might add.
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Old 12th Apr 2019, 05:28
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Not sure whether this has been posted previously...

https://seekingalpha.com/instablog/3...se-pilot-error
ex-USAF Major General. Says it all. Blame the pilots when in reality they were flying a deathtrap. What are we, testpilots, finely honed, ready to pounce into action when disaster strikes?
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Old 12th Apr 2019, 05:35
  #3894 (permalink)  
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Not sure I buy the bird taking out the AoA vane shortly after lift off...did they find a dead bird or the vane on or near the runway at ADD?- in this day and age of forensics can these items be found?
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Old 12th Apr 2019, 06:59
  #3895 (permalink)  
 
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It doesn't need to be detached to cause a reading that match fdr. Just split shaftwill do. Murphy is lazy.

I find it a impossible coincidence to have a bird strike exactly at maximum gs. Torque at the shaft is maximum at maximum g, so it looks more plausible unless we have other clues (mention of birds cvr) which I ignore.

Finding the vane and the bird wouldn't be easy either, their absence from runway doesn't prove anything, they had a bit of height and speed by then, it could have landed quite far.
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Old 12th Apr 2019, 07:07
  #3896 (permalink)  
 
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One has to wonder if the Boeing PR machine is starting to kick into gear behind the scenes, and orchestrate a smear campaign through friendlies to point the finger at the pilots (as per the Seeking Alpha The Boeing 737 MAX 8 Crashes: The Case For Pilot Error) and operators instead of Boeing. Boeing Has Called 737 Max 8 ‘Not Suitable’ for Certain Airports. The "Not suitable for certain airports" implies Jakarta as being in this category (too hot). All the hallmarks, unattributed expert opinions such as "Mark". Reporters just happened to find these U.S. International Trade Commission documents lying around?

Boeing Has Called 737 Max 8 ‘Not Suitable’ for Certain Airports

By
Anita Sharpe12 April 2019, 02:02 GMT+10

Before last month’s crash of a flight that began in Ethiopia, Boeing Co. said in a legal document that large, upgraded 737s “cannot be used at what are referred to as ‘high/hot’ airports."

At an elevation of 7,657 feet -- or more than a mile high -- Addis Ababa’s Bole International Airport falls into that category. High elevations require longer runways and faster speeds for takeoff. The Ethiopian airport’s altitude hasn’t been cited as a factor in the downing of Flight 302 and likely didn’t cause the crash. But it could have exacerbated the situation because an airplane’s performance degrades at higher altitudes, said a 737 pilot who flies into high-elevation airports such as Denver and agreed to speak on background since he’s not authorized to talk with the media.

Data released last week from the Ethiopian Airlines flight indicated the pilots didn’t cut the 737 Max 8 airplane’s speed after takeoff when they should have. The preliminary report on the disaster said the plane’s anti-stall system pushed the nose of the plane down less than two minutes into the flight because of a malfunctioning sensor. The pilots struggled to control the plane as it hurtled toward the ground at 575 miles per hour.

“The faster the airplane is going, the more force of air there is on its wings and control surfaces which requires more force on the pilots’ part to pull the control” column, said Robert Mark, a commercial pilot and senior editor with Flying Magazine.

Six Minutes to Disaster: Ethiopian Pilots Battled Boeing Max

Boeing cited the performance of the 737 Max 8 in a case brought before the U.S. International Trade Commission in 2017. Boeing charged that unfair competition from Bombardier -- which beat out Boeing for a large order from Delta Air Lines -- threatened its 737-700 and Max 7, the smallest of its upgraded single-aisle jets. By pointing out the limitations of the Max 8, the planemaker sought to preserve market share for the 700 and Max 7.

A Boeing spokesman said that Addis Ababa can handle large airplanes because it has long runways.

‘Challenging Airports’

Boeing stated in a brief filed in the trade case that the “737 Max 7 has greater performance capabilities at challenging airports. In particular, the 737 Max 7 can serve certain ‘high/hot’ airports and has a greater range operating out of constrained airfields.” The brief then cites a number of such airports -- the names of which are redacted -- that the Max 7 can fly into that “the 8, 9 and 10 cannot."

“Larger 737 variants cannot be used at what are referred to has ‘high/hot’ airports,” the brief stated. Certain U.S. airports are unsuitable for the Max 8 “due to a combination of short runway lengths, elevation, temperature, humidity and other environmental conditions."

Aviation consultant Bob Mann said airlines typically use a smaller, earlier version of Boeing’s jet, the 737-700, at higher elevations because that plane usually gets a “better rate of climb" than the Max 8.


Denver and Mexico City


Documents in the trade case referred to at least 16 U.S. airports considered “high and hot” and therefore unsuitable for the Max 8, though the names of those facilities weren’t made public. Asked during a trade commission hearing to specify which airports, an expert witness for Boeing replied that “sometimes Denver would qualify as that.” The expert, Jerry Nickelsburg, an adjunct economics professor at UCLA, added that “Mexico City certainly qualifies as that.”

Both the Denver and Mexico City airports sit at lower elevations than Addis Ababa and have runways as long or longer than the Ethiopian airfield, where they extend more than 12,000 feet, or 3,700 meters.

Denver’s airport is more than 2,000 feet lower than Addis and has five runways that measure 12,000 feet and one that is 16,000 feet (or 4,800 meters). The airport in Mexico City is 300 feet lower than Addis and has four runways that are 13,000 feet (or about 4,000 meters) and two that are 15,000 feet (or about 4,600 meters). Aeromexico flies the Max 8 as part of its fleet.

Hot airfields such as the Jakarta airport, from where the doomed Lion Air plane took off last October, produce similar air densities as high elevations, requiring faster takeoff speeds. Heat, air density and fast speed haven’t been cited as factors in that accident.


‘Detective Story’


The performance of all airplanes deteriorates in high heat or elevation, and all pilots account for that before taking off, said Steve Wallace, former director of the Federation Aviation Administration’s accident investigation branch. Even airlines operating from Orange County, California, which is nearly at sea level, occasionally have to reduce weight on their planes because of high temperatures, Wallace said.

Altitude and heat may well have played no role in either 737 Max 8 crash, but the wording from Boeing’s 2017 trade case could still be seized upon by plaintiffs lawyers.

"Even if it is BS, plaintiffs’ lawyers will focus on the quote and put that back to the company to explain it," said long-time aviation attorney Roger Clark, who teaches aviation law as a visiting professor at Rutgers University in New Jersey.

Chicago attorney Thomas Demetrio, who is leading a lawsuit against Boeing for the Lion Air crash, said he wouldn’t include altitude or heat in a complaint unless investigators or one of his experts said those factors were a proximate cause.

All the factors that contributed to the Ethiopian Airlines crash won’t be known until sometime next year when the full investigative report is completed.“It’s like a detective story right now,” said Mark, the commercial pilot. “And we don’t have all the data."

— With assistance by Michael Sasso, and Margaret Newkirk
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Old 12th Apr 2019, 08:53
  #3897 (permalink)  
 
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Originally Posted by artee View Post
An article on Bloomberg:
‘Not Suitable’ for Certain Airports

...‘Challenging Airports’

Boeing stated in a brief filed in the trade case that the “737 Max 7 has greater performance capabilities at challenging airports. In particular, the 737 Max 7 can serve certain ‘high/hot’ airports and has a greater range operating out of constrained airfields.” The brief then cites a number of such airports -- the names of which are redacted -- that the Max 7 can fly into that “the 8, 9 and 10 cannot."

“Larger 737 variants cannot be used at what are referred to has ‘high/hot’ airports,” the brief stated. Certain U.S. airports are unsuitable for the Max 8 “due to a combination of short runway lengths, elevation, temperature, humidity and other environmental conditions."...
Interesting story about the marketing of the MAX, but absolutely nothing to do with the crash, since Addis Ababa has a long enough runway. Edit: Once you are airborne, and have a positive rate of climb, it should not matter what airport you took off from. The only difference was that N1 may have been higher than at sea-level, but engine thrust certainly did not cause the crash. In any case Boeing sold the MAX 8 to Ethiopian, so that does not exactly absolve them of blame.
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Old 12th Apr 2019, 09:05
  #3898 (permalink)  
 
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Originally Posted by artee View Post
An article on Bloomberg:
‘Not Suitable’ for Certain Airports

...‘Challenging Airports’

Boeing stated in a brief filed in the trade case that the “737 Max 7 has greater performance capabilities at challenging airports. In particular, the 737 Max 7 can serve certain ‘high/hot’ airports and has a greater range operating out of constrained airfields.” The brief then cites a number of such airports -- the names of which are redacted -- that the Max 7 can fly into that “the 8, 9 and 10 cannot."

“Larger 737 variants cannot be used at what are referred to has ‘high/hot’ airports,” the brief stated. Certain U.S. airports are unsuitable for the Max 8 “due to a combination of short runway lengths, elevation, temperature, humidity and other environmental conditions."...
That's just a red herring. It talks about "short runways". Nobody in their right mind would think a 3700 m runway was short. It is a sales pitch for the MAX 7, and it has nothing at all to do with this accident or the one in Jakarta.

Documents in the trade case referred to at least 16 U.S. airports considered “high and hot” and therefore unsuitable for the Max 8, though the names of those facilities weren’t made public. Asked during a trade commission hearing to specify which airports, an expert witness for Boeing replied that “sometimes Denver would qualify as that.” The expert, Jerry Nickelsburg, an adjunct economics professor at UCLA, added that “Mexico City certainly qualifies as that.”
Yes, Denver could sometimes be called "hot and high", but would never fall in the category of "short runway". The same goes for Mexico City.

The manufacturer provides rules (usually computer software and long tables) telling the crew the required runway lengths for takeoff for a given combination of weight, elevation and temperature. These values contain ample margins for uncertainties in actual weight, temperature and wind variations and various failures including an engine failure. If the runway is long enough it is long enough.

Yes, there will be some airports, where the MAX 7 can operate with higher payloads than the 8/9/10. So what?

They are probably rather talking about small regional airports such as Telluride.

The Ethiopian airport’s altitude hasn’t been cited as a factor in the downing of Flight 302 and likely didn’t cause the crash. But it could have exacerbated the situation because an airplane’s performance degrades at higher altitudes, said a 737 pilot who flies into high-elevation airports such as Denver ,
This shows how disingenious this article is. "It is totally irrelevant but we'll blurb on about it anyway. And look, we even found a pilot who said something totally unrelated!". There certainly was no problem with aircraft performance in either accident, except perhaps there was too much of it.

Denver will not be on this list. Neither will Mexico City, Jakarta or Addis Ababa. They are all big International Airports with very long runways. The "expert" is an "adjunct economics professor". I rest my case.


Bernd
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Old 12th Apr 2019, 09:14
  #3899 (permalink)  
 
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You know, back when a young CGB was taught to fly, we didn't just consider runway length when examining departure performance................

Just sayin'
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Old 12th Apr 2019, 09:26
  #3900 (permalink)  
 
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Originally Posted by bsieker View Post
The "expert" is an "adjunct economics professor". I rest my case.
To be fair, his comments weren't made in the context of either of the Max accidents, but in an anti-competitive hearing where he was simply comparing the hot-and-high performance of the Max 8 compared to the Max 7, in other words stating the obvious. So let's not put words in his mouth.

Incidentally his CV includes being a VP at FlightSafety International, and 8 years at McD before that, so I suspect he does actually know one end of a WAT curve from the other.
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