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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 16th Apr 2019, 03:23
  #4061 (permalink)  
 
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Boeing’s 767-based tankers use a version of the pitch augmentation system that grounded the 737 Max 8 fleet, the manufacturer and U.S. Air Force officials say.
The disclosure provides a new data point in the unfolding story of how Boeing installed the Maneuvering Characteristics Augmentation System (MCAS) on narrowbody airliner fleet.
Both the KC-767 and KC-46 fleets delivered to air forces in Italy, Japan and the U.S. rely on the MCAS to adjust for pitch trim changes during refueling operations.
In the 1980s, Boeing’s engineers considered using a pitch augmentation system for the commercial version of the 767, but dropped the idea after finding that vortex generators provided adequate control.
Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.
The single-aisle airliner uses one angle of attack vane — either the captain’s or first officer’s — to generate the data used by the flight computer to activate the MCAS.
By comparison, the KC-767 and KC-46 are designed to use two sensor inputs to feed angle of attack data, Boeing says.
Boeing spokesmen declined to elaborate on which sensor inputs are used to provide the data in the tanker design. The options include using data from the angle of attack vanes on both sides of the cockpit, or an angle of attack vane an inertial gyroscope.


I find the last sentence interesting, although mis-spelled... angle of attack vane AND inertial gyroscope? The unmanned drones use the inertial system for AoA...


https://www.mro-network.com/airframe...d-pitch-system

Last edited by Smythe; 16th Apr 2019 at 03:36.
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Old 16th Apr 2019, 05:39
  #4062 (permalink)  
 
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Originally Posted by MurphyWasRight View Post
Given the "nomenclature changed" label and awkward text I would guess that at least some who might have gone "huh" would decide it had to a be label change only since it would be hard to believe that critical core functionality had changed, at least without a strong warning.
Not a pilot
still I wonder why the MAX needs a PRI and B/U cut off! Forget the label changing, what surprises me, is that on a new design the two switches are in connected basically in series, and either one is doing a cut off! Means the previous design was faulty? And in the new design was considered safermto have a back up cut off switch, just in case the primary fails? What kind of engineer will design a system with a single sensors, single computer, single motor to drive a flight control, and feels the need to add a back up cut off?
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Old 16th Apr 2019, 05:47
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Originally Posted by Smythe View Post
I find the last sentence interesting, although mis-spelled... angle of attack vane AND inertial gyroscope? The unmanned drones use the inertial system for AoA...
This is not new. It has been covered e.g. by Mentour Pilot in his 737 MAX Q&A video (sorry, can't post links yet, look it up on Youtube under Mentour Pilot - Five questions about the Boeing 737 MAX).
Key thing is that the MCAS built into the KC-46 was meant to counter a slightly different phenomenon than in case of the 737 MAX. It was designed specifically to counter CoG shifts from the moving fuel as opposed to countering the aircraft's nose-up tendency in high AoA conditions in case of the 737 MAX MCAS variant. That being said, the KC-46 potentially could have used a different selection of sensors.

However, the fact that the KC-46 did make use of sensor redundancy as well as introduced a simple manual override by the pilot's column movement, points pretty clearly to the fact, that these good engineering practices were once present at Boeing and their absence in case of the 737 MAX MCAS design constitutes a gross negligence. It should now be the role of authorities to determine, why this has been the case.

Last edited by Portallo; 17th Apr 2019 at 12:43.
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Old 16th Apr 2019, 06:03
  #4064 (permalink)  
 
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Originally Posted by FrequentSLF View Post
Not a pilot
still I wonder why the MAX needs a PRI and B/U cut off! Forget the label changing, what surprises me, is that on a new design the two switches are in connected basically in series, and either one is doing a cut off! Means the previous design was faulty? And in the new design was considered safermto have a back up cut off switch, just in case the primary fails? What kind of engineer will design a system with a single sensors, single computer, single motor to drive a flight control, and feels the need to add a back up cut off?
Well, that is precisely the point: It is so unreliable that you want to make double sure that it can be switched off. Being able to switch it on is not guarded by a backup switch.
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Old 16th Apr 2019, 07:03
  #4065 (permalink)  
 
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Stab Trim Simulation Inputs

OK, not a pilot or anything to do with aviation, but being basically housebound for the past few months have followed the LIon Air and Ethiopian accidents and the resulting Max saga on here and elsewhere (and have tried to DMOR before asking questions). They are fascinating from so many aspects which the ongoing debate on here and other forums have sought to draw out, it is just sad that it has to be on the back of such a tragic loss of life.

This post is promoted by watching the Mentour video, and in particular the struggle they had trying to use the manual wheel trim to restore stab trim. My understanding is that a flight simulator is programmed to simulate real aircraft behaviour by using test flight data from all of the flight envelope and no doubt from wind tunnel testing and other research?

So watching the struggle to manually trim under the flight conditions they were attempting to simulate gave me the obvious thought that manual trim reaction was being supplied by some algorithm, look up chart, whatever which said in my layman understanding “these are the simulated flight conditions, therefore apply a force of x to the manual trim wheel”.

If this is correct, if I were a regulator looking to recertify the MAX, or more so if I was a lawyer looking to build a case, I would be very keen to see this background data, and exactly how much of the flight envelope is actually covered while still allowing the manual trim wheel to retain authority, and not assuming the pilot was superhuman.

Alternatively, probably not sure how realistic, but if the data wasn't complete, wouldn't it be “relatively easy” for interested parties to commission wind tunnel testing to obtain the countering manual trim force required throughout a complete range of speed, altitude, stab trim angle and with say a maximum countering column elevator force being applied ?

Apologies if this is ignorant nonsense, if it is “move on nothing to see here!” If there is any logic in what I say I'd love feedback.

Alchad
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Old 16th Apr 2019, 08:08
  #4066 (permalink)  
 
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Alchad, timely and relevant questions; as to be expected from ‘West of the M5’

“ …very keen to see this background data, and exactly how much of the flight envelope is actually covered …’

This is an important issue. One scenario is that Boeing FAA accepted previous data from the 737 NG, or even 737 classics for the MAX; based on the aerodynamic design, wind tunnel and flight tests - grandfather rights. This probably involved some extrapolation, thus the associated processes are of interest.
Did Boeing convince themselves - and then the FAA, that the MAX is sufficiently similar to the NG so that deep questioning was glossed over. Unfortunately the MAX is not the same as witnessed by MCAS - probably a late addition to meet certification (not to be the same as precious variants), etc, etc.

From a flight test viewpoint (hindsight), the tests required would be very hazardous; thus data as far as was flown for certification opposed to simulator information beyond the recognised flight envelope would depend on extrapolation. Without ‘real’ data, the aircraft and simulator certification could be based on previous variants and ‘linear’ interpretations (not mathematically linear) for simulation - it’s good enough for training, because the pilots won’t get into that situation, the system does not fail that way, etc, etc.

Thus the FAA and other regulators could (should) be reconsidering these aspects, and based on piloting experiences, the concerns about trim forces and practicality of recovery for trim runaway (not MCAS because that won’t malfunction in the same way post mod) could be well founded, and thus a much bigger problem for Boeing.

If the certification approvals for the aircraft and simulator meet current requirements there should not be need for more data; this should be (has been) collected for certification approval, proof that the failures can be managed by human alleviation, and that pilots ‘will not’ (certification probability) encounter such situation again.

No need to move on, dig-in for the long battle; certification ramifications and possibly Boeing rework / rethink.
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Old 16th Apr 2019, 11:08
  #4067 (permalink)  
 
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Originally Posted by oggers View Post
I think we can agree that it is easier to hold the trim switch with the stick shaker off. Nonetheless, the data shows clearly that the thumb switch can be held closed with the stick shaker on.
But the Lion Air data also shows "off-blips" during automatic trim every now and then,
Nope. There is a clear temporary loss of input in many of the manual, but none of the automatic commands. The latter show only "ragged" flanks.

Lionair Upper: manual trim middle: automatic trim

On the ET FDR PF asks PNF to help him with the manual electric trim. So he may have had difficulties actuating his thumb switch.

Last edited by spornrad; 16th Apr 2019 at 11:27.
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Old 16th Apr 2019, 11:47
  #4068 (permalink)  
 
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Originally Posted by spornrad View Post
Nope. There is a clear temporary loss of input in many of the manual, but none of the automatic commands. The latter show only "ragged" flanks.

Lionair Upper: manual trim middle: automatic trim

On the ET FDR PF asks PNF to help him with the manual electric trim. So he may have had difficulties actuating his thumb switch.
I do not agree with your analysis. We will know in the end if that is identified as a contributing factor. I predict it will not be.
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Old 16th Apr 2019, 12:25
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There is an excellent article in Flight International this week: "Questions persist after Ethiopian loss".

If there are questions about pilot training, I feel that they should be directed not so much at type-rating and airline training, but rather at the first 200 hours of a pilot's training. There have been too many crashes where the very, very basics of flying an aeroplane seems to have been forgotten.

Quote from the 'Effect of Controls' lesson at the very beginning of flying training: "At high airspeeds, typically with a low nose attitude, the controls are harder to move, very effective and require only small movements to bring about a change of flight path. They feel firm." The last paragraph of that Flight article is very very pertinent.
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Old 16th Apr 2019, 12:42
  #4070 (permalink)  
 
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Originally Posted by FrequentSLF View Post
Not a pilot
still I wonder why the MAX needs a PRI and B/U cut off! Forget the label changing, what surprises me, is that on a new design the two switches are in connected basically in series, and either one is doing a cut off! Means the previous design was faulty? And in the new design was considered safermto have a back up cut off switch, just in case the primary fails? What kind of engineer will design a system with a single sensors, single computer, single motor to drive a flight control, and feels the need to add a back up cut off?
Am a 737 pilot.

Reason I was given was to provide redundancy in case of a rare instance of switch (or actually relay) welding. That phenomenon occurs when a relay remains in a set position for so long that it basically welds the contacts closed. I'm not an electrical engineer, so I don't know how to evaluate this statement, but it is not unlike the rationale for the split thumb switches on the yoke.

I suspect another unspoken reason was to maintain the look and feel of the 737NG switches. As long as there were two switches that were always used together, then Boeing could take the position that no additional training was required.
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Old 16th Apr 2019, 12:50
  #4071 (permalink)  
 
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Originally Posted by NoelEvans View Post
There is an excellent article in Flight International this week: "Questions persist after Ethiopian loss".

If there are questions about pilot training, I feel that they should be directed not so much at type-rating and airline training, but rather at the first 200 hours of a pilot's training. There have been too many crashes where the very, very basics of flying an aeroplane seems to have been forgotten.

Quote from the 'Effect of Controls' lesson at the very beginning of flying training: "At high airspeeds, typically with a low nose attitude, the controls are harder to move, very effective and require only small movements to bring about a change of flight path. They feel firm." The last paragraph of that Flight article is very very pertinent.
That could be one explanation of the seemingly tentative trim inputs especially by Lion Air FO, although the (possible) ergonomic factors discussed above are intriguing.
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Old 16th Apr 2019, 13:24
  #4072 (permalink)  
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Originally Posted by oggers View Post
I do not agree with your analysis. We will know in the end if that is identified as a contributing factor. I predict it will not be.
As has been pointed out many times in the two main threads discussing the 737 MAX crashes, the LT610 PF counteracted uncommanded (MCAS) nose-down trim on 21 separate occasions, yet for whatever reason did not believe he was experiencing a stab trim runaway, and failed to activate the CUTOUT switches.

There are two big questions:
  • why did he fail to recognize the stab trim runaway and activate the CUTOUT ?
  • why did he hand control of the trim to the FO with such a critical malfunction occurring ?
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Old 16th Apr 2019, 13:41
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Originally Posted by gmx View Post
As has been pointed out many times in the two main threads discussing the 737 MAX crashes, the LT610 PF counteracted uncommanded (MCAS) nose-down trim on 21 separate occasions, yet for whatever reason did not believe he was experiencing a stab trim runaway, and failed to activate the CUTOUT switches.

There are two big questions:
  • why did he fail to recognize the stab trim runaway and activate the CUTOUT ?
  • why did he hand control of the trim to the FO with such a critical malfunction occurring ?
Good questions, but as I said much much earlier, I think we can turn this one on its head and ask "what enabled the supernumerary Captain on the prior flight to recognise, at least in part, that CUTOUT was the solution?". I believe that, even then, electric trim was re-engaged albeit briefly.

So, even with 3 heads in the cockpit, one of whom was free from immediate control issues, it did not appear to that crew the Trim Runaway NNC was the obvious choice.
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Old 16th Apr 2019, 13:53
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Originally Posted by NoelEvans View Post
There is an excellent article in Flight International this week: "Questions persist after Ethiopian loss".
Thankyou for the heads-up. When looking for that I also saw this previous article from Flight Global:
Investigation into the Ethiopian Airlines Boeing 737 Max crash is likely to be scrutinised as much for impartiality and independence as for its analysis of technical and operational circumstances.

Under ICAO standards Ethiopian authorities are poised to lead the inquiry into the 10 March accident involving the Nairobi-bound flight ET302, which occurred just outside Addis Ababa.But Ethiopian investigators are likely to face pressure for full transparency – not just to satisfy concerns over the 737 Max, following the airline’s decision to ground the type, but to ensure there is no repeat of the controversy which tainted a previous fatal 737 accident probe involving the same carrier.

Lebanese investigators conducted an inquiry into the loss of Ethiopian flight ET409, a Boeing 737-800, which crashed into the sea just 4min after taking off from Beirut in February 2010.The inquiry concluded that the crew lost control of the jet as a result of “inconsistent” flight-control input and “mismanagement” of airspeed, altitude and attitude, adding that the aircraft was out of trim.It stated that the first officer failed to demonstrate sufficient assertiveness to intervene despite multiple warnings – including stick-shaker activation – and evidence that the captain, who was flying, was showing signs of disorientation and loss of situational awareness.The inquiry attributed the crash to a combination of “failure in basic piloting skills” by the captain, combined with inadequate crew resource management from the first officer, and queried the decision to pair the two.While the pilots met Ethiopian’s criteria for pairing the inquiry pointed out that their levels of experience “did not constitute a comfortable margin”, particularly for operation under demanding conditions.

Despite the in-depth analysis by the Lebanese investigators, both Ethiopian Airlines and the Ethiopian Civil Aviation Authority strongly condemned the conclusions.The ECAA claimed the inquiry report was an “unbalanced account” containing “factual inaccuracies, internal contradictions and hypothetical statements” which were not supported by evidence.In an extraordinary formal statement the authority insisted that the most probable cause of the crash was the break-up of the jet following an explosion – the result of sabotage, a lightning strike, or being shot down.The ECAA rejected the findings of crew mismanagement of the 737-800, claiming that flight-data recorder information revealed stabiliser and roll movements suggestive of damage to the tail section.....[etc]


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Old 16th Apr 2019, 13:53
  #4075 (permalink)  
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Originally Posted by Maninthebar View Post
Good questions, but as I said much much earlier, I think we can turn this one on its head and ask "what enabled the supernumerary Captain on the prior flight to recognise, at least in part, that CUTOUT was the solution?". I believe that, even then, electric trim was re-engaged albeit briefly.

So, even with 3 heads in the cockpit, one of whom was free from immediate control issues, it did not appear to that crew the Trim Runaway NNC was the obvious choice.
I disagree. It appears it occurred to someone (the jump seat pilot) pretty quickly that it was a runaway. They got pitch under control and hit the cutouts. My guess is they re-enabled stab trim in a troubleshooting / curiosity activity (lets see if its still doing it?) because clearly they did not need the electric trim to fly the plane.
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Old 16th Apr 2019, 13:56
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Originally Posted by Maninthebar View Post
Good questions, but as I said much much earlier, I think we can turn this one on its head and ask "what enabled the supernumerary Captain on the prior flight to recognise, at least in part, that CUTOUT was the solution?". I believe that, even then, electric trim was re-engaged albeit briefly.

So, even with 3 heads in the cockpit, one of whom was free from immediate control issues, it did not appear to that crew the Trim Runaway NNC was the obvious choice.
The jump seat pilot was in a better position to see the trim wheels spinning, watching the videos of runaway trim it is blindingly obvious from jumpseat view, likely much less so for pilots where it would be in peripheral vision, and has been pointed out hearing it over the stick shaker is questionable.

As to why it was not handled exactly per Trim Runaway NNC once recognised (re-enabling trim) one factor is that it did not match the at the time checklist perfectly since the 'runaway' was not continuous.
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Old 16th Apr 2019, 14:12
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AA To Have Pilots Do Sim Training on MAX: WSJ

By
Andy Pasztor

Updated April 15, 2019 5:33 p.m. ET American Airlines Group Inc., AAL +0.06% after saying for months that its pilots didn’t need additional ground-simulator experience on Boeing Co. BA +0.26% 737 MAX jets, now plans to include such instruction in training sessions for the aircraft, according to industry officials.

The decision, these officials said, means as soon as late summer, American 737 MAX pilots will start encountering some simulator scenarios tied to problems with an automated flight-control system, called MCAS, that has been implicated in two fatal nose-dives of the plane in less than five months.

The enhanced training also will deal with similar emergency situations in which pilots need to intercede to manually correct movement of flight-control surfaces on the jet’s tail.

American’s choice highlights growing differences between carriers—and in American’s case, with federal air-safety regulators—regarding the best way to ensure flight crews will be able to safely operate 737 MAX jets once they resume service.

At this point, the Federal Aviation Administration isn’t planning to mandate simulator training targeting potential MCAS misfires. American’s voluntary effort to go beyond minimum federal requirements hasn’t been reported before.

Southwest Airlines Co. and United Continental Holdings Inc., the other U.S. carriers with MAX aircraft, don’t intend to adopt similar training changes, the officials said. Some overseas carriers, however, have signaled they may opt for enhanced simulator training.

In the immediate wake of a Lion Air jet crash in Indonesia in October, American said it continued “to believe the Boeing 737 MAX aircraft is safe and that our pilots are well-trained and well-equipped to operate it.”




Investigators Blame Boeing Flight-Control System in Ethiopian Crash
An initial probe into the crash of the Ethiopian Airlines Boeing 737 MAX 8 found that the pilots followed emergency procedures. Investigators went on to recommend that the MAX fleet stay grounded until authorities validate changes that Boeing has made to the aircraft. WSJ’s Robert Wall explains. Photos: Getty ImagesAmerican’s pilots were critical of Boeing for not providing enough information initially about the MCAS system, but determined that they had learned enough about how MCAS worked to continue flying the plane without additional simulator training. But on Sunday, a spokesman for American Airlines said the carrier is “looking at the potential for additional training opportunities” in coordination with the FAA and representatives of the pilot union.

A Southwest spokeswoman said the airline’s current training covers operating in conditions present during “an MCAS misfire.” She added, “We briefed our pilots on MCAS post-Lion Air and emphasized the training for operating in unreliable airspeed conditions.”

On Monday, United said, “Our training is consistently refreshed and updated, and we will make any updates to our training necessary should the FAA decide more is required as part of their ongoing investigation.”

Within weeks of the Lion Air crash, American already was working behind the scenes on possible training changes. Without any prodding from the FAA, the carrier’s safety and training experts began considering possible additional simulator training, according to internal FAA documents reviewed by The Wall Street Journal.

According to one email at the time from a senior FAA inspector, the carrier was developing new simulator scenarios for the MCAS system malfunctions and potential consequences. The email added that FAA and American officials determined “it would be better to wait for further guidance” from the plane maker and agency certification experts before proceeding to develop full-blown simulator scenarios.

The carrier, according to one industry official familiar with the details, didn’t follow through with the proposal at the time because managers decided there was too much uncertainty about the cause of the Lion Air crash. But now, after a second fatal 737 MAX crash—in Ethiopia in March—in which MCAS was implicated, American is working in earnest to implement extra simulator training for MCAS-related events, this official said.
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Old 16th Apr 2019, 14:29
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Originally Posted by gmx View Post
I disagree. It appears it occurred to someone (the jump seat pilot) pretty quickly that it was a runaway. They got pitch under control and hit the cutouts. My guess is they re-enabled stab trim in a troubleshooting / curiosity activity (lets see if its still doing it?) because clearly they did not need the electric trim to fly the plane.
Possibly they were trying to understand the (changed) function of the cutout switches:

"I thought the right switch killed auto but allowed manual electric trim"

tries various combinations of switch positions, ending with both up..

"There it goes again"

"That's strange, I have the conversion notes in my carry on, let me go get them"
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Old 16th Apr 2019, 14:32
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Originally Posted by MurphyWasRight View Post
Possibly they were trying to understand the (changed) function of the cutout switches:

"I thought the right switch killed auto but allowed manual electric trim"

tries various combinations of switch positions, ending with both up..

"There it goes again"

"That's strange, I have the conversion notes in my carry on, let me go get them"
This

Except I **believe** that s/he had already gotten the documentation out. It is interesting that the (altered) function of the cutout switches appears to have required clarification on this forum.
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Old 16th Apr 2019, 14:39
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Originally Posted by Maninthebar View Post
This

Except I **believe** that s/he had already gotten the documentation out. It is interesting that the (altered) function of the cutout switches appears to have required clarification on this forum.
Not sure it has been confirmed either way on when the library run occurred relative to cutout.
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