MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
In the days of yore, there used to be bright red warning at the bottom of every PPRuNe page. Something along the lines: "As these are anonymous forums, contributors might not be what they seem or claim to be. Press or unscrupulous may use these fora to solicit reactions".
While PPRuNe doesn't conform to Sturgeon's law and mostly you can find quite reasonable debate on it, there are some high profile cases that tend to attract a lot of garbage posting, sometimes intentional, occasionally not. The moderators of old days had good advice for dealing with such contingencies: "Play the ball, not the man". It doesn't matter who or what the poster is, all that matters is how much his post conform to reality. Highly experienced pilot might have non-publicly-disclosed agenda that would make his post look very informative while being severely distorting and even worst of the trolls might in his copy-paste frenzy dig up something interesting and relevant. So please, concentrate on the useful content and ignore the rest, OK?
I wholeheartedly agree that signing even a letter of intention for the aeroplane that has been grounded on severe safety issue and has no realistic date of return to service because no realistic fix has been developed yet is pure "no brainer".
I predict that Lockheed Martin will return to passenger turbofan transport market in big style; this time with two widebody projects, far more succesful than its last endeavour. I wonder if T7 gets renamed "BiStar".
While PPRuNe doesn't conform to Sturgeon's law and mostly you can find quite reasonable debate on it, there are some high profile cases that tend to attract a lot of garbage posting, sometimes intentional, occasionally not. The moderators of old days had good advice for dealing with such contingencies: "Play the ball, not the man". It doesn't matter who or what the poster is, all that matters is how much his post conform to reality. Highly experienced pilot might have non-publicly-disclosed agenda that would make his post look very informative while being severely distorting and even worst of the trolls might in his copy-paste frenzy dig up something interesting and relevant. So please, concentrate on the useful content and ignore the rest, OK?
I wholeheartedly agree that signing even a letter of intention for the aeroplane that has been grounded on severe safety issue and has no realistic date of return to service because no realistic fix has been developed yet is pure "no brainer".
I predict that Lockheed Martin will return to passenger turbofan transport market in big style; this time with two widebody projects, far more succesful than its last endeavour. I wonder if T7 gets renamed "BiStar".
In the days of yore, there used to be bright red warning at the bottom of every PPRuNe page. Something along the lines: "As these are anonymous forums, contributors might not be what they seem or claim to be. Press or unscrupulous may use these fora to solicit reactions".
While PPRuNe doesn't conform to Sturgeon's law and mostly you can find quite reasonable debate on it, there are some high profile cases that tend to attract a lot of garbage posting, sometimes intentional, occasionally not. The moderators of old days had good advice for dealing with such contingencies: "Play the ball, not the man". It doesn't matter who or what the poster is, all that matters is how much his post conform to reality. Highly experienced pilot might have non-publicly-disclosed agenda that would make his post look very informative while being severely distorting and even worst of the trolls might in his copy-paste frenzy dig up something interesting and relevant. So please, concentrate on the useful content and ignore the rest, OK?
I wholeheartedly agree that signing even a letter of intention for the aeroplane that has been grounded on severe safety issue and has no realistic date of return to service because no realistic fix has been developed yet is pure "no brainer".
I predict that Lockheed Martin will return to passenger turbofan transport market in big style; this time with two widebody projects, far more succesful than its last endeavour. I wonder if T7 gets renamed "BiStar".
While PPRuNe doesn't conform to Sturgeon's law and mostly you can find quite reasonable debate on it, there are some high profile cases that tend to attract a lot of garbage posting, sometimes intentional, occasionally not. The moderators of old days had good advice for dealing with such contingencies: "Play the ball, not the man". It doesn't matter who or what the poster is, all that matters is how much his post conform to reality. Highly experienced pilot might have non-publicly-disclosed agenda that would make his post look very informative while being severely distorting and even worst of the trolls might in his copy-paste frenzy dig up something interesting and relevant. So please, concentrate on the useful content and ignore the rest, OK?
I wholeheartedly agree that signing even a letter of intention for the aeroplane that has been grounded on severe safety issue and has no realistic date of return to service because no realistic fix has been developed yet is pure "no brainer".
I predict that Lockheed Martin will return to passenger turbofan transport market in big style; this time with two widebody projects, far more succesful than its last endeavour. I wonder if T7 gets renamed "BiStar".
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Just wondering out loud here: Are we going to discover that the manual trim with the spinning wheel is essentially worthless when it actually is called upon ? Because at that stage you are basically on a wing and a prayer?
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Trim wheel forces
Uhh- not too sure where you get the worm drive screw jack bit - but the 737 series ( and others 767,777, etc - use a double recirculating ball " NUT " on the course threaded screw jack. Which has about a 90 percent efficiency and can therefore be back driven absent a braking system. While the electric motor MIGHT be overloaded at the extreme position (AND) and high speed, it is more likely that the manual (trim wheel- handle system ) is simply unable to produce enough torque absent superman along with the large number of turns required per degree and all by ONE person.
- For an aircraft not too far out of trim the trim wheels can just about overcome the Max stab actuator ie slip its clutch and turn the jackscrew (dependent on the strength of pnf)
- For an aircraft which is severely out of trim air loads on the stabiliser and hence the jackscrew are expected to be too large to be overcome by use of the trim wheels (hence the the 'porpoise' technique)
Since the stab clutch can be overcome by the trim wheels but the out of trim stabiliser forces can't doesn't this mean that in some circumstances the torque to turn the jackscrew will be higher than the actuator clutch slip torque and so manual electric trim will not work.
If this is the case then it may explain what was going on between the pilots in the final stages of ET302 when they seem to have tried re-selecting the cutout switches but could not get manual electric trim to work.
I'm conscious that the above contains assumptions about the detailed workings of the stab actuator particularly its clutch / torque limiting mechanism (it's certainly much more than a motor). Does anyone have more information about it?
If this is the case then it may explain what was going on between the pilots in the final stages of ET302 when they seem to have tried re-selecting the cutout switches but could not get manual electric trim to work.
I'm conscious that the above contains assumptions about the detailed workings of the stab actuator particularly its clutch / torque limiting mechanism (it's certainly much more than a motor). Does anyone have more information about it?
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Walkon - you make a very good point about jackscrew torque. I think the information available tells us:-
- For an aircraft not too far out of trim the trim wheels can just about overcome the Max stab actuator ie slip its clutch and turn the jackscrew (dependent on the strength of pnf)
- For an aircraft which is severely out of trim air loads on the stabiliser and hence the jackscrew are expected to be too large to be overcome by use of the trim wheels (hence the the 'porpoise' technique)
Since the stab clutch can be overcome by the trim wheels but the out of trim stabiliser forces can't doesn't this mean that in some circumstances the torque to turn the jackscrew will be higher than the actuator clutch slip torque and so manual electric trim will not work.
If this is the case then it may explain what was going on between the pilots in the final stages of ET302 when they seem to have tried re-selecting the cutout switches but could not get manual electric trim to work.
I'm conscious that the above contains assumptions about the detailed workings of the stab actuator particularly its clutch / torque limiting mechanism (it's certainly much more than a motor). Does anyone have more information about it?
If this is the case then it may explain what was going on between the pilots in the final stages of ET302 when they seem to have tried re-selecting the cutout switches but could not get manual electric trim to work.
I'm conscious that the above contains assumptions about the detailed workings of the stab actuator particularly its clutch / torque limiting mechanism (it's certainly much more than a motor). Does anyone have more information about it?
perhaps someone can provide a link- this was in April- May time period.
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How are you David? Always enjoy reading your posts.Indeed, you are correct.Companies are now charged by Boeing on the "level" of technical support (much like an extended warranty) requested after the initial support.
Why Do We Need Pilots Anyway?
Doesn't anyone else find it difficult to understand how a plane can be certified for flight when forces (torque) on the manual trim wheel can be so large that the trim wheel cannot override the forces imparted on the system by the air loading on the control surfaces? It looks like the designers expected the pilots to never trim the airplane but expected the pilots to defer all movement of control surfaces including trim to the autopilot.
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Actually what I have asserted, and continue to assert, is that 1) the Main Electric Trim controlled by the pilot’s yoke switch trumps every other electric trim input including MCAS, 2) and if the pilot does not like where the stab trim is or where it is going, then the solution is immediately available under his/her thumb.
Furthermore, this trim state is not some number read off some gauge - it is an always present tactile sensations. If the pilot is really hand-flying the aircraft, if the pilot is really trying to place the aircraft attitude in a specific place to achieve a specific result, then the pilot will feel the control pressures. If the control pressures are not what the pilot wants, then the pilot needs to do something about it. Once the aircraft is stabilized, then the crew has the opportunity to address the malfunction. We can disagree on whether the crew would recognize the Runaway Trim procedure as the best tool to handle the malfunction, but I’m pretty sure they would find their way to those cutout switches eventually. The key is to do so from a stabilized platform.
A good analogy to this situation would be attempting to ride a strong-willed horse who wants to go somewhere different than the rider. Just because you are holding the reins doesn’t mean you are in control of the horse. An experienced rider will keep a firm hold on those reins and make the horse go where he/she wants. An inexperienced rider will be driven around by the horse. What’s the solution? Give the rider more training in how to drive a stubborn horse.
At this point, you will either have a horse that willingly responds to what you’re asking or you will have a horse that begins to pull its head down. Bringing the head down is a way to throw a rider off-balance. When you are off-balance, then you do not have the same steering control through the reins.
Instead of correcting the horse if you feel a pull, remember the basics of balance and then maintain them. This will help you to be able to know how to steer a horse with reins even when the horse may have a different direction in mind.
Squeeze your legs as you execute a steering command.With your shoulders and hips stacked and balance achieved, issue the steering command through the reins as you squeeze the horse with your legs. Squeeze behind the girth of the leg which is outside of the turn you wish the horse to make. To turn right, you would be using your left leg in combination with the reins.
At the same time, use your inside leg as you rotate your hips into the turn to apply pressure to the girth of the horse. This movement should correspond with pressure on the reins on the inside of the turn as well.
Think of your position as a straight line. If you wish to turn left, then you would have left rein pressure, left inside girth pressure, and right outside girth pressure. Turning right would create the opposite need. Each cue then creates a straight line through you as the rider to encourage the turn.
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Very long time lurker...and I'm only an analyst here, but I needed to finally sign up to declare I'm team Yoko1.
Looks like he's fighting a modern day forum Battle of Thermopylae.
I, for one, find a bit of solace with putting some culpability on the crew. Training, circumstances, etc....doesn't matter to me...I want someone in the front that can recover from practically ANYTHING.
Throughout the webs, I've read other 737 pilots pov on this, and a lot of them agree that the crew has some blame here (ET302). And that's ok.
With hundreds of other catastrophic scenarios that can go wrong in flight, these forums don't reassure me that pilots are equipped with everyone consistently trying to put the blame somewhere else.
Keeping the throttles at full blast throughout is pretty crazy to me.
Certainly makes who and where I fly much more condensed and manageable if nothing else.
Looks like he's fighting a modern day forum Battle of Thermopylae.
I, for one, find a bit of solace with putting some culpability on the crew. Training, circumstances, etc....doesn't matter to me...I want someone in the front that can recover from practically ANYTHING.
Throughout the webs, I've read other 737 pilots pov on this, and a lot of them agree that the crew has some blame here (ET302). And that's ok.
With hundreds of other catastrophic scenarios that can go wrong in flight, these forums don't reassure me that pilots are equipped with everyone consistently trying to put the blame somewhere else.
Keeping the throttles at full blast throughout is pretty crazy to me.
Certainly makes who and where I fly much more condensed and manageable if nothing else.
Uhh- not too sure where you get the worm drive screw jack bit - but the 737 series ( and others 767,777, etc - use a double recirculating ball " NUT " on the course threaded screw jack. Which has about a 90 percent efficiency and can therefore be back driven absent a braking system. While the electric motor MIGHT be overloaded at the extreme position (AND) and high speed, it is more likely that the manual (trim wheel- handle system ) is simply unable to produce enough torque absent superman along with the large number of turns required per degree and all by ONE person.
As I understand you, the stab mechanical parts, forgetting the motor for now, thanks to the recirculating ball nut can not get so frictionally overloaded that they won’t run, even at high aerodynamic loads.
It could even be forced to run in reverse, if no brake is preventing this due to the efficiency of the ball bearings within the nut. Is that right?
Because if this is so, the cause of stabiliser mechanism stalling which may require yo-yo technique could only be an overloaded motor in the electrical case, or lack of trim wheel moment in the mechanical case.
The principle could even be used, if so designed, to allow an out of position stab to “freewheel” to a near unloaded position if the brake alone could be disengaged.
I have learned something, thanks.
B
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hmmm ...FAA oversight
[[url=https://en.wikipedia.org/w/index.php?title=Alaska_Airlines_Flight_261&action=edit§i on=14]edit]
[[url=https://en.wikipedia.org/w/index.php?title=Alaska_Airlines_Flight_261&action=edit§i on=14]edit]
A special inspection conducted by the NTSB in April 2000 of Alaska Airlines uncovered widespread significant deficiencies that "the FAA should have uncovered earlier".[1] The investigation concluded that "FAA surveillance of Alaska Airlines had been deficient for at least several years".[1] The NTSB noted that in July 2001, an FAA panel determined that Alaska Airlines had corrected the previously identified deficiencies. However, several factors led the Board to question "the depth and effectiveness of Alaska Airlines corrective actions" and "the overall adequacy of Alaska Airlines' maintenance program".[1]
Systemic problems were identified by the investigation in the FAA's oversight of maintenance programs, including inadequate staffing, its approval process of maintenance interval extensions, and the aircraft certification requirements.[1]
Systemic problems were identified by the investigation in the FAA's oversight of maintenance programs, including inadequate staffing, its approval process of maintenance interval extensions, and the aircraft certification requirements.[1]
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A low wing with underslung engines.
Open the throttles and the nose goes up. Close the throttles and the nose goes down.
Simple physics.
So when out of control aircraft systems were forcing the nose down at low altitude it would have taken balls of steel by the pilot to throttle back.
Keeping the throttle open was about the only tool open to him to fight to save his aircraft.
Open the throttles and the nose goes up. Close the throttles and the nose goes down.
Simple physics.
So when out of control aircraft systems were forcing the nose down at low altitude it would have taken balls of steel by the pilot to throttle back.
Keeping the throttle open was about the only tool open to him to fight to save his aircraft.
A low wing with underslung engines.
Open the throttles and the nose goes up. Close the throttles and the nose goes down.
Simple physics.
So when out of control aircraft systems were forcing the nose down at low altitude it would have taken balls of steel by the pilot to throttle back.
Keeping the throttle open was about the only tool open to him to fight to save his aircraft.
Open the throttles and the nose goes up. Close the throttles and the nose goes down.
Simple physics.
So when out of control aircraft systems were forcing the nose down at low altitude it would have taken balls of steel by the pilot to throttle back.
Keeping the throttle open was about the only tool open to him to fight to save his aircraft.
Please report here...
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As SLF, I agree. I would like the people who are responsible for my and my loved ones’ safety in the air to be more rather than less competent and generally well prepared to discharge their responsibilities. If that means paying a bit more, then I am willing to pay the price.
By the way, my recollection is that the term ‘“sock puppet” was first used against yoko1. It is unfortunate when discussion becomes acrimonious but, as a neutral reader, my view is that yoko1 is as much sinned against as sinning.
GXER - I suggest that if you have not already done so you read the very good post by XYZjim in another thread. It tackles the origins and constraints on pilot training.
https://www.pprune.org/rumours-news/...l#post10513250
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
https://www.pprune.org/rumours-news/...l#post10513250
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
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Well at least that’s one theory which can be tried out in the sim - any NG will do - get her flat out on full thrust, as much nose down trim as you can just hold level and then close the throttles or reduce the throttles to see the immediate effect and longer term effect.
Please report here...
Quite sobering.
GXER - …………..
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
Alchad
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GXER - I suggest that if you have not already done so you read the very good post by XYZjim in another thread. It tackles the origins and constraints on pilot training.
https://www.pprune.org/rumours-news/...l#post10513250
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
https://www.pprune.org/rumours-news/...l#post10513250
I tend to agree that yoko1's posts have value at the very least in the form of Socratic dialogue without which we would not have teased out many of the subtelties.
However, my own view is that s/he has been far too easily drawn into a position of giving an equivalence to pilot training and/or skill versus design, manufacture and rollout issues in the causes for the two accidents.
There are several indicators that to me represent clear signs that air travel is ‘incorrectly’ priced: it ought not be (but generally is) cheaper to fly from (say) London to Edinburgh than take a train; it ought not be (but I believe it is) cheaper to employ a fully certified FO for passenger transport than it is to employ a train driver (overground or tube).
The regulators ought to fix this by setting minimum standards. It looks like the CAA (at least) knows there is a problem - the question is whether there is the political will to grasp the nettle of weaning the flying public off the expectation of ‘cheaper than chips’ air travel.