Ethiopian plane crash
Discussion
PositronicRay said:
kev1974 said:
So the solution is going to be a rushed out software patch?
Hope that doesn't introduce worse or new problems!
Until the cause is confirmed, you can't be confident of a fix. Hope that doesn't introduce worse or new problems!
"The thrust line has changed from the NG because the engines had to be moved forward and up to accomodate the larger fan diameter. Any handling differences as a result of this have been tuned out by Boeing in the flight control system to make the types feel the same to crew. This was necessary for certification under the same type certificate."
From
http://www.b737.org.uk/737maxdiffs.htm
Ayahuasca said:
Boeing is claiming that it was its idea to ground the fleet and that it had proactively suggested this to the FAA.
Yet apparently the CEO of Boeing called Trump begging him not to ground the Max. I think both Boeing and the FAA have dug themselves a sizeable hole, they clearly appear to be in bed with each other. Just about every other country and operator already had their Max's parked on the tarmac while the US were busy declaring nothing was wrong, then performing a messy U-turn immediately grounding everything. Talk about being late to the party. On a separate note, I don't fly the Max variant but I do fly the -800, there are plenty of aspects even in the NG that suggest the 737 frame is getting long in the tooth. My personal opinion is that the Max should have been a clean sheet design. When you start requiring software to fix issues with physics, that come about from repeatedly modifying an ancient design, perhaps it's best to sharpen the pencils and wipe a clean slate.
Unbusy said:
Teddy Lop said:
What is the reason/justification for the system being able to overpower the pilot? I'd have thought moderate power and alarms if you resist but ultimately pilot always has control?
Teddy, if the Stab runs away, the aircraft is then seriously out of trim. The elevator no longer has enough authority to raise the nose. The Stab must be repositioned using the normal Stab switch on the control column. An out of trim Stab leads to big pressure on the control column making it physically harder to move and instinctively pulling back isn’t the cure, as we suspect in this accident.If so, I guess it's the equivalent of a hypothetical system in a car where it has electronically adjustable suspension geometry allowing either the car's ECU, or the driver via a small control on the dash, to adjust out any tendency for the car to pull to the left or to the right. This new system is the equivalent of them adding extra software which detects that the car is too close to the verge, and using that suspension adjustment to unbalance the geometry to get it to pull to the right and move itself away from the verge. The driver can still pull left or right on the steering wheel, it's just that the car is now wanting to drift right, so the driver would have to pull harder left if they wanted to get nearer the verge again.
In this case, though, the single sensor that system is using goes faulty, and it thinks it's too close to the verge even though it isn't. It adjusts the geometry to try to get the car to drift to the right, but the sensor still says it's too close to the verge. More and more adjustment gets wound on, and the driver has to start pulling the steering wheel harder and harder to the left. In the end, the geometry might be so far away from normal that the pull to the right overpowers the driver's attempts to fight against the steering wheel's pull to the right.
Further, as I understand it, the official "solution" is that the driver can realise what's gone wrong (despite no warning lights or error messages saying what's happening). They can push a button to stop the pull to the right from getting worse, but the pull already there will remain, so they'll carry on having to pull left on the steering to go straight until they twist a little knob on the dash round multiple times to get the car back to pulling straight. But after a short while it'll start winding the adjustment back on again automatically and the pull will get worse again. What the driver actually has to do is flick a couple of little switches on the dash to turn off this system (again with no warning to tell them that the system's faulty, or that those switches should be flicked), and then they still have to turn the little knob many times around before the pull to the right has gone and the steering is back to neutral.
If the plane is close to the ground, then this is the equivalent of all of this suddenly starting to happen whilst driving along a road with a huge drop off to the right, with the driver having to pull the wheel hard to the left to keep away from the drop all the time they're trying to solve the problem.
Have I got that right Unbusy?
The thing that I find completely baffling is that, as I understand it, there are 2 sensors. If they disagree, rather than the system saying "sensors clearly faulty, I'd better put on a warning light and not do anything stupid" (just like a car's ABS system would if one wheel sensor gave a very different reading to another wheel's sensor), it doesn't even bother checking the other one. It just assumes that the one sensor it's decided to use is perfect, and can make massive adjustments to the level flight based on that one sensor alone... I thought that the first rule of anything to do with aviation was not to rely on one system or one sensor...
Unbusy said:
I have seen elsewhere someone saying that the 757 line shouldn’t have been closed. I agree.
Air travel was a lot different in the late 90s and early 2000s to what it is today. If customer's had wanted the plane then they would have ordered it and Boeing would have continued building them. They didn't and so Boeing was left with no choice but to close the line. It's as simple as that. Hindsight is wonderful but even the best aviation analysts' crystal balls couldn't foresee that we would essentially come full circle 20 years down the road.AJB said:
Unbusy said:
Teddy Lop said:
What is the reason/justification for the system being able to overpower the pilot? I'd have thought moderate power and alarms if you resist but ultimately pilot always has control?
Teddy, if the Stab runs away, the aircraft is then seriously out of trim. The elevator no longer has enough authority to raise the nose. The Stab must be repositioned using the normal Stab switch on the control column. An out of trim Stab leads to big pressure on the control column making it physically harder to move and instinctively pulling back isn’t the cure, as we suspect in this accident.It’s actually just the “stabiliser runaway” procedure which all 737 pilots should know by memory.
It looks like this.
1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
■ ■ ■ ■
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
– – – – – – – – – – – – – –
Simply put you control the pitch with the control column and the electric trim (on the control column) then select the stab trim cut off (on the center pedestal by the thrust levers and then use the manual trim. (By your knee)
It’s the kind of thing any 737 pilot would have seen in the sim. That sorts out any of the stabiliser problems caused by MCAS immediately. Simple?
Not quite.
The main problem here isnt the stabiliser moving it’s that there would have likely been conflicting and confusing information about airspeed and stalling from the erroneous air data readings which make it more complex.
So it’s actually a combination of “unreliable airspeed” and “stabiliser runaway” so you’re (hopefully) doing the stabiliser memory items while you likely have all sorts of conflicting warnings about the airspeed and stalling.
Pretty horrendous really.
El stovey said:
The main problem here isnt the stabiliser moving it’s that there would have likely been conflicting and confusing information about airspeed and stalling from the erroneous air data readings which make it more complex.
So it’s actually a combination of “unreliable airspeed” and “stabiliser runaway” so you’re (hopefully) doing the stabiliser memory items while you likely have all sorts of conflicting warnings about the airspeed and stalling.
Pretty horrendous really.
Would it be cheaper to supply the crew with a couple of parachutesSo it’s actually a combination of “unreliable airspeed” and “stabiliser runaway” so you’re (hopefully) doing the stabiliser memory items while you likely have all sorts of conflicting warnings about the airspeed and stalling.
Pretty horrendous really.
Muddle238 said:
Ayahuasca said:
Boeing is claiming that it was its idea to ground the fleet and that it had proactively suggested this to the FAA.
Yet apparently the CEO of Boeing called Trump begging him not to ground the Max. I think both Boeing and the FAA have dug themselves a sizeable hole, they clearly appear to be in bed with each other. Just about every other country and operator already had their Max's parked on the tarmac while the US were busy declaring nothing was wrong, then performing a messy U-turn immediately grounding everything. Talk about being late to the party. On a separate note, I don't fly the Max variant but I do fly the -800, there are plenty of aspects even in the NG that suggest the 737 frame is getting long in the tooth. My personal opinion is that the Max should have been a clean sheet design. When you start requiring software to fix issues with physics, that come about from repeatedly modifying an ancient design, perhaps it's best to sharpen the pencils and wipe a clean slate.
Next gen single aisle will be 5+ years away yet, Airbus are looking at wing of the future currently!
Reading between the lines on what’s been said about the system and the characteristic it counters (with the caveat that I know few specifics about current civil airliners) could it be possible for the pilots to counter/disengage the MCAS and then immediately fly into the situation the MCAS is designed to counter?
cookie118 said:
Reading between the lines on what’s been said about the system and the characteristic it counters (with the caveat that I know few specifics about current civil airliners) could it be possible for the pilots to counter/disengage the MCAS and then immediately fly into the situation the MCAS is designed to counter?
Not at nearly 400kts.cookie118 said:
Reading between the lines on what’s been said about the system and the characteristic it counters (with the caveat that I know few specifics about current civil airliners) could it be possible for the pilots to counter/disengage the MCAS and then immediately fly into the situation the MCAS is designed to counter?
Yes, but you’d be in a situation where you’d stopped it working by cutting off the stabiliser trim (as a reaction to the MCAS working incorrectly) and then stalling for some reason. If the MCAS isn’t working you have to stop the stabiliser doing its own thing though because that will kill you. Whatever happens after that is just another thing to deal with.
The problem isn’t the MCAS it’s that it’s getting duff information and activating when it shouldn’t and also that Boeing hadn’t explained what it was and how it worked properly before the first crash.
El stovey said:
Not quite.
It’s actually just the “stabiliser runaway” procedure which all 737 pilots should know by memory.
It looks like this.
1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
? ? ? ?
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
– – – – – – – – – – – – – –
Simply put you control the pitch with the control column and the electric trim (on the control column) then select the stab trim cut off (on the center pedestal by the thrust levers and then use the manual trim. (By your knee)
It’s the kind of thing any 737 pilot would have seen in the sim. That sorts out any of the stabiliser problems caused by MCAS immediately. Simple?
Not quite.
The main problem here isnt the stabiliser moving it’s that there would have likely been conflicting and confusing information about airspeed and stalling from the erroneous air data readings which make it more complex.
So it’s actually a combination of “unreliable airspeed” and “stabiliser runaway” so you’re (hopefully) doing the stabiliser memory items while you likely have all sorts of conflicting warnings about the airspeed and stalling.
Pretty horrendous really.
With the added complexity of the MCAS system trimming for a max of 10 seconds at a time.It’s actually just the “stabiliser runaway” procedure which all 737 pilots should know by memory.
It looks like this.
1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
? ? ? ?
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
– – – – – – – – – – – – – –
Simply put you control the pitch with the control column and the electric trim (on the control column) then select the stab trim cut off (on the center pedestal by the thrust levers and then use the manual trim. (By your knee)
It’s the kind of thing any 737 pilot would have seen in the sim. That sorts out any of the stabiliser problems caused by MCAS immediately. Simple?
Not quite.
The main problem here isnt the stabiliser moving it’s that there would have likely been conflicting and confusing information about airspeed and stalling from the erroneous air data readings which make it more complex.
So it’s actually a combination of “unreliable airspeed” and “stabiliser runaway” so you’re (hopefully) doing the stabiliser memory items while you likely have all sorts of conflicting warnings about the airspeed and stalling.
Pretty horrendous really.
So as the crew starts the trim runway procedure, the MCAS stops trimming (for now). And that behaviour is new, and was poorly communicated.
One more thing to add confusion to an already very stressful situation.
Lord.Vader said:
Muddle238 said:
Ayahuasca said:
Boeing is claiming that it was its idea to ground the fleet and that it had proactively suggested this to the FAA.
Yet apparently the CEO of Boeing called Trump begging him not to ground the Max. I think both Boeing and the FAA have dug themselves a sizeable hole, they clearly appear to be in bed with each other. Just about every other country and operator already had their Max's parked on the tarmac while the US were busy declaring nothing was wrong, then performing a messy U-turn immediately grounding everything. Talk about being late to the party. On a separate note, I don't fly the Max variant but I do fly the -800, there are plenty of aspects even in the NG that suggest the 737 frame is getting long in the tooth. My personal opinion is that the Max should have been a clean sheet design. When you start requiring software to fix issues with physics, that come about from repeatedly modifying an ancient design, perhaps it's best to sharpen the pencils and wipe a clean slate.
Next gen single aisle will be 5+ years away yet, Airbus are looking at wing of the future currently!
Having the MAX was not only cheaper for Boeing but cheaper for the airlines as crew/engineer training could just be done by differences courses.
This is what the likes of South West asked Boeing for as they operate a huge number of 737 NGs so a simple conversion to the MAX is ideal
Although, it seems, this may be part of the problem.
Muddle238 said:
Yet apparently the CEO of Boeing called Trump begging him not to ground the Max. I think both Boeing and the FAA have dug themselves a sizeable hole, they clearly appear to be in bed with each other. Just about every other country and operator already had their Max's parked on the tarmac while the US were busy declaring nothing was wrong, then performing a messy U-turn immediately grounding everything. Talk about being late to the party.
There was another phone call with trump yesterday saying they were going to ground it, so trump leapt in first to claim the creditEddyBee said:
Also on the clean sheet design argument , you have to look at what customers wanted.
Having the MAX was not only cheaper for Boeing but cheaper for the airlines as crew/engineer training could just be done by differences courses.
This is what the likes of South West asked Boeing for as they operate a huge number of 737 NGs so a simple conversion to the MAX is ideal
Although, it seems, this may be part of the problem.
Customers did want a clean sheet design but Boeing couldn't come up with a compelling case to justify the selling price vs operating economics. The engine technology wasn't advanced enough without doing something risky like a propfan. Plastic aeroplanes make more sense at larger airframe sizes like the 787, not 180 seaters (albeit the C-Series / A220 is trying to make that hypothesis work). Airbus had enough headroom (structrual layout/control systems) in the A320 family to make a sense of re-engining with the best tech available in the timeframe. The MAX was simply a defensive move by Boeing that ultimately may prove to be the wrong decision. Having the MAX was not only cheaper for Boeing but cheaper for the airlines as crew/engineer training could just be done by differences courses.
This is what the likes of South West asked Boeing for as they operate a huge number of 737 NGs so a simple conversion to the MAX is ideal
Although, it seems, this may be part of the problem.
Even conservative carriers like Southwest know that ultimately you have to have a step change and ride out the transition costs (which are the same for all your competitors btw). Even the VW Beetle eventually went out of production.....
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