Ethiopian airliner down in Africa
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I wonder why MCAS is the only system in the aircraft that bypasses the Control Column Cutout Switches (and therefore the STAB OVRD switch). Normally a pilot pulling back on the control column couldn't trim nose down even if he tried. And vice-versa for push-down. However MCAS can freely trim down even if pilot is pulling back.
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I know there's little evidence at this stage for this tragedy, but to elaborate and hypothesise about MCAS function:
1. MCAS activated by errant AoA vane data. (This same data may also lead to warnings such as stall etc.)
2. So, by the time you run through checklist, source the problem and stop the MCAS from further inputs by flicking the Stab trim cutout, the stab is already at X° nose down.
3. At relatively low speed you're able to manage this by pulling back on the yoke, and the now fixed stab angle may even go unnoticed and forgotten about for a while
4. Additional engine power may already have been applied, but, if not, you do so now as you need some height, especially with advancing terrain and the loss of altitude that you'd suffered.
5. The effects of the engine cowling on aerodynamics, as stated in the comment above, helps lift, as does the thrust moment created by the engines
6. You think you have the problem somewhat under control compared to the situation you were in a minute ago. You've now been able to climb and seem to have relatively stable manual control.
7. Now you're at Y feet, (still with X° nose down stab trim) with an increased airspeed of Z, up until now has been controllable due to your elevator inputs being assisted by thrust moment and engine aerodynamics, but, at this new increased airspeed and increased altitude the yoke is becoming even more difficult to keep holding back. The stab is still in the same X° nose down it was when you switched the cut-outs, and up until now you mightn't have thought about it because you'd disabled it- in accordance with the checklist.
8. You think about returning and getting this back on the ground
9. Once you level off, or even before then, with that stab STILL at X° nose down (now with a much higher airspeed component) there's only one place you're going. Once this vertical direction change has momentum there's now no chance, no elevators in the world are going to help you.
Look at the memory item for stab runaway- i.e.- not told to manually wind back trim wheel, the instruction is to "grab and hold".
All this could be caused by one errant sensor? Madness that it was certified.
1. MCAS activated by errant AoA vane data. (This same data may also lead to warnings such as stall etc.)
2. So, by the time you run through checklist, source the problem and stop the MCAS from further inputs by flicking the Stab trim cutout, the stab is already at X° nose down.
3. At relatively low speed you're able to manage this by pulling back on the yoke, and the now fixed stab angle may even go unnoticed and forgotten about for a while
4. Additional engine power may already have been applied, but, if not, you do so now as you need some height, especially with advancing terrain and the loss of altitude that you'd suffered.
5. The effects of the engine cowling on aerodynamics, as stated in the comment above, helps lift, as does the thrust moment created by the engines
6. You think you have the problem somewhat under control compared to the situation you were in a minute ago. You've now been able to climb and seem to have relatively stable manual control.
7. Now you're at Y feet, (still with X° nose down stab trim) with an increased airspeed of Z, up until now has been controllable due to your elevator inputs being assisted by thrust moment and engine aerodynamics, but, at this new increased airspeed and increased altitude the yoke is becoming even more difficult to keep holding back. The stab is still in the same X° nose down it was when you switched the cut-outs, and up until now you mightn't have thought about it because you'd disabled it- in accordance with the checklist.
8. You think about returning and getting this back on the ground
9. Once you level off, or even before then, with that stab STILL at X° nose down (now with a much higher airspeed component) there's only one place you're going. Once this vertical direction change has momentum there's now no chance, no elevators in the world are going to help you.
Look at the memory item for stab runaway- i.e.- not told to manually wind back trim wheel, the instruction is to "grab and hold".
All this could be caused by one errant sensor? Madness that it was certified.
Compared to the 1979 Chicago DC-10 crash when it took 12 days for the FAA to ground the DC-10, 3 days is much faster.
If I were a Boeing manager, I'd much rather deal with a temporary grounding than a third crash.
Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
If I were a Boeing manager, I'd much rather deal with a temporary grounding than a third crash.
Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
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I wonder why MCAS is the only system in the aircraft that bypasses the Control Column Cutout Switches (and therefore the STAB OVRD switch). Normally a pilot pulling back on the control column couldn't trim nose down even if he tried. And vice-versa for push-down. However MCAS can freely trim down even if pilot is pulling back.
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I think that reaction time plays a big factor in this case.
You jump in an airplane thet flew in, and rght after rotation ( if all posted data are correct) you get an airframe that does not want to climb.
Meters above ground you soldier on fighting and throubleshooting untill you loose it after a mere 6 minutes of pure surprice/panic.
In this case( again if all info posted is correct) you have no room, no time, no "spare" altitude.
You jump in an airplane thet flew in, and rght after rotation ( if all posted data are correct) you get an airframe that does not want to climb.
Meters above ground you soldier on fighting and throubleshooting untill you loose it after a mere 6 minutes of pure surprice/panic.
In this case( again if all info posted is correct) you have no room, no time, no "spare" altitude.
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I wonder why MCAS is the only system in the aircraft that bypasses the Control Column Cutout Switches (and therefore the STAB OVRD switch). Normally a pilot pulling back on the control column couldn't trim nose down even if he tried. And vice-versa for push-down. However MCAS can freely trim down even if pilot is pulling back.
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Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
Last edited by Rated De; 13th Mar 2019 at 23:50.
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Compared to the 1979 Chicago DC-10 crash when it took 12 days for the FAA to ground the DC-10, 3 days is much faster.
If I were a Boeing manager, I'd much rather deal with a temporary grounding than a third crash.
Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
If I were a Boeing manager, I'd much rather deal with a temporary grounding than a third crash.
Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
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Not quite correct, the Speed Trim System (STS) will trim in opposition to control column movement. B737 pilots get used to seeing the trim wheel move without a trim input and accept this as normal. I believe this is a very subtle form of conditioning that is likely to be relevant to at least the Lionair JT610 accident.
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The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.
With more a** covers needed.
And the 787 was neasrly immediately grounded despite no injuries.
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He's back at the FAA, in charge of safety.
https://www.ainonline.com/aviation-n...viation-safety
https://www.ainonline.com/aviation-n...viation-safety
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Thank you for the clarification. Again, this highlights insidious nature of system's subtlety.
I think Boeing's ballsed this up - and the FAA have a lot of reflecting to do on the overwhelming power of public sentiment versus the facts.
There comes a point in crisis management where you must address the perceptions, arguing the facts is useless.
Few if any will likely share this sentiment, but I feel for Boeing's PR team at the moment.
As a former corporate spin doctor these crises are horrific to manage.
The public baying for your blood.
Investors trashing your stock.
Politicians jumping on the bandwagon.
And nearly always - panicked and agitated senior managers, and others right up to Board level, jumping in, trying to do your job for you, ignoring advice and only making a bad situation worse.
Seen it and lived it so, so many times - and it's always the same.
There comes a point in crisis management where you must address the perceptions, arguing the facts is useless.
Few if any will likely share this sentiment, but I feel for Boeing's PR team at the moment.
As a former corporate spin doctor these crises are horrific to manage.
The public baying for your blood.
Investors trashing your stock.
Politicians jumping on the bandwagon.
And nearly always - panicked and agitated senior managers, and others right up to Board level, jumping in, trying to do your job for you, ignoring advice and only making a bad situation worse.
Seen it and lived it so, so many times - and it's always the same.
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However the Lion Air crash and investigation has revealed not only a failed part but also a possibility of a serious design problem with the 737 MAX. Now that another 737 MAX of a similar age has crashed in not only the same phase of flight but from what information we do have, in a similar way (unreliable airspeed and difficulty gaining height) we have to take seriously the possibility that the same thing caused both crashes. Added to that, the short life of the model gives it a very high 'fatal crashes per million flights' statistic.
Given all of the above along with the fact that this isn't simply a batch of dodgy AoA sensors, but a possible design fault that could affect every aircraft in the fleet, it would be an act of sheer folly not to ground the entire fleet.
I understand - what I was thinking of was not the complexities of flight as the pilot sees them, but purely focussing on the automation aspect - why allow an automatic system to operate the airplane when AoA and pitch gyro are indicating different things? Sure, it's possible both are correct, but the pilots are there to make those decisions. Why allow the automation to continue to pitch down when the altimeter is showing accelerating loss of height? A pilot may indeed do this to recover from a stall, but surely it would be rare to rely on autopilot to get you out of a stall?
I gather there are situations where the pilots are presented with a message that indications disagree, and the automatics effectively hand the matter over to the pilot - I'm just exploring why that isn't the case when to continue with the automatics could result in catastrophe.
Edit: Replying to predictorM9
I gather there are situations where the pilots are presented with a message that indications disagree, and the automatics effectively hand the matter over to the pilot - I'm just exploring why that isn't the case when to continue with the automatics could result in catastrophe.
Edit: Replying to predictorM9
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“Evidence we found on the ground made it even more likely that the flight path was very close to Lion Air’s,”
I suspect they located the stab trim jackscrew and could tell it's position.
Also :“The FAA is ordering the temporary grounding of Boeing 737 MAX aircraft operated by U.S. airlines or in U.S. territory. The agency made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today. This evidence, together with newly refined satellite data available to FAA this morning, led to this decision," the FAA said.
I suspect they located the stab trim jackscrew and could tell it's position.
Also :“The FAA is ordering the temporary grounding of Boeing 737 MAX aircraft operated by U.S. airlines or in U.S. territory. The agency made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today. This evidence, together with newly refined satellite data available to FAA this morning, led to this decision," the FAA said.
It's more than 'a deep hole in the ground', it's also full of potential evidence, have they recovered the stabiliser jack screw mechanism for instance, also ground witness reports smoke and debris issuing from plane before impact, all the bits need to be recovered, the whole site has been grossly mismanaged.
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"The thrust line has changed from the NG because the engines had to be moved forward and up to accommodate the larger fan diameter. Any handling differences as a result of this have beentuned outby 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
Boeing 737 MAX - Differences
From
Boeing 737 MAX - Differences
