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Trevor Sumner Mar 16
1of x: BEST analysis of what really is happening on the issue from my brother in law , who’s a pilot, software engineer & deep thinker. Bottom line don’t blame software that’s the band aid for many other engineering and economic forces in effect.👇🎖🤔
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Trevor Sumner
Some people are calling the 737MAX tragedies a failure. Here's my response: It's not a software problem. It was an * Economic problem that the 737 engines used too much fuel, so they decided to install more efficient engines with bigger fans and make the 737MAX.
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Trevor Sumner Mar 16
Replying to @trevorsumner
This led to an * Airframe problem. They wanted to use the 737 airframe for economic reasons, but needed more ground clearance with bigger engines.The 737 design can't be practically modified to have taller main landing gear. The solution was to mount them higher & more forward.
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Trevor Sumner Mar 16
Replying to @trevorsumner
This led to an * Aerodynamic problem. The airframe with the engines mounted differently did not have adequately stable handling at high AoA to be certifiable. Boeing decided to create the MCAS system to electronically correct for the aircraft's handling deficiencies.
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Trevor Sumner Mar 16
Replying to @trevorsumner
During the course of developing the MCAS, there was a * Systems engineering problem. Boeing wanted the simplest possible fix that fit their existing systems architecture, so that it required minimal engineering rework, and minimal new training for pilots and maintenance crews.
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Trevor Sumner Mar 16
Replying to @trevorsumner
The easiest way to do this was to add some features to the existing Elevator Feel Shift system. Like the system, the relies on non-redundant sensors to decide how much trim to add. Unlike the EFS system, MCAS can make huge nose down trim changes.
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Trevor Sumner Mar 16
Replying to @trevorsumner
On both ill-fated flights, there was a: * Sensor problem. The AoA vane on the 737MAX appears to not be very reliable and gave wildly wrong readings. On , this was compounded by a
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Trevor Sumner Mar 16
Replying to @trevorsumner
* Maintenance practices problem. The previous crew had experienced the same problem and didn't record the problem in the maintenance logbook. This was compounded by a:
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Trevor Sumner Mar 16
Replying to @trevorsumner
* Pilot training problem. On LionAir, pilots were never even told about the MCAS, and by the time of the Ethiopian flight, there was an emergency AD issued, but no one had done sim training on this failure. This was compounded by an:
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Trevor Sumner Mar 16
Replying to @trevorsumner
* Economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed.
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Trevor Sumner Mar 16
Replying to @trevorsumner
All of this was compounded by a: * Pilot expertise problem. If the pilots had correctly and quickly identified the problem and run the stab trim runaway checklist, they would not have crashed.
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Trevor Sumner Mar 16
Replying to @trevorsumner
Nowhere in here is there a software problem. The computers & software performed their jobs according to spec without error. The specification was just shitty. Now the quickest way for Boeing to solve this mess is to call up the software guys to come up with another band-aid.
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Trevor Sumner Mar 16
Replying to @trevorsumner
I'm a software engineer, and we're sometimes called on to fix the deficiencies of mechanical or aero or electrical engineering, because the metal has already been cut or the molds have already been made or the chip has already been fabed, and so that problem can't be solved.
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Trevor Sumner Mar 16
Replying to @davekammeyer
But the software can always be pushed to the update server or reflashed. When the software band-aid comes off in a 500mph wind, it's tempting to just blame the band-aid. Follow if you want to dig in.
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MARavinder Mar 16
Replying to @trevorsumner
What does this tell us about Boeing's commitment to aircraft safety? Why would this feature not be in all of their 737MAX aircrafts by default? Economics? Profits? 🤔
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Trevor Sumner Mar 16
Replying to @rednivaram
Well it sounds like redundant sensors might solve issue.
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Anastasia Smith Mar 16
Replying to @trevorsumner
This is where it should have stopped. If it’s not stable enough according to the laws of physics to safely fly in manual mode...
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Trevor Sumner Mar 16
Replying to @Anastas17351725
Yes. Increasing system complexity to address inherent flaws rather than addressing the flaw is key to the hubris here. Just because you can apply bad aids doesn’t mean you should fix the wound.
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SGK 🔥 🚩 Mar 16
Replying to @trevorsumner
“Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. “. >>> shocking it should have been standard!
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Trevor Sumner Mar 16
Replying to @captaink99
Exactly!!
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