4 ms·

Spoiler for people who don't want to read a VERY long article- the electrical circuits in the plane did not follow the plans. A screw that was providing groundi

Spoiler for people who don't want to read a VERY long article- the electrical circuits in the plane did not follow the plans. A screw that was providing grounding (to the plane body) for the flap system had wiggled loose- causing the electricity to take a different path, through the a circuit that controlled the angle of the propellors. So pressing the flap button cause the propellor to stop spinning.

KennyBlanken 2y ago
It didn't cause them to stop spinning. It caused them to feather, which meant torque dropped enormously, and there was suddenly a huge disparity between commanded torque / fuel flow and observed torque so the engine control system figured something catastrophic happened (such as a gearbox failure or prop/feathering system failure), and cut fuel flow to keep the engine from overspeeding...and then that in turn triggered automatic deployment of both spoilers, turning the plane into a space shuttle simulator. Welcome to Dempsey's style: google a plane crash, read a bunch, slap it all together and take multiple paragraphs to say something that only needs one sentence or adding drama...get a bunch of things wrong, and call it "in depth analysis." She doesn't do the slightest bit of "analysis", she has no training or education in aeronautics or any other relevant field, and despite having spent years reading and writing about this stuff, she routinely gets things wrong. What's hilarious is that a reporter claimed she "extensively fact-checks". What? You can't/shouldn't fact check your own work. A colleague, editor, or expert in the field does. She missed one critical fact despite those five pages and numerous diagrams and photos, which was the entire reason for the crash: the Antonov design required separate grounding points for the two systems, but the factory modified the design. ...which she would have known if she'd actually read the fucking crash report, or its summary. Summary: https://www.baaa-acro.com/crash/crash-pzl-mielec-28-weston-green https://www.baaa-acro.com/crash/crash-pzl-mielec-28-weston-g... and report: https://www.baaa-acro.com/sites/default/files/2020-10/HA-LAJ.pdf https://www.baaa-acro.com/sites/default/files/2020-10/HA-LAJ... Let me go over the numerous ways Dempsey demonstrates she doesn't understand basic physics and aeronautics despite years of "researching" plane crashes. Dempsey says: "Furthermore, because a failed engine on the An-28 tends to produce a large and sudden yawing moment, the system also automatically deploys the outboard wing spoiler on the opposite side from the engine failure, in order to ensure that drag on both sides is as close to equal as possible." First off, engine failure on any non-inline-twin will cause this, it's not specific to the An-28, but I'll chalk that up to just shitty writing skills which an editor would have fixed. Second, it's not about "ensuring drag on both sides is as equal as possible" - the yaw happens because the vector of thrust shifts several feet to one side from the centerline of the aircraft - or as it's properly referred to, asymmetrical thrust. Third, she said spoilers "induce drag" - they aren't designed to cause drag. They're designed to disrupt airflow over the top of the wing - it detaches from the surface and becomes turbulent. They spoil the flow of air - literally in the fucking name, and she doesn't understand what they do. Fourth, the reason the spoilers are deployed is not to even out drag. It's to cancel the effects from the yaw, which causes the plane to start slipping/crabbing - its yaw angle doesn't match the plane's path through the air. One wing is thrust into the wind and the other retreats, causing a difference in lift...and there's also a difference in lift because the failed engine is no longer pushing air over the wing behind it, and (until feathered) in fact is blocking, and causing enormous turbulence in, air that should be going over the wing generating lift. She said "The landing gear swiftly collapsed, causing both wings to fold downward and strike the ground." If the landing gear hadn't collapsed, the wings still would have been ripped off the plane, and further, everyone aboard likely would have been more seriously injured because the plane's fuselage (and thus passengers, not in seats) would have had a much stronger vertical acceleration when it hit the ground. The wings folded downward because the heavy engines had high momentum, the airframe's vertical speed was reduced to zero almost instantly. As the airframe's vertical speed went to zero, it exerted a force on the wings that the plane could never be designed to handle. She said: "If the blades are still angled to produce thrust, then instead of the blades taking a bite out of the air, the oncoming air will start to take a bite out of the blades, so to speak, driving the propeller, and thus the turbine, in reverse." Fucking what? Propeller blades are airfoils and when the engine fails, the blades stall because the angle of attack of the blade changes enormously. There will be some windmilling - at a tiny fraction of the engine's power (in piston aircraft, around or less torque than even the starter motor) but it's in the same direction the engine normally turns - they don't fucking spin backward because air is still flowing in the same direction. The bigger problem is that the propeller is presenting what is effectively a flat face to oncoming air, and inducing turbulence in air that should be flowing past it and smoothly over/under the wing, generating lift. Kyra Dempsey writes about shit she doesn't fully understand, doesn't seem interested in or capable of educating herself in basic physics and aeronautical concepts, and as evidenced by the writeup of this crash - gets basic facts wrong because she doesn't throughly research them enough. How she still gets this stuff wrong after years of doing it is bewildering. I don't understand reddit's obsession with her, or why people keep linking to her articles here. If she was as good as everyone claimed, why is she basically unemployed? If you want to read actual informed analysis of plane crashes, read aviation news outlets. AOPA, for example, does a lot of extensive writeups about crashes in general aviation, and it's written (and reviewed by) people who are experienced, knowledgeable pilots (and often, instructors.)
WalterBright 2y ago
Sounds like the electrical faults in some older cars. Poor grounding or corroded wires lead to the current flowing in an unexpected different path, causing all kinds of bizarre effects.
- nradov 2y ago
  I just bought a new car with poor grounding. Apparently the factory had painted over the terminal where the automatic transmission grounding cable attached. This caused a variety of intermittent faults until the dealership technician figured out the root cause and sanded off the excess paint.
- alexey-salmin 2y ago
  Yep, that brings up good memories. I spend some time fixing electrical faults in my first two cars when I was 22 and knew nothing about electrical engineering (I did know math and programming though). That feeling when I understood why taillights are flashing dimly in unison with the left turning light I won't forget, along with a few other eureka moments.
- deleted 2y ago
  [deleted]
russdill 2y ago
The problem isn't that they didn't follow the plans, they did, the problem is they didn't include industry standards for safety critical systems like preventing reverse current with diodes and/or independent grounding. The design was changed slightly shortly before going into production, from two grounding screws to one. It's a minor difference though as there would be no way to detect thata single grounding screw had failed and then the failure of the second screw would cause the same problem. And if one screw is backing out/aging, there's a good chance the other one is too.
- Sebb767 2y ago
  > It's a minor difference though as there would be no way to detect thata single grounding screw had failed and then the failure of the second screw would cause the same problem. Actually, having two grounding screws would have avoided this problem - the flap switch would never have been connected to the ground via the feathering mechanism (unless both screws got loose and somehow entangled). In that case, either the flap mechanism would have failed, which would have been obvious, or the second terminal of the feathering switch would cease to be grounded, which could lead to sudden feathering with sufficient EMI. While still not great, a dual ground-screw setup would have been much better.
  - bombcar 2y ago
    That assumes the dual screw would have disconnected them from each other (which probably would have been a better design). I'm not sure that's what the diagrams showed, however.
  - Gibbon1 2y ago
    Sneaking in a comment. Two circuits sharing a common ground path causes electronic noobs no end of confusing grief. Because the two circuits are coupled via the ground inductance and resistance. And a circuit that forms with it's ground a large loop is another source of confusing grief. A big loop is an inductor. And will pickup magnetic energy passing through it.
    - 2y ago

KennyBlanken 2y ago

It didn't cause them to stop spinning. It caused them to feather, which meant torque dropped enormously, and there was suddenly a huge disparity between commanded torque / fuel flow and observed torque so the engine control system figured something catastrophic happened (such as a gearbox failure or prop/feathering system failure), and cut fuel flow to keep the engine from overspeeding...and then that in turn triggered automatic deployment of both spoilers, turning the plane into a space shuttle simulator. Welcome to Dempsey's style: google a plane crash, read a bunch, slap it all together and take multiple paragraphs to say something that only needs one sentence or adding drama...get a bunch of things wrong, and call it "in depth analysis." She doesn't do the slightest bit of "analysis", she has no training or education in aeronautics or any other relevant field, and despite having spent years reading and writing about this stuff, she routinely gets things wrong. What's hilarious is that a reporter claimed she "extensively fact-checks". What? You can't/shouldn't fact check your own work. A colleague, editor, or expert in the field does. She missed one critical fact despite those five pages and numerous diagrams and photos, which was the entire reason for the crash: the Antonov design required separate grounding points for the two systems, but the factory modified the design. ...which she would have known if she'd actually read the fucking crash report, or its summary. Summary: https://www.baaa-acro.com/crash/crash-pzl-mielec-28-weston-green https://www.baaa-acro.com/crash/crash-pzl-mielec-28-weston-g... and report: https://www.baaa-acro.com/sites/default/files/2020-10/HA-LAJ.pdf https://www.baaa-acro.com/sites/default/files/2020-10/HA-LAJ... Let me go over the numerous ways Dempsey demonstrates she doesn't understand basic physics and aeronautics despite years of "researching" plane crashes. Dempsey says: "Furthermore, because a failed engine on the An-28 tends to produce a large and sudden yawing moment, the system also automatically deploys the outboard wing spoiler on the opposite side from the engine failure, in order to ensure that drag on both sides is as close to equal as possible." First off, engine failure on any non-inline-twin will cause this, it's not specific to the An-28, but I'll chalk that up to just shitty writing skills which an editor would have fixed. Second, it's not about "ensuring drag on both sides is as equal as possible" - the yaw happens because the vector of thrust shifts several feet to one side from the centerline of the aircraft - or as it's properly referred to, asymmetrical thrust. Third, she said spoilers "induce drag" - they aren't designed to cause drag. They're designed to disrupt airflow over the top of the wing - it detaches from the surface and becomes turbulent. They spoil the flow of air - literally in the fucking name, and she doesn't understand what they do. Fourth, the reason the spoilers are deployed is not to even out drag. It's to cancel the effects from the yaw, which causes the plane to start slipping/crabbing - its yaw angle doesn't match the plane's path through the air. One wing is thrust into the wind and the other retreats, causing a difference in lift...and there's also a difference in lift because the failed engine is no longer pushing air over the wing behind it, and (until feathered) in fact is blocking, and causing enormous turbulence in, air that should be going over the wing generating lift. She said "The landing gear swiftly collapsed, causing both wings to fold downward and strike the ground." If the landing gear hadn't collapsed, the wings still would have been ripped off the plane, and further, everyone aboard likely would have been more seriously injured because the plane's fuselage (and thus passengers, not in seats) would have had a much stronger vertical acceleration when it hit the ground. The wings folded downward because the heavy engines had high momentum, the airframe's vertical speed was reduced to zero almost instantly. As the airframe's vertical speed went to zero, it exerted a force on the wings that the plane could never be designed to handle. She said: "If the blades are still angled to produce thrust, then instead of the blades taking a bite out of the air, the oncoming air will start to take a bite out of the blades, so to speak, driving the propeller, and thus the turbine, in reverse." Fucking what? Propeller blades are airfoils and when the engine fails, the blades stall because the angle of attack of the blade changes enormously. There will be some windmilling - at a tiny fraction of the engine's power (in piston aircraft, around or less torque than even the starter motor) but it's in the same direction the engine normally turns - they don't fucking spin backward because air is still flowing in the same direction. The bigger problem is that the propeller is presenting what is effectively a flat face to oncoming air, and inducing turbulence in air that should be flowing past it and smoothly over/under the wing, generating lift. Kyra Dempsey writes about shit she doesn't fully understand, doesn't seem interested in or capable of educating herself in basic physics and aeronautical concepts, and as evidenced by the writeup of this crash - gets basic facts wrong because she doesn't throughly research them enough. How she still gets this stuff wrong after years of doing it is bewildering. I don't understand reddit's obsession with her, or why people keep linking to her articles here. If she was as good as everyone claimed, why is she basically unemployed? If you want to read actual informed analysis of plane crashes, read aviation news outlets. AOPA, for example, does a lot of extensive writeups about crashes in general aviation, and it's written (and reviewed by) people who are experienced, knowledgeable pilots (and often, instructors.)

WalterBright 2y ago

Sounds like the electrical faults in some older cars. Poor grounding or corroded wires lead to the current flowing in an unexpected different path, causing all kinds of bizarre effects.

nradov 2y ago
I just bought a new car with poor grounding. Apparently the factory had painted over the terminal where the automatic transmission grounding cable attached. This caused a variety of intermittent faults until the dealership technician figured out the root cause and sanded off the excess paint.
alexey-salmin 2y ago
Yep, that brings up good memories. I spend some time fixing electrical faults in my first two cars when I was 22 and knew nothing about electrical engineering (I did know math and programming though). That feeling when I understood why taillights are flashing dimly in unison with the left turning light I won't forget, along with a few other eureka moments.
deleted 2y ago
[deleted]

russdill 2y ago

The problem isn't that they didn't follow the plans, they did, the problem is they didn't include industry standards for safety critical systems like preventing reverse current with diodes and/or independent grounding. The design was changed slightly shortly before going into production, from two grounding screws to one. It's a minor difference though as there would be no way to detect thata single grounding screw had failed and then the failure of the second screw would cause the same problem. And if one screw is backing out/aging, there's a good chance the other one is too.

Sebb767 2y ago
> It's a minor difference though as there would be no way to detect thata single grounding screw had failed and then the failure of the second screw would cause the same problem. Actually, having two grounding screws would have avoided this problem - the flap switch would never have been connected to the ground via the feathering mechanism (unless both screws got loose and somehow entangled). In that case, either the flap mechanism would have failed, which would have been obvious, or the second terminal of the feathering switch would cease to be grounded, which could lead to sudden feathering with sufficient EMI. While still not great, a dual ground-screw setup would have been much better.
- bombcar 2y ago
  That assumes the dual screw would have disconnected them from each other (which probably would have been a better design). I'm not sure that's what the diagrams showed, however.
- Gibbon1 2y ago
  Sneaking in a comment. Two circuits sharing a common ground path causes electronic noobs no end of confusing grief. Because the two circuits are coupled via the ground inductance and resistance. And a circuit that forms with it's ground a large loop is another source of confusing grief. A big loop is an inductor. And will pickup magnetic energy passing through it.
  - 2y ago