31–40 of 163 posts
"Two is one and one is none." That's pretty much been aeronautical gospel since dinosaurs strapped cardboard to their stubby arms and dreamed of soaring.
But not, by corollary, that two is none.
Despite the headline, the article ends with: That triple-sensor system isn’t foolproof, however. In 2008, on a customer-acceptance flight of an Airbus A320, two of the angle-of-attack sensors froze and those two sensors then outvoted the third. When the pilots went to demonstrate the stall-prevention system, they were not aware of the malfunctioning sensors. The plane crashed, killing the seven people on board. The s…
Yep, 3 sensors can fail too. Less often however. These sensors exist to solve a problem with the MAX design. Changing and moving the engines increased the likelihood of a stall when the engines could push the nose up (as I understand it). Fine. But here's the kicker: this should be something that pilots should be trained on. They should be aware of how the MAX is different to the previous 737s and know what to do to…
Earlier quoted context omitted.
Another way would be to stick a tab in the slipstream, and measure the pressure on its leading edge and both sides. Or just put a strain gauge on the mount of the tab and measure the bending forces (and this would have no ports to freeze or moving parts to jam). I bet there are lots of ways. P.S. I bet you could even put a strain gauge on the wing spar to measure the bending force on the wing, couple that with other…
The problem with such approaches is that you have to model all the environmental and performance factors that could cause an identical pseudo-AoA to be calculated, in all flight modes. And to do that you need a range of sensors, all redundant... so now you need additional input validation and sanitisation. For example, measuring slipstream over the wing is not sufficient. You need to known the pressure ratio between…
I'm sure a function can be constructed that takes that input, along with the airspeed, and produces AoA. It can be used as a crosscheck with the AoA sensors. Since it takes airspeed as another parameter, it can also crosscheck the pitot tubes.
Earlier quoted context omitted.
It does seem like a primitive system to use the wind for AoA, seems like there should be better and more reliable ways to determine it. Update: AoA not AoT
That's what AoA is though. It's the relative wind angle over the wing. The wind matters. You can't calculate AoA simply from pitch or vertical speed or something like that.
Despite the headline, the article ends with: That triple-sensor system isn’t foolproof, however. In 2008, on a customer-acceptance flight of an Airbus A320, two of the angle-of-attack sensors froze and those two sensors then outvoted the third. When the pilots went to demonstrate the stall-prevention system, they were not aware of the malfunctioning sensors. The plane crashed, killing the seven people on board. The s…
Earlier quoted context omitted.
It does seem like a primitive system to use the wind for AoA, seems like there should be better and more reliable ways to determine it. Update: AoA not AoT
Is there another method to measure wind direction, that doesn't involve a small physical winglet?
Despite the headline, the article ends with: That triple-sensor system isn’t foolproof, however. In 2008, on a customer-acceptance flight of an Airbus A320, two of the angle-of-attack sensors froze and those two sensors then outvoted the third. When the pilots went to demonstrate the stall-prevention system, they were not aware of the malfunctioning sensors. The plane crashed, killing the seven people on board. The s…
Despite the headline, the article ends with: That triple-sensor system isn’t foolproof, however. In 2008, on a customer-acceptance flight of an Airbus A320, two of the angle-of-attack sensors froze and those two sensors then outvoted the third. When the pilots went to demonstrate the stall-prevention system, they were not aware of the malfunctioning sensors. The plane crashed, killing the seven people on board. The s…
Yep, 3 sensors can fail too. Less often however. These sensors exist to solve a problem with the MAX design. Changing and moving the engines increased the likelihood of a stall when the engines could push the nose up (as I understand it). Fine. But here's the kicker: this should be something that pilots should be trained on. They should be aware of how the MAX is different to the previous 737s and know what to do to…
One can't teach others without having first learned the lesson oneself. I'm not convinced Boeing has. I'm not convinced the company had adequately consider all possible scenarios and how pilots would react in them based on their intuition.
Earlier quoted context omitted.
Yeah, but I get the feeling that it's more of a way to ensure that you probably get at least two components that will 'burn in' well and hopefully not fail too early: https://en.wikipedia.org/wiki/Bathtub_curve Like, you don't expect them to last forever, but you do expect at least 2/3 to meet their lifetime estimates.
I once had a discussion with a scifi author about how to design a starship to last a long time. I suggested that it being repairable would be of paramount importance. To that end, the various systems should use interchangeable parts. Starting with the obvious like nuts&bolts should be standardized, extend that to things like computer boards and components, motors, etc. For example, if you had a linux machine running…
In a plane, the aoa could be replaced by sensor fusion of gyroscopic sensors and air density sensors distributed over the hull.
Selfrepairing could be a achieved via a reservoir of peeble like standardized spare parts traveling through a conduit and applied via vibration and standardized interfaces. Final fallback, a simulation of expected circumstances, suggesting a half way accurate fallback model.
Those logics of "let's guess automatically if that sensor is failing" are just pushing the problem further. The real problem is too much reliance on automatic systems and top little human integration in the overall system (the human-machine system, that is to say).