5 ms·

Is that the component of the aircraft that allows it to yaw? If so, I imagine it’s less than ideal for this to fall off at speed.

singleshot_ 4y ago
Let’s say that it would severely complicate the remainder of the flight which would not be likely to last very long. This tragically happened to an airbus flown as American 587 shortly after 9/11. It crashed into a neighborhood in New York City after it encountered wake turbulence from another jet and one of the pilots responded too aggressively with the rudder. Truly a horrifying incident. Parenthetically I don’t recall whether this was a training issue, a software issue, or a pilot error. Accordingly, I don’t want to sound like I’m slamming the pilot. On the other hand I’ve seen a B-52 lose just about the entirety of its vertical stabilizer and it didn’t seem to care at all; landed safely.
- labcomputer 4y ago
  > Parenthetically I don’t recall whether this was a training issue, a software issue, or a pilot error. Accordingly, I don’t want to sound like I’m slamming the pilot. It was a design issue, which many people like to blame on the pilot because they don't know any better. The problem was that the rate-of-change of control-force per rudder angle is/was negative for that particular Airbus model... which is generally known to lead to PIO (pilot induced oscillations). When I say generally known, I mean it has been documented since at least as early as pre-WWII NACA (the precursor to NASA) studies. In fact, that's what led to the installation of MCAS on 737 Max's: The FAA requires that, for the elevator (but not rudder), the control force should increase as deflection increases. So Boeing tried to simulate that behavior with elevator trim + software. In other words, MCAS was a bad, hacky "solution" to a problem very similar to what happened on AA587 (but for pitch instead of yaw). > On the other hand I’ve seen a B-52 lose just about the entirety of its vertical stabilizer and it didn’t seem to care at all; landed safely. Yea, but a B-52 probably has more elevator authority than most commercial airliners (both because it is meant to go supersonic and need to deal with Mach tuck and because B-52 is expected to shed some "payload" while airborne). The problem is that the vertical stabilizer weighs a ton and is waaaay out at the end of the fuselage, so it really throws off your weight and balance if it falls off.
  - singleshot_ 4y ago
    This sounded a little sus so I read the NTSB report which did not point the finger the way you said. My limited knowledge about the BUFF is that if you achieve supersonic flight in one, you are _definitely_ doing it wrong. My impression of what the purpose of MCAS is for has, accordingly, not been influenced much by your comment.
singleshot_ 4y ago
(Yes, it controls yaw, but in some sense every vertical surface on a plane including the sides of the fuselage also contribute some yaw stability).

singleshot_ 4y ago

Let’s say that it would severely complicate the remainder of the flight which would not be likely to last very long. This tragically happened to an airbus flown as American 587 shortly after 9/11. It crashed into a neighborhood in New York City after it encountered wake turbulence from another jet and one of the pilots responded too aggressively with the rudder. Truly a horrifying incident. Parenthetically I don’t recall whether this was a training issue, a software issue, or a pilot error. Accordingly, I don’t want to sound like I’m slamming the pilot. On the other hand I’ve seen a B-52 lose just about the entirety of its vertical stabilizer and it didn’t seem to care at all; landed safely.

labcomputer 4y ago
> Parenthetically I don’t recall whether this was a training issue, a software issue, or a pilot error. Accordingly, I don’t want to sound like I’m slamming the pilot. It was a design issue, which many people like to blame on the pilot because they don't know any better. The problem was that the rate-of-change of control-force per rudder angle is/was negative for that particular Airbus model... which is generally known to lead to PIO (pilot induced oscillations). When I say generally known, I mean it has been documented since at least as early as pre-WWII NACA (the precursor to NASA) studies. In fact, that's what led to the installation of MCAS on 737 Max's: The FAA requires that, for the elevator (but not rudder), the control force should increase as deflection increases. So Boeing tried to simulate that behavior with elevator trim + software. In other words, MCAS was a bad, hacky "solution" to a problem very similar to what happened on AA587 (but for pitch instead of yaw). > On the other hand I’ve seen a B-52 lose just about the entirety of its vertical stabilizer and it didn’t seem to care at all; landed safely. Yea, but a B-52 probably has more elevator authority than most commercial airliners (both because it is meant to go supersonic and need to deal with Mach tuck and because B-52 is expected to shed some "payload" while airborne). The problem is that the vertical stabilizer weighs a ton and is waaaay out at the end of the fuselage, so it really throws off your weight and balance if it falls off.
- singleshot_ 4y ago
  This sounded a little sus so I read the NTSB report which did not point the finger the way you said. My limited knowledge about the BUFF is that if you achieve supersonic flight in one, you are _definitely_ doing it wrong. My impression of what the purpose of MCAS is for has, accordingly, not been influenced much by your comment.

singleshot_ 4y ago

(Yes, it controls yaw, but in some sense every vertical surface on a plane including the sides of the fuselage also contribute some yaw stability).