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> All jet airliners are aerodynamically unstable and use active controls to "paper over" that. This is flatly wrong. The only aerodynamically unstable planes a

> All jet airliners are aerodynamically unstable and use active controls to "paper over" that. This is flatly wrong. The only aerodynamically unstable planes are experimental and some fighter jets. No passenger plane can be certified if it can't be proven that it is aerodynamically stable. EDIT: don't take my word, here is a short explanation by a 777 pilot: https://youtu.be/EuVlbVr_jrs?feature=shared&t=129 https://youtu.be/EuVlbVr_jrs?feature=shared&t=129

Dalewyn 3y ago
Aerodynamic stability refers to the desire of an aircraft to return to straight and level flight without any control inputs. Stability is also commonly understood as the opposite of maneuverability, as a more stable aircraft is less maneuverable. Combat aircraft such as fighters are designed to be aerodynamically unstable so their maneuverability is unhindered. Likewise stunt planes and other aircraft whose job is to not fly straight and level. Aircraft such as passenger and cargo airliners are designed to be aerodynamically stable because their job is to fly straight and level with good fuel economy and minimal piloting, they do not need swift and nimble maneuverability. The safety of an aircraft has no relation to that aircraft's aerodynamic stability.
- WalterBright 3y ago
  Airliners also have to work at low speed in thick air, and high speed in thin air. Swept wings, for example, perform poorly at lower speeds. An airliner has to perform well at both, which is why wings are swept, yet have flaps and slats to modify their aerodynamic profile. Swept wings have other problems, like dutch roll. Airliners also become uncontrollable above a certain speed, which was a contributing factor to the EA crash (the crew ignored the overspeed warning).
WalterBright 3y ago
> This is flatly wrong. Look up dutch roll, the active yaw damper that suppresses it, and the FAA requirement that all of them have a yaw damper installed. Besides, the MAX is not unstable. All it was supposed to do was just nudge the nose down a bit to match the profile of the previous 737 jets.
- Dalewyn 3y ago
  >All jet airliners are aerodynamically unstable >Besides, the MAX is not unstable. You might want to address your seeming hypocrisy there.
  - WalterBright 3y ago
    MCAS was not designed to address an instability issue.

Dalewyn 3y ago

Aerodynamic stability refers to the desire of an aircraft to return to straight and level flight without any control inputs. Stability is also commonly understood as the opposite of maneuverability, as a more stable aircraft is less maneuverable. Combat aircraft such as fighters are designed to be aerodynamically unstable so their maneuverability is unhindered. Likewise stunt planes and other aircraft whose job is to not fly straight and level. Aircraft such as passenger and cargo airliners are designed to be aerodynamically stable because their job is to fly straight and level with good fuel economy and minimal piloting, they do not need swift and nimble maneuverability. The safety of an aircraft has no relation to that aircraft's aerodynamic stability.

WalterBright 3y ago
Airliners also have to work at low speed in thick air, and high speed in thin air. Swept wings, for example, perform poorly at lower speeds. An airliner has to perform well at both, which is why wings are swept, yet have flaps and slats to modify their aerodynamic profile. Swept wings have other problems, like dutch roll. Airliners also become uncontrollable above a certain speed, which was a contributing factor to the EA crash (the crew ignored the overspeed warning).

WalterBright 3y ago

> This is flatly wrong. Look up dutch roll, the active yaw damper that suppresses it, and the FAA requirement that all of them have a yaw damper installed. Besides, the MAX is not unstable. All it was supposed to do was just nudge the nose down a bit to match the profile of the previous 737 jets.

Dalewyn 3y ago
>All jet airliners are aerodynamically unstable >Besides, the MAX is not unstable. You might want to address your seeming hypocrisy there.
- WalterBright 3y ago
  MCAS was not designed to address an instability issue.