Are there any still commercial airplanes in use that are still steerable with complete loss of all electric systems? Do some commercial airplanes still have mechanical backup steering mechanisms?
Na maioria das (*) aeronaves Airbus,
In case of a complete loss of electrical flight control signals, the aircraft can be temporarily controlled by mechanical mode.
Isso é chamado de MECHANICAL BACKUP
e é o nível mais baixo da lei de controle (depois das Leis Normal, Alternativa e Direta)
A aeronave pode ser dirigida:
- Pitch control is achieved through the horizontal stabilizer by using the manual trim wheel.
- Lateral control is accomplished using the rudder pedals.
Os pilotos são notificados com:
A red MAN PITCH TRIM ONLY warning appears on the PFD.
Mas:
Both controls require hydraulic power.
Isso significa que se a aeronave perde AMBOS a energia elétrica e hidráulica, não é mais controlável.
Normalmente existem reservatórios hidráulicos pressurizados que permitem ter um mínimo de energia hidráulica, mesmo se houver perda total de energia elétrica, mas se houver danos substanciais à aeronave que cortou as linhas hidráulicas, isso não será mais aplicável.
(*): além do A320. Funcionalidades variam em da seguinte maneira : (enfatys mine)
Primary Flight controls:
Back-up Control Logical evolution of A320 / A340 / A340-600 family:
Full Fly-By-Wire, with a “Back-up” as an additional precaution to keep control of the aircraft during temporary loss of:
- all Primary Flight Control computers
- all Electrical power supply
A320 : full FBW controls, mechanical Back-up (Pitch Trim & Rudder)
A340/A330 : like A320, additional Yaw Damper to improve Dutch Roll damping even in Back-up mode (BYDU with hydraulic micro generator)
A340-600 : like A340 for pitch, Rudder becomes fully Electrical (BPS + BCM : Back-up Power Supply + Control Module)
A380 : like A340-600 for Yaw control + BPS+BCM also power:
- Electrical Pitch Back-Up (elevators) linked to side-stick
- Electrical Roll Back-Up (ailerons) linked to side-stick
- Pitch Trim (Wheel is replaced by Switches)
Para o A380, em particular:
Active Stability Control functions:
All levels of control laws (Normal, Alternate, “Direct” and even Back-up) include a Yaw and Pitch damping function