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?
På de flesta (*) flygbussar,
In case of a complete loss of electrical flight control signals, the aircraft can be temporarily controlled by mechanical mode.
Detta kallas MECHANICAL BACKUP
och är den lägsta nivån av kontrolllag (efter normala, alternativa och direkta lagar)
Flygplanet kan styras:
- Pitch control is achieved through the horizontal stabilizer by using the manual trim wheel.
- Lateral control is accomplished using the rudder pedals.
Piloterna anmäls med:
A red MAN PITCH TRIM ONLY warning appears on the PFD.
Men:
Both controls require hydraulic power.
Detta innebär att om flygplanet förlorar både elektrisk och hydraulisk kraft, är det inte mer kontrollerbar.
Vanligtvis finns det hydrauliska reservoarer med tryck, som möjliggör minimal hydraulisk kraft även om det finns total strömförlust, men om det finns väsentlig skada på det luftfartyg som har avbrutit hydraulikledningarna, är detta inte mer tillämpligt.
(*): bortom A320. Funktionaliteterna varierar i följande sätt : (betonar min)
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)
För A380, i synnerhet:
Active Stability Control functions:
All levels of control laws (Normal, Alternate, “Direct” and even Back-up) include a Yaw and Pitch damping function