reply to post by Harlequin
NO, Harlequin. The B757 and B767 are NOT flt-by-wire. I would think I know this, since I have a type-rating on those airplanes. As well as a
type-rating for the B-737 and the DC-9/MD-80 series.
Cables from the control wheel to hydraulic actuators....that is NOT the same as what Airbus has built.
It's true, though, that most modern airplanes are heavily dependant on electricity....and, BTW, not EVERY B757 or B767 has a RAT. The RAT is
required only for an ETOPS-capable airplane. I am of course speaking about the Boeings....I only flew the old A-300, not familiar with the newer
But, based on my experience, I would say that...given that the current Airbuses are completely depentant on BOTH electrics and hydraulics for flight
controls, then in the case of a dual engine failure (on the A320) and loss of normal electrics and hydraulics, then there HAS to be an ability to
maintain flight controls....which means either a RAT, or an HDG, or a combination of both....because the Battery bus is designed only for about
30-minutes of essential power, to the Captain's basic instruments, and through an inverter, can provide AC power.
The RAT, or 'Ram Air Turbine', as installed on ETOPS-equipped B-757 and B-767 will automatically deploy when, while in 'air-mode', the system
senses a loss of N1 in both engines.
The RAT, on a Boeing, supplies electricity to the Main Bus #1, which provides full power to the Captain's side of the airplane.
This ALSO provides electrical power to certain hydraulic pumps, as well as fuel pumps, but more importantly the hydraulic pumps keep the system
pressurized so the flight controls work.
I'm sure that the Airbus is similar, even if the specific designs are different.