Envelope Protection, Automation, etc. comparison

[Pugachev Cobra]

Hello all,

Can someone compare to me how the Embraers 170, 175, 190, 195 compare to the envelope protection (taking the control out of the pilot or just making it hard to move the controls) and automation of Boeings (737NG's, 777 even being fbw, 787 maybe) and Airbuses?

Thanks!

[FE Hoppy]

Ejets don't have envelope protection in the same sense as airbuses. They do however have AOA limiting and Tail Strike Avoidance which are the only two high level functions that really override the pilots input.

AOA limiting calculates the AOA equivalent to Clmax in the current configuration taking into account all kinds of stuff like Mach number and g. If the pilot reaches this maximum AOA the fly by wire system ignores any further pitch up and/or trim up inputs. This means as soon as AOA max is reached the pilot can pull the stick back to the stop but the aircraft will sit at max AOA. The pitch attitude will change in order to maintain the AOA but there is no auto throttle input so if there isn't enough thrust the aircraft will sink as the V^2 in the lift equation gets smaller while the Cl part remains at max.

Tail strike protection works in a similar way but protects the maximum pitch angle and rate depending on the aircrafts heigh above the ground. It works for take off and landing but unlike AOA limit which has full authority over the elevators TSA only has partial authority so if you really try you can beat it and scrape the tail.

If they ever are active at the same time AOA limiting has priority.