A320 PITCH AXIS
A320 PITCH AXIS
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I think I know what you are asking. By 'manual control', do you mean manually moving the stick?
The normal operating law is: normal law!
When you're on the ground, getting ready for takeoff, the airplane is in the ground mode.
In the pitch axis, the stick deflection is directly proportional to elevator deflection. In the roll axis, there is also a direct relationship between stick deflection and aileron/ spoiler deflection.
Now you're rolling down the runway. while you accelerate, the nosewheel steering authority decreases to zero with increased effectiveness of the rudder, the elevator max deflection becomes limited. A few moments after lift off, the airplane blends into the flight mode.
Pitch now is loadfactor demand. Stick deflection now is a demand for load factor. The more you deflect the stick, the higher the load factor you demand, until you reach the maximum pitch angle allowed or until you enter either the low or the high speed protection modes or when you reach the g limits for the current configuration. Moving the stick left or right now demands a roll rate up to the limit of 67 degrees of bank. There are a few more things, of course.
This flight mode stays active ubtil the airplane is at 50 radio altitude when it enters the 'flare mode'. All this is to help the pilots and give them a conventional aircraft feel for the touch down. At 30 feet, the aircraft pitch is reduced so the pilot has to pull a bit on the stick for the flare to touchdown.
So there is really nothing that makes any difference of being above or below 500'.
I assume the accident you are referring to is the one in France where they went into the trees after a low altitude fly-by.
That had nothing to do with the flight control system. To my knowledge, the airplane was in landing configuration and flew across the field below 100 radio altitude. The pilot let the plane get really slow. The main thing during low speed protection is that the flight control computer don't allow the AOA to decrease so that the airplane stalls. There is also another 'protection', independant of the flight control system. If the plane gets slow, it gets to what is called 'alpha floor', this happens before the plane gets to the minimum allowable speed/AOA. If the Autothrottle system is operable (it doesn't have to be on, just be in working condition) it automatically applies Go-around thrust when it reaches this alpha floor. They were waiting for this function to kick in, for demo purposes to the people who were with them in the cockpit at that time. But nothing happened and when they finally pushed the thrust up manually, it was already too late and they started hitting the tree tops. Why didn't it work? This function is inhibited below 100' radio altitude to avoid Go-around thrust if you accidentally hit alpha floor AOA during normal landing flare, where you operate at low speeds. If they would have done the whole maneuver above 100', it would have been just fine.
The normal operating law is: normal law!
When you're on the ground, getting ready for takeoff, the airplane is in the ground mode.
In the pitch axis, the stick deflection is directly proportional to elevator deflection. In the roll axis, there is also a direct relationship between stick deflection and aileron/ spoiler deflection.
Now you're rolling down the runway. while you accelerate, the nosewheel steering authority decreases to zero with increased effectiveness of the rudder, the elevator max deflection becomes limited. A few moments after lift off, the airplane blends into the flight mode.
Pitch now is loadfactor demand. Stick deflection now is a demand for load factor. The more you deflect the stick, the higher the load factor you demand, until you reach the maximum pitch angle allowed or until you enter either the low or the high speed protection modes or when you reach the g limits for the current configuration. Moving the stick left or right now demands a roll rate up to the limit of 67 degrees of bank. There are a few more things, of course.
This flight mode stays active ubtil the airplane is at 50 radio altitude when it enters the 'flare mode'. All this is to help the pilots and give them a conventional aircraft feel for the touch down. At 30 feet, the aircraft pitch is reduced so the pilot has to pull a bit on the stick for the flare to touchdown.
So there is really nothing that makes any difference of being above or below 500'.
I assume the accident you are referring to is the one in France where they went into the trees after a low altitude fly-by.
That had nothing to do with the flight control system. To my knowledge, the airplane was in landing configuration and flew across the field below 100 radio altitude. The pilot let the plane get really slow. The main thing during low speed protection is that the flight control computer don't allow the AOA to decrease so that the airplane stalls. There is also another 'protection', independant of the flight control system. If the plane gets slow, it gets to what is called 'alpha floor', this happens before the plane gets to the minimum allowable speed/AOA. If the Autothrottle system is operable (it doesn't have to be on, just be in working condition) it automatically applies Go-around thrust when it reaches this alpha floor. They were waiting for this function to kick in, for demo purposes to the people who were with them in the cockpit at that time. But nothing happened and when they finally pushed the thrust up manually, it was already too late and they started hitting the tree tops. Why didn't it work? This function is inhibited below 100' radio altitude to avoid Go-around thrust if you accidentally hit alpha floor AOA during normal landing flare, where you operate at low speeds. If they would have done the whole maneuver above 100', it would have been just fine.
