A320 - why pitch limits in Normal Law?
 

I done my A320 rating recentley. I understand the 67* roll
limit.

But why does this thing have pitch limits? The high and low
speed protections cover any speed excursions.

Cant find nothin in FCOM.

Run the speed up a bit and pull back and you could put the aircraft in an unrecoverable attitude, all while having a "safe" airspeed. :}

Dreamland. would Abnormal attitude law not take care of this

No. Abnormal law is to enable you to continue to fly the aircraft (in a degraded mode) should it be inadvertently displaced outside the normal law envelope (think severe turbulence or something going wrong with multiple FCCs).

It does not guarantee that every attitude you can get the aircraft in is recoverable.

i think you're getting yrself confused here.

the pitch limits and the high and lowspeed limits coincide.

the aircraft monitors the limits of yr pitch vs airspeed and from this it calculates comes yr low speed and high speed and also yr load protections.

its not 2 seperate things. they work all together to get these protections. if u are talking about pitch on take off... well... if u ain't thinking tailstrike then........................................................ .......................:confused:

There are separate limits to pitch (+30, -15 deg) and roll (+-67 deg) , as well as load factor protections and high and low speed (alpha) protections.

Aspen, I'm not at expert at all on the system but I would say Gary has explained it well, sort of like the superior pilot skills saying, only the attitude limitation is there to avoid having to use the Abnormal Attitude Law.

So say a pitch-mark on the PFD of say 27* up in Normal Law
would therefore corespond to VLS if I pulled up to that
attitude and held it? What about the nose-down case?

Or are these pitch limits that, if exeeded, would put it in
Abnormal Attitude Law?

(No Im not talking SRS which is somethin else entirely).

No, they would not coincide. Their is no connection between airspeed and the pitch limits, other than they are both protected parameters.
If you pulled to the pitch limit you would first be held at that angle till the speed bled off. Airpseed would plunge right past Vls, and at somepoint Alpha Prot and Alpha Floor would kick in, depending on the rate at which all this happens. Abnormal attitude law kicks in (and stays in) after exceeding the indicated limits of normal law.

The pitch limitations have initially been put into the flight control laws because while such high attitudes have no operational applications, avoiding them ensures a better efficiency of the "hard" protections.

In other words, the pitch protections restrain the potential dynamics of the maneuvers in order to improve the efficiency of angle of attack or overpeed protections.

If we consider the low speed flight domain for instance, a pitch attitude of +50° would lead to a very quick loss of speed (in kts per second) which might lead to a maximum angle of attack being overshot (during the maneuver) because the alpha-protection is not designed to react that hard or early (in terms of speed).