Adding to what others said, the PC12 has those stalling characteristics shown in the video at high power, high pitch, and low weights. If you’ll notice that they were at full flaps in the video. I suspect these stall characteristics are not much different than those exhibited by most high-performance singles in this extreme condition.

The stick pusher in the PC12 is a well designed system and provides safety benefit, but like Mike C posted, it does add significant cost. I think Pilatus would make a better investment in safety with some of flight envelope protection that is in the Cirrus/Garmin, but the technology didn’t exist when the PC12 was certified. Hopefully they can start building some envelope protection technology into the Honeywell Apex/Epic.

Here is a video of a PC12 stall and push that my instructor took during a training event. The pusher activates approximately 1 knot above the aerodynamic stall and is based off the AOAs. Both AOAs (one on each wing) must agree before there is a push.

[youtube]https://youtu.be/wnRkgEAYcfs[/youtube]

I agree. In addition, I don’t think power on stalls in high powered turboprops provide much training benefit, at lower altitudes where air density and engine power is high. Not many Pilots are going to keep pushing an airplane to such an extreme condition without correction.

In the flight levels, power on stalls do provide training benefit and could represent some real world situations. High altitude stalls (preformed in a simulator) were eye opening to me. Altitude loss is much higher because of the time it takes to build enough airspeed to prevent a secondary stall in the recovery.

Wouldn't you want the pusher to activate if either wing stalls? Isn't an asymmetry reasonably likely?

Ashley

Wouldn't you want the pusher to activate if either wing stalls? Isn't an asymmetry reasonably likely?

It could be a bad day but I have never heard of any incidents of a inadvertent push, nor has Flight Safety. Flight Safety recurrent training always gives an inadvertent push and it can be surprising but is an easy recovery.

There is a spring loaded pusher override button on the yoke, you must hold it continuously to keep the system from pushing (during a malfunction). In addition, the pusher system has the only collared circuit breakers, one on the pilot side and another on the co-pilot side. The pusher system is tested before each flight as well as the override button. It’s no go item if the test fails.

If I recall correctly, Airbus designed the system for Pilatus.

It could be a bad day but I have never heard of any incidents of a inadvertent push, nor has Flight Safety. Flight Safety recurrent training always gives an inadvertent push and it can be surprising but is an easy recovery.

There is a spring loaded pusher override button on the yoke, you must hold it continuously to keep the system from pushing (during a malfunction). In addition, the pusher system has the only collared circuit breakers, one on the pilot side and another on the co-pilot side. The pusher system is tested before each flight as well as the override button. It’s no go item if the test fails.

If I recall correctly, Airbus designed the system for Pilatus.

The NGs, at least the way they are configured from the factory, the pusher breakers are the only ones that have collars. Not sure on the legacies.

The most important function of a pusher system is the ability to turn it off.

The NGs, at least the way they are configured from the factory, the pusher breakers are the only ones that have collars. Not sure on the legacies.

In a PC12, you should never do this. EVER.
Uncommanded push only happens in the sim.

Couldn't you get asymmetric incidence with a yaw? The airflow will be faster over the outside wing, inducing a difference in the angle of attack. I don't know if the PC12 has dihedral, but if has, wouldn't any departure from level wings induce a difference of the angle of incidence on the wings? If the stall shaker operates at one know from the critical angle of attack, there's not much room for error.

Ashley

Stick shaker activates between 5-10kts from stalling.

Yes.


The PC-12 has significant dihedral as is typical for low wing airplanes.

The change in left/right angle of attack is not due to wings not being level, but the plane flying sideways due to rudder input, that is, ball out of center in a yaw. With the dihedral, the wing with airflow from the side has higher angle of attack and the other wing is lower. Thus you can roll the plane with rudder (a certification requirement, BTW).

The issue here is that the left/right AOA sensors are unlikely to be setup such that the measure the AOA of the WING when it has sideways airflow, but instead the AOA relative to the fuselage axis. So both AOA sensors, despite being on each wing, will measure basically the same thing, the AOA relative to the fuselage axis, not each wing's true AOA. The reason there are two sensors is for redundancy, not to measure each wing.

What this means is that you can probably stall one wing in a hard rudder over before the stick pusher activates. This is a spin entry and would only occur for a severely uncoordinated flight condition.

Mike C.

Thanks Mike and Mikko, Ashley

Yes.


The PC-12 has significant dihedral as is typical for low wing airplanes.

The change in left/right incidence is not due to wings not being level, but the plane flying sideways due to rudder input, that is, ball out of center in a yaw. With the dihedral, the wing with airflow from the side has higher incidence and the other wing is lower. Thus you can roll the plane with rudder (a certification requirement, BTW).


Mike C.