Inop. stick pusher - cancel flight?

Center_Mid

Center_Mid

Well-Known Member
I got a chance to ride as wannabe co-pilot in a Pilatus PC-12 this past weekend. Yes, it's a nice improvement over my usual ride - the trusty but not-quite-as-sexy 172N.

As we were discussing the aircraft systems, the pilot/owner mentioned that the stick pusher system was inoperative because of a computer or electronics problem (I don't think he really knew the source of the problem). Anyway, it got me thinking. Is a stick-pusher in a high-perf, single-pilot turboprop required for flight? IFR flight? I would think not, but I don't recall if there are any exotic regs covering exotic equipment in high end GA aircraft.

The PC-12 flew fine, by the way. Anyone got a spare $3 million?
 
I'm not sure I know what a stick pusher is, but reguardless, for any equipment on any aircraft you need to ask yourself the following: (assuming no MEL)

1. Is it required by the type design?

2. Is it required by the FARs? (91.205, 91.207 etc.)

3. Is it listed as a required item in the equipment list/KOL?

4. If the answer is no to all of the above, the item must be either deactivated or removed (with a weight and ballance update) and placarded as "INOP". If the answer is yes to any of the above the aircraft is unairworthy and cannot be flown until the equipment is repaired or replaced.

5. PIC makes a decision as to whether or not the aircraft can be flown safely.


For aircraft with an MEL, if the item is listed in the MEL, follow the directions in the MEL for deactivation/removal etc. If the equipment is not listed in the MEL the aircraft is unairworthy.
 
I would be supprised it the PC-12 actually has a pusher.

We are all used to the stall horn that will warn when we get close to stall speed. Even if the horn does not work, all trainers will give a good buffet before the stall.

When you go to a swept wing, there can very little or no buffet before the stall. It is possible to add stall strips to the wings, but this will still not give the warning you are accustomed to.

The other problem is that swept wings tend to stall from the tips inward, which can cause the aircraft to pitch up when it stalls, instead of pitching down and breaking the stall like most small aircraft.

For this reason, many jets have a stick shaker which consist of an electric motor swinging an out of balance flywheel fastened to the back of the control column. As the name implies, when an impending stall is sensed by the aircraft it will activate the shaker, causing the yokes to vibrate, and a rather loud noise.

If the airplane has particularly poor stall characteristics, it will have a 'pusher'. If you ignore the shaker and continue to increase the angle of attack, the pusher will activate and hydraulic pressure will cause the yokes to go foreward with considerable force (you can override it with some effort). This will cause a decrease in angle of attack.

Since the PC-12 has a normal wing planform, pushers should not be necessary. If it has anything, it probably only has a shaker, which is not uncommon on turboprops.

The only way to tell if it is legal to fly is to check the MEL (if you are curious you can find copies of all the Master MEL's on the FAA website). If both shakers are out of service, it is probably not legal to fly.
 
Ain't the stick pusher the pilot (aka, yoke actuator)--nope, can't fly without one of those functioning....Mechanics humor and I couldn't resist.
grin.gif
 
Thanks for the answers. The airplane defintely had a shaker/pusher because the owner was kind of excited to show me how it worked, but he couldn't. It had just about every bell & whistle you could ask for, except a tail hook!
smile.gif
 
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Gotta check the MEL.

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Ding ding ding!
 
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Since the PC-12 has a normal wing planform, pushers should not be necessary. If it has anything, it probably only has a shaker, which is not uncommon on turboprops.

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the Brasilia has a straight wing and it has a pusher.

still...MEL
 
I fly the PC-12 for a charter company. There is a shaker/pusher installed. It has to be checked before takeoff and must be operating to fly. It had something to do with certification due to the stall speed being so close to the single engine limit of Part 23.

The test itself is pretty simple, run the power up to 5-10 PSI (yes, Torque is measured in PSI in the Pilatus, not Foot/Pounds), push the Pusher Test button, and pull back on the yoke, let it shake twice, push once, and then override the push feature with the override button on the yoke. Then let go of the test button. After that test, you push the override button on the yoke until you get a chime and a CAWS annunciation.

Chris
It's published in a letter from Pilatus that stall recovery with gear and flaps down is pretty much impossible without the stick pusher.
 
Do all the PC12 have a stick pusher? I flew one a while back, and I have no recollection of a stick pusher; but then again I wasnt looking for one...

So, is it MELable or not? I flew other planes, straight and swept wings, but you couldnt MEL it.
 
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Do all the PC12 have a stick pusher? I flew one a while back, and I have no recollection of a stick pusher; but then again I wasnt looking for one...

So, is it MELable or not? I flew other planes, straight and swept wings, but you couldnt MEL it.

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Yes, as far as I know, all PC-12's have stick pushers. The only way to "look" for it is to look for the pusher test switch (on the Series 10 models [newer models], it's on the overhead panel. on older models it's to the left and slightly behind the pilot's seat), the pusher interrupt (on the yoke), or the pusher annunciator (on the CAWS panel).

An inop pusher is not something that can be deferred with an MEL.

Chris
 
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