Once I tell you Wally, you're gonna wanna go and do one,
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The cloud break procedure. One of my favourite maneouvers to do during our proficiency checks,
. Although, I think if I had to perform one for real, I dunno if it'd be my favourite part of the ride down! I'm very confident it would be successful though, unless you had absolute rubbish conditions (ie. below 700ft).
The whole idea of the cloud break is to obtain maximum speed (up to Vne) and hopefully come out the bottom below the cloud, and then use the inertia to fly a circuit and land.
The SOP for the company I work for would be pretty similar, if not the same for everyone else who operates the PC-12. After all, we learnt it from another section.
Ok, let's say you're cruising along at FL180 and your engine has failed, you've feathered it, and you've started with the normal engine failure procedures (ie. GA mode on the FD activated, with the autopilot engaged, so you can pitch the nose up, obtain some more height, and obtain your glide speed of 114kts at MTOW). Next step is to find the nearest airfield. As a good practice, we put as many airfields into our GPS' as possible, around the area's we fly, should this event ever occur. Direct To the nearest airfield, and let the autopilot fly the aircraft. It's always going to do a better job at it than you are at this point.
Typical ROD with a failed engine in the PC-12 is around 800-1,000fpm. And from FL180 down to the ground (assuming ground is at MSL) would give you a glide range of pretty close to 45nm's, if not a bit more. Pilatus have always said that it glides even better with the prop in feather, compared to the zero thrust setting we use during training.
Ok, so you're on autopilot, captured on your best glide speed, and tracking direct to the nearest airfield. Next step is to set up the aircraft's Altitude Alert and RADAlt. We set the Altitude Alert to 1,200ft above the aerodrome, and the RADAlt to 700ft above the aerodrome. The idea being you get the alert passing 1,200ft, and are starting to level out to be level at 700ft if you're still in cloud. Continueing below this at the speed's you're doing the cloud break, could end in certain tragedy (yeah yeah, I know, the engine's already failed, but what would you rather, hit a hill at 236kts or hit a hill at 80kts?
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The main part of the procedure of course is to set yourself up on a 7nm arc from the aerodrome. Continue around on the arc until you are 7,000ft above the aerodrome, and then disconnect the autopilot, turn direct to the airfield, and point her down on a 1:1 descent profile, which will bring you up to near Vne (236kts). Pop out the bottom of the cloud, up near Vne, and then use the inertia to fly yourself a circuit and land. It's hard to believe how well the PC-12 does really glide until you try it for yourself, but you will find even doing this procedure, you'll often find yourself higher than you think on final, and side slipping to get the thing down. I was doing one of these one day in training, and once I 'broke visual', I had to swing around and join crosswind. Up on a 45 degree AOB turn, and still doing 220kts, ohhhhhhh yeah,
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So if that's scared a few of you, then that's ok, I'll keep my PC-12 to myself,
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morno