Page 13 - March 2016

Turboprops
to the varied harmonics in any given airframe, a lower RPM is not always better. Sometimes, quite oddly, 1,700 can seem less noisy than 1,600 for those sitting aft of the cockpit. So, it is wise to ask the passengers what setting they like best, before you start dinking around too much with the propeller RPM controls. Besides, too much unannounced variation will just confirm the negative opinion of your piloting skills that was formed during the takeoff roll.
As High As You Can Go
You are now at FL280 and going along nicely with the passengers reading magazines, but then the cloud tops gradually start coming up to your flight level, causing a bouncy ride. In the jet, you would be higher to start with, and can nearly always climb above the tops, even if it requires going to FL 450. But, unlike jets, many of the turboprops are not RVSM equipped, and few have the power output to perform well at those levels. So there you stay, bouncing along in and out of the sunlight. A piston passenger would expect this sort of thing, but in a “jet prop” they might wonder if you are doing this just to get them upset.
Finally, it is time to start down, and this is one area where turboprops really shine. Unlike pistons, you need not worry at all about shock cooling, so just bring the power back and point the nose down. And, unlike jets, those big four-blade propellers out there make wonderful speed brakes, so spoilers, with their buffeting noise, are not required. Down you go, with everything going along just fine,
MARCH 2016
until the over-speed horn sounds off, reminding you that the power increases all by itself as you descend unless you continuously pull the throttles back...the reverse of what was required during the climb.
Now, when it comes to entering the pattern...do you leave the propellers set at 1,700 RPM, or push them up to 1,900 as the checklist suggests?Push them up and the passengers will wonder what all the noise is about; in addition, the extra drag will cause a sudden and firm touchdown when you pull the power back during the flare. But, if you leave them set at a quiet 1,700 RPM you will need to remember to push them back up before applying reverse thrust or attempting a go-around. All things to consider that are not an issue in jets.
Slowing Down
Having successfully managed a reasonable landing, you taxi in and find the airplane is going way too fast at idle power. Of course, you could ride the brakes, but that is an expensive idea, and you just might wear them out and they won’t be there when really needed. Your other options are pulling the propeller on one engine (usually the right) back into feather. This slows things down to a comfortable pace, but creates a disharmony some people find objectionable. It also looks odd, one propeller turning like crazy and the other just barely moving. This can cause the passengers to wonder if you landed just before theengine quit. The other option is to pull both power levers back into Beta range, or even slightly reversed. You can completely stop the airplane by
doing this, and even back up a bit if not too worried about FOD. It does, however, cause that loud propeller buzz you often hear from big commuter turboprops at large airports. Big airplane buzz must be good, so that is what you choose.
Once parked, shutting down the PT6’s is reasonably simple. There is no long wait for the cylinder head temperatures to cool down, and with the propellers barely turning there is no concern about prop blast or jet exhaust blowing something over behind you while you work through the shutdown checklist. So, you just wait for the ITTs to drop below 610 degrees (which they almost always are), then pull the red fuel-control levers aft, which promptly shuts the engines down with a satisfying whine.
When you exit the airplane there
is that smell of burnt kerosene
wafting aft toward you, something
pilots find particularly intoxicating.
those turboprops. T&T •
And so, nostrils flaring, you wander
away thinking...great machines,
Kevin Ware is an ATP who also holds CFI, MEII and helicopter ratings, and is typed in several business jets. He has been fly- ing for a living on and off since
he was 20, and currently works as a contract pilot for several corporations in the Seattle area. When not working as a pilot, he is employed part-time as an emergency and urgent care phy- sician for a large clinic in the Seattle area.
TWIN & TURBINE • 11