Transition To A Turboprop

There's a class of airplanes that offer performance well beyond any piston twin, but can be legally flown by any pilot with a private license, complex and high-performance endorsements, a high-altitude/pressurized endorsement and instrument rating: cabin-class turboprop singles, including the Epic LT, Pilatus PC-12, Piper PA-46-500TP Meridian and Socata TBM-700/850 series. A multi-engine license isn't required with one engine, and a type rating isn't required because these airplanes have a maximum gross weight below 12,500 pounds and have a prop.

Moreover, while all of these airplanes are legal for single-pilot IFR, most are equipped with dual flight instruments suitable for a crew of two---which is key to getting experience in the flight levels without winning the lottery. All you have to do is find a pilot who flies an airplane like this on FAR Part 91 operations, and ask if he or she would like some company on their next flight (if the flying is done under Part 135 or 121, then a fully qualified co-pilot may be required).

I don't recommend doing this without an instrument rating: Turboprops spend most of their time in the flight levels (class A airspace) above 18,000 feet. If you don't have an instrument rating, you won't be able to log the time. And, filing and flying IFR gives you experience dealing with air traffic control. That's a necessity when flying in the flight levels, and means you can offer your perspective. Captain the ability to do some of the radio work, which will make bringing you along attractive on long legs.

If the pilot says yes, ask if you can borrow a copy of the pilot owner's handbook (POH)/airplane flight manual (AFM). That will show that you're serious about learning to fly an advanced airplane. You'll need to set aside some serious study time---the POH/AFM for a turboprop will likely be several times the size of any POH you've seen up to now. If the pilot offers you books from a simulator training course, they'll be better organized and easier to read than the POH/AFM, but it will take just as long to understand.

The books are big because airplanes in this class have significantly more complex systems than piston singles and light twins. As with any airplane, you've got a power plant, flight controls, fuel system and airframe. But for cabin-class turboprops, you can also expect to deal with pressurization, complex hydraulics and pneumatics, a more complex electrical system with multiple buses and weather equipment, including heated prop and windshield, de-ice boots and probably weather radar. You'll also find some unfamiliar instrumentation in the panel.

Don't panic---as the pilot who first invited me to fly right-seat in a turboprop single pointed out: "It's just an airplane."

Main Differences
In the space available for this article, I can't possibly cover everything that's different about flying a turboprop, but here are some issues common to turboprop operations that stand out as very different from what I was used to from my years flying piston singles.

In flight training, and as we move from one piston airplane to another, we memorize certain airspeeds (or, at least, learn how to find them on the airspeed indicator): stall (clean and with flaps), best glide, never exceed, etc. In all airplanes, V-speeds are weight and temperature dependent, but in bigger airplanes such as turboprops, the variation in weight is enough to matter so that values are often computed before each flight. The one exception to this is V_ne, which we'll get to later.

With GPS pretty much standard in these airplanes, the route can sometimes be direct from the departure airport (or a nearby navigational aid) to the first fix on an arrival procedure. Altitude is usually selected by comparing winds at several altitudes above FL 200. Any lower, and the turboprop isn't very efficient. Turboprops typically go as high as possible for the best economy. With climb rates of nearly 1,000 fpm at FL 270, most turboprop singles will have no trouble "popping up" to an altitude above FL 200 on all but the shortest flights.

A two-pilot cabin will be a big adjustment---and potentially for the pilot you're flying with. This isn't like flying as a student with an instructor---for one thing, you'll start in the seat on the right, rather than the left, and the captain's job is to complete the mission as efficiently as possible, rather than just to prevent a student under instruction from doing something terminally dumb. You'll probably start out observing the pilot and helping with radio work and charts. If that works out well and the pilot is impressed with your diligence (you've actually read most of the AFM, asked intelligent questions, participated in the preflight and flight planning, and didn't make any major mistakes with the radio) you may be invited to do some of the flying. Take that opportunity when and if it's offered. And, you might want to look up some references on "crew resource management."

Let's Go Flying!
Probably the biggest surprise I had initially as a turboprop copilot came at engine start. Up to that time, the pilot---a CFII who taught me most of what I know about instrument flying---had been a stickler for detailed checklists, someone who never did anything in a rush: but not now. Turboprop pilots use a combination of "flow" (a memorized series of steps that move smoothly from one part of the flight deck to the next) and a much more limited set of checklist items to get the job done as efficiently as possible. You don't want to waste time on the ground, because even at idle, a turboprop engine might be drinking well over a gallon of Jet A every two minutes. Expect some checks to be completed while taxiing, with the goal of being ready for takeoff when you reach the runway threshold. If you've studied the AFM enough to help, you can back the pilot up by reading checklist items to confirm nothing was missed during the flow checks.

While taxiing, you'll probably see (and later, have the opportunity to do) one of the coolest things about flying a turboprop: reverse thrust. It's done using the Power Control Lever (PCL), which most of the time works like the throttle on a piston airplane---but pull it past idle (usually after operating some sort of protective guard, much like putting a car transmission into reverse), and the prop pitch will reverse, slowing you down. The sound is impressive. It's used on the ground (never in the air) to save wear on the brakes to shorten your ground run.

The next coolest thing on a turboprop flight deck is the Flight Director--- although it took me a while to understand why. A function of the autopilot, the flight director makes a visual presentation with one or more "command bars" on the altitude and direction indicator (ADI) in older round-gauge airplanes, or the primary flight display (PFD) on newer glass panels. Basically, the autopilot uses the command bar to show you what it thinks you should be doing, and you function as the servo, translating that command into action with the aircraft yoke. Why not just engage the autopilot---or leave it turned off and hand-fly (without command bars) in climb? By following the flight director, you'll learn how best to control the airplane---follow the command bars, and you'll find yourself controlling the airplane much more smoothly and precisely than you otherwise would. That pays off when you need to hand-fly.

The pilot will probably set the cruise altitude (or an intermediate altitude as instructed by ATC) and arm the autopilot for altitude capture before you leave the ground---and there's one more thing to set: the target altitude for the cabin. That's a function of the cabin pressurization system, usually driven by bleed air from the gas generator section of the engine. This is yet another topic I haven't space to cover in detail; suffice it to say that in most modern turboprops, it's necessary only to set the altitude climbing (or descending) to. But it's really important to do that---if you don't, the results can be embarrassing and potentially dangerous.

The pilot should also show you where the quick-donning oxygen masks are, and that's important in case of a pressurization failure. Time of useful consciousness at FL 180 is 20 to 30 minutes; at FL 220, it's five to 10 minutes Also, during the climb, you (or your pilot) will reset the altimeter to 29.92 as you pass through 18,000 feet---or when you're cleared into the flight levels.

I mentioned that most V-speeds depend on weight and temperature, but the never-exceed speed was an exception. In climbing, this becomes apparent---especially in older airplanes with round gauge panels. The airspeed indicators we're used to from piston singles/twins have a single indicator hand. But in turboprops there are two, a solid-color hand that behaves as we've come to expect, and a second hand with alternating stripes called a "barber pole." Glass panels offer an equivalent presentation.

Barber pole is really a variable red line. As you climb, and the air thins out, the speed of sound changes. At some point, it gets low enough to be an issue. Barber pole reflects this---as you climb, it comes down. Exceeding barber pole is just like flying beyond the never-exceed speed in a piston airplane---don't do it!

Descending from the flight levels takes time---even at 2,000 fpm, descending from 20,000 feet to sea level takes 10 minutes, and at four miles per minute, covers a lot of ground. Most turboprops these days have at least a GPS navigator (if not a full flight management system) with a vertical navigation feature, which can be set to show the descent rate required to reach pattern altitude a reasonable distance from your destination. This is where one of the nicest features of a turbine engine comes into play. Forget everything you ever heard about shock cooling. It's a non-issue for this class of airplane. And most of the time, you won't need to worry about ear pain for passengers (or yourself). Cabin altitude is determined by the maximum cabin pressurization differential, which varies by airplane. Many single-engine turboprops have a maximum cabin altitude of 8,000 feet or slightly higher: 9,000 for the TBM 850 at maximum certified altitude and 10,000 feet for the PC-12.

If you've impressed the pilot to this point, you may be offered the controls for the final approach and landing. Stick forces will probably be heavier than you're used to, but shouldn't be overwhelming. Some of these airplanes have special features, including angle-of-attack (AOA) indication and trailing link landing gear, that make it almost impossible to botch a landing. After all the wheels are on the ground and the flaps are retracted, keep your feet off the brakes and pull the PCL back to reverse the prop, and you'll hear that way-cool sound again---and probably get slowed down enough to make the first turnoff. Do it well, and there's a good chance you'll be invited back for another flight!

There's a lot more that I haven't space to cover here---including ground handling, which involves a lot more than just a towbar and muscle, external power, converting pounds to gallons for your fuel order (which depends on temperature), caution and warning systems (think annunciator panel on steroids) and advanced weather avoidance gear, among much else.

One last point: This may all sound quite challenging---and it is---but it's also a ton of fun! As with any kind of flight training, it's always a good idea to go with professional instruction or mentoring when transitioning to a turboprop.

John D. Ruley is an instrument-rated pilot and freelance writer based in central California. He co-owns a Cessna Skylane but has recently been logging time in a Pilatus PC-12. Ruley is a volunteer pilot with www.ligainternational.org, which operates medical missions in northwest Mexico, and with Angel Flight West, providing free transport for medical patients. You can reach him by email to jruley@ainet.com.