The Amazing PT-6 Engine!

As you saw from the last post, what makes the entire Pilatus experience (and business model) possible is the fantastically reliable Pratt and Whitney PT-6 engine. The PC-12NG is equipped with a PT6A-67P model engine. This is capable of about 1800 thermodynamic horsepower but is de-rated to 1200 shaft horsepower for normal operation on the PC12. It runs at a constant 1700 rpm in flight (yup, no rpm controller on a turbine) You just push that one big lever forward and make all the power you want. (and don’t forget to push lots of right rudder)

The technical term for the PT6 is reverse flow, radial inlet (with screen for foreign object damage protection), 4 stage, free turbine (two shaft) engine. The air intake is in the rear of the engine and flows forward toward the prop as it is compressed and ignited, incorporating 3-stage axial and 1-stage centrifugal compressor sections and two power turbines. The compressor turbines turn at around 35,000 rpm and are not mechanically connected to the power generating (propeller) side of the engine. These two shafts actually turn in opposite directions.

This video provides a very good overview of the parts of the engine:

You probably have seen a PT6 start on the ramp. The batteries (or external power) bring the engine up to a speed of about 13% NG to provide enough airflow so the fuel can be safely introduced without an overtemp. This is the only operator task on starting. At this point the engine picks up speed (sometimes with a little “poof” of smoke) and winds up to a “self-sufficient” (50%NG) speed where the generators cycle on line and the propeller comes out of feather. All this is all handled with one automated process. The only pilot task is hit “start” and introduce the fuel at 13%NG. At this point the pilot is only monitoring and watching for an overtemp or abnormal indications. If it is a hot engine being started, what you watch is decreasing ITT temp  (from 200 or so depending on how long you have been sitting) down to 150 degrees ITT before introducing the fuel and starting the automated cycle.

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The History of the PT6 Engine

As you can see, lots of moving parts and not much operator intervention in the production or maintenance of the power section. The incredible reliability is a result of a durable design and careful manufacturing process as well as constant monitoring and attention to detail. The website PT6Nation covers the engine development and history in detail (it is almost a cult). We are required to record engine trend once a day in cruise and the automated system downloads the data stream constantly for any abnormal indications to be detected.

This cut-away animation and description (OSH last year) gives you more of a complete idea of what is going on with the PT6 engine operation (and the basics of turbine mechanics) Follow the airflow…

I am continually amazed (and thankful) at the efficiency and reliability of this engine. I might have joined the PT6 cult (I should order the t-shirt!) Next time we will talk about cruise considerations for various missions we encounter. Our trip to Montana is pushing this airframe to it’s limit, we will see how that goes soon.

“Selling” a Single…Pilatus PC-12NG Vs King Air B200GT

Screen Shot 2016-06-15 at 9.59.00 PMThe economy, utility and safety of various aircraft, be they private singles or corporate carriages, are hotly debated subjects on the ramp among pilots and in boardrooms among CFOs. This controversy also fuels the sale of many flying magazines. (See this recent Flying Magazine article). There are a huge number of variables to consider when making a sensible decision and it most often comes down to specific mission requirements or just personal preference. For some owners, money is no object and its “image not numbers.” For them, the question is a simple what you “want” to fly in. You see some crazy big jet/short flight operations at every airport.

But for a charter company interested in  payload, range, economy and comfort (not to mention safety, utility and versatility) the Pilatus wins most of these discussions hands down for the shorter missions. The Pilatus PC-12, once spartan and utilitarian in their offerings (the utility moving van) has stepped up it’s game with luxurious BMW interiors and sophisticated Honeywell avionics. Consequently, Pilatus is flourishing while Beechcraft is struggling through bankruptcy (always other issues there too). This article will dig into the safety considerations of single vs twins first then compare the most common corporate twin, the Beech King Air, directly to the Pilatus PC-12NG. “Just the facts mam!”

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Data for this table was derived from this study.

The early days of aviation often required numerous engines for safety since early engines were remarkably unreliable. This all changed with the amazing PT-6 Pratt and Whitney engine and other similar turboprop engines. The PT-6 rate of in-flight failure is under 1 shut-down per 500,00 hours of operation; a remarkable reliability! OK, so why not increase safety with two PT-6 engines on board like the Beechcraft King Air?  Unfortunately, with the safety record with two engines on board, like the Beech King Air, is actually worse than flying a single. How can this be true? Largely because most twin engine aircraft almost *require* both engines to fly at all. When an engine failure occurs, cool thinking and superior piloting skill are a necessity to keep the twin in the air. And the safety consequences of mishandling a failed engine on a twin are much more catastrophic to safety and survival (due to Vmc roll over) than a “fail and glide” single engine scenario. Pilatus spent a lot of research and money “selling the single” and developed the compelling slide share “Sweet to be Single.” This is very well researched and presented and I encourage you to look through their presentation.

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In summary though, Richard N. Aarons, a safety analyst put it succinctly summarizing the NTSB data on the FAA safety website: ” An engine failure-related accident in a twin-turboprop is four times more likely to cause serious and fatal injuries.” As the facts about single-engine safety have become known, one big paddle out front ends up safer than the “perceived safety” of a twin. Also the aerodynamically clean Pilatus PC-12 can glide remarkably well providing additional options in the unlikely event of an engine shut-down. From 30,000 ft (service ceiling) a PC-12 can glide 32 minutes and 90 statue miles and is certified to land safely on grass or dirt runways. To prove the remarkable reliability of the PC-12, Pilatus recently sponsored an around the world flight piloted by Amelia Rose Earhart (no relation). This took 18 days, covered 14 countries, and used the 1 remarkable PT-6 engine that had 0 squawks!

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It is important to remember however, that when the PC-12 was being developed and introduced, single engine passenger 135 operations were not allowed in the US! Pilatus bet their whole company on the incredible safety record of the Pratt and Whitney PT-6 engine and the evolution of the regulatory environment. The demonstrated safety record of single engine turbo props has led to the FAA approval of single engine (and even single pilot) IFR/VFR charter in the US. Quite an impressive turn-around in policy.  The final frontier is the safety perception of the charter flying customers.

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In the King Air realm, Wheels Up operates exclusively in King Airs (and now Cessna Excel Jets for longer missions). Their justification for the King Airs here.

 

In the PC-12 corner is Plane SenseScreen Shot 2016-06-14 at 3.32.36 PM operating an airline and charter exclusively with the PC12s. Their justification for the PC-12 here.

 

 

Comparison of a Beechcraft King Air and a Pilatus PC-12:

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The PC-12 carries 866 lbs more payload and has 480nm more range with the same six passengers.

The Pilatus is also bigger inside than the King Air and has that incredible four foot wide cargo loading door to make all kinds of items a cinch to bring most anything along. This adds to the versatility and utility of the PC-12 and the results in the common term “Turbine SUV.”

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The PC-12 uses less runway (while carrying more weight) for both take off and landing when compared with the King Air. Those incredible fowler flaps yield a stall speed of only 67K and no Vmc roll danger here (see single-engine vs twins above)

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The Pilatus is a pretty simple single at less than 12,500 max gross weight so consequently is a lower step for transitioning pilots. This reduces the cost of pilot acquisition, training, and currency for the operator.  Of course, some clients just want a twin, regardless of the cost or convenience. The “perceived safety”of a twin still wins out over the actual accident data. And of course, some clients can only be happy with a jet and that is what they buy and fly; whatever the cost penalty.

When Flying Magazine compared the newer B-250 to the PC-12, the twin was only 30 knots faster but cost $1.5 million more on original purchase.  Screen Shot 2016-06-07 at 4.25.06 PMThe fact that the PC-12 performs better in every other category on about half the fuel just about closes the deal right there for most companies. The amazing increase in the PC-12 fleet is a testimony to the popularity and versatility of this airframe (especially in the geographically dense  NYC metro area and Eastern coastal operators).

So that’s the facts;  the Beech twin costs more money to buy and fly, carries less and uses more runway for T/O and landing. The newer King Air models do go a little faster and have the “perceived safety” of two engines but the extra HP results in an obviously diminished range and higher fuel burn. The King Air lacks the cargo capability making it less versatile if the missions are various. Finally, safety, when you actually examine the data, also favors the PC-12. More personal experience coming as we head to Boston Logan and a future trip to Missoula, MT. Everyday is an adventure.

The “Fleet” Challenge and Legacy PC-12s

My Flight Safety training and check ride was in this amazing “PC-12 NG” with the Honeywell APEX system (max T/O weight 10,450 and fully redundant systems). This plane is a masterful, fully realized expression of automated flight control. You can program it from 500′ on T/O to 200′ AGL decision height and it will fly it flawlessly. There may certainly be times where this is undesirable but the capability is there and the systems are reliable and predictable. Our fleet however contains only two NGs and a variety of other Pilatus versions that can provide challenges and surprises.

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We fly a variety of older “legacy” airframes and avionics systems in the fleet and often are flying right down to minimums with our shuttles to the islands (why do they want to go there if it is gray?) Since we dispatch on an app, anything may change by the next day and various different systems are at our disposal depending on the schedule and maintenance. Our oldest plane, the famous Pilatus #2 (“NE” or fondly called”Never Ever”) has only the Bendix King EFS 40/50 5″ attitude indicators and HSI with a primitive autopilot and completely non-intuitive vertical speed controller. One knob sets altitude, twist for vertical speed, arm and then activate. It has the evil habit of memorizing the last input (even after shutdown) When you next take-off you better not activate this system immediately or it will direct your last descent for approach (and into the weeds). This is one of those “live and learn” training lessons you discover just when you want it to work.

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The flight management controllers on the older models reside just above the throttle quadrant and have little in common with the functionality found in the “NG.” A particularly annoying habit of this set-up is not switching the nav source when you set up an ILS. And you will certainly still be on GPS unless you carefully select and verify a LOC source. And of course no paperless charts here (horrors) Just get out the Jepp books and search out your diagrams for the approach.

Between the NG and NE is another “legacy” that has G600 on both sides and the GTN 650/750 stack. This plane has touch screen with another unique functionality. This has the Garmin chapter/page logic that I rather like. We seldom get to fly longer legs in any of the legacy aircraft but I am almost familiar with this set-up and it works well. We recently shot two missed approaches trying to get into  East Hampton on a flight from KBWI. The only wart here was the vertical speed would not command a climb with the flight director. Anyway, the bigger plan was obviously was not working and we had the client send his transportation to Montauk where we flew a visual for their pick up. (And that was the end of a 14 hour duty day).

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The back end of the Pilatus also can come in astonishingly different configurations. Our oldest PC-12 has all the charm of a big yellow school bus. This plane was limited in weight and also does not have fully redundant generators. This plane is often utilized for the shuttle to the islands of Nantucket and Martha’s Vineyard.

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Another feature of the older model 45 are remarkably heavy aileron forces. In the newer model 47, Pilatus added “Flettner tabs” that use aerodynamic forces to assist the ailerons and lighten the roll handling considerably. These are much nicer to handle. The interior of the new NG was created by BMW Designworks. It’s pretty luxurious.

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These later Pilatus models, starting with serial  #683 also have a 530 lb. gross weight increase, creating the PC-12/47 (which also has fully redundant electrical capacity). This happened in 2006 and makes it possible to do long-distance flights with a full cabin. With full fuel you can load 900 lbs in back! Here is the very cool iPad app for figuring weight and balance.

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We flew the trip to Chicago in this plane and have a trip scheduled to Missoula, MT later in the month I am looking forward to. Unfortunately, you never do know if these will happen though since they are totally at the whim of our customers. This Sat. we are scheduled to be at SYR at the same time as the airshow…but who knows? I will keep you posted!

Learning and Burning (Jet A): Teterboro Challenge!

It has been a very busy week with Memorial Day and many charter runs to Nantucket and the outer Long Island airports. All these flights inevitably originate in the NYC metro area with an intense pace in the air and then coordinating catering, passenger loading, fuel, luggage (and wheelchairs) on the ground. If you get any personal time for a sandwich you are lucky. Departing in the 5PM crush of traffic requires some special techniques to avoid waiting forever in the usual conga line of jets. I am glad I have done this many times in little planes, it makes getting up to speed on the charter side more manageable. Five legs a day through this gantlet (“a form of punishment in which people armed with sticks or other weapons arrange themselves in two lines and beat a person forced to run between them”) certainly feels a little like work.

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Teterboro is every east coast charter pilot’s nemesis [see this YouTube] but ends up being our daily workspace in the metro area. I remember teaching the techniques to a new private pilot here years ago. She became livid because ground would not even call her back and talk with her. She thought this was because she was a woman with a foreign accent, but it’s pretty universal and nothing personal, just a super busy environment where everyone can get a little frustrated. It is very important to stay cool and know the rules (written and not) and essential to be totally prepared and situationally aware. Changes and opportunities happen quickly. Having a toolkit of essential tricks sure helps.

Flying the Pilatus with it’s wonderful versatility is also a huge advantage. Controllers are aware what this plane can do in the hands of a competent pilot so we often get quite an privilege for this capability. On approach, we stay fast on final, slow instantly airborne and land in under 1500 ft (love that reverse thrust). We are usually taxiing in on the first or second exit. (One of our pilots actually holds the record in the Flight Safety sim. She landed in under 700ft ground roll at max gross!) On departure a Pilatus can leave VFR (most charter jets cannot), so we can get out quick, turn low and immediately transfer to departure for efficiency. This is almost bush flying in the megalopolis.

KTEB_DeparturesThe usual traffic procedure in light winds is to land everyone on 19,  doing 180 knots to the marker, 120 knots to the numbers please, then immediately get off and free up the runway. For departure the usual taxi procedure is a conga line of frustration to runway 24. There is a “holding pen” between the ends of 19 and 24 where everyone queues up an waits endlessly for departure. Our favorite shortcut, since we are a turboprop and can depart VFR, is to request immediate departure on 19 if we see a gap in the incoming traffic. This requires your being immediately ready and responsive (you do not want to screw this up with ATC). On take-off, execute a quick left turn and disappear up the Hudson staying below the Bravo (1500MSL). The challenge here is avoiding the Bravo shelf west of the Hudson, staying under 200 knots and avoiding all the helicopters (fortunately we have sophisticated traffic avoidance systems and synthetic vision). Coordinating a climb ASAP is next action item.

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If there is weather and you must depart IFR on 24 the challenge is accurately flying the famous RUDY 5 departure with it’s mandatory 1500/2000 crossing altitudes threading the needle above and belowRudyFiveKTEB  Newark inbound traffic. I have been told this is responsible for the most pilot violations of any procedure in the whole US. Either way you are ready to pivot and respond immediately to opportunities and get flying to expedite your customers transportation. They did not hire us to watch jets on the ground in NJ for an hour.

Once airborne it is “game on” with NY Center if we are VFR to coordinate an early climb. All turbine engines burn a lot of fuel down low so “up” is essential. If we are lucky we might even be able to pick-up our IFR clearance for Part 135 flight tracking. Being fast, concise and accurate on the radio and doing exactly what you told the controller you could do are the primary skills for the pilots in any busy airspace. It certainly helps that usually one pilot is flying and one is talking (though we have single pilot 135 approval also). All KHOT_Ramptraffic flow along the coast of Connecticut is either low or over 12K to accommodate inbound traffic to the NYC airports so getting to altitude before CMK eastbound is the goal or you will be caught “in the weeds.” The arrival and ground ops at East Hampton resemble an aircraft carrier deck on the weekends with Blade running shuttles in their helicopters. Recently we had three amphibious Caravans, five helicopters taking off from the ramp mixing it up with  the usual jets and turbo props on the small ramp.

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So far LaGuardia seems like a pussycat to me compared to the challenges of  KTEB. Usually we start this procedure VFR at the Tappan Zee and call tower inbound. They keep us 1000 ft down the Hudson and direct either a right downwind 31 or base to 22. Similar to KTEB; “keep the speed up,  land short and get off my runway.” (With all the inherent contradictions involved). At KLGA you turn off right at Foxtrot/Echo and go to the “five antennas” for parking. The restaurant here is wonderful but parking is expensive for GA.

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Sheltair is always ready and picks us up here with a van and you get to enjoy one of the most beautiful FBOs in the East. For me, Sheltair has an amazing resonance of aviation history being located in the old Pan Am terminal. The Boeing 324 Clippers once landing and departing right here delivering fashionable clientele to exotic destinations all over the world. The Art Deco interior has not changed a bit since the 30s and 40s. In my next installment I will talk about the challenge and fun of the island airports and operating in minimal weather operations. Several trips to South Carolina have been challenging with all kinds of crazy schedules. Every day is a new adventure!

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