Category Archives: PT6A Engine

A Flying Swiss Army Knife: The Many Faces Of The Pilatus PC–6 Porter

It’s a missionary and a mercenary. A soldier and a spy. A record-setter and an also-ran. After 60 years of continuous production, the Pilatus PC–6 Porter, a legendary Swiss turboprop that has played more supporting roles than Kevin Bacon, will cease production in 2019.

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5 Quick Tips For Servicing Your Engine’s Oil System

This article originally appeared on the P&WC Airtime Blog.

Our expert shares 5 oil maintenance best practices that will help give you a clear picture of your oil status and keep your engine performing optimally.

1. RESPECT THE MIN AND MAX LEVELS

If your engine oil is at a level below the minimum, the oil supply during operation may be insufficient. Conversely, a level that exceeds the maximum may impede proper operation of the air/oil separator or breather, leading to possible bearing seal distress and loss of oil through the engine breather tube.

An oil level that’s too high or too low could also result in oil pressure fluctuations, low-pressure indications and engine damage.

2. MONITOR OIL USAGE OVER AT LEAST 10 HOURS

To perform engine oil system servicing effectively, you should continuously monitor your oil consumption. Careful monitoring will give you advance warning of abnormal oil consumption allowing you to carry out preventive troubleshooting.

PT6A

For more accurate results, we recommend recording oil consumption data over at least 10 hours of accumulated flight time and plotting the data for oil consumption trend analysis. This will give you a more realistic portrait of your engine’s functioning.

On a related note, be wary of oil level readings taken when the aircraft is parked on uneven ground, since they may not be accurate.

Aircraft attitude may affect engine oil level readings, especially in the case of helicopters, which land on all kinds of uneven surfaces. You shouldn’t use readings taken when the aircraft is resting at an angle.

ANDRÉ GALLANT, TRAINING SPECIALIST, FIELD SUPPORT OFFICE

3. ALWAYS PERFORM SERVICING AT THE DESIGNATED TIME

Always check and service your engine oil system at the same time, based on the instructions in the engine maintenance manual. Typically, the designated time is around 15 to 30 minutes after shutdown. This is fundamental to obtaining reliable and accurate oil consumption trend data. If you wait longer than the indicated time to check the oil level, it may affect the readings, since hot oil in a still-warm engine has more volume than cold oil.

Checking the level as recommended by the engine maintenance manual can also help you identify issues. For instance, if you checked the oil level shortly after shutdown, then come back the next morning and notice that it’s notably lower, internal static oil transfer may have occurred overnight.

In a situation like this, do not simply refill the oil tank. If you do, there may be too much oil in the system and it could overflow via the engine breather. Perform troubleshooting instead to resolve the matter. On a PT6A engine, the cause could be a leaky oil filter check valve.

4. USE THE SAME LEVEL EVERY TIME

Likewise, you should always service your oil system to the same level. If you fill the oil tank to the maximum one day and to the minimum the next, it could skew your data. No matter what the oil level indicator configuration is, we recommend always servicing your engine oil system to a level somewhere between the minimum and maximum.

If you keep your oil levels at the maximum all the time, it could increase your oil consumption rate, since some oil has a tendency to exit through the engine breather. This could even happen at one or two quarts below the maximum, so you should adjust accordingly and service the oil system to a level where consumption is acceptable.

ANDRÉ GALLANT, TRAINING SPECIALIST, FIELD SUPPORT OFFICE

5. USE THE RIGHT DEVICE AND OIL

When topping up your engine oil tank, be sure to use an appropriate filling device such as a funnel or fluid servicing cart with the appropriate attachment. Using the wrong device could lead to spills and leakages, as well as an inaccurate oil usage recording.

You should also exercise caution when inter-mixing different brands or types of oil and always follow the recommendations in the applicable engine maintenance manual and oil service bulletin. When permitted, switching to another kind of oil might require additional maintenance, such as oil analysis and filter inspection, paying attention to carbon deposits. As different oils may have different properties. And in some situations, such as engines that have accumulated a lot of hours, switching oil type may be prohibited.

The best thing you can do is to stick with the same brand and type of oil. If you have to change, always check the applicable engine maintenance manual and oil service bulletin first to see whether you can and what oil brands and types are acceptable.

ANDRÉ GALLANT, TRAINING SPECIALIST, FIELD SUPPORT OFFICE

Putting these handy tips into practice while also following the standard procedures in your maintenance manual will allow you to maintain a normal main oil pressure during engine oil system servicing.

With the help of P&WC’s new Oil Analysis Technology –which is 100 times more sensitive than other oil monitoring technologies on the market –your engine oil can also provide you with insights into the health of bearings, gears, carbon seals and other engine parts. By analyzing data taken from periodically collected oil samples, this technology monitors engine health on wing and supports predictive and preventive maintenance without intrusive inspections. To learn more, check out Oil Analysis Technology Makes Proactive Maintenance Easier.

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Air Tractor Releases 800th Aircraft in AT-802 Series

Olney, Texas aircraft manufacturer Air Tractor, Inc. passed a major production milestone with the recent delivery of the 800th aircraft in the AT-802 series. The 800-gallon capacity airplane, Air Tractor’s largest, took off from Air Tractor on a northeast heading toward its new home in Arkansas to work as a single engine air tanker.

Continue reading Air Tractor Releases 800th Aircraft in AT-802 Series

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A Quick Look at the Twin PT6A Powered Cheyenne II & IIXL

In the mid-1960s, Piper, noting the success of Beech’s King Air, decided to explore the possibility of producing its own twin turboprop. The manufacturer hired legendary aircraft designer Ed Swearingen to retrofit a Piper PA–31P pressurized Navajo with 550-shaft-horsepower Pratt & Whitney Canada PT6A-20 turboprops. After a successful first flight in April 1967 and further tests indicated that the Pratt powerplant and Piper airframe were a good match, the PA–31T Cheyenne was launched.

The Cheyenne was a simple and reliable entry-level turboprop that was more affordable and faster than the King Air 90. However, the Cheyenne’s smaller cabin could only accommodate two pilots and four passengers—plus a fifth passenger if the belted potty seat were used. Baggage space was limited, but the airplane could operate from relatively short runways and be flown by a single pilot.

Piper Cheyenne II from BJTOnline.com

The initial production model of the Cheyenne was powered by two 620-shaft-horsepower Pratt & Whitney Canada PT6A-28 turboprops and included 30-gallon wingtip fuel tanks. Dual King Gold Crown avionics were standard. The Cheyenne first flew in October 1969 and was certificated in May 1972. Cheyenne deliveries began in 1974.

When Piper introduced the lower-powered and less expensive Cheyenne I in 1978, the manufacturer renamed its original twin turboprop the Cheyenne II. Essentially the only difference between the original Cheyenne and the Cheyenne II were some cabin configuration changes. The stretched PA–31T2 Cheyenne IIXL, which had a two-foot-longer fuselage than the original Cheyenne, entered production in 1981. The IIXL has an extra cabin window on the left side, a nearly 500-pound higher max takeoff weight, and is powered by more powerful 750-shaft-horsepower PT6A-135s. Besides offering more interior room, the IIXL’s longer fuselage eliminated the need for the stability augmentation system.

A Piper Cheyenne XLII from Jetphotos.com

Over the years, many enhancements for the Cheyenne II have been developed, with the most notable being Blackhawk Modifications, Inc.’s XP engine upgrade, which involves replacing the Cheyenne’s original engines with new 750-shaft-horsepower PT6A-135A turboprop engines. The simple bolt-on upgrade enables operators to cruise approximately 20 knots faster.

The PT6A-135A engine was also the cornerstone of the Super Cheyenne conversion, which was offered by T-G Aviation of Hamilton, Ontario, Canada. Some Cheyenne operators have also boosted the speed of their airplanes by fitting them with cowl/ram air and exhaust stack aftermarket kits.

In addition, numerous panel upgrades have been developed for the Cheyenne II, including installation of lighter, more capable new-generation avionics from Aspen, Cobham (Chelton and S-TEC), and Garmin.

Piper built a total of 526 original Cheyennes and Cheyenne IIs, and 228 remain on the FAA registry, according to Vref. Prices range from $310,000 for a 1974 model to $520,000 for a 1983 model. Of the 81 Cheyenne IIXLs produced, 46 remain on the FAA registry. Prices range from $620,000 for a 1981 model to $680,000 for a 1984 model.

SPEC SHEET

Cheyenne II

Engines | Two Pratt & Whitney PT6A-28s, rated at 620 shp 
Seats | Seats: Up to 8 (including two pilots)
Max takeoff weight | 9,000 lb
Max cruise speed | 277 kt
Takeoff distance (over 50 ft obstacle) | 1,980 ft
Range | 1,195 nm
Wingspan | 42 ft, 8 in
Length | 34 ft, 8 in
Height | 12 ft, 9 in

Cheyenne IIXL

Engines | Two Pratt & Whitney PT6A-135s, rated at 750 shp
Seats | Seats: Up to 8 (including two pilots)
Max takeoff weight | 9,474 lb
Max cruise speed | 273 kt
Takeoff distance | 2,042 ft
Range | 1,060 nm
Wingspan | 42 ft, 8 in
Length | 36 ft, 8 in
Height | 12 ft, 9 in

Information via AOPA

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Videos: The Secrets of Engine Rigging Revealed

This article originally appeared on the P&WC Airtime Blog.

A new P&WC-produced video helps aircraft mechanics by breaking down engine rigging into simple, repeatable steps. Airtime spoke to the two men behind this handy PT6A resource to learn more.

THE IMPORTANCE OF WELL-RIGGED ENGINES

Jan Hawranke, Externals, Controls & Nacelles (ECN) Program Leader for PT6A engines, remembers exactly when he started to worry that the art of engine rigging was in danger of disappearing.

During the course of one year, an aircraft OEM sent back a dozen fuel control units that appeared to be faulty and couldn’t be matched to each other on a twin-engine aircraft. This was a significant concern, since engines must be rigged exactly the same way to perform in harmony.

Jan didn’t understand why the units were being returned, though, since they were in perfectly good condition. That’s when the “aha” moment hit him: the real issue was that the OEM’s mechanics didn’t have the information they needed to rig the fuel control units properly.

Rigging—the process of hooking up engines to an aircraft’s body—is an integral part of the engine’s installation process. It has to be done with the utmost care each time an engine is installed, Jan explained to Airtime.

On an aircraft with two engines, if both are not rigged exactly the same way, one might produce more power than the other. The pilot will then have to compensate by adjusting the power lever positions. It would be like driving a car with brakes that pull the car to one side, requiring the driver to turn the wheel to keep the vehicle straight.

Rigging information is available in aircraft maintenance manuals (AMMs), but it’s a complex process that cannot fully be captured in a written document or reviewed at a glance.

“There’s an art to good rigging,” says Jan. “A lot of it comes down to the mechanic’s feel and experience. The fuel control units being returned were a red flag to us that something was changing.”

A lot of the veteran mechanics who mastered rigging 20 or 30 years ago are retiring now. The know-how that existed years ago, the unwritten details that make for good rigging, are being lost. We realized it was important to pass that knowledge on to younger mechanics. 

– JAN HAWRANKE

A VIDEO THAT MAKES MECHANICS’ WORK EASIER

While the airframer is ultimately responsible for providing rigging information, P&WC has always worked closely with OEMs to develop clear and thorough explanations. Indeed, two decades ago, Jan worked on a video designed to complement the information found in AMMs with tips on the rigging process.

For various reasons, he was never satisfied with the original video, which was now out of date anyway. He decided it was time for take two. Jan turned to a master of the rigging craft, P&WC veteran Rob Winchcomb, to star in a new rigging video.

You want both engines to behave the same way all the time, especially when landing, which is one of the most stressful moments of a flight. It’s a handling issue. Well-rigged engines make the pilot’s workload easier by ensuring that the response from each engine is identical whenever the levers are operated.

– ROB WINCHCOMB,
PT6A CUSTOMER MANAGER

THE FUNDAMENTAL RULE OF RIGGING

The pair spent two weeks in Australia with a local production crew to create the video. To make it as authentic and useful as possible, it features in-service PT6A-powered aircraft, generously made available by Australia’s Royal Flying Doctor Service.

The video provides detailed instructions on every aspect of rigging, such as the differences between fine and coarse adjustment of the serrated washer, or how to match the travel of propeller levers. As Rob emphasizes, no matter what action is being performed, the number-one rule of rigging remains the same: whatever you do physically to one engine, do exactly the same thing to the other one.

As mentioned in the video, it’s also a good idea to have two people in the cockpit when performing this complex job, with one operating the engine and the other following the instructions and writing down the results. The more efficient you are, the less fuel you will burn during the final checks in the engine run bay.

P&WC will eventually release two different versions of the video for two different fuel control unit models, starting with the first one below. Click on the links to watch:

MACKAY, QUEENSLAND – APR 1, 2006: Beech B200 Super King Air medical plane from the Royal Flying Doctor Service on the tarmac of Mackay airport.

Rigging your PT6A engines for King Air B200:

Rigging your PT6A engines for King Air B350:

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The PT6A Powered C-12 Huron Military Passenger and Transport Aircraft

The C-12 Huron is a military version of an executive passenger and transport aircraft based on the Beech Model 200 Super King Air. It is primarily used by the US Air Force, US Navy, US Army and US Marine Corps for several functions, including range clearance, embassy support, medical evacuation, VIP transport, passenger and light cargo transport. The C-12 took its maiden flight on 27 October 1972 and entered service with the US Army in 1974.

Continue reading The PT6A Powered C-12 Huron Military Passenger and Transport Aircraft

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The PT6-A Powered Basler BT-67: Turbine-Charged

Since 1990 Basler Turbo Conversions has given new life to dozens of DC-3s.

By Mark Huber | from 2000 in Air & Space Mag

The hulks of seven DC-3 fuselages are parked alongside Basler Turbo Conversions’ 75,000-square-foot facility in Oshkosh, Wisconsin. Three more DC-3s sit inside, disemboweled, bracketed by yellow scaffolding in a main hangar that looks like a surgical theater. With them, a shiny white and blue BT-67, a “Basler-ized” DC-3, awaits its new owner. Fly-away price: about $4 million.

Since 1990 Basler has given new life to dozens of DC-3s. (In the 33 years prior to that, Basler Flight Service had reworked more than a hundred DC-3s, modifying interiors, restoring airframes, and overhauling engines.) Basler installs Pratt & Whitney Canada PT6A-67R turboprop engines and Hartzell five-blade metal propellers in place of the piston engines and props that powered the original aircraft. The company increases the DC-3’s volume 35 percent by inserting a 40-inch plug in the fuselage forward of the wing and moving the cabin bulkhead forward five feet. A BT-67 boasts 45 more mph of cruise speed and almost 4,000 more pounds of useful load than the original DC-3.

This DC-3 has been converted to a Basler BT-67, which makes it perfect for the Antarctic climate. This plane is part of a small fleet that operates with NASA’s Operation Ice Bridge. Photo by @planeschemerdesign

The aircraft’s notoriously temperamental 14-cylinder piston radial engines have always been seen as its weakest feature, so hanging turbines on DC-3s is not a new idea. The British tried it at the end of the 1940s using Armstrong-Siddeley Mamba and Rolls-Royce Dart turboprop engines. The engines helped, but the unpressurized aircraft couldn’t be flown at an altitude that would use the engines to their best advantage, and the project was quickly dropped. The idea was resurrected in the 1960s: In California, a few “Super Turbo Threes” were made and sold, but that project also fizzled. A Taiwanese venture failed as well.

One of the most interesting turbo conversions was done by aviation legend Jack Conroy in the 1960s. His modified DC-3 initially featured three Dart engines, two on the wings and one stuffed in the nose. He sold the airplane to the Specialized Aircraft Corporation, which replaced the engines with Pratt & Whitney models. DC-3 experts then trace the Tri-Turbo to Santa Barbara Polair, Inc., which leased it to the U.S. Navy as a ski-equipped arctic research aircraft. Some have suggested it flew missions for the CIA. The late Warren Basler bought the aircraft in 1992 from a salvage yard in Tucson. It was so distinctive that Basler insisted it be preserved as an important part of the DC-3’s history, and today it sits in Oshkosh, stripped and weathered, awaiting rebirth.

Read the rest of the story over at Air & Space Magazine

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