From Legacy to Leading Edge:

Still redefining technology

It is remarkable that after 50 years, the PT-6 is still redefining the possibilities of turbine engine technology. Former P&WC president and CEO Gilles Quimet said, “The PT-6 turboprop family is one of our great success stories. Over the past five decades, it has established an enviable record for reliability and durability and proven to be a workhorse for thousands of aircraft around the world.”

Through the years, P&WC design engineers have been busy modifying and improving the core PT-6 engine. Pilots now have digital electronic controls. Other modifications have reduced exhaust emissions, and increased maintenance intervals. New aerodynamic and material technologies have enabled the PT-6 engine to gain more power without significantly increasing in size.

It now appears that DNA from that prototype PT-6 developed 50 years ago will live on in new P&WC turbine engines. During EBACE 2010, P&WC announced the creation of a new multidisciplinary team with a mandate to create an even more impressive PT-6 engine. “The technology that will come from this development initiative may also be applied to existing PT-6 engine models.”

Durability and maintainability

I wanted to corroborate the PT-6’s reputation for durability and maintainability. I called Chris Pratt, director of marketing and strategic planning, engine repair and overhaul for Dallas Airmotive. I asked Chris if he could put me in touch with some maintenance folks that had extensive PT-6 experience. I received a call from Joe Capra, program manager; Ryan Saxer, senior customer service representative; and Olof Beyer, chief engineer/customer service engineer. I asked them what makes the PT-6 so reliable. These experts said that for what it is designed to do, the PT-6 is a rugged, perfectly designed turbine engine. It is the “John Deere Tractor” of turboprops.

“It is very forgiving and hard to over temp and over torque. There are limited AD notes and the main bearings are not a life-limited item when operated under basic times between overhaul (TBO). You can separate the engine at the C flange and inspect the hot section on the wing and the TBO is about 3,600 hours. If you do need service in the field, the free turbine design makes this engine easy to maintain. The PT-6 is so widely used that if it does require maintenance, regardless of where you are, you can get parts within a couple of days.”

I asked Joe Capra for some customer feedback. Some customers commented that “Engine dependability is not something that concerns us.” “Reliability is not an issue, they just don’t break.”

In April of 1991, the dependability of the PT-6 engine was demonstrated during a high-profile emergency medical rescue mission to extract an ailing Dr. Ronald Shemenski from the Amundsen-Scott South Pole research center. The mission was made during the brutal, totally dark, -60 F Antarctic winter. The plane used for the mission was a Twin Otter turboprop powered by two aircraft quality PT-6 engines. The Twin Otter was piloted by Captain Mark Cary who flew from Canada to the South Pole and back without a hitch.

Happy 50th birthday to the PT-6. You remind me of one of my favorite children’s story about another little engine that could. AMT

Charles Chandler is AMT’s Field Editor. He received his A&P from Spartan College of Aeronautics.