Jetrader - January/February 2013 - 15

with Pure Power, so the turboprop is a slam dunk, right? Well, sort of, and this is where caution has to come into the considerations of the new lessor. What has to be realized is just how much progress has taken place under the old skins, and particularly the cowlings of the A320 and 737. While the fuselage of a 737 is essentially that of a 50 year old 707 and the wing of the A320 is unchanged in 25 years, the engines have developed and matured year on year into the most phenomenally reliable and cheap to operate machines in the history of transportation. Not so the turboprop and this leads to some incredible comparisons in the area of powerplant maintenance cost. For the turboprop you only have one real choice, the phenomenally successful Pratt and Whitney Canada PW 100 series. For 50 years PWC have mined this little gold seam, from the earliest 500hp PT 6s through to the mighty PW 150 with ten times the power, the formula has remained essentially unchanged. A big centrifugal impeller, just like Frank Whittles ﬁrst jets, driven by a turbine, another “ high pressure “ impeller

driven by another turbine, a reverse ﬂow combuster section and a free turbine on the back to drive a reduction gearbox which in turn drives a big “unducted fan” on the front. No aircraft powerplant could be simpler - agricultural even. And therein lies the problem that drives maintenance costs through the roof! Labor is more expensive all the time and materials costs climb at 5-6 percent above the rate of inﬂ ation every year, given the business model all engine OEMs use to offset the upfront purchase price discounts. In the big jet world, this has been masked by the steady march of technology. Where once we were happy if our JT8 stayed on its 737 wing for 5,000-6,000 hours and were then amazed by the CFM56 -3 doubling this to 15,000 hours, now we are so blasé that we get quite surprised if a - 7 doesn’t make it to its ﬁrst LLP limiter at 20,000 cycles and maybe 35,000 hours. The shop visits might cost a lot, but on an hourly basis they have hardly changed in 20 years . Not so the turboprop. Just as its technology is rooted in the 60s (the overall pressure ratio of a PW 120 is lower than

a JT8, and half that of a CFM), so are its maintenance intervals. If the operator has been allowed to go “on condition,” or at least soft time it cuts a little slack but in reality is little better than a hard time program. There they will be faced with a hot section inspection shop visit at 4,500 hours, another at 9,000 hours and a full overhaul at 13,500. This means a constant ﬂow of engines to the shop for a 4 week shop visit every 2 years. In basic terms these are not so expensive, but as we will show later, the cost per hour, or more importantly, per passenger seat kilometer come as quite a shock! For the ﬁrst HSI we may get away with between $250,000 and 300,000, (though not in hot and dusty countries). Four thousandﬁve hundred hours later, the next HSI may creep in under 400,000 dollars. The third shop visit is an overhaul, hot section, cold section and reduction gearbox together. The budget is $800-900,000. So by now we have spent $1.5 million. The CFM 56 that started life on the same day as our engine is little more than half way through its ﬁrst run and, God willing, won’t have a cent spent on her for years yet to come. Jetrader 15

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Jetrader - January/February 2013

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