Some pilots refuse to fly piston-powered helicopters, insisting instead on turbine-powered machines. Turbine engines, their argument goes, are much less likely to fail in flight than piston engines. Though more expensive to purchase and to operate, the reliability of turbine-powered helicopters makes them safer than their piston-powered counterparts.
Does that mean the new Robinson R66, with its Rolls-Royce turbine engine, will be a safer helicopter than Robinson’s R44, with it’s Lycoming piston engine?
Not according to Robinson.
In fact, for years Robinson has taken a contrarian view, suggesting that pilots are in fact safer in piston-powered helicopters. Though the large turbine engines used in airliners are incredibly reliable, the small turbine engines used in helicopters are not. According to Robinson, accident statistics favor piston helicopters.
Tim Tucker, a Robinson factory pilot, caused a stir when he published the data supporting that argument in a 2003 issue of Rotor and Wing magazine. Unfortunately, his article, ("Turbine Reliability: Fact or Fiction") is no longer available on the internet (or at least I can’t find it). But Robinson R44 owner and flight instructor Philip Greenspun sums up the substance of the argument pretty well:
Turbine engines have a reputation for extreme reliability, but physically small turbines, such as those that go into low-power helicopter engines, are subject to a lot of thermal stress and are not nearly as reliable as the turbines in an Airbus. Piston engines have a reputation for unreliability, but that was earned when the engines were operated at 100 percent power. The R44 is a demonstration of the most reliability that you could ever get from a piston engine; the Robinson R66 and similar light turbine helicopters demonstrate the least reliability that you could ever get from a turbine engine. . .
The Robinson factory stops short of saying that the turbine engine makes its new R66 more dangerous than the R44. But it’s not saying that it makes it any safer either. Deftly avoiding the issue, the company president told AOPA Pilot magazine (December 2010 issue):
The decision to use a turbine engine really had nothing to do with reliability. Data has shown the Lycoming 0-540 installed in the R44 to be extremely reliable.
But If Robinson believes small turbine engines are less reliable that the piston engines, then why is Robinson introducing a turbine-powered helicopter at all?
According to Robinson, the market wants a helicopter with improved performance at high altitude and a better power-to-weight ratio. It also wants a ship that can use jet fuel, since avgas is in some parts of the world becoming harder to come by. Only a turbine-powered helicopter can meet those demands.
Fair enough. Just don’t think that shelling out the big bucks for the R66 ($790,000 for the R66 vs. $415,00 for the R44) is going to buy a greater extra margin of safety. In fact, if you believe what Robinson has been saying about small turbine engines for the past 10 years or so, the R66 should prove to be less reliable, and thus less safe, than Robinson’s cheaper piston version.